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Evaluating skyscraper design and construction technologies on an international basis Abo Moslim, Saad Allah Fathy 2017

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 EVALUATING SKYSCRAPER DESIGN AND CONSTRUCTION TECHNOLOGIES ON AN INTERNATIONAL BASIS  by  Saad Allah Fathy Abo Moslim   B.Sc., Mansoura University, Egypt, 1984 M.Eng., The University of British Columbia, Canada, 2000  A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF  THE REQUIREMENTS FOR THE DEGREE OF   DOCTOR OF PHILOSOPHY  in  THE FACULTY OF GRADUATE AND POSTDOCTORAL STUDIES  (Civil Engineering)   THE UNIVERSITY OF BRITISH COLUMBIA  (Vancouver)    November 2017  © Saad Allah Fathy Abo Moslim, 2017   ii  Abstract Design and construction functions of skyscrapers tend to draw from the best practices and technologies available worldwide in order to meet their development, design, construction, and performance challenges. Given the availability of many alternative solutions for different facets of a building’s design and construction systems, the need exists for an evaluation framework that is comprehensive in scope, transparent as to the basis for decisions made, reliable in result, and practical in application. Findings from the literature reviewed combined with a deep understanding of the evaluation process of skyscraper systems were used to identify the components and their properties of such a framework, with emphasis on selection of categories, perspectives, criteria, and sub-criteria, completeness of these categories and perspectives, and clarity in the language, expression and level of detail used. The developed framework divided the evaluation process for candidate solutions into the application of three integrated filters. The first filter screens alternative solutions using two-comprehensive checklists of stakeholder acceptance and local feasibility criteria/sub-criteria on a pass-fail basis to eliminate the solutions that do not fit with local cultural norms, delivery capabilities, etc. The second filter treats criteria related to design, quality, production, logistics, installation, and in-use perspectives for assessing the technical performance of the first filter survivors in order to rank them. The third filter evaluates the financial performance expressed in terms of Net Present Value of a skyscraper project over its life cycle as a function of system solutions being considered, and involves treatment of all major cash flow streams (revenues and expenditures), and their timing. Product and process models are developed to provide the cash flow model with the required scope and time information. The most preferred solution is recommended on the basis of filter two and three results. Efficacy of the developed framework and each filter were assessed through their application to many case studies and through interviews with construction professionals. Findings show that the framework addresses the deficiencies identified in the existing literature and can improve the quality of the decision-making process when selecting preferred solutions for building a specific skyscraper in a specific geographic area.    iii Lay Summary The research goal is to develop an evaluation framework for assessing skyscraper engineering and construction technologies in order to recommend the most preferred solution(s) for a specific skyscraper in a specific geographic area to the decision maker. This framework involves the use of three filters and reflects the informal thought processes applied in practice by design and construction personnel.  This thesis is a manuscript-based document and has five chapters. Chapter 1 includes an extensive thesis overview given adoption of manuscript thesis format and describes the background, problem statement, proposed solution, methodologies, research motivations, summary of literature review, and contributions of the research. Chapters 2 through 4 describe the findings of filters 1 through 3 of the research work, respectively. Chapter 5 concludes the thesis through summarizing the research work and contributions, and suggests future work for tackling challenges/limitations encountered in this research endeavor.    iv  Preface The research reported in this thesis consists of: identification of research problems and questions, formulation of research methodologies in pursuing answers to the research questions, comprehensive and critical review for related literature, analysis of design guidelines and development methods of an evaluation framework, and implementation of the framework and its three filters. Case studies related to an iconic skyscraper and interviews with construction practitioners are used for validating and verifying the framework and each filter. The lessons learned from these applications as well as the received feedbacks from these interviews are incorporated in the current version of the framework.  The topic of dissertation was proposed by the author who had the passion of conducting research on skyscrapers primarily because of the previous experience in the Middle East in the context of high rise buildings; and agreed by PhD program supervisor Dr. Alan Russell. Process modeling that forms part of filter 3 made use of a linear planning software system (Repcon) developed by Dr. Alan Russell. With the guidance from Dr. Alan Russell, the author was solely responsible for all components of this research including collecting data of the case study project, Abraj el-Bait, Makkah, Saudia Arabia.  The content of this dissertation is in the form of three manuscripts prepared for publication, namely Chapters 2 to 4.  For each of these, the dissertation author was the primary manuscript author, while the co-author provided guidance on the development and application of various aspects of the research as well as manuscript review and editing.     The following peer-reviewed conference papers are incorporated in Chapter 2and have been published:  i. AboMoslim, S. and Russell, A. (2005), “Evaluating Innovative Design and Construction Technologies for Super Hi-rise Buildings on an International Basis”, Proceedings-33rd CSCE Annual Conference 2005: 6th Construction Specialty Conference, pp CT-189-1-10. ii. AboMoslim, S. and Russell, A. (2005), “Innovative Design and Construction Technologies for Building Internal Partitions for Super Hi-Rise Buildings on an International Basis”, Sixth International Conference on Tall Buildings, Hong Kong, China, World Scientific Publishing Co, pp. 594 - 603.  Similarly, the following journal paper is presented as Chapter 2 and has been published: iii. AboMoslim, S. and Russell, A. (2014), “Screening skyscraper design and construction technologies on an international basis”, Construction Innovation: Information, Process, Management, Vol. 14 No 3, pp. 307-445.  A version of each manuscript that represent Chapters 3 and 4 is ready for submission to a journal.     v Table of Contents Abstract   ............................................................................................................................................. ii Lay Summary   ............................................................................................................................................ iii  Preface   ............................................................................................................................................. iv Table of Content   .............................................................................................................................................. v  List of Tables   ............................................................................................................................................. ix List of Figures   ............................................................................................................................................. xi  List of Abbreviations ...................................................................................................................................... xiii Glossary   ............................................................................................................................................ xv  Acknowledgements ......................................................................................................................................... xvi  Dedication   ......................................................................................................................................... xvii  Chapter 1 Introduction ............................................................................................................ 1 1.1 Chapter overview .................................................................................................................. 1 1.2 Problem statement ................................................................................................................. 1 1.3 Overview of the proposed framework for evaluating skyscraper technologies .................... 2 1.3.1 First filter .............................................................................................................................. 3 1.3.2 Second filter .......................................................................................................................... 3 1.3.3 Third filter............................................................................................................................. 4 1.4 Research motivations ............................................................................................................ 7 1.5 Research questions, objectives, and hypothesis .................................................................... 8 1.6 Research scope, limitations, and assumptions .................................................................... 10 1.6.1 Research Scope ................................................................................................................... 10 1.6.2 Research limitations ........................................................................................................... 10 1.6.3 Research assumptions ......................................................................................................... 11 1.7 Research methodology ........................................................................................................ 12 1.8 State-of-the-art review and its shortcomings ...................................................................... 14 1.8.1 Literature review as it relates to the structure of the framework ........................................ 14 1.8.2 Literature shortcomings ...................................................................................................... 15 1.9 Research contributions ........................................................................................................ 16 1.9.1 Structure of the three-filter framework and first filter ........................................................ 16  vi 1.9.2 Second filter ........................................................................................................................ 19 1.9.3 Third filter........................................................................................................................... 33 Chapter 2 Screening design and construction technologies of skyscrapers ...................... 46 2.1 Introduction ......................................................................................................................... 46 2.2 Literature review ................................................................................................................. 47 2.3 Research methodology ........................................................................................................ 50 2.4 Development of framework overview ................................................................................ 52 2.5 Development of filter one: criteria, categories, criteria checklists and state values ........... 56 2.6 Project background and description of case studies ............................................................ 60 2.6.1 Case study 1: alternative solutions for construction of wet areas ....................................... 61 2.6.2 Case study 2: alternative solutions for construction of internal partitions .......................... 62 2.6.3 Case study 3: alternative solution for construction of cladding system .............................. 63 2.7 Applying the first filter of the evaluation framework to the three case studies .................. 64 2.7.1 Applying the first filter to candidate solutions for wet area construction ........................... 65 2.7.2 Applying the first filter to candidate solutions for internal partition construction ............. 65 2.7.3 Applying the first filter to candidate solutions for exterior enclosure ................................ 67 2.7.4 Summary of first filter screening results ............................................................................ 68 2.8 Assessment of the evaluation framework by practising professionals ................................ 69 2.8.1 First practising professional’s feedback ............................................................................. 71 2.8.2 Second practising professional’s feedback ......................................................................... 71 2.8.3 Third practising professional’s feedback ............................................................................ 72 2.9 Conclusion .......................................................................................................................... 72 Chapter 3 Performance Evaluation Tool for Skyscraper Design and Construction Technologies ................................................................................................................................ 75 3.1 Introduction ......................................................................................................................... 75 3.2 Proposed framework ........................................................................................................... 76 3.3 Research methodology for development of the second filter .............................................. 77 3.4 Literature review ................................................................................................................. 79 3.5 Development details of the second filter ............................................................................. 86  vii 3.5.1 Hierarchical tree structure of perspectives, criteria, and sub-criteria ................................. 86 3.5.2 Relative weights for perspectives and criteria .................................................................... 89 3.5.3 Sub-criteria statuses ............................................................................................................ 89 3.5.4 Sub-criteria measuring scales, units, and types .................................................................. 91 3.5.5 Sub-criteria rating questionnaire ......................................................................................... 91 3.5.6 Sub-criteria state values and scores .................................................................................... 96 3.5.7 Bottom-up approach for aggregating criteria, perspectives, and solutions’ weighted values .   ............................................................................................................................................ 97 3.5.8 Prerequisite information for the performance evaluation of feasible solutions .................. 98 3.6 Applications of the second filter to three case studies ...................................................... 102 3.6.1 Case study 1: ranking feasible solutions for wet area construction .................................. 103 3.6.2 Case study 2: ranking feasible solutions of internal partitions construction .................... 105 3.6.3 Case study 3: ranking feasible solutions for exterior enclosure construction ................... 107 3.6.4 Discussion of second filter application results for the examined case studies ................. 109 3.7 Assessment of the performance evaluation tool by three practising professionals ........... 109 3.7.1 First practising professional’s feedback ........................................................................... 110 3.7.2 Second practising professional’s feedback ....................................................................... 110 3.7.3 Third practising professional’s feedback .......................................................................... 111 3.8 Conclusion ........................................................................................................................ 112 Chapter 4 Evaluating Impacts of System’s Solutions on Skyscraper Cash Flow Streams and Their Timelines ............................................................................................. 114 4.1 Introduction ....................................................................................................................... 114 4.2 Evaluation framework ....................................................................................................... 115 4.3 Research methodology ...................................................................................................... 116 4.4 Literature review ............................................................................................................... 118 4.5 Development of filter-three models .................................................................................. 120 4.5.1 Cash flow model ............................................................................................................... 121  4.5.2 Cost model ........................................................................................................................ 122 4.5.3 Project product models ..................................................................................................... 124 4.5.4 Project process model ....................................................................................................... 127  viii 4.5.5 Models integration and application steps ......................................................................... 131 4.6 Applications of product and process models to a case study skyscraper .......................... 137 4.6.1 Applications of product models ........................................................................................ 137 4.6.2 Case study1: the base case time model for a skyscraper build of locally preferred solutions   .......................................................................................................................................... 138 4.6.3 Case study 2: base case and Pods for wet areas ................................................................ 140 4.6.4 Case study 3: base case and Acotec for internal partitions ............................................... 142 4.6.5 Case study 4: base case and precast panels for exterior cladding ..................................... 143 4.6.6 Case study 5: base case and all innovations ..................................................................... 145 4.7 Assessment of the evaluation framework by practicing professionals ............................. 148 4.7.1 First practising professional’s feedback ........................................................................... 149 4.7.2 Second practising professional’s feedback ....................................................................... 149 4.8 Conclusion ........................................................................................................................ 150 Chapter 5 Conclusions ......................................................................................................... 152 5.1 Overview of the conclusion .............................................................................................. 152 5.2 Summary of thesis objectives and methodologies ............................................................ 152 5.3 Research conducted .......................................................................................................... 152 5.3.1 First research objective: development an overview of the evaluation framework ........... 153 5.3.2 Second research objective: development of the first filter................................................ 153 5.3.3 Third research objective: development of the second filter .............................................. 154 5.3.4 Fourth research objective: development of the third filter ............................................... 155 5.3.5 Fifth research objective: usefulness of the framework for improving the quality of decision-making process ................................................................................................................. 157 5.4 Summary of research contributions .................................................................................. 158 5.4.1 First research objective, overview of the evaluation framework, contribution ................ 158 5.4.2 Second research objective, filter one, contribution ........................................................... 158 5.4.3 Third research objective, filter two, contribution ............................................................. 159 5.4.4 Fourth research objective, filter three, contribution ......................................................... 159 5.4.5 Fifth research objective: usefulness of the framework ..................................................... 160 5.5 Suggestions for future work .............................................................................................. 160 Bibliography   .......................................................................................................................................... 162  ix List of Tables Table 1-1 Filter 1 categories, criteria, and state values ...................................................................................... 4 Table 1-2 Filter 2 perspectives, criteria and possible state values ..................................................................... 5 Table 1-3 Filter 1 stakeholder acceptance and high level risk sub-criteria checklist ....................................... 18 Table 1-4 Filter 1 local technical feasibility sub-criteria checklist .................................................................. 19 Table 1-5 Sec.1 of evaluating details for filter 2 perspectives, criteria, and sub-criteria ................................. 23 Table 1-6 Sec. 1 of state values analysis for a sample of criteria and sub-criteria ........................................... 29 Table 1-7(a) Product model 2: project hierarchical structure levels 1 - 4 ........................................................ 38 Table 2-1 Filter 2 evaluation perspectives, criteria and possible state values .................................................. 55 Table 2-2 Filter 1 categories, criteria, and state values .................................................................................... 57 Table 2-3 Filter 1 stakeholder acceptance and high level risk sub-criteria checklist ....................................... 58 Table 2-4 Filter 1 local technical feasibility sub-criteria checklist .................................................................. 60 Table 2-5 Case study 1 evaluation of stakeholder acceptance including risk issues ........................................ 66 Table 2-6 Case study 1 - evaluation of local technical feasibility .................................................................... 67 Table 2-7 Case study 1 - summary of filter 1 findings for wet areas construction alternatives ....................... 68 Table 2-8 Case study 2 - summary of filter 1 findings for internal partition alternatives ................................ 69 Table 2-9 Case study 3 - summary of filter 1 findings for cladding alternatives ............................................. 69 Table 2-10 Summary of filter 1 screening results for the three case studies examined ................................... 70 Table 3-1 Sec. 1 of related literature to filter 2: perspectives, criteria and sub-criteria ................................... 81 Table 3-2 Sec. 1 of filter 2 perspectives, criteria, and sub-criteria ................................................................... 92 Table 3-3 Sec. 1 of state values analysis for a sample of criteria and sub-criteria on three sections ............... 99 Table 3-4 Feasible solutions for the three case studies of Abraj Al-Bait Project systems ............................. 102 Table 3-5 Scores of perspectives, criteria and sub-criteria for wet areas solutions ........................................ 104 Table 3-6 Calculation of overall weighted performance values for wet areas solutions ................................ 106 Table 3-7 Calculation of overall weighted performance values for internal partition solutions .................... 107 Table 3-8 Calculation of overall weighted performance values for cladding solutions ................................. 108  x Table 4-1(a) Product model 2: project hierarchical structure levels 1 – 4 ..................................................... 128 Table 4-2 Product model scope of work data for selected aspects of the Case Study project ....................... 139 Table 4-3 Typical Durations Production rates (days/floor) of traditional and innovative solutions .............. 139 Table 4-4 Summary of completion dates and time saving for all case studies ............................................... 148     xi List of Figures Figure 1-1 Overview of the evaluation framework ............................................................................................ 3  Figure 1-2 An example of skyscraper time model ............................................................................................. 6 Figure 1-3 West Bay Complex Project, Doha, Qatar ......................................................................................... 8 Figure 1-4 Abraj Al Bait project, Saudi ............................................................................................................. 9 Figure 1-5 Kingdom project, Saudi.................................................................................................................... 9  Figure 1-6 Development steps of the three-filter framework ........................................................................... 13 Figure 1-7 Weights calculation example for evaluating perspectives, criteria, and sub-criteria ...................... 22 Figure 1-8 Scales with continuous values ........................................................................................................ 32 Figure 1-9 Scales with discrete values ............................................................................................................. 32  Figure 1-10 A simplified version of project cost cash flow model .................................................................. 34 Figure 1-11 Product model 1: geometric and spatial model ............................................................................ 36 Figure 1-12 Elements of process model: (a) hierarchical project structure; (b) linear planning chart for packages/sub-packages .................................................................................................................. 40 Figure 1-13 Models integration process ........................................................................................................... 43  Figure 1-14 Sequence of applications for filter three models .......................................................................... 45 Figure 2-1 Development steps of the main structure of the framework and the first filter details .................. 52 Figure 2-2 Overview of evaluation framework ................................................................................................ 54 Figure 2-3 Macro level time model.................................................................................................................. 56  Figure 3-1 A framework for evaluating the skyscraper design and construction technologies ........................ 77 Figure 3-2 Research methodology of the second filter .................................................................................... 79 Figure 3-3 Second filter perspectives, related criteria and their sequence of application ................................ 88 Figure 3-4 Quality perspective role of a solution across skyscraper life cycle phases .................................... 89 Figure 3-5 Weights calculation example for evaluating perspectives, criteria and sub-criteria ....................... 90 Figure 3-6 Scales with continuous values ........................................................................................................ 97 Figure 3-7 Scales with discrete values ............................................................................................................. 97   xii Figure 4-1 Framework for evaluating skyscrapers systems’ solutions .......................................................... 116 Figure 4-2 Research methodology of third filter............................................................................................ 117 Figure 4-3 A simplified version of project cost cash flow model .................................................................. 122 Figure 4-4 Product model 1: geometric and spatial model ............................................................................ 125 Figure 4-5 Schedule acceleration strategies (Russell et al., 2014) ................................................................ 130 Figure 4-6 Elements of process model: (a) hierarchical project structure; (b) linear planning chart for packages/sub-packages ................................................................................................................ 132 Figure 4-7 Models integration process........................................................................................................... 135  Figure 4-8 Sequence of applications for filter three models .......................................................................... 136 Figure 4-9 Base case ...................................................................................................................................... 141 Figure 4-10 Joining between podium and tower ............................................................................................ 141 Figure 4-11 Base case and pods (pink) .......................................................................................................... 144 Figure 4-12 Base case and Acotec (green) interior panels ............................................................................. 144 Figure 4-13 Base case and precast cladding panels (light blue) .................................................................... 146 Figure 4-14 Base case and all innovations ..................................................................................................... 146 Figure 4-15 Comparison bar chart – base (green) vs. all innovations simultaneously (blue) ........................ 147 Figure 5-1 Overview of evaluation framework .............................................................................................. 154    xiii List of Abbreviations 0 Score  Solution Is Fail 1 Score  Solution Is Least Preferred 2 Score   Solution Is Acceptable 3 Score  Solution Is Preferred C    Activity Cost  CSI   Construction Specifications Institute D    Duration in Days f    Fraction of Direct Cost to Cover the Indirect Cost  F    Degree of Fast-Tracking of Construction Phase over Design Phase G1    Literature Group of Logistics G2    Literature Group of Quality  G3    Literature Group of Sustainability G4    Literature Group of Evaluation Frameworks for System Solutions G5    Literature Group of Evaluation of Prefabricated Solutions G6    Literature Group of Innovation Diffusion Criteria G7    Literature Group of Evaluation Tools for Project Success H    Cycle Time of Major Rehabilitation of a System  HVAC   Heating, Ventilation, and Air Conditioning J    Number of Substructure Lifts K    Number of Superstructure Lifts  LCC   Life Cycle Cost LP    Linear Planning Methodology M    Number of Zones Per Floor  NPV   Net Present Value O & M Operation and Maintenance Phase  O    Overlap of T&C Phase with Project Start-up and Revenue Generation Phase P    Local Productivity Rate  xiv Q    Scope of Physical Component of a Skyscraper R    Local Resources Usage Rate T & C   Testing and Commissioning Phase T    Activity Time V1    First State Value for a Sub-criterion V2    Second State Value for a Sub-criterion  V3    Third State Value for a Sub-criterion  Y/N   Applicable or not Applicable State Values of a Sub-Criterion that Are Equivalent to Score (1/0)    xv Glossary Terminology and associated definitions used for the framework presented in this thesis are as follows.  1. Skyscraper: a super-tall building which has a height more than 300 m (984 feet). 2. Solution: conventional as well as innovative or novel candidates for the design and/or construction of a physical system or subsystem of a skyscraper. 3. Innovative design and construction technology: direct or adaptive use of new or existing products, methods or processes not previously used within the project context or by the project stakeholders.  4. Logistics: process of planning, implementing, and controlling the efficient, cost-effective flow and storage of permanent material, products, in-process inventory, applied resources, and related information from all supplier/subcontractor/fabricators to a project; building and completing project systems in accordance with project requirements; and removing redundant material and waste from the site after system completion.  5. Bottom-up evaluation approach: determining the value of overall project performance by aggregating upward through a hierarchy of evaluation criteria, starting with an assessment of performance at the lowest level in the criteria hierarchy.  6. Performance evaluation tool: sets of criteria and their corresponding sub-criteria used to quantitatively measure all achieved physical characteristics of a skyscraper system or solutions to assess satisfaction of project/stakeholder goals and objectives across all project life-cycle phases: design, production, logistics, installation, in-use, and demolition.  7. Design performance: solution characteristics relevant to in-use functions, fire safety, structural serviceability, aesthetics, and compatibility with and impacts on other building systems.  8. Production performance: treats solution properties related to off-site production such as constructability, production environment, and production characteristics.  9. Logistics performance: solution characteristics relevant to the supply of material and equipment to the site, site mobilization, and reverse logistics (removal of equipment and material).  10. Installation performance: treats solution properties that affect installation environment, installation characteristics, and efficiency of material used.  11. In-use performance: solution characteristics relevant to end-user expectations that include durability, maintainability, flexibility, and impact on the living environment.  12. Quality performance: treats characteristics of solution quality assurance and control plans that are used for managing solution’s life-cycle phases in terms of their inputs, transformation processes, and outputs, to achieve specified performance objectives.   xvi Acknowledgements Generally, I would like to pay thanks to almighty Allah, who has given me the opportunity, ability, support, and knowledge to complete this challenging research undertaking. My long and interesting journey could not come to an end without the help, guidance, and support of many individuals. First, I am very much grateful to my supervisor Professor Alan Russell for his continued moral, and technical support throughout my research program. He has guided me throughout this research and kept me on track through his broader vision, vast knowledge, and expertise in the academia.  Second, my respectful gratitude goes to my supervisory committee members: Professor Sheryl Staub-French, Professor Siegfried F. Stiemer, and Professor Scott Dunbar for their invaluable guidance throughout the research program.  Third, I would like to express my thanks to the experts of Abraj Al-Bait project, Saudi Arabia: engineer Nabil Batrawi, engineer Adel Shideed, engineer Musadak Parmada, and engineer Wageh for their valuable input with regard the case study.  Fourth, I am grateful to all colleagues at the project and construction management group for their valuable suggestions, and positive discussions: Mr. Jehan Zeb, Mr. Madav Nepal, Mr. Chao-Ying Chiu, and Mr. Roland Awuni.  Finally, I would like to express my warmest and deepest thanks to my mother, sister, and brothers for their moral and financial support. Dedication must go to my wife Mrs. Amal; daughters: Shaymaa, Sara, Maryam, and Ola; and sons: Anas, Mohamad, and Ali; for bearing with me throughout the long hours of work and for making this journey more joyful.  Saad AboMoslim    xvii    Dedication     To my father, Fathy      my mother, Um Alkhair      my lovely wife, Amal      my lovely daughters, Shaymaa, Sara, Maryam and Ola      my sons, Anas, Mohamad, and Ali      and my sister and brothers,  Ebtisam, FathAllah and AbdAllah     1 Chapter 1 Introduction 1.1 Chapter overview  This thesis is a manuscript-based document. The research centers on seeking answers to five questions.  (i) How should a framework for evaluating skyscraper design and construction solutions be structured and developed?; (ii) How should a tool for preliminary screening (filter 1) of skyscraper design and construction solutions be developed?; (iii) How should a technical performance evaluation tool (filter 2) for assessing skyscraper design and construction solutions be developed?; (iv) How should economic and time models (filter 3) for evaluating impacts of design and construction solutions on skyscraper cash flow streams and their timing be developed?; and (v) How does the use of the evaluation framework help in recommending the most preferred design and construction solutions to the decision makers that cannot be done with current tools and practices? Chapter 1, in the form of an extensive thesis overview given the adoption of the manuscript thesis format, describes the background, problem statement, proposed solution, methodologies, research motivations, summary of literature review, and contributions of the research. Chapters 2 through 4 describe the findings of filter 1 through 3 of the research work respectively. Chapter 5 concludes the thesis through summarizing the research work, contributions, and suggests future work for tackling challenges/limitations encountered in this research endeavor. Chapter 2 has already been published (AboMoslim and Russell, 2014), and the intent is to seek publication of the manuscripts presented in Chapters 3 and 4. 1.2 Problem statement Skyscrapers, whose design and construction draw from the best practices and technology available on a world-wide basis, are very large and complex engineering projects that can be characterized by several features. First, they require very large scale of investments over long design and construction durations (Watts et al., 2007), which may involve two or more economic cycles with significant exposure to changing inflation, interest and exchange rates. Second, the mixed-use aspect of such projects leads to multiple intermediate milestones of partial occupancy before overall project completion. The speed with which they are delivered, including attainment of intermediate milestones, considerably affects capital expenditures including the effects of inflation and financing costs, revenues, and resultant returns on total and equity capital. Third, skyscraper projects are characterized by significant repetition of horizontal and vertical features (Shaked and Warszawski, 1995), which can on one hand create economies of scale and open up totally new solutions, and on the other hand, require very costly infrastructure for temporary facilities. Fourth, a limited in-situ work area creates many challenges in accessing the work-face (Watts et al., 2007) and requires the use of specialized transportation arrangements and means. Fifth, skyscraper projects require massive amounts of human, material and equipment resources and involve complex and innovative systems for their design and construction leading to the sourcing of technical expertise, material and equipment from around the globe. Finally, such projects have very long operating lives with significant operating and maintenance (O&M) and rehabilitation costs (Ali and Armstrong, 2008).   2 Skyscraper projects worldwide provide a unique opportunity and special incentive for assessing a multiplicity of solutions, especially innovative ones. To do this, two distinct challenges exist: the identification of potential solutions (both conventional and innovative) for a specific design and/or construction problem; and an evaluation of these candidate solutions in terms of feasibility and preference. In general, any solution to a design or construction method decision problem, either conventional or innovative, is preferred only if the advantages offered outweigh any attendant disadvantages (Toole, 2001; Gibb and Isack, 2003; Blismas et al., 2006; Jaillon et al., 2009); as measured in terms of one or more performance metrics such as capital cost, life cycle cost, time, quality, safety and durability (Tatum, 1984) and given satisfaction or compliance with all must have feasibility criteria. To facilitate the solution selection process, the need exists for an evaluation framework that is comprehensive in scope, provides transparency as to the basis for decisions made and is easy to use. This framework can help to simplify the choice process for decision-makers in the early stages of a project and evaluate the efficiency and the effectiveness of potential solutions.  To increase the efficiency (i.e. the ease with which it can be applied) and effectiveness (determining the preferred choice in as objective a manner as possible) of the design and construction solution evaluation process, the framework should address the following issues: (1) incorporation of construction context and project stakeholder values and needs; (2) assessment of the technical and environmental performance of the building system of interest as well as its possible interactions with other systems; (3) evaluation of the time and life cycle cost performance of the system as well as its impact on the whole building; (4) specific consideration, and mitigation to the extent possible, of risks associated with the solutions being evaluated; and (5) compatibility with the informal structure of existing industry decision-making processes in terms of narrowing the choice of feasible solutions as quickly as possible to conserve resources, but with considerably more structure, completeness, and rigor.  1.3 Overview of the proposed framework for evaluating skyscraper technologies  As explained later, an evaluation framework comprised of three filters was determined to be the most appropriate structure for assessing skyscraper technologies. This proposed approach is compatible with the thought processes applied by engineering and construction practitioners in terms of (1) eliminating as quickly as possible solutions that fail ‘must have’ criteria; (2) assessing the technical/environmental performance of viable candidates – does each solution address essential criteria in a satisfactory manner? (while elimination at this step is not the goal, it is possible that one or more solutions cannot deliver satisfactory technical/environmental performance); and (3) assessing solutions based on quantitative measures of cost (capital, life cycle), time, and risk. This paradigm is observed in practice on a recurring basis, but without a consistent level of rigor and often on an ad-hoc basis.  The framework set out herein is intended for use by construction practitioners, designers, developers, and even policy makers for skyscraper projects targeted for residential, commercial, institutional, or mixed use. Although the framework can be used at any time during the building life cycle, the earlier it is used, the greater are the potential benefits. Figure 1-1 shows an overview of the framework. The evaluation goal is to recommend the most preferred solution that meets specified system characteristics; satisfies stakeholder performance requirements, goals, and expectations; improves the construction work environment and process characteristics; reduces environmental impact; and enhances the living environment of end-users. To achieve this goal, the framework divides the evaluation process for candidate solutions into  3 the application of three filters.  1.3.1 First filter Application of the first filter provides a quick (preliminary) screening of potential solutions to determine feasibility for a specific skyscraper project context and a particular geographic area. The goal is to determine if there is an initial match between the project, the candidate solutions, and local market conditions. Application of this filter helps to avoid a large commitment of resources to an infeasible solution. Criteria considered at this stage relate to factual information pertaining to project characteristics, site conditions, market conditions, and local codes and regulations. These criteria are incorporated under the two categories of stakeholder acceptance and technical feasibility. Perspectives of interest under the stakeholder acceptance category are end-user, designer and developer, contractor, regulator and code, and risk. The technical feasibility category embraces local capability to manufacture and/or construct the technology using locally available human resources, materials, and infrastructure, and/or the ability to import related production equipment and technical expertise. All criteria for the first filter are judged on a pass-fail basis. A pass mark must be achieved for each relevant criterion. Some criteria are hard (i.e. non-negotiable), while others are soft or act as constraints and may be subject to negotiation—e.g., local regulations and codes. Failure on a hard criterion results in immediate dismissal of the solution being examined. If a failed soft criterion cannot be made into a pass by negotiation, evaluation of that solution is terminated. Table 1-1 shows the summary table of first filter categories, criteria, and their state values. In-depth treatment of the first filter criteria and sub-criteria and screening process and its application in practice is presented the following sections and in Chapter 2.  Figure 1-1 Overview of the evaluation framework 1.3.2 Second filter Given success with the first filter, the second filter involves a detailed performance evaluation process for potential solutions from perspectives of design, quality, production, logistics, installation, and in-use. Its application starts the  First Filter Second Filter  Third Filter  First Filter Categories Stakeholder acceptance Local technical feasibility Second Filter Perspectives Design                  Quality Production            Logistics Installation           In-use Third Filter Models Project cost cash flow model Product models Process models  Screening Recommending  Ranking Unlimited no. of design and construction solutions Feasible solutions Ranked solutions Most preferred solutions  4 process for ranking the feasible solutions (exclusive of detailed consideration of cost, time, and risk). For each perspective, a set of critical evaluation criteria has been identified and, for each criterion, a set of driving sub-criteria must be evaluated. The criteria states are defined based on the states of the lower level sub-criteria. In defining criteria states for the second filter, a simple four-state evaluation scheme is used with value states of: 3 for preferred, 2 for acceptable, 1 for least preferred, and 0 for fail. Criteria and state values under these perspectives are listed in Table 1-2. While alternatives can be rank ordered at this step, elimination of an alternative at this step is unlikely unless its performance in terms of one or more essential performance dimensions is determined to be non-compliant with the minimum performance level required. Such a situation can occur, as assessment at the second filter level is considerably more comprehensive than that for the first step. In assigning the value for a sub-criterion, use is made of a parameterized description of the solution in the form of performance threshold values that must be achieved (two-hour fire safety, service life of 50 years, crane lifting capacity of 15 tons, etc.). Supplementary tables of sub-criteria have been developed to treat relevant ‘tests’ for each of the criteria listed in Table 1-2. In-depth treatment of the second filter, evaluation process and its application in practice is presented in chapter 3. Table 1-1 Filter 1 categories, criteria, and state values  1.3.3 Third filter The third filter focuses on quantifiable measures related to off-site and on-site production, total project delivery time, intermediate milestone requirements, construction cost, total capital cost, and life-cycle cost, and the uncertainty associated with these values. A set of integrated project models as a function of the project being examined are used to evaluate the impacts of alternative solutions in cash flow streams and their timing. Evaluation of the economic and financial desirability of a project and attendant design and construction choices is assessed using Net Present Value (NPV) as this performance metric allows trade-offs to be made between various costs / revenues within a given project phase and between project phases.  A hierarchy of the developed models is as follows. First is the project cost cash flow model that treats all cost and revenue flows over the project life cycle in order to calculate NPV. The project cost model treats the constant dollar direct and indirect costs associated with design, procurement, and construction activities. These costs are then converted to current dollar costs when expenditures are positioned in time.   Pass, (P) Fail, (F) N/AStakeholder acceptanceEnd-users hard acceptable unacceptable N/AContractor soft acceptable unacceptable N/ADesigners & developer hard acceptable unacceptable N/ARegulators and codes soft acceptable unacceptable N/ARisk hard acceptable unacceptable N/ALocal technical Technology soft available or can be infeasible to be imported N/AHuman resources soft available or can be infeasible to be imported N/AMaterials soft available or can be infeasible to be imported N/AInfrastructure hard exists or can be built unavailable from any N/ACategories/criteria Type State values 5 Table 1-2 Filter 2 perspectives, criteria and possible state values  Second are project product models that treat the physical characteristics of the project in terms of spatial and geometric context and physical systems and sub-systems in order to calculate the scope quantities for usage in cost and time models. Third are the project process/time and work package models that treat project design, construction and testing and commissioning (T&C) phases as well as off and on site production in order to calculate any changes in duration, start and finish dates, and/or resources used. Emphasis has been placed on the treatment of time because of its significant impact on cost and revenue. A project time model in the form of a linear planning model using high level work packages is employed to identify the criticality of work packages and milestone dates, including project completion (see Figure 1-2 for an example). The model is hierarchical in nature, allowing for more fine-grained modelling of work package details as appropriate to the solution being considered. Output from this model is used in turn to assess the consequences for project cost-cash flow models such as inflation and financing costs.  The third filter models focus on determining if there are significant differences amongst the various alternatives examined, as distinct from a very detailed or fine-grained analysis that might require information not readily available. Details of the models used and their applications are treated in chapter 4. It is at the third filter level when the decision on the preferred solution is made, taking into account quantitative results of the analysis and second filter scoring. It is observed that the Preferred Acceptable Least preferred Fail3 2 1 0Design perspectiveFunction preferred acceptable least preferred failFire safety preferred acceptable least preferred failStructural serviceability preferred acceptable least preferred failCompatibility with other systems preferred acceptable least preferred failImpacts on other building systems no impact minor impact / no redesignminor redesign failAesthetics more than two two option one option failQuality perspectiveQuality of inputs high acceptable low failQuality of transformation processes high acceptable low failQuality of outputs high acceptable low failProduction perspective (non workface work)Constructability high acceptable low failProduction environment high acceptable low failProduction process characteristics high acceptable low failLogistics perspectiveSupply logistics high acceptable low failSite logistics high acceptable low failDemobilization logistics high acceptable low failInstallation perspective (workface work)Installation environment high acceptable low failInstallation process characteristics high acceptable low failMaterial usage efficiency high acceptable low failIn-use perspectiveDurability high acceptable low failMaintainability high acceptable low failFlexibility high acceptable low failPerspectives and criteria Criteria state values and scores 6 most highly ranked solution as determined by quantitative assessment at the third filter step may not be the top-ranked alternative at the second filter step. The eventual choice of the preferred solution involves a judgment by the decision-maker as to how best to balance quantitative criteria such as time and cost with the multitude of performance criteria considered in filter 2.  Figure 1-2 An example of skyscraper time model    7 To achieve meaningful results from use of the framework, information required from one or more of the project’s designer, project manager, developer, or general contractor/construction manager as a prerequisite for the evaluation process includes: (1) local construction business context characteristics (current and future economic conditions—e.g., interest, inflation and exchange rates, resource availability, facility usage, local codes and regulations); (2) project and site constraints and stakeholder needs and preferences; (3) design performance thresholds required; and (4) the set of alternative solutions that could be utilized for the design and/or construction of a given function/system and their related information such as productivity rates and resource costs. 1.4 Research motivations  Research motivations overviewed are: (i) skyscraper construction context, (ii) proposed research topic, and (iii) personal interests. The field of skyscraper construction is booming as the number, size, and height of these buildings are constantly being pushed upward. There is a kind of unofficial contest between leading cities to attain the record for the world’s highest skyscraper. Such buildings play an important role in expanding housing and office choices as they provide options ranging from affordable housing for low income renters through to luxury units in the most prestigious locations. Whether for residential or commercial use, construction of skyscrapers has become the only available option for densely populated modern cities, as land becomes limited and extremely expensive. Developing an assessment framework for evaluating engineering and construction technologies for skyscraper projects on an international basis is a complex, challenging, and interesting topic for many reasons as discussed earlier.  In terms of personal experience, I have over thirty years in construction management of major, prestigious, commercial and residential building projects in Canada, Qatar, Saudi Arabia and Egypt including three mega high rise projects. First is the West Bay Complex Project (Figure 1-3), which is located in the prime developed area of Doha coast, Qatar with a construction value of $247 Million USD. The project consists of a marina, parking, recreation areas and four towers. Second is the Kingdom Project (Figure 1-4), which is located in Riyadh, Saudi Arabia and is one of the local landmarks with a height of 310 m. The project consists of three parts: East Podium, West Podium and tower building with a total construction cost $400 million USD. Third is the Abraj Al-Bait project, Figure 1-5, which is a monumental skyscraper located in Makkah, Saudi Arabia. This project is a design, build, operate, and transfer skyscraper complex that consists of a 17-floor podium topped by seven skyscrapers ranging in height from 240 m to 601 m, and houses hotels and condominiums. The building holds and has broken several world construction records including: the tallest hotel in the world, the tallest clock tower in the world, and the world’s largest clock face. This project has the world’s largest building floor area of some 1,500,000 m2, and was, at least temporarily, the second tallest building in the world as of its 2012 completion, surpassed only by Dubai’s Burj Khalifa. The project capital cost is $US 15 billion (Wainwright, 2012) and the complex can host 100,000 people. A phased construction plan started in 2002 and the project was completed in 2012. As detailed in chapters 2, 3, and 4; the Clock tower which is the highest building of this project, is used as a case study for validating the developed framework. Based on my experience in these mega highrise projects in the Arabian Gulf region, the number of skyscrapers is increasing; but there is a shortage of experts who can keep these projects on track. Moreover, research in the context of skyscraper design and construction needs to be intensified to capitalize on the potential economies of scale and to match  8 the ever-increasing development of innovative engineering and construction technologies. Through my research, I have sought to solidify my background, organize my ideas, update my knowledge related to the state-of-the-art engineering and construction technologies and contribute to construction practitioners through devising the framework presented herein to aid in recommending the most preferred solutions for building a skyscraper to the decision maker.  Figure 1-3 West Bay Complex Project, Doha, Qatar 1.5 Research questions, objectives, and hypothesis  Main research objectives include development of an overview of a multiple filter evaluation framework and validation of the usefulness of the framework for improving the quality of the decision-making process. As explained later, an evaluation framework comprised of three filters was determined to be the most appropriate structure.  Reference to this structure is made in the discussion that follows. Research questions posed to guide the work along with the research hypothesis to be addressed in support of the primary research objectives are as follows: 1. How should a framework for evaluating skyscraper design and construction solutions be structured and developed?   What are the status and gaps of current evaluation concepts, tools, models, practices and processes for both system solutions and entire building projects?  What categories, perspectives, and criteria from the literature can be adopted/adapted for developing the framework?  What are the key features required for the framework in terms of purpose, evaluation approaches, level of detail, measurement scales, and methods of quantifying and aggregating overall value for a solution to assess its likely performance? 2. How should a tool for preliminary screening (filter 1) of skyscraper design and construction solutions be  9 developed?  What are the criteria and sub-criteria that need to be considered for the preliminary screening of skyscraper design and construction solutions?   What are the properties (e.g., structure, level of detail, measurement scales, and methods of assessing sub-criteria, criteria, perspectives, and overall value for a solution) required of a screening tool in order to be able to treat all life-cycle phases and a wide range of skyscraper solutions?   What is the information necessary for the solution screening process for a specific skyscraper project and attendant construction market?   Figure 1-4 Kingdom project, Saudi  Figure 1-5 Abraj Al Bait project, Saudi  3.   How should a technical performance evaluation tool (filter 2) for assessing skyscraper design and construction solutions be developed?  What criteria and sub-criteria need to be considered when evaluating the technical performance of design and construction solutions of a skyscraper?   What properties (e.g., structure, level of detail, measurement scales, criteria weighting, and methods of quantifying performance of sub-criteria, criteria, perspectives, and overall value for a solution) are required of a technical performance evaluation tool to be able to treat all life-cycle phases and a wide range of skyscraper design and construction solutions?   What information is required for a technical performance evaluation filter for potential solutions?   10 4. How should economic and time models (filter 3) for evaluating impacts of design and construction solutions on skyscraper cash flow streams and their timing be developed?  What models need to be considered when evaluating impacts of system design and construction solutions on skyscraper cash flow streams and their timings?   What properties (e.g., level of detail, and methods of quantifying value of each model and overall value for a skyscraper function of system solutions) are required of the evaluation models to be able to treat all life-cycle phases and a wide range of skyscraper solutions?   What information is required for each evaluation model about skyscraper physical context, local construction market and solution under consideration?  5. How does the use of the evaluation framework help in recommending the most preferred design and construction solutions to the decision makers that cannot be done with current tools and practices? The formulation of and seeking answers to these five questions along with research assumption 3 (see next section) form the guiding research hypothesis as: The use of an appropriately developed evaluation framework helps construction management personnel screen an unlimited number of existing skyscraper design and construction solutions including innovative ones to a shortlist of feasible ones, assess technical and environmental performance of these short-listed feasible solutions in order  to rank them in order of preference, and evaluate alternative solutions in terms of  cash flow streams and their timing in order to recommend the most preferred solution thereby improving the quality of the decision-making process 1.6 Research scope, limitations, and assumptions  To explore meaningful answers to the previously formulated research questions, it is essential to have a clear and focused scope of work along with supporting assumptions. This is essential to understand the context (assumptions/conditions) for which the answers sought are valid. Research assumptions and scope of work that underlie the thesis are as follows:  1.6.1 Research Scope The research scope is to develop an evaluation framework for assessing skyscraper engineering and construction technologies. This framework should be able to screen any number of available design and construction solutions including innovative ones and recommend the most preferred solution(s) for a specific skyscraper in a specific geographic area to the decision maker that meets specified system characteristics; satisfies stakeholder performance requirements, goals, and expectations; improves the construction work environment and process characteristics; reduces environmental impact; and enhances the living environment of end-users.  1.6.2 Research limitations  The following issues are beyond the proposed scope of the research:   System design: The evaluation process focuses on recommending the most preferred engineering and construction technologies which could achieve or exceed a given design and design thresholds and that comply with other  11 system constraints.  Development of an electronic library for classifying conventional and innovative construction technologies.   For the case of a novel, previously unproven innovation. formulation of special function tests and procedures for validating the concept and getting local municipality approval are beyond the scope of the research.  Not addressed in the research is the relative uncertainty / risk surrounding the economic performance of the various alternatives considered. However, the way in which the models for the product, process and cost views of a project are formulated (in concert with the context view – not discussed herein) allows for direct extension of the third filter evaluation process to treat a risk adjusted value of economic performance.  How best to make the final selection from competing solutions using the findings from application of filters 2 and 3 is left to the decision makers (designer, contractor, client).  1.6.3 Research assumptions  Several assumptions have been made for simplifying the evaluation process and its presentation herein.   Overall project feasibility has been proven and the decision has been taken to proceed with the project.   A single tower project is used for discussion purposes; but the model is readily extendable to treat multi-building projects.   NPV calculation assumptions: for modeling capital expenditure, O&M expenses and revenues inclusive of financing arrangements, continuous compounding and the shape functions used for each system are reflective of project scope and typical industry practice.   Project cost calculation process assumptions: overtime and shift work cost can be reflected for a work package as required in order to match the production rate of predecessor work. Economies of scale that accompany skyscraper projects can be exploited in terms of the cost of built facilities (off or on site) for system fabrication. Revenue, O& M cost, and loan and repayment are calculated in terms of a complete subproject or project lift (dedicated functional section of the overall project).  Product representation assumptions: the physical parameters that describe the scope of a skyscraper project are characterized in terms of three subprojects: foundation, substructure and superstructure. The substructure and superstructure subprojects may be viewed as being comprised of multiple work lifts, with each lift being comprised of one or more levels, and each lift having different physical characteristics, system solutions and / or different usages. Large floor plates (the horizontal dimension) may be viewed as comprised of multiple zones, depending on floor plate size.   Time (process) modeling assumptions: learning curve effects and buffer work are considered in the average productivity and production rates; no consideration is given to height impacts when estimating production rates; logic between activities reflects construction practices appropriate to the region where the case study project is located; work continuity of the same kind of work as one moves from one lift or subproject to the next is imposed;  12 advantage is taken of the large scale of superstructure projects in that successor work can start on one half of a floor before predecessor work is finished on the second half. 1.7 Research methodology  A challenge faced in the skyscraper context is the lack of a readily available and carefully structured and formalized approach or framework for identifying and evaluating alternative solutions for the design and construction of various building systems, including their interfacing. The correspondence between research questions for which answers are sought and research methodologies for searching for them can be found in Figure 1-6. The research methodologies employed were conducted in an iterative fashion and applied in the following sequential research phases:  Phase 1: Structure and development of outlines for the evaluation framework and the first filter to address research questions one and two and their related sub-questions. Phase 1 is discussed in detail in chapter 2. Research techniques for phase one are represented in Figure 1-6 by the first three steps. First, the research started with an extensive literature review which involved two dimensions: (1) examination of work by others on evaluation frameworks, innovation, and new technologies; and (2) work by others based on criteria and their assessment as they pertain to the design, construction, and life-cycle performance of different building systems. This review was broad based, treating buildings in general, not just skyscrapers. The strengths and weaknesses of the literature were identified and, as observed in the literature review section, it was determined that no general framework exists that is applicable to the wide range of decision problems faced by project clients and their designers and contractors. As appropriate, relevant contributions of other researchers have been incorporated into the framework developed. Also, the properties (e.g., clarity of language, performance dimensionality, early screening out of unsuitable alternatives, objective measurement scales) required of a general framework were identified in an iterative manner through examination of the literature, direct involvement in decision-making processes associated with actual projects, and in-depth discussion with seasoned industry professionals.  Second, an overall structure of a three-step framework, similar in nature to the approach used by Lutz et al. (1990) was formulated. This structure reflects the properties identified previously along with associated working details for each step. This structure also mirrors aspects of the informal and ad hoc processes typically applied by engineers and construction personnel for design and construction method decision-making. Third, a key feature of evaluation processes is the minimization of expenditure of effort by screening out solutions that are non-compliant in one or more ‘must have’ performance dimensions. To achieve this goal, an extensive literature review related to screening tools and processes and their properties was conducted to choose screening criteria, driving factors, and state values. The efficacy of the first filter in practice was assessed through its application to three case studies of candidate solutions and decisions (washroom facilities, internal partitioning, and cladding system) made on a skyscraper project located in Saudi Arabia. Feedback on the overall structure of the framework, along with first filter categories, criteria, and checklists was sought from several practicing professionals to assist with its validation.  Phase 2: Development of filter two in response to research question three and its related sub-questions. Phase 2 is discussed in detail in chapter 3.  Research techniques for phase two are represented in Figure 1-6 as the fourth step, and involved an extensive review of literature related to criteria and sub-criteria useful for assessing technical and sustainability performance tools, logistics, quality, project success, innovations diffusion, and production and installation methods in  13 order to identify and prioritize a list of criteria and sub-criteria and explore appropriate ways to develop a second filter. This was followed by development of a hierarchical structure (e.g., design, production, and quality) along with corresponding criteria and sub-criteria and a weighting system for this structure; and a scoring system for evaluating sub-criteria including measuring scales, a rating questionnaire, and state values.  A bottom-up approach for aggregating sub-criteria scores was utilized to quantify the weighted values for criteria, perspectives, and overall performance of a solution. Validation and refinement of the evaluation tool was sought through its applications to three case studies drawn from a mega skyscraper project and through seeking opinions from three experts to identify and contrast the usefulness of filter 2 against leading industry practices.  Figure 1-6 Development steps of the three-filter framework Phase 3: Development of filter three and overall evaluation of the usefulness of the framework in search of answers to research questions four and five and their related sub-questions. Phase 3 is discussed in detail in chapter 4. Research techniques for phase three are represented in Figure 1-6 as the step.  An extensive literature review was conducted in the contexts of building projects in general and skyscrapers in particular in an iterative manner on the topics of life cycle cash flow modeling, cost, physical/product, spatial, and process models and their properties for both overall project and system levels. The strengths and weaknesses of the related literature were identified and relevant contributions of other researchers were incorporated as appropriate to formulate the project cost cash flow, product, and process models and their associated properties. The responsiveness of the product and time models was assessed through application of the models to five case studies of a skyscraper project located in Saudi Arabia. Emphasis was placed on the time model as it is one of the main determinants of the consequences of selecting a specific alternative system on project performance. Figure 1-6 summarizes the steps of the research methodology. Also, the models developed were discussed in depth with knowledgeable construction professionals and the received feedback was incorporated resulting in enhanced model properties. Finally, as Research methodology for developing the evaluation framework for skyscraper design and construction solutions.1. Literature review for existing evaluation tools for solutions and projects and their properties. 2. Definition of the most appropriate structure for an evaluation framework (three filters) and function and evaluation approach of every filter.3. Literature review related to screening tools and their properties; development and validation of the first filter.4. Literature review related to performance evaluation tools and their properties; development and validation of the second filter. 5. Literature review related to project cash flow evaluation tools and their properties; development and validation of the third filter; evaluation usefulness of the framework  6. Conclusion by research summary, contributions and suggestions for future work. 14 per step 6 in Figure 1-6, research conclusions are summarized along with suggestions for future work in Chapter 5. 1.8 State-of-the-art review and its shortcomings Detailed literature reviews are done to get answers to the main five research questions and their related sub-questions as detailed in chapter 2 through 4. Finding, shortcoming and used principals, criteria, and sub-criteria are highlighted as appropriate. In the following section, the literature review related to the first and second research questions are discussed as it justifies the development of research framework. 1.8.1 Literature review as it relates to the structure of the framework  Topics pertaining to assessment of design and construction solutions for skyscraper projects that helped to guide the literature review are: (1) innovation classification, representation, and diffusion; (2) project performance criteria and sub-criteria; (3) technologies that could potentially be utilized, such as prefabrication and off-site production; (4) evaluation frameworks for design and construction solutions; and (5) evaluation case studies for new or current design and/or construction technologies. A summary of the findings from the literature reviewed is presented, with special emphasis on the gaps and limitations of existing evaluation tools. Literature directly relevant to the first filter of the evaluation framework is treated in the section that elaborates on the details of this filter.  Researchers who have addressed the topics of innovation classification and diffusion include Tatum (1988) who provided four classifications for new technologies: material and equipment resources, construction-applied resources, construction processes, and project requirements and constraints. With respect to innovation diffusion, Rogers (1983) identified five innovation-diffusion characteristics: relative advantage, compatibility, complexity, trialability, and observability. Toole (2001) considered four technological trajectories for innovation diffusion: location of the work, means of production, materials used, and system design. Rosenfeld (1994) examined four aspects of technology diffusion: manufacturing vs. on-site construction, functionality and performance, process logistics, and strengths and limitations. Al-Hammad and Hassanain (1996) considered value engineering principles for measuring successful implementation of cladding systems.  Other topics relevant to evaluation criteria include project success criteria and multiple sub-criteria such as time, cost, and quality (Atkinson, 1999); meeting user requirements, achieving the project’s purpose, completing on time and within budget, and achieving quality requirements (Wateridge, 1998); project management success and product success sub-criteria (Baccarini, 1999); project success from a macro viewpoint in terms of time, cost, performance, quality, and safety and from a micro viewpoint in terms of user and stakeholder satisfaction (Lim and Mohamed, 1999); positive appreciation of client, project personnel, project users, contracting partners, and stakeholders (Chan et al., 2002 and Westerveld, 2003); quantitative measures of time, cost, and safety, and qualitative measures of quality, functionality, and satisfaction of project participants (Chan and Chan, 2004); cost, time, meeting the technical specification, and customer and stakeholder satisfaction (Bryde and Robinson, 2005); project success and market success (Blindenbach-Driessen, 2006); environmental impact, customer satisfaction, quality, cost, and time, (Ahadzie et al., 2008); cost, time, profitability, maintenance cost, and project goals (Frodell, 2008); learning and exploitation, client satisfaction, stakeholder objectives, operational assurance, and user satisfaction (Takim and Adnan, 2008); owner, designer, and contractor satisfaction (Elattar, 2009); and project management success, product success, and market success (Al-Tmeemy et al., 2011).   15 Prefabrication and off-site production are technologies that may fit into a skyscraper project context. Gibb and Isack (2003) defined pre-assembly as the off-site manufacture and assembly of buildings or parts of buildings prior to their subsequent installation within the building. They established four categories: component manufacture and subassembly, non-volumetric pre-assembly, volumetric pre-assembly, and modular buildings. The benefits of prefabrication and off-site production have been elaborated on by many researchers as contributing to progressive improvements in time and cost (Ting, 1997; Gibb and Isack, 2003), quality (Cheung et al., 2002; Goodier and Gibb, 2007), health and safety (Tam et al., 2006), efficiency and productivity (Chan and Poh, 2000), sustainability and logistics (Blismas et al., 2006), flexibility (Tam and Tam, 2007), construction waste reduction (Baldwin et al., 2009; Jaillon et al., 2009), maintenance (Pan and Gibb, 2009), and design, production, and installation optimization (Li et al., 2011).  In terms of evaluation frameworks, several researchers have addressed the issue of evaluating new or existing design and construction technologies. Rosen and Bennett (1979) developed a general systematic approach for the evaluation and selection of construction materials based on nine performance attributes: structural serviceability, fire safety, habitability, durability, practicability, compatibility, maintainability, code acceptability, and economics. Chang et al. (1988) identified new building technologies for the U.S. Army based on a data acquisition questionnaire, and evaluated these technologies using a cost-benefit and risk rating system. Lutz et al. (1990) evaluated new technologies in three steps: technical assessment utilizing the performance attributes of Rosen and Bennett (1979), economic analysis based on life cycle cost, and risk-assessment using the rating system of Chang et al. (1988).  Researchers have also used different criteria to evaluate buildings or individual systems on a sustainability basis, as follows: integration, synergy, simplicity, input and output characteristics, functionality, adaptability, diversity, and carrying capacity (Baetz and Korol, 1995); safety, habitability, and sustainability (Foliente et al., 1998); economic and environmental friendliness (Jönsson, 2000); structural serviceability and stability, fire and moisture safety, user health and safety, thermal and operational comfort, durability, and dimensional flexibility (Becker, 2002); environmental and economic impact, quality, knowledge management, business performance, and technical assessment (Nelms et al., 2005, 2007); maximization of wealth and external benefits and minimization of resources and environmental impact (Ding, 2005, 2008); and economic, social, environmental risk and uncertainty (Chen et al., 2010a, 2010b). 1.8.2 Literature shortcomings The literature review led to the observation that the existing tools for evaluating design and construction technologies for buildings in general, and skyscraper projects in particular, lack completeness. Although many useful contributions towards developing a comprehensive and versatile evaluation tool have been made, assessment frameworks developed to date do not adequately address one or more of the following issues, which in turn provide useful criteria along with other tests for assessing the responsiveness of the proposed framework to industry needs:  The ability to consider a specific project context/type. Required is an evaluation framework that mirrors the nature of skyscraper projects in terms of applicable codes, procurement, duration of construction, complex site logistics, limited in-situ workspace and storage capacity, site safety hazards, extensive duplication of building elements, and large scale of investment.   16  Generality of the framework. It should be applicable to alternative design solutions for the complete spectrum of systems that comprise a building and to the construction methods and technologies, including temporary works, available to realize the design and construction of a building system.   The ability to reflect a global perspective in terms of sourcing ideas, technical talent, solutions, equipment, material, and labour. Skyscraper systems’ needs, due to their scale and profile, the financial resources involved, modern methods of transportation, and information exchange capabilities, are not limited to local solutions.  The ability to screen out non-compliant solutions early on: Solutions, for which an early qualitative assessment of performance in terms of acceptability to end users, code bodies, etc. demonstrates lack of fit or non-compliance with hard constraints, should be eliminated early on to limit or minimize the waste of resources.  Consideration of a comprehensive spectrum of stakeholder viewpoints. Skyscraper projects by their very scale affect many diverse groups/constituencies. Especially important in some parts of the world are the iconic nature of many skyscraper projects and the accompanying need to respond to the cultural beliefs and expectations of users and those in the surrounding community. Also, the value systems of project participants drawn from around the world may not be wholly aligned.  In-depth consideration of sustainability performance. Due to the very large consumption of resources in both the construction and operating phases of skyscraper projects and their high profile which reflects on the reputation of their developers/owners, an in-depth consideration of sustainability and the impact on the environment is warranted.  Consideration of the consequences of solution choices on other systems in terms of design, construction, and life cycle performance. The scale of skyscraper projects, coupled with their multifunctional nature and diverse sets of users, necessitates careful consideration of solution implications for the design and construction of other systems and overall project performance. Trade-offs between systems and performance measures can be complex. Quantitative evaluation models must be capable of reflecting interactions amongst design solutions, construction methods, and operating and maintenance processes.  Explicit consideration of risk. The scale of skyscraper projects magnifies the consequences of risks realized. This necessitates a more formal consideration of risk as part of the evaluation process in terms of risk drivers, outcomes if a risk is realized, possible mitigation measures, and the attitude of key decision-makers towards risk.  1.9 Research contributions The primary research contributions are the three-filter framework depicted in Figure 1-1, overview of the first filter already presented in Table 1-1, the second filter already presented in Table 1-2, and the third filter models as previously depicted in Figure 1-2. Further development details and contributions for these three filters are detailed in chapter 2 to 4. Research contributions presented in these chapters are summarized as follows.  1.9.1 Structure of the three-filter framework and first filter Filter 1, which is summarized in Table 1-1, is supported by two more detailed tables that address the categories of  17 stakeholder acceptance (Table 1-3) and technical feasibility (Table 1-4). Perspectives of interest under the stakeholder acceptance category are end-user, designer and developer, contractor, regulator and code, and risk. The technical feasibility category embraces local capability to manufacture and/or construct the technology using locally available human resources, materials, and infrastructure, and/or the ability to import related production equipment and technical expertise. For the first filter, use of a two-point scale has proven to be a cost effective and accurate way to both elicit and evaluate available factual information about the wide range of candidate solutions because responses will be given by a professional/practitioner who understands stakeholders’ needs and local construction market capabilities and constraints. Answers to these yes/no questions are then used to determine the state value of each criterion as follows: if all answers on relevant criteria pass, the criterion state value will be a pass. If just one criterion fails and cannot be resolved to become a pass, the criterion state will be a fail.  To evaluate every criterion category of the first filter in as objective, transparent, and replicable manner as possible, all relevant sub-criteria need to be examined. As shown in Table 1-3 for stakeholder acceptance criteria, the questions are designed to collect available facts, requirements, and commercial information about the project at hand, the system under evaluation, the available solutions, the potential innovations, and local market conditions and culture. To avoid confusion and ambiguity in checklist question wording, the following guidelines have been utilized (Leung, 2001; and Eiselen, 2005): use short, simple questions; ask for only one piece of information at a time; avoid the use of negative questions; use common design and construction terms; and define any new terms used. For the stakeholder acceptance checklist, designer and developer issues of interest include project, site, and system requirements/constraints. Contractor acceptance questions treat issues related to production, logistics, and site installation. End-user acceptance questions examine end-user expectations and preferences. Regulator and code acceptance questions focus on legal approval, local regulations, and code requirements.  As a companion to Table 1-3, Table 1-4 provides a checklist of questions pertaining to local technical feasibility. This checklist treats issues pertaining to the possibility of adopting the solution using local resources and/or outsourced resources that are within the project budget and schedule. These two checklists are meant to be completed by the project stakeholder (coupled with whatever specialist assistance is required) charged with a leadership role. This role includes encouraging the search for innovative solutions as well as proposing potential solutions through meetings with consultants and suppliers, all based on a comprehensive understanding of available facts about the project and local market and culture context. Completion of the tables for candidate solutions allows the project team to identify feasible ones for a more in-depth examination in the second step in the evaluation process. This process gets repeated for the various design and construction decision problems that confront the project’s leadership. Contributions to this step include the breadth of criteria treated, its applicability to a wide range of design and construction decision problems, the transparency of decision-making offered, ease of use, and comprehensiveness in terms of performance dimensions treated. As formulated, the framework is tailored to the resource and expertise-rich context of skyscraper projects and the need for rigor in decision-making, as the consequences of poor decisions are magnified by the scale of such projects.   18 Table 1-3 Filter 1 stakeholder acceptance and high level risk sub-criteria checklist   Pass Fail N/AEnd-user acceptance: Will the solution’s: ·   impact on end-user flexibility for change be acceptable? soft·   durability be acceptable? soft·   operation & maintenance cost be affordable? soft·   impact on end-user livability be acceptable? soft·   material be culturally acceptable? hardContractor acceptance:  Will the solution’s:·   potential safety-issues be manageable? soft·   productivity rate be acceptable? soft·   constructability be practical? soft·   in-situ scope of work be manageable? soft·   material wastage be acceptable? soft·   site-logistics be manageable? soft·   installation infrastructure requirements be affordable? softDesigner & developer  acceptance: Will the solution’s: ·   quality meet compliance requirements? soft·   aesthetics be acceptable? soft·   impact on other-building systems be manageable? soft·   capital cost be affordable? soft·   life cycle cost be acceptable? soft·   structural serviceability complies with requirements? hard·   features be compatible with other-building systems? hard·   design concept be culturally acceptable? hard·   functionality fulfill all primary and secondary requirements? hardRegulator and code acceptance:  - Is the local regulatory body receptive to the solution? soft  - Are permits for production, transportation and installation obtainable? soft  - Is the local regulatory body open to the use of international codes? soft Risk acceptance: Will the solution: ·   be obtainable from a reliable source? soft·   increase delivery time certainty? soft ·   increase cost certainty? soft ·   increase quality certainty? soft ·   be warrantable and / or insurable? soft ·   facilitate management of its disadvantages? soft ·   satisfy at least one of the following conditions: it has been utilized before in another country; it has not been used but the concept has been accepted by an international code; it is untested but performance tests are verifiable by standard tests and/or an international code?hardEvaluation checklist of sub-criteria re stakeholder acceptance including risk issues Type AnswerOverall end-user acceptance criterion state valueOverall contractor acceptance criterion state valueOverall designer and developer acceptance criterion state valueOverall regulator and code acceptance criterion state valueOverall risk acceptance criterion state value 19 Table 1-4 Filter 1 local technical feasibility sub-criteria checklist  1.9.2 Second filter Development of the performance evaluation tool, Filter 2, is an extension to existing ones (Rosen and Bennett, 1979; Lutz et al., 1990; Chew, 2003; Becker, 2002; Nano, 2005; Nelms et al., 2005 and 2007). Second filter details are shown in Tables 1-5 and 1-6. Those details are discussed column by column in the following sections. 1.9.2.1 Hierarchical tree structure of perspectives, criteria, and sub-criteria  Performance refers to all applicable physical characteristics of a skyscraper system from six perspectives: design, quality, production, logistics, installation, and in-use. These perspectives along with relevant criteria and sub-criteria have been extracted from the literature and are presented in Table 1-5. This Table is structured in the form of a four-level hierarchical tree. The first level corresponds to the second filter goal of ranking the feasible solutions based on their overall weighted performance values. The second level is the six performance perspectives that, in turn, correspond to the life-cycle phases of a skyscraper.  The third level treats the criteria relevant to each level two perspective. The fourth level identifies the sub-criteria relevant to each level three criterion.  Pass Fail N/ATechnology: Will the solution’s ·   design principles be acceptable to the engineer? soft·   production location be acceptable? soft·   technology be capable of being  locally fabricated? soft·   technology be able to be imported with affordable cost and time? softHuman resources:  Will the solution’s·   in-situ human resource requirements in terms of  number be manageable? soft·   human resource skills required be obtainable? soft·   human resources be available  locally? soft ·   human resources have to be sought from other jurisdictions and can this be done in an cost effective and timely manner? softMaterials:  Will the solution’s: ·   method of disposal at the end of the building life cycle be acceptable? soft ·   construction have a reasonable utilization of the raw material? soft ·   materials be locally available? soft·   materials be obtainable from other jurisdictions in a cost effective and timely manner? softInfrastructure: Are the solution’s :·   requirements for production, storage & construction areas feasible &  affordable? soft·   production, transportation and installation requirements feasible & affordable? soft·   infrastructure needs able to be  locally built or internationally outsourced in an  affordable and timely manner? hardEvaluation checklist sub-criteria re local technical feasibility Type AnswerOverall technology criterion state valueOverall human resources  criterion state valueOverall material criterion state valueOverall infrastructure criterion state value 20 The primary advantage of adopting a hierarchical structure is that it provides a practical and transparent means for calculating an overall performance value for each of the solutions being considered for the design/construction problem at hand. Each perspective is defined using a set of criteria and every criterion has a set of sub-criteria for evaluating its performance. Consider for example the perspective of quality. Related sub-criteria reflect the four measures outlined by De Toni and Tonchia (2001): (1) produced quality that is represented by the number of defects during any life-cycle phase or in the warranty period; (2) perceived quality as regards customer satisfaction and the technical assistance service performance; (3) input (supply) quality, including the results of controls on certified and non-certified purchasing, and vendor quality rating; and (4) quality costs including the quality system costs and the amount of rework.  For example, the sub-criterion, quality of design inputs sets out quality control measures for design inputs in terms of owner briefing, applicable codes and regulations, tests of materials used, solution knowledge, quality assurance and control requirements, inputs from other perspectives, quality of temporary and permanent resources, and required laboratory and field tests. Also, the sub-criterion, quality of design process, measures the capabilities of the local project design team in generating detailed design drawings and specifications plus a quality assurance and control requirement to avoid redesign actions. The maintenance process quality sub-criterion sets the standard for maintaining quality of service delivered in the usage phase considering the capabilities of local operation and maintenance teams, required training, duration of the manufacturer’s warranty, quality of materials used, and the operation and maintenance manual. The quality of design outputs sub-criterion measures the anticipated percentage of redesign costs due to incomplete details, errors, or defects. Utilizing the same principles, sub-criteria are assigned to evaluate quality management abilities in both the production and installation phases. 1.9.2.2 Relative weights for perspectives and criteria  In ranking alternative system solutions, consideration must be given to the weights assigned to evaluation perspectives and their criteria, and sub-criteria in order to reflect the values of the country involved, the skyscraper context, and decision-maker values. Cole (1998) highlighted that the relative importance of performance evaluation criteria is a crucial part of the decision-making process and criteria weighting should be done to reflect project development objectives and context. Lee et al. (2002) stated that although there is no consensus-based approach or wholly satisfactory method to guide the assignment of weightings, weighting is at the heart of all assessment schemes. Thus, the question arises as to how best weight the different levels in the evaluation hierarchy. This topic, however, is not a primary focus of the work described herein. Rather, a simple approach to weighting has been adopted—one that represents what is commonly done in practice. First, if one solution dominates others in terms of all perspectives and criteria, then weighting is irrelevant.  Weights only need be elicited directly when solution dominance does not exist. For the case when weights are required, consideration should be given to carrying out a sensitivity analysis to assess the robustness of the ranking of solutions (Dodgson et al., 2000). The approach employed to define the relative weights for perspectives and criteria in the case studies conducted is a procedure similar to that outlined in Pahl and Beitz (1996).  This method is transparent, practical, and compatible with the evaluation tree structure and allows for quantitative evaluation of alternatives using weighted factors. Figure 1-7 summarizes the process used for calculating relative weights for perspectives and criteria.  Relative weighting is a top-down approach and the sum of all relative weights for all factors equals one. For practicality and  21 simplicity of the calculation process, sub-criteria weighting is excluded, in effect assigning the same weight to each criterion’s sub-criteria.  To clarify the weight calculation process, for illustrative purposes only, see the example shown in Figure 1-7. The relative weights are calculated based on the following assumptions: the weight of each perspective equals the division of the number of its criteria by the total number of all criteria (22) (this assumes that all criteria are relevant to the decision problem at hand), and the criteria related to each perspective are equally important. Based on these assumptions, the design perspective has a weight of (0.27) that is equal to six divided by 22; similarly, other perspective weights are calculated as (0.14) for quality, logistics, production, and installation, and (0.18) for in-use. Relative and local weights for each perspective are equal. The relative weight for each criterion equals the product of its local weight and relative weight of the perspective to which it belongs. As an example, the production perspective has three criteria. The local weight for each criterion is (0.33), equal to one divided by the total number of related criteria (3). Thus, the relative weight for each criterion is (0.046) which equals its local weight (0.33) multiplied by the relative weight of production perspective (0.14). Relative weights for other criteria can be similarly calculated. In practice, if the use of weights is required, then a transparent and documented process should be used to elicit weights. 1.9.2.3 Sub-criteria statuses  Sub-criteria have two statuses as treated in columns C2 and C3 in Table 1-5. The first (C2) classifies the sub-criteria as applicable or not applicable (Y/N) to the design/construction decision at hand. Numeric values that are given to this status are (1/0). Applicable sub-criteria mean that they are applicable to all solutions under consideration (not just a subset of them). The main reason for this is to avoid bias in the evaluation process. For example, when one of the solutions is built in-situ and the others are prefabricated, sub-criteria related to the production environment criterion are not applicable to all solutions and are therefore excluded. Although, those sub-criteria are not applied, the advantages of prefabricated solutions are reflected in the sub-criteria of installation perspective. This status enables an early selection of the applicable sub-criteria, which simplifies the evaluation process and narrows the focus of the evaluation team to the applicable ones. The second status (C3) classifies the sub-criteria as essential or not essential (Y/N) to the design/construction decision at hand. Numeric values that are given to this status are (1/0). Essential means that the sub-criterion must not receive a failing grade in terms of performance. This step works as a filter for eliminating solutions that do not achieve a minimum required performance threshold. The solution is dismissed when one of its sub-criteria has an essential value of (1) and performance score of (0). 1.9.2.4 Sub-criteria measuring scales, units, and types Measurement scale units and their type classifications are included in columns C4 and C5 of Table 1-5. Absolute scales based on an individual unit of measurement and a measurement scale are used. Three measurement scales are utilized to evaluate the sub-criteria: an ordinal scale for ranking qualitative values in order of preference from the highest to lowest, such as values of technology origin, production location, and production means; an interval scale used for ranking quantitative values such as jointing material life cycle, maintenance cycle, and warrantee period; and a ratio scale used for ranking quantitative values where percentages are required, such as material waste, tower crane usage, and off-site  22 production degree. Two types of measurement units are used in the evaluation process: the majority is quantitative, Q, such as function and structural stability sub-criteria, and the minority is qualitative, q, such as quality of inputs sub-criteria.  Figure 1-7 Weights calculation example for evaluating perspectives, criteria, and sub-criteria 1.9.2.5 Sub-criteria rating questionnaire The rating questionnaire for sub-criteria is included in column C6 of Table 1-5. To quantitatively evaluate the sub-criteria, a closed-ended questionnaire with defined answers of four-state values has been developed. Users are asked to choose one of these values. The advantages of this approach are that it is less time-consuming to complete and it is easy to compute overall value. Questions are affirmative and short, employ common design and construction terms, and are grouped for every criterion and perspective to simplify the evaluation process (Leung, 2001 Eiselen, 2005). The questions are used to rate the solution from highest to lowest by selecting one of the four ordered state values. Developed measurement scales and their measurement units are based on specific definitions for the four ordered state values using design thresholds, applicable codes, available test results, literature, and commonly used industry values. 0.27 0.23 0.14 0.14 0.14 0.14 0.14 0.14 0.14 0.14 0.18 0.180.045 0.33 0.045 0.33 0.045 0.33Level 4 Production areaStorage areaRequired workers skills Safety hazardPollution generationInstallation perspective In-use perspectiveAssumptions for this weight calculation example: weight of each perspective equals the division of number of its criteria by sum of all evaluation criteria (22 one), criteria related to each perspective are equally important and sub-criteria weightings are ignored for practicality and simplicity of the tool.Level 3Constructability Production environmentProduction characteristicsLevel 2Design perspectiveQuality perspectiveProduction perspective Logistics perspectiveLevel 1Overall performance weighted value for a solution Sum of relative weights for all evaluation levels equal one. Also, Sum of local weights of relevant evaluation factors at any level equal one.Relative weighting factor  = 1Local weighting factor = 1 23 Table 1-5 Sec.1 of evaluating details for filter 2 perspectives, criteria, and sub-criteria  Column 1 C2 C3 C4 C5 C6 C7 C8 C9 C10Applicable? Essential? Preferred Acceptable Least preferred FailY/N (1/0) Y/N (1/0) Unit Type 3 2 1 0Design perspectiveFunctionWater tightness Tightness rating Q - water tightness rating. preferred acceptable least preferred failAir tightness Tightness rating Q - air tightness rating. preferred acceptable least preferred failAcoustics Acoustics rating Q - acoustics rating. preferred acceptable least preferred failDaylight Lighted area Q - daylight efficiency considering possible lighting area. preferred acceptable least preferred failThermal resistance U value Q - thermal resistance considering u value. preferred acceptable least preferred failSpatial connectivity Flexibility degree q - flexibility degree in doors and windows locations. preferred acceptable least preferred failFire safetyFire resistance Fire rating Q - fire resistance rating. preferred acceptable least preferred failSmoke development Development classification Q - smoke development classification. preferred acceptable least preferred failFlame spread Spread value Q - flame spread value. preferred acceptable least preferred failCombustibility Combustibility rating Q - combustibility rating. preferred acceptable least preferred failStructural serviceabilityStructural stability Stresses values Q - Tension, compression and shear stresses values. preferred acceptable least preferred failDeformation resistance Deflection value Q- acceptable deflection normal to system length value. preferred acceptable least preferred failSeismic and wind resistanceInterstory drift limit. Q - interstory drift limit. preferred acceptable least preferred failCompatibility with other systemsJointing material Life cycle/years Q- ability to receive and retain jointing material with other building systems considering joint service life in years.>25 25 - 10 <10 failCoating material Life cycle/years Q- ability to receive and retain coating material considering its service life in years.>25 25 - 10 <10 failAccommodation of internal finishes Accommodation% Q- ability to accommodate internal finishes. >60% 30% - 60% <30% failAccommodation of MEP rough in Accommodation% Q - ability to accommodate MEP rough in. >60% 30% - 60% <30% failImpacts on other building systemsUseable floor area Redesign need q - floor area used by the solution. no impact minor impact / no redesign minor redesign failProject aesthetics Redesign need q - project aesthetics considering colour, joint locations and material nature. no impactminor impact / no redesign minor redesign failStructural system Redesign need q - structural system considering solution dead load. no impactminor impact / no redesign minor redesign failEnclosure system Redesign need q- enclosure system considering connection details and transferred structural load.no impact minor impact / no redesign minor redesign failElectrical system Redesign need q - electrical system considering electrical load. no impactminor impact / no redesign minor redesign failMechanical system Redesign need q - mechanical system considering mechanical load. no impactminor impact / no redesign minor redesign failVertical transportation Redesign need q- vertical transportation systems considering impacts on internal finishes, transferred load and MEP.no impact minor impact / no redesign minor redesign failPlease rate the following function measures of the solution in terms of:Please rate the following fire safety measures of the solution in terms of:Please rate the following structural serviceability measures of the solution in terms of:Please rate the following compatibility measures with other building systems of the solution in terms of:Please rate solution impacts on the following systems in terms of redesign need assuming no time impact:Perspectives, criteria and sub-criteriaSub-criteria state values and scoresSub-criteria rating questionnaire and their measurement scalesUnits and types: (Q) quantitative/(q) qualitativeSub-criteria  status 24 Table 1-5 Sec. 2 of evaluating details for filter 2 perspectives, criteria, and sub-criteria  Column 1 C2 C3 C4 C5 C6 C7 C8 C9 C10Applicable? Essential? Preferred Acceptable Least preferred FailY/N (1/0) Y/N (1/0) Unit Type 3 2 1 0AestheticsUnit shape and size No. of options Q - unit shape and size. more than two two option one option failJoint location and size No. of options Q - joint location and size. more than two two option one option failMaterial nature and color No. of options Q - material nature and colour. more than two two option one option failQuality perspective   Quality of inputsDesign inputs Inputs quality q - quality of design inputs. high acceptable low failProduction inputs Inputs quality q - quality of production inputs. high acceptable low failInstallation inputs Inputs quality q - quality of installation inputs. high acceptable low failQuality of transformation processesDesign process Process quality q - quality of design process. high acceptable low failProduction process Process quality q - quality of production process. high acceptable low failInstallation process Process quality q - quality of installation process. high acceptable low failMaintenance process Process quality q- quality of maintenance process to keep the delivered quality. high acceptable low failQuality of outputsDesign outputs Redesign% Q - quality of design outputs. <5% 5% -10%  >10% failProduction outputs Remedial action% Q - quality of production outputs. <5% 5% -10%  >10% failInstallation outputs Remedial action% Q - quality of installation outputs. <5% 5% -10%  >10% failProduction perspective (non workface work)Constructability QComponent standardization Standardization% Q- percentage of component standardization. >60% 30% - 60% <30% failScalability Production volume Q - scalability of standardized components for mass production or purchase.use existing facility built factorygood purchase price failField tolerances Tolerances value Q - field tolerances value of the solution. high acceptable low failJointing material Material type q - type of jointing material between solution sub-systems. none dry material wet material failJointing material with other systems Material type q- type of jointing material between solution and other building systems. none dry material wet material failProduction environmentProduction area Production area Q - required production area considering cost/m2. minor acceptable high failStorage area Storage area Q - required storage area considering cost/m2. minor acceptable high failRequired workers skillsWorker classifications q- classifications of required production workers. unskilled trades skilled tradesspecialist technicians failSafety hazard Hazard degree q- safety hazard considering impact on work continuity of other production activities.no impactminor / other  activities could continueother activities must stop occasionally failPollution generation Pollution volume q- air, water and soil pollution considering impact on work continuity of other production activities.no impactminor / other  activities could continueother activities must stop occasionally failPlease rate the capabilities of project team and local construction industry for managing and producing the required quality inputs measures of the solution considering: quality assurance and control requirements, solution knowledge, quality of temporary and permanent resources and required laboratory and field tests in terms of:Please rate the capabilities of project team and local construction industry for managing the required transformation-process quality measures of the solution considering: quality assurance and control requirements, solution knowledge, quality of temporary and permanent resources and required laboratory and field tests in terms of:Please rate the following  output quality measures of the solution considering anticipated percentage of rework due to incomplete details, errors or defects in terms of:Please rate the following solution constructability measures in terms of:Please rate the following solution production environment measures in terms of:Perspectives, criteria and sub-criteriaSub-criteria  status Units and types: (Q) quantitative/(q) qualitative Sub-criteria rating questionnaire and their measurement scalesSub-criteria state values and scoresPlease rate the following aesthetics measures of the solution considering the number of available options and architectural match degree in terms of: 25 Table 1-5 Sec. 3 of evaluating details for filter 2 perspectives, criteria, and sub-criteria  Column 1 C2 C3 C4 C5 C6 C7 C8 C9 C10Applicable? Essential? Preferred Acceptable Least preferred FailY/N (1/0) Y/N (1/0) Unit Type 3 2 1 0Production process characteristicsTechnology origin Technology origin q - origin of production technology. local national international failProduction location In-situ to off site q - location of production process. on site & not in-situ off site in-situ failProduction means Machine usage degree Q - means used in production process.machine intensive40%-60% machine labour intensive failOff-situ production degree Production% Q - percentage of off-situ production. >60 % 30% - 60% <30% failProduction wastage Waste% Q - percentage of production waste. <5% 5% -10%  >10% failLogistics perspectiveSupply logisticsManagement of information flow Supplier origin q- management of information flow considering solution supplier. local national international failRoad constraints Roads regulation q- roads constraints considering allowable travel timings and associated safety requirements. no restriction specific travel timesspecific safety arrangements failTransportation means Means type Q - proposed means for transportation. light trucks heavy trucks special means failSite inventory area Inventory area Q - required site inventory area <90% 90%-110% >110% failSite logisticsSite access requirement Access requirement q- site access safety and lifting requirements. noneflag people neededspecial lifting requirement failMaterial handling times Handling times Q - site and in-situ handling times. one handling double handling three or more failTower crane usage Cranes usage% Q - usage percentage of tower crane for handling and installing the solution. none <50% ≥50% failIn-situ workforce number Worker number Q- number of in-situ workers considering type of installed structure.volumetric preassemblynon volumetric preassemblycomponent manufacture failDemobilization logisticsWaste disposal Waste% Q - percentage of installation waste to be disposed. <5% 5% -10%  >10% failRejected and unused items disposal Item% Q- percentage of rejected and unused items to be disposed. <5% 5% -10%  >10% failTemporary structures disposal Structure type q- type of in-situ temporary installation structures to be demobilized. mobile scaffold fixed scaffold other structures failInstallation perspective (workface work)Installation environmentInstallation area Installation area Q- required installation area considering impact on work continuity of other building systems.no impactminor / other  activities could continueother activities must stop occasionally failSafety hazard Hazard degree q- safety hazard considering impact on work continuity of other building systems.no impactminor / other  activities could continueother activities must stop occasionally failLabor intensity at workface Worker number Q- number of in-situ workers considering type of installed structure.volumetric preassemblynon volumetric preassemblycomponent manufacture failPollution generation Pollution volume q- air, water and soil pollution considering impact on work continuity of other building systems.no impactminor / other  activities could continueother activities must stop occasionally failPlease rate the following solution demobilization logistics measures in terms of:Please rate the following solution in-situ installation environment measures in terms of:Please rate the following solution site logistics measures in terms of:Please rate the following solution supply logistics measures in terms of:Please rate the following solution production process characteristic measures in terms of:Perspectives, criteria and sub-criteriaSub-criteria  status Units and types: (Q) quantitative/(q) qualitative Sub-criteria rating questionnaire and their measurement scalesSub-criteria state values and scores 26 Table 1-5 Sec. 4 of evaluating details for filter 2 perspectives, criteria, and sub-criteria  Column 1 C2 C3 C4 C5 C6 C7 C8 C9 C10Applicable? Essential? Preferred Acceptable Least preferred FailY/N (1/0) Y/N (1/0) Unit Type 3 2 1 0Installation process characteristicsRequired labor skills Workers classifications q - classifications of installation workers. unskilled trades skilled tradesspecialist technicians failInstallation means Means type Q - type of in-situ installation means. machine intensive40%-60% machine labour intensive failWet trades usage Usage% Q - percentage of wet trades usage. none <50% ≥50% failProductivity Structure types Q - productivity rate considering types of installed structures.volumetric preassemblynon volumetric preassemblycomponent manufacture failMaterial usage efficiencyMaterial origin Material origin q - origin of construction material. local national international failMaterial type Natural to engineered q - type of installation material. engineered mixed natural failSystems design No. of engineering functions Q- number of engineering functions included in the design. three or more two systems one system failSystem recyclability Recyclability method q- material recyclability method at the end of service life using current available technologies.reuse recycle landfill failIn-use perspectiveDurabilityWear resistance Resistance value. Q - wear resistance value. preferred acceptable least preferred failDeterioration resistance Resistance value. Q - deterioration resistance value. preferred acceptable least preferred failCorrosion resistance Resistance value. Q - corrosion resistance value. preferred acceptable least preferred failDimensional stabilityStrengths/stresses values Q- dimensional stability resistance value  considering swelling and shrinkage impacts.preferred acceptable least preferred failMaintainabilityReliability Warrantee period Q - manufactory warrantee period in years. >10 5 -10 <5 failService life Life/years Q - system service life in years. >50 50 - 25 <25 failMaintenance cycle Cycle / years Q - maintenance cycle of components and sub-systems in years. >10 5 -10 <5 failMaintenance accessibility Ease of access q - maintenance accessibility ways. direct access access panel/s custom access failCleanability Ease of cleaning q - ease of cleaning considering used means. hand tools light machines heavy machines failRequired labour skillsWorkers classification q - classifications of maintenance workers. unskilled trades skilled tradesspecialist technicians failMaintenance material Supplier origin q - origin of maintenance material. local national international failFlexibilityLayout flexibility Flexibility degree q - architectural layout flexibility degree. flexible changeable with minor cost inflexible failReplaceability Ease degree q - ease of replacement considering dismantling method.dismantle with no costdismantle with minor cost need demolition failUpgradeability Ease degree q - ease of components and sub-systems upgrading considering used method. add sections change sections custom upgrade failIn-use impactsSimplicity of use Difficulty degree q - difficulty degree of solution use.  easy acceptable need a catalogue failIn-door air quality impact Air quality Q- indoor air quality considering fresh air changing rate. no impactminor impact / no redesign minor redesign failEnergy use impact Consumption rate Q - energy consumption rate. no impact minor impact / no redesign minor redesign failWater use impact Consumption rate. Q - water consumption rate. no impact minor impact / no redesign minor redesign failWaste water impact Discharge rate. Q - waste water discharge rate. no impact minor impact / no redesign minor redesign failPlease rate the following solution flexibility measures in terms of:Please rate the following solution in-use impact measures in terms of:Please rate the following solution in-situ installation process characteristics measures in terms of:Please rate the following solution material usage efficiency measures in terms of:Please rate the following durability measures of the solution in terms of:Please rate the following solution maintainability measures in terms of:Perspectives, criteria and sub-criteriaSub-criteria  status Units and types: (Q) quantitative/(q) qualitative Sub-criteria rating questionnaire and their measurement scalesSub-criteria state values and scores 27 1.9.2.6 Sub-criteria state values and scores Sub-criteria state values and scores are shown in columns C7 through C10 of Table 1-5. State values of sub-criteria are quantified using four-state scores: three for preferred, two for acceptable, one for least preferred, and zero for fail. Preferred means that the solution performance falls within the highest possible range of technical performance. Acceptable means that the score of the preferred solution falls in the mid-range of technical performance. Least preferred means that the solution performance equals the least acceptable range of performance. Fail means that the solution fails to meet the minimum threshold of performance required for a sub-criterion, which may or may not be essential. Performance thresholds are defined by the designer, code or regulatory requirements, and/or the client. Fail, as a grade, is applicable only to certain types of sub-criteria (i.e. non-negotiable or must have) that must pass the definite performance thresholds such as function and fire safety sub-criteria. For example, the material usage efficiency sub-criterion has no fail state value. Dismissal of a solution occurs when a sub-criterion has an essential value of (1) and performance score of (0). When a non-essential (i.e. good to have) sub-criterion fails to pass the definite performance threshold, the solution will receive a score of zero. The aim of the scoring scheme as shown in Figures 1-8 and 1-9 is to achieve dimensionless values, which allow scoring of individual measures which may be expressed in different units so as to develop a meaningful total overall or aggregated score. Thus, a transformation from a state value definition relevant to a specific sub-criterion to a non-dimensional value must be made. Sub-criteria state values are expressed in terms of a measurement scale and measurement units. Sub-criteria can have continuous or discrete state values with ascending or descending ranges. Figures 1-8 and 1-9 show an example of each. The scoring system involves the use of two axes: the vertical one (the transformed sub-criterion non-dimensional state value) has four score values (0, 1, 2, 3) while the horizontal one treats sub-criterion values in terms of the most relevant quantitative measurement units.  As an example of a sub-criterion whose performance is measured in a continuous manner, the service life sub-criterion has three relative state values. The preferred option is the best performance on the horizontal scale, accorded a score of three, which means that the solution service life is more than 50 years. An acceptable option, accorded a score of two, means that the solution service life is between 25 and 50 years. The least preferred option, accorded a score of one, means that the solution service life is less than 25 years. A solution is accorded a zero score if it failed to meet the required service life (e.g., 15 years). A solution with a long service life is preferred as it requires less rehabilitation. Examples of sub-criteria whose performance is measured using discrete scales are ones related to their impact on other building system criteria. Those are scored based on the need for redesign as follows: preferred option, accorded a score of three—reflects no impact on other building systems; acceptable option, accorded a score of two—implies minor impact without the need for redesign; least preferred option, accorded a score of one—reflects the need for a minor redesign; and fail option, accorded a score of zero—implies the need for a major redesign.  Sub-criteria state values vs. score are shown in Table 1-6 for 12 sub-criteria related to four criteria. These examples reflect development principles, analysis details, and challenges of the proposed quantitative evaluation of choices for a skyscraper system design or construction technology decision. The procedure of evaluating every criterion means that each sub-criterion performance is defined in terms of its measurement scale, unit of measurement, four-state scores, and score  28 evaluation. Examples cited reflect the case study project examined later. As a specific example, evaluation principles of the material usage efficiency criterion and its corresponding sub-criteria are as follows. In our context, material usage efficiency is defined drawing on the work of Longman (2011) and Neely et al. (1995) to mean building a solution as specified using a minimum amount of raw materials, utilizing local material to the maximum, generating the minimum waste, and planning for maximum recyclability of materials at the end of service life.  In terms of sub-criteria evaluation, the material origin sub-criterion is measured based on a preference for local material because of its sustainability benefits—provided that it is cheaper and is of the same quality or better than imported materials. State values for this sub-criterion are: local material is preferred, national material is acceptable, international material is least preferred; there is no fail state value assigned to this sub-criterion. The sub-criterion of material type is measured based on a preference for using engineered materials because of their consistent properties, better performance, and lower cost (Toole, 2001), provided that natural material is not specified as a required solution.  State values specified for this sub-criterion are: engineered materials are preferred, natural material is least preferred, their mix will be acceptable; no fail state value is assigned to this sub-criterion.  The systems design sub-criterion is measured based on a preference for maximizing the number of engineering functions incorporated into a solution, as this may offer cost, time, performance, or quality advantages. For example, structural insulated partitions integrate building structure and insulation subsystems. Engineering functions refer to structural, thermodynamics, fluid dynamics, or material science functions served (Toole, 2001). State values developed for this sub-criterion are: three or more engineering functions are preferred, two are acceptable, one is least preferred; no fail state value is assigned to this sub-criterion. The system recyclability sub-criterion is measured based on a preference for minimizing the environmental impact of a solution through the ability to recycle a solution’s material at the end of its service life using currently available technology. State values for this sub-criterion are: re-use is preferred, recycle is acceptable, landfill disposal is least preferred; no fail state value is assigned to this sub-criterion. Napier (2011) defined these options as follows: re-use is the subsequent use of a material, product, or component upon salvage; recycle is introducing a material into some process for remanufacture into a new product; landfill disposal is depositing materials in a solid waste disposal facility.  1.9.2.7 Bottom-up approach for aggregating criteria, perspectives, and solution weighted value The second filter goal is to rank the feasible design and construction solutions that passed the first filter on the basis of their overall weighted performance values. A bottom-up approach is utilized to calculate these values using the properties shown in Table 1-5 as follows: (1) Prerequisite information for the evaluation process that is relevant to feasible solutions, skyscraper context, stakeholders, and the local construction market as discussed in the next z needs to be identified. (2) Based on the nature of the decision problems, applicable sub-criteria are selected in column C2 and related sub-criteria are accorded values of one. (3) Relevant sub-criteria are classified as essential or not using column C3. Essential sub-criteria are accorded values of one and all others get a value of zero. (4) Sub-criteria performances are computed using the defined state values and are then mapped using the four non-dimensional scoring values described earlier. All solutions that fail to meet the definite performance threshold for the essential sub-criteria are eliminated in this step. (5) For solutions that passed the previous step, scores of the applicable sub-criteria are quantified as set out in Tables 1-2 and 1-3.   29 Table 1-6 Sec. 1 of state values analysis for a sample of criteria and sub-criteria   30 Table 1-6 Sec. 2 of state values analysis for a sample of criteria and sub-criteria    31 Table 1-6 Sec. 3 of state values analysis for a sample of criteria and sub-criteria   32 1.9.2.8 Bottom-up approach for aggregating criteria, perspectives, and solution weighted value The second filter goal is to rank the feasible design and construction solutions that passed the first filter on the basis of their overall weighted performance values. A bottom-up approach is utilized to calculate these values using the properties shown in Table 1-5 as follows: (1) Prerequisite information for the evaluation process that is relevant to feasible solutions, skyscraper context, stakeholders, and the local construction market as discussed in the next section needs to be identified. (2) Based on the nature of the decision problems, applicable sub-criteria are selected in column C2 and related sub-criteria are accorded values of one. (3) Relevant sub-criteria are classified as essential or not using column C3. Essential sub-criteria are accorded values of one and all others get a value of zero. (4) Sub-criteria performances are computed using the defined state values and are then mapped using the four non-dimensional scoring values described earlier. All solutions that fail to meet the definite performance threshold for the essential sub-criteria are eliminated in this step. (5) For solutions that passed the previous step, scores of the applicable sub-criteria are quantified as set out in Tables 1-2 and 1-3.  Criteria scores are the total sum of their applicable sub-criteria as shown in Table 1-5. (6) Test for dominance or near dominance should be done for all criteria scores of alternative solutions (i.e. use of non-weighted scores).  If one choice fails to dominate all others, then relative weights need to be assigned to the assessing perspectives and criteria by the evaluating team as detailed in Figure 1-7. (7) Criteria weighted values are computed as the product of their relative weights and scores; perspectives weighted values as the sum of their criteria weighted values; and solution overall weighted performance value as the sum of its criteria weighted values. These calculations are detailed in Table 1-6. (8) The same process is repeated for every feasible solution and solutions are ranked in order of preference. It should be noted that the solution most preferred at the filter 2 level is not necessarily the solution that will ultimately be selected. The most preferred solution is identified at the filter 3 level when monetary, time, and risk performance is assessed in conjunction with technical performance.  Figure 1-8 Scales with continuous values  Figure 1-9 Scales with discrete values  The novelty of the developed performance evaluation approach lies in its holistic list of treated criteria and sub-criteria, four-state values defined to answer the ranking questions, an elimination scheme for solutions that fail to achieve one or more essential technical performance thresholds, a quantification method used for performance evaluation, and its applicability to a wide range of design and construction decision solutions.  33 1.9.3 Third filter Models developed as a function of system solutions being considered are as follows: project cost cash flow model, project product models in terms of spatial and geometric context and physical systems and sub-systems, project process/time and work package models. An overview of these models is summarized in the following section and detailed in chapter four. The research contributions with respect to these models are the formulation of an integrated set of models in terms of parameters and variables relevant to the decision problem at hand.  1.9.3.1 Cash Flow Model Project cash flow consists of cash in and cash out (Needles et al, 1999; Park et al, 2005). Considering the client perspective, cash in includes financial arrangements to cover design and construction cost in terms of cash drawdown profiles, revenue streams, and residual project value. Cash out includes capital cost (design and construction cost), O&M, rehabilitation cost, and debt servicing cost as well as other client internal and external expenses essential to the design, construction, service provision and operation and maintenance of the facility. Revenues of subprojects/lifts are estimated using skyscraper local market sales and/or rent rates that may be driven by low or high seasons or special revenue events such as the FIFA world cup. Government tax incentives for utilizing innovative solutions can be an additional revenue (Nelms et al., 2005&2007). Project residual value equates to the value of resale or the disposal, salvage, or scrap cost at the end of service life, whichever is most relevant. Operation costs include energy, water supply and any other service costs. Rehabilitation cost incurs at the end of service life of each system and incorporates cost of major retrofit to this system and to its connections with other building systems. Loan repayment expenses are estimated function of design and construction cost, interest rate, inflation rate, risk rate, repayment start date and duration, and repayment profile. Building on Russell and Ranasinghe (1991), Fuller and Petersen (1995), Shohet and Laufer (1996), and Abdel-Aziz and Russell (2006), Figure 1-10 shows a simplified version of the cost cash flow model of a skyscraper. All flows are assumed to be in current dollars. Data describing each component is derived from the project’s product, cost and time models. For simplicity of presentation, cash flow shape functions are not shown in Figure 1-10; but any shape function appropriate for a specific cash flow component can be employed. The model incorporates all possible negative and positive cash flow streams for the current baseline solutions plus any adjustments made to reflect an alternative design and/or construction approach inclusive of any interactions with other cash flow components that may be impacted by the choice of a system solution. The nomenclature used in Figure 1-10 is defined as follows. The words substructure and superstructure relate to all systems/components required to produce one or more complete lifts of the project (e.g. structural, electrical, mechanical, enclosure, finishing). The parameters F, O and h define the degree of fast-tracking, overlap of T&C with project start-up and revenue generation, and cycle time for major rehabilitation.  For evaluating the impact of a solution on cash flow streams and their timing for a project, consideration must be given to the durations and sequencings of expenditure and revenue cash flow functions for the design / construction alternative being considered, their shape, and applicable inflation, interest and exchange rate(s). The latter requires a context model (not elaborated upon herein) which reflects important characteristics of the natural (e.g. weather) and man-made environments (economic – interest, inflation and currency exchange rates as a function of time and geographic location, regulatory regime, and resource constraint.).  34 1.9.3.2 Cost Model Figure 1-10 shows the life cycle cost model developed for all project phases. The level of detail for each project component is selected from the hierarchical structure of Tables 1-7(a) and (b) and is reflective of the decision problem at hand. Cost model inputs are derived from the product model (scope quantities) and time model (work packages and their sequencing, resources and time information). Life cycle cost of a project includes capital and usage costs and revenue. Capital cost consists of indirect and direct costs for designing and constructing of a project.   Figure 1-10 A simplified version of project cost cash flow model Indirect cost extends over construction duration and covers general conditions requirements such as mobilization and material testing. Owner costs expended over design and construction time cover project management, legal issues, insurance, marketing, and other overhead costs. Design cost, field design services, indirect construction cost, and owner cost are normally estimated as a fraction of the direct cost. Project direct cost is estimated as function of its systems and equals total cost of subprojects, packages, and sub-packages. For example, the services sub-package cost equals total cost of: plumbing, HVAC (heating, ventilation, and air conditioning), fire protection, electrical, and conveying systems. T&C (testing and commissioning) cost, according to common construction practices, is considered as a part of construction cost and contractor price. Service life TimeResidual valueSuperstructure O & M cost lift KSub-structure cost lift 1Sub-structure cost lift JSuperstructure cost lift KDesign / tenderingDesign field servicesT & CLoan drawdownIndirect construction costsDirect construction cost including procurementProject management, legal, insurance, etc.Sub-structure O & M cost lift 1Debt servicingSub-structure revenue lift 1Superstructure revenue lift 1Superstructure revenue lift KSub-structure O & M cost lift JProject design and construction durationRehabilitation work carried out every h yearsh hDesign / tendering phaseTesting & commissioning phaseConstruction phaseUsage phase FOAmortization periodSuperstructure cost lift 1Superstructure O & M cost lift 1Sub-structure revenue lift JCapital cost and finance streamsDesign and Construction phaseOperation cost and revenue streams 35 Direct cost of a work package/system choice equals the costs of the design and construction activities. These activities depend on the production location which could be on or off site and include: design, build facility, production and T & C of subsystems, logistics, installation, and T & C of the installed system. Work package activities for offsite produced solutions are summarized in Figure 1-12(d). In terms of cost, the function of the work package model is to analyze the required time and resources of each activity.  1.9.3.3 Project Product Models  The purpose of product models is to provide scope measure values for the use in cost and process models that are reflective of the solution being examined.  Depicted in Figure 1-11 is a relatively simple physical configuration model used to represent aspects of the product view. Features of this model are further defined in Tables 1-7(a) and (b) with respect to system product models, inclusive of their process and work package models. A contribution of the first model includes selecting parameters/variables from the dividing the substructure and superstructure into an unlimited number of vertical lifts and a typical floor in each lift to an unlimited number of work zones. A contribution of the second model relates to the hierarchical structure of building elements and their organization into in six levels, and defining each level at a level of detail required for the cost and process models. 1.9.3.3.1 Product model 1: geometric and spatial model The product model as formulated and depicted in Figure 1-11, while relatively simple, is comprised of three subprojects: foundations, substructure and superstructure. The foundation subproject model has two possible design solutions: a deep foundation structure (piles, pile caps and raft) or a shallow foundation structure (raft and column and wall footings). The sub-structure and superstructure subprojects can be highly layered with different floor configurations in terms of height, length, width and shape (circular, elliptical, twisted, etc.). To accommodate changes in the vertical direction, consecutive floors with the same configuration or with the same function (parking, retail, residential, commercial or mixed use) are considered as part of the same lift, the reason being that floors with different areas could lead to additional capital cost and floors with different usage may lead to different cost and revenue. The number of substructure lifts is assumed from 1 to J and superstructure lifts from 1 to K. A large skyscraper floor plate is assumed to have number of zones from 1 to M, with horizontal zoning being used to define the logic between sequential trades. This spatial model is linked with the system component product model to enable computation of the scope of work as a function of system solutions and building configuration. 1.9.3.3.2 Product model 2: system components of project hierarchical structure Presented in Table 1-7(a) and (b) is the hybrid hierarchical structure that combines the product and process models. For representing all building features, the model divides a project into six levels: (1) subprojects, (2) packages, (3) sub-packages, (4) systems, (5) design and construction sub-systems/activities, and (6) in-use activities during the service provision and operating and maintenance phase of a project Foundation, substructure and superstructure lifts represent the first level of subprojects. The second level identifies the work packages for each subproject. For example, a superstructure lift has the following possible work packages: structural works, interior finishes and exterior enclosure. The third level treats possible sub-work packages for each work package. For example, services sub-packages include: plumbing, HVAC (heating, ventilation, and air conditioning), fire protection, electrical, and conveying systems. Another example, the interior  36 finishes sub-package incorporates: wet areas (toilets and washrooms), dry areas (all other areas of units) and public areas (major lobbies and corridors).   Figure 1-11 Product model 1: geometric and spatial model The fourth level treats the possible systems for every sub-package including their descriptions, scope and units of measure. For example, the dry area is described in terms of services rough in, partitions, rough finishes and final finishes. System description defines the type of system, number of sub-systems, production locations, productivity rates, crew size, and temporary infrastructure and equipment requirements. Scope measures define the quantum of work to be performed.  For example, rough and final finishes scope measures include the surface areas of partitions, ceilings, and floors. Scope units are context independent as highlighted in the unit column. The fifth level includes activities associated with realizing a particular system choice. Included are activities related to design, build a facility, production, T &C of subsystems in the factory, logistics, installation and T&C of system in situ. The sixth level includes activities involved in use of a system and incorporates O&M, rehabilitation works and impacts of the system on subproject/lift revenue and on the residual value of the project. ` `Average Length, Avg LLift 1Average Width, Avg WShallow FoundationDeep foundationSubstructure lift JSubstructure lift 1UsageUsageUsageLift 1UsageLift KSuperstructure lifts from 1 to KCase study focusLift JSubstructure lifts from 1 to JGround levelSuperstructure lift KSuperstructure lift 1ZMZ1 37 1.9.3.4 Project process model  To evaluate the potential time savings in key project milestones as a function of the system solutions being examined, as formulated, the process/time model is comprised of the four elements shown in: Figures 1-12 (a) a hierarchical project structure that is linked with the scope definition of the product model and identifies the level of details required for the evaluation process; Figure 1-12(b) a linear planning modeling algorithm and linear planning schedule representation / visualization showing the locations spanned by various process steps that defines timings of project milestones and purpose further improvement in the time modelling; Figure 1-12(c) a summary bar chart representation that summarized the time information required for calculating the NPV; and, Figure 1-12(d) a work package model that treats both off and on site aspects of a system’s realization in order to define durations and sequencings of system activities. The contributions of these models relate to the activities list of the process model derived from project hierarchical structure of Tables 1-7(a) and (b), the work package structure model, the level of detail used, and the use of linear planning for planning and scheduling purposes, and synthesising all of these elements into a complete time evaluation tool that is capable of measuring time changes in project milestones as a function of system solution(s) being evaluated, either separately, or in combination.  The linear planning schedule representation and visualization is chosen for the time model; as it has many advantages especially when it is applied to skyscrapers where a significant repetition of both physical components and activities is involved.  These advantages have been extolled in the literature by many researchers and commercial developers who developed their own software such as (Arditi et al., 2002; Bonnal et al., 2005; Tokdemir et al., 2006; Russell et al., 2006; Kenley and Seppänen, 2010; VICO, 2016). Tran at el. (2012) and Russell at el. (2014) highlighted that linear planning provides a powerful tool for modeling the process dimension of a project that involves significant repetition of elements and communicates results in a compact visual form that helps in: (i) analyzing production rates, durations, logic, lag, and work continuity between work zones on a floor  as well as between floors; (ii) assessing, floor cycle times, and overall project or project-component durations; (iii) suggesting where improvements to the plan and schedule can be made and by how much.. For development of the time model, a combined top-down and bottom up approach is used. Top down in terms of definition of major work packages to be treated (Figure 1-12(c)), bottom up in terms of the processes involved in each work package (Figures 1-12(a) and 12(d)). Scope quantities for work packages come from the product model (Table 1-7(a) and (b)) and its mapping to work packages. Productivity rates relevant to local practice or practice in other venues from which innovations may be drawn are used to calculate time requirements of a single repetition instance for a given lift and then extended to determine work package duration as a function of number of repetitions, and number of crews used, with each crew assigned to its own location instance.  For solutions that are truly novel, logic and work package/activity durations need to be determined using a bottom-up approach which involves identification of all of the steps involved in producing the product of interest for a given location instance.    38 Table 1-7(a) Product model 2: project hierarchical structure levels 1 - 4   Level 1 Level 2 Level 3Piles No of piles and depth noPile caps no * area * depth m3Raft Foundation area*depth m3Shoring Perimeter*depth m2Dewatering Area * depth m3Excavation Area * depth m3Backfilling Area * depth m3PlumbingElectricalSpecial serviceColumn & wall footings ∑Areas * depth m3Waterproofing & Insulation Surface area m2Slab on grade Floor area m2Core walls Core walls Columns, walls & stairsSlabsSteel fire Proofing Surface area m2Conveying systemsPlumbingHVACFire ProtectionElectricalServices rough in Subsystems no/specs LSPartitions Partitions areaRough finishesFinal finishesServices rough in Subsystems no/specs LSPartitions Partitions areaRough finishesFinal finishesServices rough in Subsystems no/specs LSPartitions Partitions areaRough finishesFinal finishesWallsInternal rough finishesInternal finishesExternal finishesRoof coveringsOpenings coveringHard landscapeSoft landscapeParking lotsRoadwaysSite utilities Utilities connections No of connections LSLevel 4Subproject Packages Sub-packages Systems Description Scope Measure Units FoundationsDeep foundations Piles worksShallow foundationsShoring worksEarth workFoundationsLump sum, LSWet areas (toilets and  washrooms) m2Ceiling + Wall+ floor areasUnder ground services Subsystems no/specsLump sum, LSLifts of sub-structure from 1 to J and superstructure from 1 to KStructural packageConcrete volume & steel structure weightm3 or tonVerticals and slabsInterior finishesServices Subsystems no/specsDry areas (all other areas of units) m2Ceiling + Wall+ floor areasPublic areas (major lobbies and corridors) m2Ceiling + Wall+ floor areasSite worksSite Improvements Work area m2Exterior enclosureExterior enclosureTypical floor perimeter *height  m2Roofing Roof and openings areas m2 39 Table 1-7(b). Product model 2: project hierarchical structure levels 5 – 6  Level 4Design Build a facility ProductionSubsystemsT & C Logistics InstallationSystem T & CPilesPile capsRaft ShoringDewateringExcavation Backfilling PlumbingElectricalSpecial serviceColumn & wall footings Waterproofing & InsulationSlab on grade Core walls Columns, walls & stairsSlabsSteel fire ProofingConveying systemsPlumbingHVACFire ProtectionElectricalServices rough inPartitionsRough finishesFinal finishesServices rough inPartitionsRough finishesFinal finishesServices rough inPartitionsRough finishesFinal finishesWallsInternal rough finishesInternal finishesExternal finishesRoof coveringsOpenings coveringHard landscapeSoft landscapeParking lotsRoadwaysUtilities connectionsLevel 5: design and construction activities for the systems Level 6: in-use activities for the systemsRevenue per subprojectN/AOn site activitiesO&M Rehabilitation Loan repayment Revenue ResidualsSystemsOff site activitiesN/AN/A 40 Figure 1-12 Elements of process model: (a) hierarchical project structure; (b) linear planning chart for packages/sub-packages  41  Figure 1-12(c) Summary bar chart exclusive of off-site activities(c)  42 Workability of the process model is measured in two ways (Russell at el. 2014): qualitatively through the matching of production rates between work packages plus  achievement of work continuity for individual trade work within a work package to the extent possible; and, quantitatively through the ability to achieve production rates through the supply of necessary resources (design information, manpower, equipment) effective  means to move resources to the work face, and the provision of sufficient space for the work force to work at optimum efficiency. Once the summary work package bar chart is produced, then a reasonably accurate cash flow model for the design and construction phase can be generated, thus providing valuable input into the NPV evaluation of the project.   Figure 1-12(d) Work package model (off and on site activities) 1.9.3.5 Models integration and application steps The model ingredients of Filter 3, namely product, process, and cash flow models need to be integrated, coherent and compatible. Model integration involves their mapping onto one another in the lower level of evaluation details, inclusive of use of a common scope measure (out product model) for determination of cost and duration for a work package / physical product. Figure 1-13 depicts the issues of integration, mapping and shared scope measure and is further supported by the contents of Tables 1-7(a) and 7(b). As highlighted in Figure 1-13, every product should be represented in the process model, Figures 1-12(a), (b), (c), and (d); but not all process model constituents map onto  43 product model members. The reason for this is that process model includes milestones to connect with cash flow streams for operations, revenue, and financing.    Figure 1-13 Models integration process In comparison to existing evaluation models (Lutz et al., 1990; Dell’Isola and Kirk, 1995; Navon, 1995; Shohet and Laufer, 1996; Toole, 2001; Nelms et al., 2005 & 2007; and Goosen, 2008), the strengths of the developed approach relates to the following capabilities. First, the degree of coarseness used to represent a design / construction solution is the level of detail necessary to capture any substantive interactions that exist between the physical systems / components impacted by the solution. Considering that the assessment process for a system of interest (conventional as well as a novel or innovative one) takes place in the front-end phases of a project, the level of detail used for assessment is considered sufficient to accept or reject a solution. Second, most of the terms used in formulating filter 3 models are commonly utilized in the construction industry – e.g.  elemental structures, product, process, cost and PRODUCT MODEL, Figure 1-11, Tables 1-7(a) & (b) Level of detail used for the evaluation process for the building systems of interest is derived from the hierarchical structure of physical components from levels one to six. Each project package should be described by at least one scope measure or union of scope measures. PROCESS MODEL, Figure 1-12(a), (b), (c), (d) Hierarchical structure of work packages including indirect costs; work package scope measure(s) should reflect product model scope measures; includes milestones to connect with operations, revenue, financing cash flow streams. Durations and logic of system solution(s) to be built bottom up from their design, construction and usage activities using work package model.  Every product should be represented in the process model; not all process model constituents map onto product model members COST MODEL, Figure 1-10 Hierarchical structure of work package costs including indirect costs. Work package scope measure(s) should reflect product model scope measures. Cost for system solutions to be built bottom up from their design, construction and usage activities in terms of labour, temporary and permanent material and equipment resources using work package model.   CASH FLOW MODEL, Figure 1-10 Cash flow streams for all work package, O&M, revenue and financing streams used the output data from cost and time data to calculate NPV. Cost models should be priced out using the same scope measure as in the product model  44 cash flow models, etc.  Third, assumptions used for formulation of each model are clearly stated and evaluation results are mainly presented graphically (product, time, cost and cash flow models) to facilitate analysis and discussion of results, follow up actions (e.g. model refinements), and decision making. Fourth, evaluation models are applicable to the entire project life cycle – design through ultimate sale or disposal of the facility.  Fifth, the potential for offsite work as well as on-site work is explicitly treated. Finally, as an economic performance metric for decision making, the use of NPV accounts for all trade-offs in terms of cash flow streams and their timing. A step-by-step overview of the project cash flow modeling process inclusive of capturing the features of a proposed solution for a project component/system or combination of proposed solutions for multiple components/solutions that incorporates the constituents of the modeling process as depicted in Figures 1-10, 1-11, and 1-12(a) through 1-12(d) and Tables 1-7(a) and 7(b), is set out below and summarized in Figure 1-14.   Step 1: The current parent cash flow model need to be updated in terms of its constituent product, process, cost and cash flow models to form a new base case model in order to reflect all design and/or construction method solution decisions taken to date.  Performance of any new alternative/solution must be measured against this base.  Step 2: Identify a new alternative or combination of new alternatives for the system(s) under consideration and all information related to scope, cost, finance, revenue and off and on site work package properties.  Step 3: Adjust the current product model in terms of applicable subprojects and required level of detail for packages, sub-packages, systems and sub-systems for the alternative(s) being examined. Consideration needs to be given to any interactions between the alternative(s) and other current baseline systems.   Step 4: Adjust the process model to reflect alternative(s) solution activities, production rates, and logic vis a vis other system activities, recompute the schedule, and determine revised intermediate and project completion milestone dates.   Step 5: Compute alternative system costs (capital, O&M, rehabilitation), and adjust the overall project cash flow model to reflect the timing and magnitude of all cash flow streams, both expenses and revenues over the project life cycle.   Step 6: Compute performance measures of interest, including milestone dates (step 4), overall capital cost inclusive of financing and net present value.   Step 7: Assess the performance measures from Step 6 in concert with technical performance determined in filter two for each solution or combination of solutions currently being examined.  Step 8: Decide on the adoption or rejection of the alternative(s) currently under consideration. Return to step 1 until all system choice candidates have been examined.  45  Figure 1-14 Sequence of applications for filter three models   1 – Update base models to reflect decisions taken to date regarding systems' solutions.2 – Identify new alternative or combination of alternatives to be assessed.3 – Adjust project product models in terms of applicable subprojects and required level of details.4 – Adjust process models to reflect alternative(s) solution activities, production rates, and logic.5 – Compute alternative system costs and adjust project cash flow model to combine all revenues and cost cash flow streams.6 – Compute performance measures of interest, including cost, time, and net present value.7 – Assess performance measures in concert with technical performance determined in filter two.8 – decide on the adoption or rejection of the alternative(s) currently under consideration. Return to step 1 until all system choice candidates examined 46 Chapter 2 Screening design and construction technologies of skyscrapers1 2.1 Introduction Skyscraper projects worldwide provide a unique opportunity and special incentive for assessing a multiplicity of solutions, especially innovative ones, to questions involving selection of the various systems that comprise a building project and the methods of constructing them. These driving factors include challenging design criteria, unique architectural image, reputation, scale, cost, revenue potential and schedule (Tatum, 1984), as well as stakeholders’ expectation, particular to a specific location or region of the world. Any solution to a design or construction method decision problem, either conventional or innovative, is preferred only if the advantages offered outweigh any attendant disadvantages (Toole, 2001; Gibb and Isack, 2003; Blismas et al., 2006; Jaillon et al., 2009), as measured in terms of one or more performance metrics such as capital cost, life cycle cost, time, quality, safety and durability (Tatum, 1984). Potential advantages in the context of skyscraper projects include large-scale investment which creates the potential for economies of scale to enhance cost and time performance; high standardization potential for horizontal and vertical elements (Warszawski, 2003); and the potential for developing or enhancing an international reputation for project participants through the successful completion of a unique architecture signature project. Disadvantages within the same context include the possible catastrophic consequences of a system failure in use; limited in situ work space; elevated safety hazards during construction; complicated material and manpower logistics; and exposure to an array of economic conditions due to the extended time period involved in realizing such projects. To facilitate the solution selection process, the need exists for an evaluation process that is comprehensive in scope, provides transparency as to the basis for decisions made and is easy to use. Such a process is the focus of this paper, along with an emphasis on the evaluation of innovative approaches to design and construction. Many definitions exist for a skyscraper and its required height. The most common one is by Emporis (2011) that described it as a “a multi-storey building whose architectural height is at least 100 metres”. In modern times, the Empire State Building built in New York in 1931 with a height of 1,250 feet (381 m) held the tallest building record until 1972. The Council on Tall Buildings and Urban Habitat defined a super-tall building as a building > 300 m (984 feet) in height (CTBUH, 2011). This definition serves as a useful surrogate for skyscraper scale (height, area, occupancy, etc.) for the purposes of this paper. In the search for a working definition of “innovation”, useful to both the design and construction phases of a                                                           1 A version of this chapter has been published. AboMoslim, S. and Russell, A. (2014), “Screening skyscraper design and construction technologies on an international basis”, Construction Innovation: Information, Process, Management, Vol. 14 No 3, pp. 307-445.  47 project, Freeman and Soete (1997) defined innovation as “actual use of non-trivial change in a process, product or system that is novel to the institution developing the change”. Firth and Mellor (1999) referred to innovation as “new processes, and social and organisational change”. Sexton and Barrett (2003) emphasised that the concept or idea that marks the starting point of innovation need not be new to the world – just new to the adopting organisation. Tatum (1984) defined innovation as changes in the construction methods or sequences, expansion or new application of a special technique, scale-up of previous methods, changes in design to accomplish the same function at a lower cost, simplification of design requirements and construction operations, changes in construction methods to allow more favourable engineering techniques and use of alternative materials or equipment. Rosenfeld (1994) defined construction innovation as minor changes to existing methods, utilisation of imported proven methods and substantial improvements to an existing system. Slaughter (1998) introduced five innovation models: incremental; modular; architectural; system; and radical. Building on the foregoing, the term “innovative design and construction technology” is used here in the context of skyscraper construction to mean the direct or adaptive use of new or existing products, methods or processes not previously used within the project context or by the project stakeholders. While adoption or adaptation of these innovative technologies can produce gains in terms of a project’s objectives (time, cost, quality, client satisfaction, reputation, etc.) and outcomes, there are always risks with respect to workability and outcomes that highlight the need for a careful and comprehensive evaluation of all performance dimensions of potential solutions, especially innovative ones. Two distinct challenges exist: the identification of potential solutions (both conventional and innovative) for a specific design and/or construction problem; and an evaluation of these candidates in terms of feasibility and preference. The focus here is on the second of these challenges – to select a beneficial technology for a particular component of a project in a specific geographical area, described here is an assessment framework for screening and evaluating previously proven solutions as well as innovative ones. This framework can help to simplify the choice process for decision-makers in the early stages of a project; to evaluate the efficiency and the effectiveness of potential solutions, looking at both the individual system and the implications for other aspects of the project; and to evaluate and mitigate risks associated with the solution. For the remainder of the paper, the word “solution” is used to refer to conventional as well as innovative or novel candidates for the design and/or construction of a physical system or subsystem of a skyscraper project. 2.2 Literature review An important backdrop to the evaluation approach presented in this paper is an appreciation of the rich literature relevant to its various dimensions. Topics pertaining to assessment of design and construction solutions for skyscraper projects which helped to guide the literature review are: innovation classification, representation and diffusion; project performance criteria and sub-criteria; technologies that could potentially be utilised, such as prefabrication and offsite production; evaluation frameworks for design and construction solutions; and evaluation case studies for new or current design and/or construction technologies. A summary of the findings from the literature reviewed is presented, with special emphasis on the gaps and limitations  48 of existing evaluation tools. Literature directly relevant to the first filter of the evaluation framework is treated in the section that elaborates the details of this filter. Researchers who have addressed the topics of innovation classification and diffusion include Tatum (1988) who provided four classifications for new technologies: material and equipment resources; construction-applied resources; construction processes; and project requirements and constraints. With respect to innovation diffusion, Rogers (1983) identified five innovation–diffusion characteristics: relative advantage; compatibility; complexity; trialability; and observability. Toole (2001) considered four technological trajectories for innovation diffusion: location of the work; means of production; materials used; and system design. Rosenfeld (1994) examined four aspects of technology diffusion: manufacturing vs onsite construction; functionality and performance; process logistics; and strengths and limitations. Al-Hammad and Hassanain (1996) considered value engineering principles for measuring successful implementation of cladding systems.  Other topics relevant to evaluation criteria include project success criteria and multiple sub-criteria such as time, cost and quality (Atkinson, 1999); meeting user requirements, achieving the project’s purpose, completing on time and within budget and achieving quality requirements (Wateridge, 1998); project management success and product success sub-criteria (Baccarini, 1999); project success from a macro viewpoint in terms of time, cost, performance, quality, and safety and from a micro viewpoint in terms of user and stakeholder satisfaction (Lim and Mohamed, 1999); positive appreciation of client, project personnel, project users, contracting partners and stakeholders (Chan et al., 2002 and Westerveld, 2003); quantitative measures of time, cost and safety and qualitative measures of quality, functionality and satisfaction of project participants (Chan and Chan, 2004); cost, time, meeting the technical specification and customer and stakeholder satisfaction (Bryde and Robinson, 2005); project success and market success (Blindenbach-Driessen, 2006); environmental impact, customer satisfaction, quality, cost and time, (Ahadzie et al., 2008); cost, time, profitability, maintenance cost and project goals (Frodell, 2008); learning and exploitation, client satisfaction, stakeholder objectives, operational assurance and user satisfaction (Takim and Adnan, 2008); owner, designer and contractor satisfaction (Elattar, 2009); and project management success, product success and market success (Al-Tmeemy et al., 2011). Prefabrication and offsite production are technologies that may fit into a skyscraper project context. Gibb and Isack (2003) defined pre-assembly as the offsite manufacture and assembly of buildings or parts of buildings prior to their subsequent installation within the building. They established four categories: component manufacture and subassembly; non-volumetric pre-assembly; volumetric pre-assembly; and modular buildings. The benefits of prefabrication and offsite production have been elaborated by many researchers as contributing to progressive improvements in time and cost (Ting, 1997; Gibb and Isack, 2003), quality (Cheung et al., 2002; Goodier and Gibb, 2007), health and safety (Tam et al., 2006), efficiency and productivity (Chan and Poh, 2000), sustainability and logistics (Blismas et al., 2006), flexibility (Tam and Tam, 2007), construction waste reduction (Baldwin et al., 2009; Jaillon et al., 2009), maintenance (Pan and Gibb, 2009) and design, production and installation optimisation (Li et al., 2011). In terms of evaluation frameworks, several researchers have addressed the issue of evaluating new or existing design  49 and construction technologies. Rosen and Bennett (1979) developed a general systematic approach for the evaluation and selection of construction materials based on nine performance attributes: structural serviceability, fire safety, habitability, durability, practicability, compatibility, maintainability, code acceptability, and economics. Chang et al. (1988) identified new building technologies for the U.S. Army based on a data acquisition questionnaire, and evaluated these technologies using a cost-benefit and risk rating system. Lutz et al. (1990) evaluated new technologies in three steps: technical assessment utilizing the performance attributes of Rosen and Bennett (1979), economic analysis based on life cycle cost, and risk-assessment using the rating system of Chang et al. (1988).  Researchers have also used different criteria to evaluate buildings or individual systems on a sustainability basis, as follows: integration, synergy, simplicity, input and output characteristics, functionality, adaptability, diversity, and carrying capacity (Baetz and Korol, 1995); safety, habitability, and sustainability (Foliente et al., 1998); economic and environmental friendliness (Jönsson, 2000); structural serviceability and stability, fire and moisture safety, user health and safety, thermal and operational comfort, durability, and dimensional flexibility (Becker, 2002); environmental and economic impact, quality, knowledge management, business performance, and technical assessment (Nelms et al., 2005, 2007); maximization of wealth and external benefits and minimization of resources and environmental impact (Ding, 2005, 2008); and economic, social, environmental risk and uncertainty (Chen et al., 2010a, 2010b).  The literature review prompts the observation that the existing tools for evaluating design and construction technologies for buildings in general, and skyscraper projects in particular, lack completeness. Although many useful contributions towards developing a comprehensive and versatile evaluation tool have been made, assessment frameworks developed to date do not adequately address one or more of the following issues, which in turn provide useful criteria along with other tests for assessing the responsiveness of the proposed framework to industry needs:  The ability to consider a specific project context/type. Required is an evaluation framework that mirrors the nature of skyscraper projects in terms of applicable codes, procurement and duration of construction; complex site logistics; limited in situ workspace and storage capacity; site safety hazards; extensive duplication of building elements; and large scale of investment.  Generality of the framework. It should be applicable to alternative design solutions for the complete spectrum of systems that comprise a building and to the construction methods and technologies, including temporary works, available to realise the design of a building system.  The ability to reflect a global perspective in terms of sourcing ideas, technical talent, solutions, material and labour. Skyscraper systems’ needs, due to their scale and profile, the financial resources involved, modern methods of transportation and information exchange capabilities, are not limited to local solutions.  The ability to screen out non-compliant solutions early on. Solutions for which an early qualitative assessment of performance in terms of acceptability to end users, code bodies, etc. demonstrate lack of fit or non-compliance with hard constraints should be eliminated early on to limit or minimise the waste of resources.  50  Consideration of a comprehensive spectrum of stakeholder viewpoints. Skyscraper projects by their very scale affect many diverse groups/constituencies. Especially important in some parts of the world are the iconic nature of many skyscraper projects and the accompanying need to respond to the cultural beliefs and expectations of users and those in the surrounding community. Also, the value systems of project participants drawn from around the world may not be wholly aligned.  In-depth consideration of sustainability performance. Due to the very large consumption of resources in both the construction and operating phases of skyscraper projects and their high profile which reflects on the reputation of their developers/owners, an in-depth consideration of sustainability and the impact on the environment is warranted.  Consideration of the consequences of solution choices on other systems in terms of design, construction and life cycle performance. The scale of skyscraper projects, coupled with their multifunctional nature and diverse sets of users, necessitates careful consideration of solution implications for the design and construction of other systems and overall project performance. Trade-offs between systems and performance measures can be complex. Quantitative evaluation models must be capable of reflecting interactions among design solutions, construction methods and operating and maintenance processes.  Explicit consideration of risk. The scale of skyscraper projects magnifies the consequences of risks realised. This necessitates a more formal consideration of risk as part of the evaluation process in terms of risk drivers, outcomes if a risk is realised, possible mitigation measures and the attitude of key decision-makers towards risk. In summary, seminal literature offer valuable contributions, mainly with respect to specific criteria and sub-criteria that should be considered when assessing potential design and construction solutions. Use has been made of these contributions in developing the design and construction technology assessment framework presented here. However, as evidenced from an intensive review of the literature and direct participation in and observation of practice, no general, yet comprehensive, evaluation tool, suitable for both design and construction decision-making that responds to the needs of practising professionals for very large-scale building projects has yet been developed. 2.3 Research methodology  A challenge faced in the skyscraper context is the lack of a readily available and carefully structured and formalised approach or framework for identifying and evaluating alternative solutions for the design and construction of various building systems, including their interfacing. Addressed in this paper is such a framework. In the lexicon of those engaged in social research, there are two approaches – the ontological (nature of reality) and the epistemological (relationship between the researchers and reality) perspectives (Hudson and Ozanne, 1988). The reality is context-dependent (skyscraper projects), in that it relates to large-scale resource-rich projects that can source expertise, solutions and physical inputs from around the world. Client goals are not solely related to financial return, cost and time; a very large number of decisions must be made, and the consequences of poor decisions can be magnified by project scale. Understanding of this reality is derived from an in-depth review of related literature. The research  51 viewpoint reflected here is more akin to an interpretivist than a positivist one (Hudson and Ozanne, 1988), i.e. a meaningful research contribution requires a context-dependent solution and understanding of the thought processes of construction industry personnel. Development of the framework structure and details of its first filter involved several steps, conducted in an iterative fashion. Figure 2.1 shows these steps. First, an extensive literature review was conducted which involved two dimensions: examination of work by others on evaluation frameworks, innovation and new technologies; and work by others based on criteria and their assessment as they pertain to the design, construction and life cycle performance of different building systems. This review was broad based, treating buildings in general, not just skyscrapers. The strengths and weaknesses of the literature were identified and, as observed in the literature review section, no general framework exists that is applicable to the wide range of decision problems faced by project clients and their designers and contractors, although previous related work on the topic has been conducted, including that of Rosen and Bennett (1979), Lutz et al. (1990), Becker (2002), Ding (2005, 2008) and Chen et al. (2010a, 2010b). As appropriate, relevant contributions of other researchers have been incorporated into the framework described.  Second, the properties (e.g. clarity of language, performance dimensionality, early screening out of unsuitable alternatives and objective measurement scales) required of a general framework were identified in an iterative manner through examination of the literature, direct involvement in decision-making processes associated with actual projects and in-depth discussion with seasoned industry professionals. Third, an overall structure of a three-step framework, similar in nature to the approach used by Lutz et al. (1990) was formulated. This structure reflects the foregoing properties and associated working details for each step, and mirrors aspects of the informal and ad hoc processes typically applied by engineers and construction personnel for design and construction method decision-making. A key feature of these processes is the minimisation of expenditure by screening out solutions that are non-compliant in one or more “must have” performance dimensions. Fourth was an examination of how best to “measure” or express assessments and the adoption of a binary (pass/fail) approach for the first step which provides the central focus of this paper.  Fifth, the efficacy of the first filter in practice was assessed through its application to three case studies of candidate solutions and decisions (washroom facilities, internal partitioning and cladding system) made on a skyscraper project located in Saudi Arabia. The case study approach (Gerring, 2004) was an essential component of the research with case studies executed in a sequential manner assisted by way of an iterative approach in achieving framework completeness in terms of the criteria considered and breadth of applicability, and in determining how best to express and measure relevant criteria. The three case studies within the single case study project provided an opportunity, albeit limited, to assess, using elements of a quasi cross-case study analysis, the framework’s ability to respond to a diverse range of design and construction decision problems. Finally, feedback on the overall structure of the framework, along with first filter categories, criteria and checklists was sought from several practising professionals to assist with its validation. Ideally, as a future step in the research, given the access and resources required, further generalisation and robustness of the framework could benefit from a formal cross-case study analysis (analysis of themes, similarities and differences) of several projects and a diverse range of decision problems. Greatest benefit  52 from such an analysis would be derived from case study projects sourced from different world venues (e.g. North America/Europe, the Middle East and Asia) and decision problems ranging from ones that involve a preponderance of quantitative criteria through to ones that involve mostly qualitative criteria. Figure 2-1 Development steps of the main structure of the framework and the first filter details With respect to the framework itself, an overview of and rationale for its structure are described, followed by a more in-depth treatment of the first step in the three-step process. Given the scope of steps 2 and 3, an in-depth treatment of their features and application will be addressed in separate papers. Challenges involved included how best to express categories or classes of criteria and individual members of a class; how best to measure them in as objective and replicable a manner as possible; how to aggregate measurements across criteria and the role of weighting; how to achieve thoroughness without undue complexity; and the development of simplified yet robust unified predictive models for time, cost and risk. 2.4 Development of framework overview To increase the efficiency (i.e. the ease with which it can be applied) and effectiveness (determining the preferred choice in as objective a manner as possible) of the design and construction solution evaluation framework proposed, the framework is founded on the following considerations: incorporation of construction context and project stakeholder values and needs; assessment of the technical and environmental performance of the building system of interest as well as its possible interactions with other systems; evaluation of the time and life cycle cost performance of the system as well as its impact on the whole building; specific consideration, and mitigation to the extent possible, of risks associated with the solutions being evaluated; and compatibility with the informal structure of existing industry decision-making processes in terms of narrowing the solution focus as quickly as possible to conserve resources, but with considerably more structure, completeness and rigor. Research methodology for developing the main structure of the evaluation framework and the details of the first filter.1. Literature review for existing evaluation tools for solutions and projects and their properties.2. Defining main structures, functions and evaluation approaches of the three filters.3. Literature review for existing screening tools of system solutions and their properties.4. Developing the first filter screening categories, criteria, sub-criteria and checklists. 5. Validating the first filter through its application to three case studies.  6. Validating the first filter and main structures of the second and third filters by construction professionals. 53 In formulating the framework, tests imposed to ensure responsiveness to decision-making needs include: comprehensiveness (range of building systems treated, total project life cycle); transparency (explicit identification of items treated and how valuation is achieved and expressed); precision/clarity of language; no inherent bias (rewards possible for only a subset of solutions); effective use of resources (e.g. a screening out of infeasible solutions as quickly as possible); ability to aggregate results within a class of criteria; robustness of simplified, aggregated and unified performance models (e.g. time, capital cost, life cycle cost and risk); and practicality in terms of information requirements. The three-step process is compatible with the prevailing thought processes applied by engineering and construction practitioners in terms of: eliminating as quickly as possible solutions that fail “must have” criteria; assessing the technical/environmental performance of viable candidates – does each solution address essential criteria in a satisfactory manner? (although elimination at this step is not the goal, it is possible that one or more solutions cannot deliver satisfactory technical/environmental performance); and assessing solutions based on quantitative measures of cost (capital and life cycle), time and risk. This paradigm is observed in practice on a recurring basis, but without a consistent level of rigor and often on an ad hoc basis. The framework is intended for use by construction practitioners, designers, developers and even policymakers for skyscraper projects targeted for residential, commercial, institutional or mixed use. Although the framework can be used at any time during the building life cycle, the earlier it is used, the greater are the potential benefits. The evaluation goal was to recommend the preferred solution that meets specified system characteristics; satisfies stakeholder performance requirements, goals and expectations; improves the construction work environment and process characteristics; reduces environmental impact; and enhances the living environment of end-users. To achieve this goal, the framework divides the evaluation process for candidate solutions into the application of three primary filters. Figure 2.2 shows an overview of the framework. The first filter screens potential solutions using relevant qualitative criteria on a pass–fail basis to narrow the choices to feasible ones in terms of a number of essential stakeholder acceptance and technical feasibility criteria, and sub-criteria. Application of this filter helps avoid a large commitment of resources to an infeasible solution. Details of the first filter and its application to the three case studies are discussed later in the paper. Given success with the first filter, the second filter treats design, quality, production, logistics, installation and in-use details and issues to rank the feasible solutions by evaluating their technical and environmental performance. It involves an evaluation of each relevant criterion category and related criteria on a four-point scale, mapped where feasible to quantitative measures. While alternatives can be rank-ordered at this step, none is eliminated unless the performance of an alternative in terms of one or more essential performance dimensions is determined to be non-compliant with the minimum performance level required. Such a situation can occur, as assessment at the second filter level is considerably more comprehensive than that for the first step. The third filter deals with choice of the preferred solution from the set of ranked solutions from the second filter, based on a quantitative assessment of time, cost and risk consequences. It is observed that the most highly ranked solution, as determined by quantitative assessment at the third filter step, may not be the top-ranked alternative at the second filter step. The eventual choice of the preferred  54 solution involves a judgement by the decision-maker as to how best to balance quantitative criteria such as time and cost with the multitude of performance criteria considered in filter 2. At the third filter level, to date, emphasis has been placed on the time dimension, given its importance to overall project performance, in terms of both cost and revenue.  Figure 2-2 Overview of evaluation framework In terms of a high-level overview, the second filter involves a detailed performance evaluation process for potential solutions from the perspectives of design, quality, production, logistics, installation and in-use and starts the process for ranking the feasible solutions (exclusive of detailed consideration of cost, time and risk). Relevant criteria under these perspectives are listed in Table 2.1. For each perspective, a set of critical evaluation criteria has been identified and, for each criterion, a set of driving criteria must be evaluated. The criteria states are defined based on the states of the lower-level criteria (i.e. sub-criteria). In defining criteria states for the second filter, a simple four-state evaluation scheme is used with value states of: 3 for preferred; 2 for acceptable; 1 for least preferred; and 0 for not applicable (N/A). In assigning the value for a sub-criterion, use is made of a parameterised description of the solution in the form of performance threshold values that must be achieved (two-hour fire safety, service life of 50 years, crane lifting capacity of 15 tons, etc.). Supplementary tables of sub-criteria have been developed to treat relevant “tests” for each of the criteria listed in Table 2.1. In-depth treatment of the second filter and its application in practice is presented in a separate publication. Again, in terms of a high-level overview, the third filter focuses on quantifiable criteria related to offsite and onsite production, total project delivery time, intermediate milestones, construction cost, total capital cost and life cycle cost and the uncertainty associated with these values. Macro models are used to quantify these values as a function of the solution being examined. As stated earlier, particular emphasis has been placed on the treatment of time because of its  55 significant impact on both cost and revenue. For assessment of the time consequences of various solutions to a system design or its construction method, a macro model in the form of a linear planning model using high-level work packages is employed to capture consequences of criticality of work packages and milestone dates, including project completion (Figure 2.3). The model is hierarchical in nature, allowing for more fine-grained modelling of work package details, as appropriate to the solution being considered. Output from this model is used, in turn, to assess the consequences for project cash flow, inflation costs and financing costs. These macro-level models focus on determining if there are significant differences among the various alternatives examined, as distinct from a very detailed or fine-grained analysis that might require information not readily available. Details of the models used and their application are treated in a separate paper. It is at the third filter level when the decision on the preferred solution is made, taking into account quantitative results of the analysis and second filter scoring. Table 2-1 Filter 2 evaluation perspectives, criteria and possible state values   Preferred Acceptable Least preferred N/A3 2 1 01.00 Design perspective1.10 Function superior standard inferior N/A1.20 Aesthetics superior standard inferior N/A1.30 Structural serviceability superior standard inferior N/A1.40 Constructability superior standard inferior N/A1.50 Compatibility with other systems high average low N/A1.60 Impact on other systems/features no impact minor impact / no redesign minor redesign N/A2.00 Quality perspective2.10 Quality of inputs high standard low N/A2.20 Quality of transformation processes high standard low N/A2.30 Quality of outputs high standard low N/A3.00 Production perspective3.10 Production environment preferred acceptable least preferred N/A3.20 Production characteristics preferred acceptable least preferred N/A4.00 Logistics perspective4.10 Supply logistics low average high N/A4.20 Site logistics low average high N/A4.30 Demobilization logistics low average high N/A5.00 Installation perspective5.10 Installation environment preferred acceptable least preferred N/A5.20 Installation characteristics preferred acceptable least preferred N/A5.30 Material usage efficiency high average low N/A6.00 In-use perspective6.10 Durability superior standard inferior N/A6.20 Flexibility superior standard inferior N/A6.30 Maintainability high average low N/A6.40 In-use impacts low average high N/APerspective / CriteriaState valuesNo. 56  Figure 2-3 Macro level time model To achieve meaningful results from use of the framework, information required from one or more of the project’s designer, project manager, developer or general contractor/construction manager as a prerequisite for the evaluation process includes: local construction business context characteristics (current and future economic conditions – e.g. interest, inflation and exchange rates, resource availability, facility usage, local codes and regulations); project and site constraints and stakeholder needs and preferences; design performance thresholds required; and the set of alternative solutions that could be utilised for the design and/or construction of a given function/system. The remainder of this paper provides a detailed description of the features of filter 1. Three case studies drawn from the same project demonstrate the use in practice of this approach, thereby contributing to validation of the approach. Lessons learned from these case studies assisted with filter one and overall framework refinements. 2.5 Development of filter one: criteria, categories, criteria checklists and state values As observed in the framework overview, the purpose of the first filter is to provide a quick (preliminary) screening of potential solutions to determine feasibility for use in a specific skyscraper project context and particular geographic area. The goal is to determine if there is an initial match between the project, the candidate solutions and local market conditions. Criteria considered at this stage relate to factual information pertaining to project characteristics, site  57 conditions, market conditions and local codes and regulations. For example, Chen et al. (2010b) identified 12 pre-screening attributes for the applicability of prefabrication under four main categories: project characteristics; site conditions; market attributes; and local regulations. Table 2-2 Filter 1 categories, criteria, and state values  Several researchers have addressed compliance with local codes and regulations (Rosen and Bennett, 1979; Jönsson, 2000;Becker, 2002; Ding, 2008; Chen et al., 2010b). Rück (2000) stressed that although each country has its own regulations and directives governing the construction of skyscrapers, these regulations are similar in content and aligned with leading international standards, in particular, USA, British and German ones. Rück (2000) described the four main groups of codes, standards and regulations applicable to skyscraper design and construction: fire protection and operational security; stability and construction physics; protection against natural hazards; and social aspects and protection of the surroundings (e.g. sustainability). Abdullah and Egbu (2010) concluded that selection criteria for new technologies should have a wider perspective that includes: structure and material design; site orientation; safety; client perspectives; environmental issues and sustainability; organisational issues; and risk. Including consideration of the foregoing, the first filter involves the application of a number of criteria under the categories of stakeholder acceptance and technical feasibility. Perspectives of interest under the stakeholder acceptance category are end-user, designer and developer, contractor, regulator and code and risk. The technical feasibility category embraces local capability to manufacture and/or construct the technology using locally available human resources, materials and infrastructure and/or the ability to import related production equipment and technical expertise. As stated previously, all criteria for the first filter are judged on a pass–fail basis. A pass mark must be achieved for each relevant criterion. Some criteria are hard (i.e. non-negotiable), while others are soft or act as constraints and may be subject to negotiation – e.g. local regulations and codes. Failure on a hard criterion results in immediate dismissal of the solution being examined. If a failed soft criterion cannot be made into a pass by negotiation, evaluation of that solution is terminated. Pass, (P) Fail, (F) N/AStakeholder acceptanceEnd-users hard acceptable unacceptable N/AContractor soft acceptable unacceptable N/ADesigners & developer hard acceptable unacceptable N/ARegulators and codes soft acceptable unacceptable N/ARisk hard acceptable unacceptable N/ALocal technical Technology soft available or can be infeasible to be imported N/AHuman resources soft available or can be infeasible to be imported N/AMaterials soft available or can be infeasible to be imported N/AInfrastructure hard exists or can be built unavailable from any N/ACategories/criteria Type State values 58 Table 2-3 Filter 1 stakeholder acceptance and high level risk sub-criteria checklist Pass Fail N/AEnd-user acceptance: Will the solution’s: ·   impact on end-user flexibility for change be acceptable? soft·   durability be acceptable? soft·   operation & maintenance cost be affordable? soft·   impact on end-user livability be acceptable? soft·   material be culturally acceptable? hardContractor acceptance:  Will the solution’s:·   potential safety-issues be manageable? soft·   productivity rate be acceptable? soft·   constructability be practical? soft·   in-situ scope of work be manageable? soft·   material wastage be acceptable? soft·   site-logistics be manageable? soft·   installation infrastructure requirements be affordable? softDesigner & developer  acceptance: Will the solution’s: ·   quality meet compliance requirements? soft·   aesthetics be acceptable? soft·   impact on other-building systems be manageable? soft·   capital cost be affordable? soft·   life cycle cost be acceptable? soft·   structural serviceability complies with requirements? hard·   features be compatible with other-building systems? hard·   design concept be culturally acceptable? hard·   functionality fulfill all primary and secondary requirements? hardRegulator and code acceptance:  - Is the local regulatory body receptive to the solution? soft  - Are permits for production, transportation and installation obtainable? soft  - Is the local regulatory body open to the use of international codes? soft Risk acceptance: Will the solution: ·   be obtainable from a reliable source? soft·   increase delivery time certainty? soft ·   increase cost certainty? soft ·   increase quality certainty? soft ·   be warrantable and / or insurable? soft ·   facilitate management of its disadvantages? soft ·   satisfy at least one of the following conditions: it has been utilized before in another country; it has not been used but the concept has been accepted by an international code; it is untested but performance tests are verifiable by standard tests and/or an international code?hardEvaluation checklist of sub-criteria re stakeholder acceptance including risk issues Type AnswerOverall end-user acceptance criterion state valueOverall contractor acceptance criterion state valueOverall designer and developer acceptance criterion state valueOverall regulator and code acceptance criterion state valueOverall risk acceptance criterion state value 59 First filter criteria categories including criteria types and state values are summarised in Table 2.2. As discussed later, their values are determined through application of two checklists (Tables 2.3 and 2.4) that treat, in turn, stakeholder acceptance and local technical feasibility. Both checklist tables are based on yes/no questions. Such an approach has been used successfully in other research fields. Percy et al. (1976) recommended utilisation of a 2-point Likert scale, dichotomous questions or binary answers, as it achieves, largely, the same information as use of a multi-point Likert scale. Jacoby and Matell (1971) indicated that re-scoring of the responses of a multi-point rating scale to a dichotomous measure does not result in any significant decrement in reliability or validity of findings. Farrington and Loeber (2000) and Dolnicar et al. (2011) highlighted that use of binary answers or dichotomous questions provides an attractive alternative to multi-category formats, is easily understandable and simple to use, saves respondent time and provides reliable results. Battey (2013) indicated that a dichotomous variable (pass/fail and agree/disagree) is suitable for collecting actual and observable information and can be used in screening products. For the first filter of the framework described, use of a 2-point scale has proven to be a cost-effective and accurate way to both elicit and evaluate available factual information about the wide range of candidate solutions because responses will be given by a professional/practitioner who understands stakeholders’ needs and local construction market capabilities and constraints. Answers to these yes/no questions are then used to determine the state value of each criterion as follows: if all answers on relevant criteria pass, the criterion state value will be a pass; and if just one criterion fails and cannot be resolved to become a pass, the criterion state will be a fail. To evaluate every criterion category of the first filter in as objective, transparent and replicable manner as possible, all relevant criteria need to be examined. As shown in Table 2.3, for stakeholder acceptance criteria, the questions are designed to collect available facts, requirements and commercial information about the project at hand, the system under evaluation, the available solutions, the potential innovations and local market conditions and culture. To avoid confusion and ambiguity in checklist question wording, the following guidelines have been utilised (Eiselen, 2005): use short simple questions; ask for only one piece of information at a time; avoid the use of negative questions; use common design and construction terms; and define any new terms used. For the stakeholder acceptance checklist, designer and developer issues of interest include project, site and system requirements/constraints. Contractor acceptance questions treat issues related to production, logistics and site installation. End-user acceptance questions examine end-user expectations and preferences. Regulator and code acceptance questions focus on legal approval, local regulations and code requirements. As a companion to Table 2.3, Table 2.4 provides a checklist of questions pertaining to local technical feasibility. This checklist treats issues pertaining to the possibility of adopting the solution using local resources and/or outsourced resources that are within the project budget and schedule. These two checklists are meant to be completed by the project stakeholder (coupled with whatever specialist assistance is required) charged with a leadership role. This role includes encouraging the search for innovative solutions as well as proposing potential solutions through meetings with consultants and suppliers, all based on a comprehensive understanding of available facts about the project and local market and culture context. Completion of the tables for candidate solutions allows the project team to identify feasible ones for a more in-depth examination in the second step in the evaluation process. This process gets repeated for the various design and construction decision problems that confront the project’s leadership.  60 Table 2-4 Filter 1 local technical feasibility sub-criteria checklist  2.6 Project background and description of case studies The configuration of most skyscrapers consists of a complex and normally deep substructure, a few atypical superstructure floors in the lower and uppermost levels and a large number of typical floors in the middle. As a result, a very large number of typical volumetric units such as washroom facilities, non-volumetric elements such as cladding panels and modular elements such as internal partitions have to be built. Therefore, it is important to seek solutions that offer economies of scale, even if they require substantial investments in on or offsite production (e.g. prefabrication) facilities. The scale of skyscraper facilities allows one to contemplate technologies that cannot be considered for smaller buildings because of the different mix of fixed and variable costs. Wet areas, internal partitions and cladding systems provide the focus for the three case studies examined. Activities associated with these systems are generally on the critical path of a skyscraper project. The specific context of the case studies is a monumental skyscraper project – the Abraj Al-Bait project located in Makkah, Saudi Arabia. This project is a design, build, operate and transfer skyscraper complex that consists of a 17-floor podium topped by seven skyscrapers ranging in height Pass Fail N/ATechnology: Will the solution’s ·   design principles be acceptable to the engineer? soft·   production location be acceptable? soft·   technology be capable of being  locally fabricated? soft·   technology be able to be imported with affordable cost and time? softHuman resources:  Will the solution’s·   in-situ human resource requirements in terms of  number be manageable? soft·   human resource skills required be obtainable? soft·   human resources be available  locally? soft ·   human resources have to be sought from other jurisdictions and can this be done in an cost effective and timely manner? softMaterials:  Will the solution’s: ·   method of disposal at the end of the building life cycle be acceptable? soft ·   construction have a reasonable utilization of the raw material? soft ·   materials be locally available? soft·   materials be obtainable from other jurisdictions in a cost effective and timely manner? softInfrastructure: Are the solution’s :·   requirements for production, storage & construction areas feasible &  affordable? soft·   production, transportation and installation requirements feasible & affordable? soft·   infrastructure needs able to be  locally built or internationally outsourced in an  affordable and timely manner? hardEvaluation checklist sub-criteria re local technical feasibility Type AnswerOverall technology criterion state valueOverall human resources  criterion state valueOverall material criterion state valueOverall infrastructure criterion state value 61 from 240 to 601 m and house hotels and condominiums. The floor height varies between 4.0 and 7.5 m depending on the finishing grade of the floor. High-finish grade floors require a greater floor height to accommodate the luxury designed finishing. The building holds and has broken several world construction records including: the tallest hotel in the world; the tallest clock tower in the world; and the world’s largest clock face. The project has the world’s largest building floor area of some 1,500,000 m2 and was, at least temporarily, the second tallest building in the world as of its 2012 completion, surpassed only by Dubai’s Burj Khalifa. The project, with a capital cost of US$15 billion (Wainwright, 2012) can host 100,000 people. A phased construction plan started in 2002 and the project was completed in 2012. With respect to the first case study, the residential component of the project required approximately 7,000 typical washroom and bathroom units (a washroom has a toilet and a sink while a bathroom has a toilet, sink and bath tub). Traditional methods for building the wet areas include concrete block, plastering and in situ finishing and drywall and in situ finishing. In the second case study, the total area of internal partitions for the project was 1.07 million m2. Potential traditional solutions include brick and plaster, concrete block and plaster and drywall. In these case studies, the owner’s requirement was that the recommended solution should satisfy stakeholders and meet the project objectives of time, cost, appearance and reputation. In the third case study, the project cladding system involved some 12,000 panels, each with an average width of 8.0 m and height of 6.0 m. As expressed by the owner, the preferred cladding system should conserve the Islamic architectural context in a modern international style; utilise Islamic elements and vocabulary as required by the regulatory body; utilise energy-conscious materials with luxurious and durable finishes; complement the cladding system of the “Makkah Holy Haram” area; and function to accommodate the annual temperature range of 18 to 40°C. Potential traditional solutions for the cladding system are: aluminium composite panels; glass curtain wall; and stone-faced cast in situ concrete wall. Top management of the project sought state-of-the-art system solutions in terms of current/traditional and innovative design and construction technologies that would be locally acceptable and meet project requirements with regard to speed of delivery, high quality and life cycle cost. Potential innovative solutions considered as part of the three case studies correspond to prefabricated wet facilities called pods which can be manufactured using a variety of materials, Acotec for internal partitions (a prefabrication concrete technology developed and used in Finland and based on the same principles as hollow core slab panels) and an upgraded pre-cast concrete cladding system for the building enclosure. For the actual project, these innovations were adopted as the solutions of choice. Discussed in the following sections are the alternatives considered for the three case studies, followed by application of the first filter screening step to determine which solutions are viable candidates. 2.6.1 Case study 1: alternative solutions for construction of wet areas Traditionally, wet areas made of blocks, plaster and in situ finishes enjoy social acceptance in the Middle East. This solution involves two major activities that have to be done in a specified sequence – roughing in (block, plastering and mechanical, electrical and plumbing rough-in – MEP) and final finishing (wall, floor and ceiling finishes and interior MEP finishing and testing and commissioning). Challenges associated with the traditional solution include building in situ, using wet activities that require mortar mixes and curing periods; low productivity rates; labour  62 intensive, space intensive methods; considerable wastage of materials; a high level of safety hazard; difficult logistics in terms of lifting materials, equipment, tools and human resources; and a long testing and commissioning process for MEP works. Wet areas made of moisture-resistant drywall partitions and in situ finishes are not acceptable to end-users. The main reason is the perception that it is a non-rigid, non-durable and impermanent system, despite the pervasive use of such an approach in other jurisdictions around the globe and the benefits such a solution offers. The question becomes what other technologies exist that can provide the sense of permanence and quality offered by existing partition systems, while addressing the objectives of cost, speed and quality and offering economies of scale? One potential alternative is the use of a pods system that originated in Italy. The interior design of pods in terms of useable area, finishing works and MEP systems can be changed to suit project requirements. Several materials can be used for their manufacture: fibreglass; steel; and reinforced concrete. All pod modules are structurally designed and have lifting eyes for site installation. Advantages offered by a concrete pods system are: moisture resistance; fire resistance of more than two hours; sound-proofing up to 50 dB; fine tolerances; high finishing quality; high installation productivity; construction costs comparable to the traditional method; efficient use of input materials in production with no site waste; simple logistics; and minimal site manpower and onsite work scope. As noted previously, pods system was the solution of choice. The prefabrication and storage facilities for pods were built in Jeddah (about 100 km from the project location) as an extension to an existing pre-cast factory. Transportation to the project site was not a significant issue. The production system adopted allows walls and ceiling to be cast monolithically, followed by the floor. The expensive setup costs are offset by economies of scale of production, and the offer of construction time saving and high-quality pods with accurate sizes. Eight typical pods models were required to meet the project design needs. Depending on the model size, a pod weighs between 8 and 14 t, which can be handled readily in the prefabrication yard by mobile cranes and on site by the tower cranes. The production cycle of a typical pod from start of production to readiness for installation is approximately three weeks. The site installation process is carried out straight from a truck to the destination slab using a tower crane outfitted with a special lifting beam. Pods can be installed in the building either vertically from above before casting the slab or horizontally with a roller platform after casting. Site installation involves two stages. First, a pod is hoisted to its final location and temporarily levelled by rubber shims to allow structural creep and deflection of the slab to take place. Second, final levelling is done using a hydraulic jack. After final levelling, grouting under the pod is done and MEP hook-ups are connected using simply designed flanges and sockets. 2.6.2 Case study 2: alternative solutions for construction of internal partitions Acceptable methods for building internal partitions include traditional block or brick and mortar. The traditional method involves three main activities: building a wall; MEP roughing in; and applying plaster. Building a wall takes several steps: preparing the mortar; building block or brick in layers and placing reinforcement and wall ties; conducting random inspections to ensure quality for all of the building process steps; and curing each block wall for at least one week before plaster can be applied. In addition to the foregoing is a constraint on the maximum height of wall that can be built in one day between 2.5 and 3.0 m for initial curing, to maintain the stability of the fresh wall. Also, cast in situ concrete tie beams may be required, depending on the area of the wall. The average mason production  63 rate of block work is between 15 and 20m2 per day. Second, after one week of wall curing, MEP rough-in work is performed, cutting the wall to install MEP elements as required. Third, after completion of the MEP rough-in, the plastering activity begins; this involves several steps: affixing plastering accessories (e.g. expanded metal lath, corner and stop beads); laying out of guide points; applying mortar slurry; and applying mortar to level the guide points.  Two weeks are required for plaster curing before painting can start. The average production rate for plastering varies between 12 and 16m2/day/crew (one mason and one helper) depending on the area and the number of corners and openings in the wall. An alternative to the traditional internal partition method is the use of the innovative Acotec system. This system is comprised of prefabricated hollow core concrete wall panels, ideal for non-load-bearing internal partitions. The panels have a smooth finish surface for paint application, eliminating the need for plastering. Acotec panels are fabricated in standard dimensions: width 60 cm and an adjustable length up to a maximum of 330 cm. Panel thickness increases as height increases: 6.8 cm for cavity walls < 300 cm in length, 12 cm for a height < 510 cm and 14 cm for a height > 510 cm and < 610 cm. Panels are tongue and groove, allowing easy alignment of panels and providing a vertical shear key for wall stability. Advantages of the system include a rapid installation rate up to 6 m2/h per crew (crew consists of four workers); moisture resistance; fire resistance up to two hours; sound resistance up to 45 dB; potential time and cost savings; efficient use of raw materials; and simple logistics. The production line for Acotec panels is fully automated and can be adapted to new or existing facilities close to the site. The Acotec system was chosen and the production facility for the project was built in Jeddah. Actual panel production makes use of local materials and locally trained labour. Once the site is ready for erection, the panels are shipped and lifted to the installation location using a just-in-time delivery policy. The tools, accessories and adhesive material required for panel installation are all standard off-the-shelf items. In terms of onsite work, Acotec panels can be used horizontally as a lintel or vertically as common wall panels. If the wall height is < 330 cm, the panels are installed in one course; for a wall height of > 330 cm and < 680 cm, two courses will be required. In terms of site installation productivity, a wall of 14 cm thickness with area equal to 48 m2, length 8.0 m and height 6.0 m requires three working days, a crew of two tradesmen and two helpers and a curing period of seven days for the grout. 2.6.3 Case study 3: alternative solution for construction of cladding system All cladding systems have six basic components: three are visible and three are hidden. The visible components are exterior cladding material such as: aluminium panels or brick veneer; the treatment of external cladding joints using sealant or other treatment; and an interior wall such as painted gypsum board. The three hidden components include: the supporting frame; water and air barriers; and, thermal insulation. Currently, used and innovative cladding systems applicable to the case study project are aluminium composite cladding, glass curtain wall, stone-faced cast in situ concrete wall cladding system and upgraded stone-faced pre-cast panels. The last of these embodies a modification and enhancement of traditional pre-cast panels. An aluminium composite material (ACM) cladding system is a rain screen system that has no sealant. It is a pressure equalised system where the joints are open to allow instantaneous pressure equalisation in driving rain conditions. This system is suitable for all kinds of weather, especially heavy rain or extreme heat, and panels are designed to resist  64 positive and negative wind loads. Stiffeners are included to prevent wind-induced vibrations and fatigue problems. Panel assemblies are fastened to the building structure and transmit all loads to the stiffeners. Advantages of the ACM system include dry joints with no exposed fasteners; simple and fast installation; an aesthetically pleasing colour; flexibility of panel shapes and custom design; energy savings; and light weight. The main disadvantage is that most system components are built in situ which increases safety hazards, the number of site workers and the logistics burden. A unitised glass curtain wall is a pressure-equalised rain screen system. The units are completely factory-assembled, bundled in crates, shipped to the site for installation as required and lifted to the floors using the tower crane. Installation of the panels can be done using a small hoist that can move easily on and between floors. Units are simply snapped together onsite for a weatherproof installation. System advantages include high speed of installation; high performance in terms of allowable movement; load bearing capacity; water penetration; minimum in situ scope of work and number of workers; energy savings; relatively light weight; potential cost and time savings; and simple logistics. A stone-faced cast in situ concrete wall cladding solution enjoys cultural acceptance in the Middle East where it has been used for many years. System construction involves: casting external concrete walls concurrently with the columns and shear walls for each floor, followed by casting the slab; after curing the external walls, fixing stone anchors to the external side of the wall; applying external wall waterproof material followed by the thermal insulation; on top of the insulation, installing granite and/or marble cladding using mechanical connectors with treated or void joints; applying plaster and finishes to the internal side of the wall; and installing aluminium windows. Disadvantages of the system include: wet activities with low production rates and long curing periods; intensive labour and space usage; a significant logistics burden; inefficient use of material; heavy weight; and high safety hazard due to the need to work at significant height on the exterior of the building. The upgraded pre-cast cladding system adopted for the case study project significantly enhances the traditional pre-cast system. It is used to give a rich architectural look by incorporating stone, marble or granite sheets as a finish face for the pre-cast panels. Pre-cast panels can be designed and produced in a variety of colours, textures and forms. As a manufacturing process for the Abraj Al-Bait Project, an extension to an existing pre-cast factory some 100 km from the project was used to produce pre-cast panels. System advantages include: high quality; moisture resistance; fire resistance of >two hours; sound proofing; and an efficient use of raw materials. The adoption of large capacity hauling and lifting equipment for handling and erecting pre-cast concrete elements allows installation of larger panels, reduced construction cost and time and faster enclosure of the building. The main disadvantage of this system is its heavy weight which might require an increase in the size and reinforcement of structural and foundation system components. 2.7 Applying the first filter of the evaluation framework to the three case studies In practice, seasoned professionals who have local market experience, are familiar with the project context and have access to material describing the features of potential solutions would complete the checklists set out in Tables 2.3 and 2.4 based on considered judgement of the properties of the solution being examined and its fit with the project at hand. This judgement may involve extended discussions among various project team members on specific criteria – in some cases (e.g. local availability of human resources and materials), a single individual is well positioned to provide a  65 definitive response; for other criteria (e.g. risk and designer and developer acceptance), discussions internal to the project team are required, augmented in some cases with consultation with external suppliers or regulatory officials. These checklists were completed for the three case studies in the case study project by making use of the discussions held with Abraj Al-Bait project management team members regarding various options combined with observation of best construction practices on other high profile projects in the UAE. 2.7.1 Applying the first filter to candidate solutions for wet area construction As shown in Tables 2.3 and 2.4, application of the first filter to the four alternatives identified for washroom and bathroom construction for the hotel and residential area of the project led to the conclusion that drywall with in situ finishing and fibre glass and steel pods systems all fail because they did not meet one or more criteria under end-user and designer and developer acceptance. The block, plaster and in situ finish and concrete pods systems passed because end-user culture is accepting of the materials used – i.e. the design concepts provide a sense of permanency and durability. Findings from Tables 2.5 and 2.6 are summarised in Table 2.7. In the screening process, discussion about the feasibility of concrete pods focused on the production facility location and required area, transportation to the site, the heavy weight of pods, site logistics and installation. It was concluded that all of these issues could be addressed in a satisfactory manner. 2.7.2 Applying the first filter to candidate solutions for internal partition construction Only a summary of the first filter findings for the choices with respect to internal partition construction is provided here due to space constraints. Applying the checklists contained in Tables 2.3 and 2.4 led to the results shown in summary Table 2.8. Two of the four possible choices failed – brick and plaster and drywall. At the detailed analysis level, the brick and plaster alternative failed because of the low productivity rate under the productivity sub-criterion, the high damage potential that accompanies the use of bricks under the material wastage sub-criterion, the inability to achieve a two-hour fire resistance rating under the fire safety sub-criterion for the separation wall between the units and for not meeting the seismic reinforcement and connection requirement under the structural stability sub-criterion. The drywall alternative failed because it did not meet end-user acceptance under the material used sub-criterion as well as designer and developer acceptance under the design concept sub-criterion. In the screening process, discussion focused on the Acotec productivity rate, constructability and structural serviceability for partitions > 3.30 m. A design proposal of using two layers of Acotec with a staggered horizontal connection resolved concerns with the foregoing issues.  66 Table 2-5 Case study 1 evaluation of stakeholder acceptance including risk issues Block, plastering & in-situ finishingDry wall & in-situ finishingFibreglass & steel PodsConcrete podsEnd-user acceptance: Will the solution’s: ·   impact on end-user flexibility for change be acceptable? P P P P·   durability be acceptable? P P P P·   operation & maintenance cost be affordable? P P P P·   impact on end-user livability be acceptable? N/A N/A N/A N/A·   material be culturally acceptable? P F F POverall end-user acceptance criterion state value P F F PContractor acceptance:  Will the solution’s:·   potential safety-issues be manageable? P P P P·   productivity rate be acceptable? P P P P·   constructability be practical? P P P P·   in-situ scope of work be manageable? P P P P·   material wastage be acceptable? P P P P·   site-logistics be manageable? P P P P·   installation infrastructure requirements be affordable? P P P POverall contractor acceptance criterion state value P P P PDesigner & developer  acceptance: Will the solution’s: ·   quality meet compliance requirements? P P P P·   aesthetics be acceptable? P P P P·   impact on other-building systems be manageable? P P P P·   capital cost be affordable? P P P P·   life cycle cost be acceptable? P P P P·   structural serviceability complies with requirements? P P P P·   features be compatible with other-building systems? P P P P·   design concept be culturally acceptable? P F F P·   functionality fulfill all primary and secondary requirements? P P P POverall designer and developer acceptance criterion state value P F F PRegulator and code acceptance:  - Is the local regulatory body receptive to the solution? P P P P  - Are permits for production, transportation and installation obtainable?P P P P  - Is the local regulatory body open to the use of international codes?P P P POverall regulator and code acceptance criterion state value P P P PRisk acceptance: Will the solution: ·   be obtainable from a reliable source? P P P P·   increase delivery time certainty? P P P P·   increase cost certainty? P P P P·   increase quality certainty? P P P P·   be warrantable and / or insurable? P P P P·   facilitate management of its disadvantages? P P P P·   satisfy at least one of the following conditions: it has been utilized before in another country; it has not been used but the concept has been accepted by an international code; it is untested but performance tests are verifiable by standard tests and/or an international code?P P P POverall risk acceptance criterion state value P P P POverall  state value for stakeholder acceptance and risk issues P F F PEvaluation checklist of sub-criteria re stakeholder acceptance including risk issuesPotential solutions  67 Table 2-6 Case study 1 - evaluation of local technical feasibility Block, plastering & in-situ finishingDry wall & in-situ finishingFibreglass & steel PodsConcrete podsTechnology: Will the solution’s ·   design principles be acceptable to the engineer? P P P P·   production location be acceptable? P P P P·   technology be capable of being  locally fabricated? P P P P·   technology be able to be imported with affordable cost and time?P P P POverall technology criterion state value P P P PHuman resources:  Will the solution’s·   in-situ human resource requirements in terms of  number be manageable?P P P P·   human resource skills required be obtainable? P P P P·   human resources be available  locally? P P P P·   human resources have to be sought from other jurisdictions and can this be done in an cost effective and timely manner? P P P POverall human resources  criterion state value P P P PMaterials:  Will the solution’s: ·   method of disposal at the end of the building life cycle be acceptable?P P P P·   construction have a reasonable utilization of the raw material? P P P P·   materials be locally available? P P P P·   materials be obtainable from other jurisdictions in a cost effective and timely manner?P P P POverall material criterion state value P P P PInfrastructure: Are the solution’s :·   requirements for production, storage & construction areas feasible &  affordable? P P P P·   production, transportation and installation requirements feasible & affordable?P P P P·   infrastructure needs able to be  locally built or internationally outsourced in an  affordable and timely manner? P P P POverall infrastructure criterion state value P P P POverall state value for local technical feasibility P P P PPotential solutionsEvaluation checklist sub-criteria re local technical feasibility  2.7.3 Applying the first filter to candidate solutions for exterior enclosure Applying the screening process to cladding solutions led to the results shown in summary Table 2.9. Both aluminium composite rain screen and glass curtain wall cladding systems fail as there is no acceptance from the designer and developer with respect to colour and finish matching under the design concept sub-criterion and a lack of local regulatory authority acceptance with respect to the building permit sub-criterion, even after a second round of  68 negotiation by top management with regulatory officials. The main disadvantage of unitised glass and ACM cladding systems is the potential reflection of light from the cladding system to the surrounding “Makkah Holy Haram” area and the difficulty of conserving the Islamic architectural context in a modern international style while utilising Islamic elements and vocabulary to complement the existing cladding systems of the “Makkah Holy Haram” area. This is an example where the cultural dimension plays a definitive role in the screening process. Although stone faced cast in situ walls and upgraded pre-cast systems contributed substantial load to the structure and foundation system, both of them passed the first filter screening. An example of a critical issue in the screening process was the site logistics sub-criterion. It was recognised that some of the pre-cast panels in the podium would be beyond the reach of the tower crane. This problem could be resolved, however, through use of a mobile crane. Table 2-7 Case study 1 - summary of filter 1 findings for wet areas construction alternatives  2.7.4 Summary of first filter screening results Summarised in Table 2.10 are the findings from application of the first filter of the three-step evaluation process. Of some 12 alternatives for a total of three system design decisions, only half of them passed the screening process, yielding candidate solutions consistent with those actually explored in more depth for the case study project. It is emphasised that the focus of the first step is on assessing feasibility, not ranking feasible alternatives in order of desirability. There were some surprises from the screening process. For example, steel and fibre glass pods have many advantages, including required end-user rigidity and light weight in comparison to concrete pods, yet they did not pass the screening process, the reasons being the risk associated with the relative newness of these types of pods and concern about acceptance in the local market. Another example relates to use of the ACM rain screen – it can achieve the external Islamic look required by the developer and is lightweight, a real benefit for the structure; however, its use was rejected by local authorities. External validity related to the generalisability of results (Lucko and Rojas, 2010) is achieved for the framework’s first filter through application of the framework to three case studies that represent a wide range of building systems: cladding; internal partitions; and wet areas which, collectively, touch on all of the criteria and sub-criteria set out in Tables 2.3 and 2.4. Block, plaster and in-situ finishesDry wall and in-situ finishesFibreglass and steel Pods Concrete PodsStakeholder acceptanceEnd-users P F F PContractor P P P PDesigners & developer P F F PRegulators and codes P P P PRisk P P P PLocal technical feasibilityTechnology P P P PHuman resources P P P PMaterials P P P PInfrastructure P P P POverall first filter state value P F F PState values of potential solutionsCategories/criteria 69 Table 2-8 Case study 2 - summary of filter 1 findings for internal partition alternatives  These three studies reflect different pre-assembly degrees of volumetric pre-assembly (e.g. pods), non-volumetric pre-assembly (e.g. pre-cast panels) and component manufacture (e.g. Acotec). These studies facilitated a quasi cross-case study analysis within a project case study, quasi because lessons learned from applying the first filter sequentially to the case studies were incorporated as one moved from the first to the second to the third case study, with each case study representing a different decision problem. Refinements made included the addition of important sub-criteria (e.g. aesthetics in the case of cladding systems) and fine-tuning of the expression of various sub-criteria to ensure a single interpretation of meaning, thus helping to ensure the applicability of the first filter to a wide range of design and construction decision problems. Table 2-9 Case study 3 - summary of filter 1 findings for cladding alternatives  2.8 Assessment of the evaluation framework by practising professionals Discussed in this section are the perspectives offered by seasoned professionals involved in showcase Middle East projects on the structure of the approach proposed for evaluating system design and construction choices, along with Bricks & plaster Block & plaster Dry wall AcotecEnd-users P P F PContractor P P P PDesigners & developer F P F PRegulators and codes P P P PRisk P P P PTechnology P P P PHuman resources P P P PMaterials P P P PInfrastructure P P P POverall first filter state value F P F PCategories/criteria State values of potential solutionsStakeholder acceptanceLocal technical feasibilityACM rain screen Glass curtain wall Stone faced cast in situ concrete walls Upgraded precast systemStakeholder acceptanceEnd-users P P P PContractor P P P PDesigners & developer F F P PRegulators and codes F F P PRisk P P P PLocal technical feasibilityTechnology P P P PHuman resources P P P PMaterials P P P PInfrastructure P P P POverall first filter state value F F P PCategories/criteriaState values of potential solutions 70 their observations on the utility of the first step in the three-step process, including use of a pass/fail response for each criterion. These interviews were used as a face validity technique for the framework evaluation details (El-Diraby and O’Connor, 2004). “Face validity requires the approval of non-researchers regarding the validity of a study” (Lucko and Rojas, 2010). Three interviews were conducted with senior construction industry personnel, all professional engineers, to: identify the range of stakeholder viewpoints and criteria that should be considered in evaluating design and construction technologies for skyscraper projects; determine their views on how choices are assessed in practice; and obtain specific feedback about the structure and the advantages and disadvantages of the proposed evaluation framework, with emphasis on the first and second steps in the process. Table 2-10 Summary of filter 1 screening results for the three case studies examined  These interviews aim to ensure that the framework provides an organised way of thinking that mirrors what occurs in practice both formally and informally. It is useful to note that the structure of firms in the Middle East differs from most of those in North America in that they tend to be full-service firms providing architectural and multi-discipline engineering capabilities – they thus possess the ability to make decisions relatively quickly and accurately in-house for many kinds of solutions. The individuals interviewed were a developer, a designer and a contractor. The developer is a project director with 35 years of experience who works for an international developer managing skyscraper projects. The designer is a country manager with 31 years of experience, employed by an international full service design firm that has managed design and construction of many large-scale projects, including skyscraper projects. The contractor is a member of the board of directors of an international general contracting firm who has 27 years of work experience and whose firm has constructed many skyscraper projects. All interviews were conducted in person and each lasted approximately one and a half to two hours. The interviews were conducted in two steps. First, an overview of the assessment tool for evaluating design and construction technologies was given, including the initial version of Tables 2.3 and 2.4. Second, the interviewees were asked three questions. What are the most important criteria to consider when evaluating solutions for the various building systems used in skyscrapers? What personal experience have they had in selecting and evaluating building systems in general and skyscraper projects, in particular? What feedback could they offer specific to the evaluation framework in terms of the three-filter evaluation process, its practicality, usefulness, advantages and disadvantages? The responses of the three professionals interviewed are described below.  Application/Choices Results Application/Choices Results Application/Choices ResultsBlock, plastering & in-situ finishing P Brick & plaster F ACM rain screen FDry wall & in-situ finishing F Block & plaster P Glass curtain wall FFiberglass & steel pods F Drywall F Stone-faced cast-in-situ concrete walls PConcrete pods P Acotec P Upgraded precast system PFirst case study Second case studyWet area construction Internal partition constructionThird case studyExterior enclosure 71 2.8.1 First practising professional’s feedback The developer emphasised that the cost, construction time, associated risk, in situ scope of work and logistics are the most important criteria to be considered in the context of skyscrapers. Based on the developer’s personal experience in evaluating building system choices including innovative ones, priority considerations in the selection of an innovative solution must be based on its advantages in comparison to conventional solutions in terms of availability from a reliable source, constructability, use of local resources, cost, time and potential risks. If the solution will have a direct impact on end-users, the developer emphasised that end-user preferences should be considered, especially for residential condominium projects. After the initial screening step, all information gathered about the innovation is passed to the company’s technical professionals for a comprehensive performance assessment, including consideration of the time, cost and risk consequences. If the innovation successfully passes this evaluation process, it may be considered for utilisation. The developer cited the example of adopting pods technology for a current project. After seeing this technology for the first time at a construction fair in Europe, the developer gathered all available information, analysed it with the assistance of the company’s technical team and convinced company’s top management to use the pods. With respect to the framework, the developer agreed with the three-step structure for screening, performance evaluation and evaluating cost and time savings and associated risks, including any impact on the whole project. The developer agreed with the use of binary answers in the screening process, as it would save time and cost in the assessment process. The developer also emphasised the importance of evaluating the impact of the solution on the project as a whole, but highlighted the difficulty of having to make the most important decisions early on when not a great deal of information is available. The developer advised that, to the extent possible, innovative solutions should be considered in the design phase of the project to avoid potential redesign work. As a final comment, the developer suggested that, when completed, the framework would be a useful and practical tool for design and construction practitioners and policymakers. 2.8.2 Second practising professional’s feedback The designer emphasised that cost, construction time, associated risk, the scope of in-situ work, logistics terms, code compliance, functionality and quality are the most important criteria to be considered in the context of skyscrapers. Speaking from personal experience in evaluating new technologies, the designer stated that the ability to acquire an innovation from a reliable source is the most important selection criterion, as this will contribute to better service after installation, such as training of staff, availability of spare parts, technical support and a high-quality product. As an example, the designer cited the screening and selection of an innovative technology for desalination of sea water in Saudi Arabia. Although many international companies offered alternative innovative equipment, the designer selected equipment that was not the most innovative but came from the most reliable source. The designer screened all available solutions down to two options based on an initial evaluation of function efficiency, life cycle cost, procurement lead time and construction time. Detailed performance evaluation was followed by a comprehensive evaluation of life cycle cost, construction cost and associated risk. The designer emphasised that the choice of utilising this technology for the whole project, especially for construction duration, was made to avoid huge contractual delay damages as manufacturing of this innovative equipment requires a long procurement lead time. In terms of specific feedback about the framework, the designer agreed with the three-step approach proposed for its efficiency in saving evaluation time  72 and cost. This individual also highlighted the importance of evaluating the impact of new technologies on the overall project cost, construction duration, and associated risks, especially for equipment/systems involving a long lead time, and indicated that the framework when completed would provide a comprehensive and systematic tool for the decision-maker. 2.8.3 Third practising professional’s feedback The contractor similarly highlighted that cost, construction time, associated risk, scope of in situ work, logistics terms, code compliance, functionality, quality, safety and productivity are the most important criteria to be considered in the context of skyscrapers. Speaking from personal experience in evaluating new building systems, the contractor stated that innovations based on simple site construction tasks are preferred as they help to reduce required worker skills, minimise the number of workers on site, increase productivity and minimise safety hazards. The individual interviewed gave an example of utilising an innovative aluminium formwork technology in one of the firm’s skyscraper projects. Use of this system allowed columns and slabs to be cast monolithically in a three-day cycle. The contractor pointed out the major advantages of this system are simple assembly tasks, minimum safety hazards, as neither wood nor nails were used, high productivity rate, simple logistics, as no tower crane was required, and high-quality concrete work. In terms of specific feedback about the framework, the contractor agreed with the three-step evaluation methodology and was accepting of the use of binary answers for the screening process for its ease of use and acceptable accuracy. The contractor also stated that the framework is useful for evaluating not only design and construction technologies but also construction innovations such as formwork or concrete pumping technologies. Nevertheless, the contractor observed that because construction technologies have a minimal impact on the final product and interrelation with other system solutions, a simplified version of the evaluation process could be used. The interview process produced valuable comments regarding stakeholder viewpoints and evaluation criteria, the proposed framework, and the approach to expressing criterion values for both the first and second steps in the framework methodology. This feedback was incorporated into a revised version of the framework – the version presented in this paper. This feedback combined with use of findings from the literature and lessons learned from conducting the case studies contributed to the generality and completeness of the framework. 2.9 Conclusion Described in this paper is an assessment tool for evaluating design and construction technologies relevant to skyscraper projects. This evaluation tool involves the use of three filters and reflects the informal thought processes applied in practice by design and construction personnel to assess alternatives as well as approaches adopted by other researchers (Lutz et al., 1990). The first filter is for preliminary screening of all potential solutions to assess feasibility regarding “must have” criteria. The function of the second filter is to conduct an extensive technical/environmental performance evaluation of those solutions deemed to be feasible in the first step and to provide a preliminary ranking of feasible solutions. The third filter deals with choice of the preferred solution from the set of ranked solutions from the second filter, based on a quantitative assessment of time, cost and risk consequences. The eventual choice of the preferred solution involves a judgement by the decision-maker as to how to best balance quantitative criteria such as time and cost with the multitude of technical/environmental performance criteria considered in filter 2. Details of the first filter  73 and its criteria tests were presented along with a brief overview of the other two filters. As formulated, the framework addresses a number of deficiencies of evaluation frameworks identified in the literature and a significant contribution lies in the breadth of performance criteria and sub-criteria treated. For the first of the three filters, the primary focus of the paper, although applicable as well to steps 2 and 3, considerable effort was expended to identify the properties required of a comprehensive yet practical tool which can assist in providing objective and replicable assessments of the options available to decision-makers. These properties include completeness of the categories of evaluation criteria and relevant sub-criteria; clarity in the expression of criteria; simplicity of measurement of criteria, with emphasis on objective measurement; and practicality. This was achieved by a thorough examination of the literature, an iterative process of evaluation framework design and testing on actual decision problems and consultation with industry experts. Nevertheless, absolute completeness of criteria and sub-criteria and how best to express them cannot be claimed. As with any evaluation tool, refinement occurs over an extended period of time as the tool is applied to a large number of decision problems by multiple decision-makers. The decision was made to elicit decision-maker responses to individual criteria in a binary (pass/fail) format to ensure clarity of response and to eliminate marginal or wholly unacceptable (non-compliant) solutions as quickly as possible – an approach supported in the literature and prevailing industry practice.  Detailed application of the evaluation framework was conducted on three distinctly different case studies within the same case study project for all three steps of the evaluation process, with findings from the first step examined in this paper. Feasible candidate solutions identified include system choices actually made. The usefulness of the overall approach was assessed through extensive interviews with senior personnel representing the perspectives of developer, designer, and contractor with experience on skyscraper projects. Findings from three interviews with respect to framework structure, specific evaluation criteria and use of binary answers for assessing evaluation criteria provide support for the evaluation framework. The strength of the approach lies in the breadth of criteria treated its applicability to a wide range of design and construction decision problems, the transparency of decision-making offered, ease of use and comprehensiveness in terms of performance dimensions treated. As formulated, the framework is tailored to the resource and expertise-rich context of skyscraper projects and the need for rigor in decision-making, as the consequences of poor decisions are magnified by the scale of such projects. The design and operation of the second and third filters is to be presented in separate papers. Topics and challenges addressed include: ensuring a comprehensive identification of relevant evaluation criteria and sub-criteria; determining how best to express and measure these criteria as a function of the building component, system or construction technology being examined; combining different measurement scales including the opportunity to weight the different criterion categories; developing a high-level hierarchical time model for predicting intermediate and completion milestone performance as a function of system design and construction technology choices made, including treatment of the interfaces between systems; formulating a cash flow model that captures all life cycle flows including financing issues and project revenues; and quantifying risks to facilitate meaningful comparison between system choices. Further enhancement and validation of the framework to ensure generality, completeness and ease of usability within  74 the context of design and construction decision-making for skyscraper projects will require access to a broad range of decision problems and arm’s length application by and feedback from knowledgeable industry participants. Formal cross-case study analysis involving projects from different world venues and a diverse range of decision projects within and across projects will assist in this enhancement and validation effort. A real challenge lies in getting the level of cooperation experienced with the case study project examined in this paper so that other in-depth case studies can be conducted. The time commitment required of practitioners and researchers for the documentation and analysis of in-depth studies is considerable.    75 Chapter 3 Performance Evaluation Tool for Skyscraper Design and Construction Technologies2 3.1 Introduction Neely et al. (1995) quoted Lord Kelvin’s proposition as follows: When you can measure what you are speaking about, and express it in numbers, you know something about it …, (otherwise) your knowledge is a meagre and unsatisfactory kind; it may be the beginning of knowledge, but you have scarcely in thought advanced to the stage of science. Chew (2003) defined performance as the measurement of achievement against intention, and the integration of building systems as the act of creating a whole functioning building through utilizing specific building systems combinations. Neely et al. (1995) defined a performance measurement system as a set of metrics used to quantify the efficiency and effectiveness of actions. They defined effectiveness as the extent to which customer requirements are met, and efficiency as a measure of how economically resources are utilized to provide a given level of customer satisfaction. Neely and Wilson (1992) highlighted that performance measurement systems usually involve a number of multidimensional performance indicators. Toole (2001) defined performance of a building system as all physical characteristics of the product, and divided it into three sets: construction performance, installed performance, and design performance. Aygun (2003) defined the physical characteristics of a building system as (1) location that may be external, internal, or semi-enclosed; (2) inclination that could be horizontal, vertical, or inclined; (3) sub-systems, including geometry, texture and color, material, and intra and inter-component joints. As described herein, a performance evaluation tool refers to sets of criteria and their corresponding sub-criteria used to quantitatively measure all achieved physical characteristics of a skyscraper system or solutions to promote its intended goals and objectives across its life-cycle phases: design, production, logistics, installation, in-use, and demolition.  While the definition of most project phases is self-evident, it is useful to provide a working definition of the logistics phase with its critical importance in skyscraper construction due to limited in-situ workspace, site storage capacity, lifting equipment requirements, and the large scope of work and scale of investment (Sacks and Goldin, 2007). Drawing on the various definitions of logistics (Canadian Association of Logistics Management, 1998; Council of Logistics Management, 1998; Feld, 2001; Jang et al., 2003; and Ebel and Clausen, 2007), a working definition of logistics in the context of this paper relates to the process of planning, implementing, and controlling the efficient, cost-effective flow and storage of permanent material, products, in-process inventory, applied resources, and related information from all supplier/subcontractor/fabricators to a project; building and completing project systems in accordance with the project requirements; and removing redundant material and waste from the site after system completion.  Skyscrapers are prominent features of modern cities and increasingly dominate urban skylines around the world. They                                                           2 A version of this chapter is ready for submission to a journal.  76 are large-scale engineering projects with extended construction duration and involving international effort (Watts et al., 2007). Skyscrapers are composed of several different groups of modular floors; each group has its own function and configuration and most of the floors have a repetitive modular nature (Shaked and Warszawski, 1995). Skyscraper projects present many challenges (Watts, et al., 2007) because of their scale—especially height. These can be categorized under the headings: development, design, construction, and performance. Development challenges include the large scale of investment, the extended project duration, the fact that full revenue is realized only at the end of the project, and the varying capability and availability of design and construction specialists. Design challenges relate to providing an efficient and suitable floor plate and an efficient superstructure solution; the integrity of the building; a façade specification that provides high quality performance; and effective design solutions for mechanical, electrical, and vertical transportation systems.  Construction challenges involve achieving construction time, cost, and quality objectives while considering a unique building shape, a limited in-situ work area, a constrained work sequence, and difficult in-situ logistics. Skyscrapers utilize building systems that can benefit from meeting these challenges. System solutions that minimize construction time, capital cost, logistics, in-situ scope of work, construction waste, maintenance and operation cost, and risk and maximize health and safety, efficiency of used material, productivity, sustainability, and in-use flexibility are candidate solutions of particular interest for skyscrapers. For example, sustainable technologies offer radical changes to the built environment in terms of energy usage, system performance, and environmental effects. A high-performance skyscraper warrants an approach designed for maximum sustainability (Ali and Armstrong, 2008). Design and construction functions of skyscrapers tend to draw from the best practices and technologies available worldwide to meet their design, construction, and usage performance challenges. Consequently, given the availability of many design and construction solutions for different facets of a building’s design and construction that offer performance advancements, the need exists for a performance evaluation tool that is comprehensive in scope, reliable in result, and practical in application. 3.2 Proposed framework As discussed in AboMoslim and Russell (2014), the proposed assessment framework for evaluating skyscraper design and construction technologies on an international basis aims to provide the preferred solution for a specific system design and/or construction technology/method problem that meets specified system characteristics; satisfies stakeholder performance requirements, goals, and expectations; improves the construction work environment and process characteristics; reduces environmental impact; and enhances the living environment of end-users.  This evaluation process involves application of three primary filters. Figure 3.1 shows an overview of these three filters with filter 2 being the central focus of this paper. The first filter screens all potential design and construction solutions for the problem at hand, in order to narrow the choices to feasible ones. The screening process is based on a bottom-up assessment using relevant sub-criteria checklists for both stakeholders’ acceptance and technical feasibility criteria. Sub-criteria are evaluated using a questionnaire and pass or fail answers; these answers are then used to determine the state value of each criterion as follows: if all answers on relevant sub-criteria pass, the criterion state value will be a pass. If just one criterion fails and cannot be resolved to become a pass, the criterion state will be a fail and the solution will be dismissed. Application of this filter helps to avoid a large commitment of resources to an  77 infeasible solution.  The second filter involves a detailed performance evaluation process for feasible solutions that passed the first filter, from the perspectives of design, quality, production, logistics, installation, and in-use. The function of this step is to eliminate solutions that fail to meet definite performance requirements and to rank successful filter 1 solutions in order of preference. For each perspective, a set of critical evaluation criteria has been identified and, for each criterion, a set of driving criteria that must be evaluated are used. The criteria states are defined based on the states of the lower level sub-criteria. In evaluating sub-criteria, a simple four-state evaluation scheme is employed: preferred (score of 3); acceptable (score of 2); least preferred (score of 1); and fail (score of 0), determined through a mapping of technical performance vs. rating values. Weighted performance values of criteria, perspectives, and solution are aggregated using sub-criteria scores. Details of the second filter and its application in practice are presented in this paper.  Figure 3-1 A framework for evaluating the skyscraper design and construction technologies The third filter focuses on evaluating the impact of solutions on quantitative monetary (NPV, LCC, etc.) and schedule performance values using a unified general project cash flow model and its detailed sub-models. These models are used to quantify incremental benefits of a solution to skyscraper delivery time and intermediate milestones, and various monetary measures. The models have been formulated to facilitate the formal treatment of risk. Particular emphasis has been placed on the treatment of time given its significant impact on both cost and revenue. A hierarchical linear planning model using high-level work packages captures the consequences of a solution for work packages and milestone dates, including project completion. The output of this model is transferred to other models to assess the impacts on skyscraper cash flow. Details of the models used and their application are treated in a separate paper.  3.3 Research methodology for development of the second filter Hudson and Ozanne (1988) and Tuli (2011) highlighted that research should have two perspectives: the ontological (nature of reality) and the epistemological (relationship between the researchers and reality). Based on the extensive literature review, the field of skyscraper construction lacks a carefully structured, general, and comprehensive tool for Feasible Solutions Focus of This Paper Candidate Skyscraper  Design and  Construction Solutions 1-Screening  3- Recommending  2- Ranking Ranked Solutions Most Solutions Preferred  78 evaluating the performance of feasible design and construction solutions across the building’s life-cycle. The reality of skyscraper construction includes large-scale and resource-rich projects that can source solutions from around the world. The design of such projects requires making a large number of decisions when selecting the building systems; and the consequences of poor decisions can be magnified by project scale.  To develop a performance evaluation tool necessary for assessing design and construction technologies tailored to the specific needs of skyscraper projects, the following questions need to be addressed. (1) What are the criteria and sub-criteria that need to be considered when evaluating the performance of design and construction solutions for buildings in general and skyscraper projects in particular? (2) What are the properties (e.g., structure, level of detail, measuring scales, criteria weighting, and methods of quantifying performance of sub-criteria, criteria, perspectives, and overall value for a solution) required for a performance evaluation tool capable of treating all life-cycle phases and a wide range of skyscraper solutions? (3) What is the information necessary for a performance evaluation of solutions about the skyscraper and local construction market and the solutions under consideration? (4) How can generality, comprehensiveness, usability, usefulness, and reliability of the developed tool be verified and validated?  Drawing on the previous work of Rosen and Bennett (1979), Lutz et al. (1990), Becker (2002), Ding (2005, 2008), and Chen et al. (2010a, 2010b), and using the principles of Dodgson et al. (2000) for a multi-criteria decision tool, the research methodology employed for development of the second filter involved several steps as shown in Figure 3-2, conducted in an iterative fashion as follows. The first step involved an extensive review of literature related to general building and skyscrapers.  The literature related to criteria and sub-criteria useful for assessing technical and sustainability performance, logistics, quality, project success, innovations diffusion, and production and installation methods in order to identify and prioritize a list of criteria and sub-criteria that should be used in performance evaluation of skyscraper design and construction solutions. Other literature related to properties of current performance evaluation tools in order to explore appropriate ways to develop a second filter.  The strengths found in the literature are utilized and the weaknesses are addressed in the tool described and relevant contributions of other researchers that have been incorporated are referenced as appropriate. The second step involved development of a hierarchical structure based on skyscraper life-cycle phases expressed from various perspectives (e.g., design, production, and quality), corresponding criteria and sub-criteria, and a weighting system for these levels.  Third, came development of a scoring system for evaluating sub-criteria including: measuring scales, a rating questionnaire, and four-state values.  A bottom-up approach for aggregating the sub-criteria scores was utilized to quantify the weighted values for criteria, perspectives, and overall performance of a solution. The fourth step was to define the required information related to local construction industry, skyscrapers, and design and construction solutions for the performance evaluation process. The fifth step involved validating and refining the evaluation tool through its applications to three case studies drawn from a mega skyscraper project. Adesola and Baines (2005) recommended several tests for verifying and validating measurement tools: feasibility—can the methodology be followed? usability—is the methodology workable and are the steps, tools, and techniques easy to use and apply? and usefulness—is the methodology worth following and does it produce helpful results? The three-case studies approach (Gerring, 2004) is used in an iterative way to test the tool’s completeness in terms of the criteria  79 considered and breadth of applicability, reliability, and ability to respond to a diverse range of design and construction decision problems.  The final step involved evaluating and refining the performance evaluation tool by seeking opinions from three experts to identify and contrast this tool against leading industry practices.  Figure 3-2 Research methodology of the second filter 3.4 Literature review The first phase in the comprehensive literature review focused on the performance evaluation literature in the context of skyscrapers and general buildings to identify, prioritize, and select relevant evaluation perspectives, criteria, and sub-criteria. Phase two included reviewing existing evaluation tool structures, ranking questionnaires, measurement scales, scoring systems, weighting strategies, calculation methods for overall weighted performance value, and tests to validate and verify performance tools to provide a superior foundation for the proposed evaluation tool.  Table 3-1 groups the literature review findings in seven sections (horizontal dimension of the table) from multiple performance perspectives. These groups are: G1, logistics; G2, quality; G3, sustainability; G4, evaluation frameworks for system solutions; G5, evaluation of prefabricated solutions versus traditional ones; G6, innovation diffusion criteria; and G7, evaluation tools for project success. The first column of this table contains the performance perspectives of interest, and relevant criteria and sub-criteria included in filter 2. Although many criteria and sub-criteria were treated in the references cited, only ones relating to the evaluation tool described herein are highlighted in Table 3-1. Literature groups related to logistics, quality, and sustainability were reviewed to identify potential evaluation criteria and sub-criteria.  Logistics: Jang et al. (2003) divided project logistics into supply logistics and site logistics. Supply logistics include all activities related to planning and coordination processes for getting procured items, raw material, and other applied resources to their required location. Site logistics incorporate all activities needed for facilitating the flow of physical elements such as materials, purchased parts, production tools, and equipment. Feld (2001), Ebel and Clausen (2007), and Sacks and Goldin (2007) added demobilization or reverse logistics that include disposal of installation structures Methodology for development of a technical performance evaluation tool for skyscraper design and construction technologies1- Select evaluation criteria, sub-criteria and properties 2- Develop hierarchical structure of perspectives, criteria and sub-criteria, and top-down weighting system 3- Develop sub-criteria questionnaire, measurement scales, and state values; develop  bottom-up method to calculate criterion, perspective and overall performance values4- Define inputs required for  the performance evaluation process5- Validate and refine the performance evaluation tool by applying it to several case studies6- Evaluate and refine the performance evaluation tool through interviews with construction professionals 80 and means, redundant material, and waste out from the project site after handing over a system. Quality: criteria used to evaluate solution quality include: quality of inputs, quality of outputs, and quality of the transformation process (Garvin, 1984; Arditi and Gunaydin, 1999; Tang et al., 2004; Zhang et al., 2006; Newton and Christian, 2006). Sustainability: criteria identified  include: safety, habitability, and sustainability (Foliente et al., 1998); structural serviceability and stability, fire and moisture safety, user health and safety, thermal and operational comfort, durability, and dimensional flexibility (Becker, 2002); environmental impact, quality, knowledge management, and technical assessment (Nelms et al., 2005, 2007); and minimization of resource usage and environmental impact (Ding, 2005, 2008; Chen et al., 2010a, 2010b).  A second set of literature related to performance evaluation criteria for building systems and project success criteria. Performance evaluation: criteria used to evaluate building system performance in general are: structural serviceability, fire safety, habitability, durability, practicality, compatibility, maintainability, and code acceptability (Rosen and Bennett, 1979; Lutz et al, 1990; Chew, 2003). Evaluation of prefabricated solutions: criteria used to evaluate a specific system and prefabricated innovation or to compare new and traditional systems include: health and safety, material usage efficiency and productivity, sustainability, and logistics (Gibb and Isack, 2003; Blismas et al., 2006; Nadim and Goulding, 2011); construction waste reduction (Jaillon and Poon, 2008; Baldwin et al., 2009; Jaillon et al., 2009); maintenance (Blismas and Wakefield 2009; Arif and Egbu, 2010); and design, production, and installation efficiencies (Jaillon and Poon, 2008; Baldwin et al., 2009; Li, 2011). Innovation diffusion: criteria used to assess diffusion of an innovation include: relative advantage, compatibility, complexity, trialability, and observability (Rogers, 1983); and location of the work, means of production, materials used, and system design (Toole, 2001). Project success: criteria included meeting user requirements, achieving the project’s purpose, and achieving quality requirements (Wateridge, 1998); positive appreciation of project users, contracting partners, and stakeholders (Chan et al., 2002; Westerveld, 2003); designer and contractor satisfaction (Elattar, 2009); and product success (Al-Tmeemy et al., 2011). Skyscraper performance: Chew (2003) classified skyscraper performance dimensions as: spatial performance, thermal performance, indoor air quality, acoustical performance, visual performance, and building integrity. Collins et al. (2008) highlighted that sustainability should be incorporated into the design stage of skyscraper projects and modern methods of manufacture and that off-site fabrication could contribute to sustainability benefits. Aminmansour and Moon (2010) urged that skyscraper systems’ integration, sustainability impact, quality, and operation and maintenance be taken into consideration at the design stage. Sacks and Partouche (2010) highlighted that logistics, system production methods, and quality are critical issues for the success of skyscraper projects.    81 Table 3-1 Sec. 1 of related literature to filter 2: perspectives, criteria and sub-criteria                 ReferencesPerspectives, criteria, and sub-criteria Feld (2001). Jang et al. (2003)Ebel and Clausen (2007) Shakantu et al. (2008)Garvin (1984)Arditi and Gunaydin (1998)Zang et al. (2006)Newton and Christian (2006)Tang et al. (2004)Foliente (1998)Becker (2002)Nano (2005)Gerdsri and Kocaoglu (2007) Nelms et al. (2005, 2007)Ding  (2005, 2007)Chen et al. (2010 A)Chen et al. (2010 B)Wateridge (1998)Chan et al. (2002)Westerveld (2003)Elattar (2009)Al-Tmeemy et al. (2011)Rosen and Bennett (1979)Lutz et al. (1990)Chew (2003) Gibb and Isack (2003)Blismas et al. (2006)Jaillon and Poon (2008)Jaillon et al. (2009)Blismas and Wakefield (2009)Arif and Egbu (2010)Li et al. (2011)Nadim and Goulding (2011)Rogers (1983)Toole (2001)Literature review groupsGroups descriptionsDesign perspective √ √ √ √ √ √Function √ √ √ √ √ √ √ √ √ √ √ √ √ √ √ √ √ √ √ √ √ √ √ √ √ √ √ √Water tightness √ √ √ √ √ √ √Air tightness √ √ √ √ √ √ √Acoustics √ √ √ √ √ √ √Daylight √ √ √ √ √ √ √Thermal resistance √ √ √ √ √ √Spatial connectivity √ √ √ √Fire safety √ √ √ √ √ √ √ √Fire resistance √ √ √ √Smoke development √ √ √ √Flame spread √ √ √ √Combustibility √ √ √ √ √ √ √Structural serviceability √ √ √ √ √ √ √ √ √ √ √ √ √ √ √ √ √ √ √ √ √ √ √ √ √Structural stability √ √ √ √ √ √ √Deformation resistance √ √ √ √ √ √Seismic and wind resistance √ √ √ √ √ √Compatibility with other systems √ √ √ √ √ √ √ √ √ √ √ √ √ √ √ √Jointing material √ √ √ √ √Coating material √ √Accommodation of internal finishes √ √Accommodation of MEP rough in √ √Impacts on other building systems √Useable floor area √ √ √ √ √ √Project aesthetics √ √Structural system √ √Enclosure system Electrical system Mechanical systemVertical transportationAesthetics √ √ √ √ √ √ √ √ √ √ √ √ √ √ √ √ √ √ √ √ √Unit shape and size √Joint location and size √Material nature and color √ √ √Quality perspective √ √Quality of inputs √ √ √ √ √ √ √ √ √ √ √ √ √ √ √ √ √Design inputs √ √Production inputs √Installation inputs √ √ √Quality of transformation processes √ √ √ √ √ √ √ √ √ √ √Design process √ √ √Production process √Installation process √ √ √Maintenance process √ √G 7Solutions evaluation toolsProj. toolsLogistics SustainabilityG 6G 5G 1 G 3 G 4G 2Quality 82 Table 3.1 Sec. 2 of related literature to filter 2: perspectives, criteria and sub-criteria                 ReferencesPerspectives, criteria, and sub-criteriaFeld (2001). Jang et al. (2003)Ebel and Clausen (2007) Shakantu et al. (2008)Garvin (1984)Arditi and Gunaydin (1998)Zang et al. (2006)Newton and Christian (2006)Tang et al. (2004)Foliente (1998)Becker (2002)Nano (2005)Gerdsri and Kocaoglu (2007) Nelms et al. (2005, 2007)Ding  (2005, 2007)Chen et al. (2010 A)Chen et al. (2010 B)Wateridge (1998)Chan et al. (2002)Westerveld (2003)Elattar (2009)Al-Tmeemy et al. (2011)Rosen and Bennett (1979)Lutz et al. (1990)Chew (2003) Gibb and Isack (2003)Blismas et al. (2006)Jaillon and Poon (2008)Jaillon et al. (2009)Blismas and Wakefield (2009)Arif and Egbu (2010)Li et al. (2011)Nadim and Goulding (2011)Rogers (1983)Toole (2001)Literature review groupsGroups descriptionsQuality of outputs √ √ √ √ √ √ √ √ √ √ √ √ √ √ √ √ √ √ √ √ √ √ √ √Design outputs √ √ √ √ √ √ √ √Production outputs √ √ √ √ √ √Installation outputs √ √ √ √ √ √ √ √ √ √Production perspective (non workface work) √ √ √ √ √ √ √Constructability √ √ √ √ √ √ √ √ √ √ √ √ √ √ √ √ √ √Component standardization √ √ √ √ √ √ √ √ √ √ √Scalability √ √ √Field tolerances √ √ √ √ √ √ √ √ √ √ √ √ √Jointing material √ √ √ √ √ √ √ √ √ √ √ √ √Jointing material with other systems √ √ √ √ √ √ √ √ √ √ √ √ √Production  environment √ √ √ √ √ √ √Production area √ √ √ √ √ √Storage area √ √ √ √ √ √Required workers skills √ √ √ √ √ √ √ √Safety hazard √ √ √ √ √ √ √ √ √ √Pollution generation √ √ √Production process characteristics √ √ √Technology origin √ √ √ √Production location √ √ √ √ √ √ √Production means √ √ √ √ √ √ √Off-situ production degree √ √ √ √ √ √Production wastage √ √ √ √ √ √ √ √ √ √ √ √Logistics perspective √ √Supply logistics √ √ √ √ √ √Management of information flow √ √ √ √ √Road constraints √ √ √ √ √ √Transportation means √ √ √ √ √ √ √ √ √ √Site inventory area √ √ √ √ √ √ √ √ √ √Site logistics √ √ √ √ √ √Site access requirement √ √ √ √ √ √ √Material handling times √ √ √ √ √ √ √ √ √ √ √ √ √Tower crane usage √ √ √ √ √ √ √ √In-situ workforce number √ √ √ √ √ √Demobilization logistics √ √ √Waste disposal √ √Rejected and unused items disposal √ √Temporary structures disposal √ √ √ √G 6 G 7Logistics Quality Sustainability Proj. tools Solutions evaluation toolsG 1 G 2 G 3 G 4 G 5 83 Table 3.1 Sec. 3 of related literature to filter 2: perspectives, criteria and sub-criteria                 ReferencesPerspectives, criteria, and sub-criteriaFeld (2001). Jang et al. (2003)Ebel and Clausen (2007) Shakantu et al. (2008)Garvin (1984)Arditi and Gunaydin (1998)Zang et al. (2006)Newton and Christian (2006)Tang et al. (2004)Foliente (1998)Becker (2002)Nano (2005)Gerdsri and Kocaoglu (2007) Nelms et al. (2005, 2007)Ding  (2005, 2007)Chen et al. (2010 A)Chen et al. (2010 B)Wateridge (1998)Chan et al. (2002)Westerveld (2003)Elattar (2009)Al-Tmeemy et al. (2011)Rosen and Bennett (1979)Lutz et al. (1990)Chew (2003) Gibb and Isack (2003)Blismas et al. (2006)Jaillon and Poon (2008)Jaillon et al. (2009)Blismas and Wakefield (2009)Arif and Egbu (2010)Li et al. (2011)Nadim and Goulding (2011)Rogers (1983)Toole (2001)Literature review groupsGroups descriptionsInstallation perspective (workface work) √ √ √ √ √Installation environment √ √Installation area √ √ √ √ √ √ √ √ √Safety hazard √ √ √ √ √ √ √ √ √ √ √Labor intensity at workface √ √ √ √ √ √ √ √ √ √ √ √Pollution generation √ √ √ √ √ √ √Installation process characteristics √Required labor skills √ √ √ √ √ √ √ √ √ √Installation means √ √Wet trades usage √ √ √ √ √ √ √ √ √Productivity √ √ √ √ √ √ √ √ √ √ √ √ √Material usage efficiency √ √ √ √ √ √ √ √ √ √Material origin √ √ √ √ √Material type √ √ √ √ √ √ √Systems design √ √ √ √ √ √ √System recyclability √ √ √ √ √In-use perspective √ √ √ √Durability √ √ √ √ √ √ √ √ √ √ √ √ √ √ √ √ √ √ √ √ √ √ √ √ √ √ √Wear resistance √ √ √ √Deterioration resistance √ √ √ √Corrosion resistance √ √Dimensional stability √ √ √ √ √Maintainability √ √ √ √ √ √ √ √ √ √ √ √ √ √ √ √ √ √ √ √ √ √ √ √ √ √Reliability √ √ √ √Service life √ √ √ √ √ √Maintenance cycle √Maintenance accessibility √ √Cleanability √ √ √Required labour skills √ √ √ √ √ √ √ √ √Maintenance material √ √ √ √ √ √ √ √ √Flexibility √ √ √ √ √ √Layout flexibility √ √ √ √ √ √Replaceability √ √Upgradeability √In-use impacts √ √ √ √Simplicity of use √ √In-door air quality impact √ √ √ √ √Energy use impact √ √ √ √ √ √Water use impact √ √ √ √ √Waste water impact √ √ √ √G 6 G 7Logistics Quality Sustainability Proj. tools Solutions evaluation toolsG 1 G 2 G 3 G 4 G 5 84 Structure of evaluation tool:  Toole (2001) divided building system performance into three sets: design performance, construction performance, and installed performance. Several researchers have used various ways to structure criteria and related sub-criteria to evaluate buildings or individual systems (Rosen and Bennett, 1979; Baetz and Korol, 1995; Foliente et al., 1998; Becker, 2002). Suwignjo et al. (2000) recommended using a hierarchical tree structure, with its clear representation for quantitative performance measurement systems, and employed a cause and effect method of relating criteria and sub-criteria.  Criteria-ranking questionnaires: Salam (1999) defined the questionnaire as a bridge between researchers and respondents, and highlighted that the accuracy and validity of data collected depend on the questions asked and how they are responded to. Rossi et al. (1983), Leung (2001), and Eiselen (2005) presented both open-ended and closed-ended questions and recommended using multiple-choice closed-ended questions for the following reasons: (1) they provide an appropriate means to obtain factual information and opinions that provide a high level of control to the questioner; (2) respondents are obliged to answer particular questions through choosing one of the answers with minimal effort; (3) this approach is less time-consuming for the interviewer, the participant, and the evaluator to complete and is therefore a cost-effective evaluation method; and (4) standard answers are easier to interpret, code, and analyze and a comprehensive way to derive an overall performance value. Alreck and Settle (1985) suggested that a large number of questions should be grouped into sections or sub-sections to simplify eliciting responses and analyzing results. Eiselen (2005) and Krosnick and Presser (2010) proposed the following rules for wording questions to avoid confusion and ambiguity: (a) use short and simple words; (b) seek only one piece of information at a time; (c) avoid negative questions; (d) use common terms and define any new one used; and (e) strive for wording that is specific and concrete.  Measurement scales, and type of measures: Dato et al. (2007) discussed four measurement scales as follows. First, a nominal scale is not really a scale because it simply labels objects and does not scale them along any dimension.  Second, an ordinal scale uses numbers to place objects in order, but these numbers contain no information regarding the differences (intervals) between points on the scale. Third, an interval scale is one in which intervals between objects are equal and the interval differences are meaningful, but ratio relationships cannot be defended. Fourth, a ratio scale has a natural origin, equal intervals, and meaningful order. Allen and Seaman (2007) discussed two types of sub-criteria state values: discrete—that have a relatively small set of possible individual values; and continuous—that can assume any value between the lowest and highest points on the scale. Lutz et al. (1990) used a three-state comparable scale: exceeds, equals, and less than, to compare building system performance with owner requirements.  Scaling, scoring, weighting and calculation methods for computing overall performance value: Chew and De Silva (2004) used three ranking state values: easy, moderate, and difficult, to evaluate the performance of building facades. Jacoby and Mattel (1971) and Lehmann and Hulbert (1972) emphasized that increasing the number of scale points reduces error as a benefit but may also increase costs of administration, non-response bias, and respondent fatigue. They recommended that a three-point scale is good enough for aggregating multi sub-criteria values to produce a value for a criterion. Krosnick and Presser (2010) identified four features for performance measure scales: (1) the points offered should cover the entire measurement continuum; (2) the scale points must appear to be ordinal, progressing  85 from one end of a continuum to the other; (3) the meaning of each point on the scale should be understandable; and (4) each scale point should have a unique interpretable value. Trochim (1999) defined scaling as transferring qualitative measurement to quantitative units. Tummala et al. (1997) recommended using an odd- numbered interval scale, as it has a midpoint. Lee et al. (2002) urged that weighting is the heart of all assessment schemes, as it will govern the overall performance score. Todd et al. (2001) recommended using the weights to reflect regional differences and stakeholders’ preferences. In terms of overall performance value calculation methods, Pugh (1991) proposed a method based on a qualitative evaluation of criteria with equal weight. Howe et al. (1986) suggested that Dominic’s method which is based on a qualitative evaluation of criteria using multi-state values and various importance levels, provides a good means for rating alternative solutions. Pahl et al. (1996) proposed a method that allows quantitative evaluation of alternatives using a large number of weighted criteria.  Based on the extensive literature search, it was concluded that existing performance evaluation tools lack generality in terms of applicability to a wide range of system solutions, a balance between simplicity and comprehensiveness, and completeness. Required is a tool capable of systematically evaluating the performance of design and construction solutions throughout a project’s life-cycle phases. Although useful contributions towards developing a comprehensive and versatile tool have been made by others, tools developed to date lack comprehensiveness with respect to the evaluation of one or more of the following performance dimensions and issues:  Design and in-use performance: the scale of skyscraper projects, coupled with their multifunctional nature and diverse sets of users, necessitates careful consideration of solution implications on other building systems and building function, aesthetics, durability, maintainability, and usability.  Production and installation performance: due to the very large consumption of resources in skyscraper projects, an evaluation tool should be able to assess different methods of production and installation such as on- and off- site production and local and international solutions in terms of constructability, material usage efficiency, and enhancement of the work environment.  Logistics performance: the supply and site logistics of permanent and temporary materials, in-process inventory, and applied resources, and the demobilization logistics of removing excess material and waste from the site are critical issues for skyscraper projects that need to be assessed in detail.   Quality performance: doing the right thing the first time is a crucial issue, especially in the skyscraper context, because of the high cost of re-work during construction and maintenance cost during the usage phase, necessitating the comprehensive assessment of inputs, transformation processes, and output quality across the life-cycle phases of a potential system solution.  Clarity of tool structure, detailed scaling system and justifiable method for determining an overall weighted performance value for a potential solution: due to the large number of evaluation criteria and sub-criteria employed to assess the performance of a given candidate solution, an evaluation tool should have a clear presentation structure, practical measuring scales, a reliable scoring system, and a meaningful calculation method for assessing overall performance value.    86 In summary, an intensive review of the literature and observation of practice revealed that currently there is no general and comprehensive performance evaluation tool suitable for assessing skyscraper design and construction technologies that responds to the needs of practising professionals. Valuable contributions from existing tools mainly arise with respect to the evaluation criteria and sub-criteria that should be considered when assessing the performance of design and construction solutions. Also, consideration of the literature related to the structure of evaluation tools, ranking questionnaires, measurement scales, scoring systems, weighting, and calculation methods for solution performance value facilitated selection of the best fit for the proposed evaluation tool. 3.5 Development details of the second filter To efficiently evaluate the performance of system solutions within skyscraper life-cycle phases, the developed tool should have the following features: (1) a bottom-up performance evaluation approach that examines the sub-criteria first to quantitatively measure their performance against required and preferable performance measures and then aggregates these values to calculate the relevant criteria, perspective, and overall solution performance values; (2) a method of assessing in detail the technical and sustainable performance in terms of designed function and impacts on other skyscraper systems; quality and logistics; production and installation; and in-use impacts; (3) generality, to treat a wide range of design and construction solutions including innovative ones that treat both on- and off-site work; (4) usability in terms of clarity of language and evaluation steps, ease of formulation and application, and outputs that are sufficiently accurate and logically justifiable; and (5) comprehensiveness in terms of the level of details used and the ability to assess solution life-cycle impacts on project life-cycle phases.  Second filter development steps address the following issues: the literature used to build a hierarchical tree structure of perspectives, criteria, and sub-criteria; a way to assign weights; a sub-criteria evaluation using a rating questionnaire, state values, measuring scales, and a scoring scheme; aggregation of sub-criteria measures using a bottom-up approach to compute relevant criteria, perspectives, and overall performance values; and a verification of the tool through its applications to multiple case studies and by construction professionals. The proposed model is meant to be used in the early design phase of the skyscraper to help the decision-maker rank the feasible solutions. The goal of this tool is to provide a better understanding and justification of the long-term performance consequences of solution selection decisions. Potential users include a knowledgeable client, designer, contractor, fabricator, or regulatory decision-maker who has local market experience, is familiar with the project context, and has access to material describing the features of feasible solutions. The developed tool is an extension to existing ones (Rosen and Bennett, 1979; Lutz et al., 1990; Chew, 2003; Becker, 2002; Nano, 2005; Nelms et al., 2005 and 2007). Developed second filter details are shown in Tables 3-2 and 3-3. Those details are discussed column by column in the following sections. 3.5.1 Hierarchical tree structure of perspectives, criteria, and sub-criteria  Drawing on the definition by Toole (2001), performance as used herein refers to all applicable physical characteristics of a skyscraper system/component from six perspectives: design, quality, production, logistics, installation, and in-use. These perspectives along with relevant criteria and sub-criteria have been extracted from the literature and are presented in Table 3-1. This Table is structured in the form of a four-level hierarchical tree. The first level corresponds  87 to the second filter goal of ranking the feasible solutions based on their overall weighted performance values. The second level is the six performance perspectives that, in turn, correspond to the life-cycle phases of a skyscraper.  The third level treats the criteria relevant to each level two perspective. The fourth level identifies the sub-criteria relevant to each level three criterion. The primary advantage of this structure is that it provides a practical and transparent means for calculating an overall performance value for each of the solutions being considered for the design/construction problem at hand.  Many challenges exist in structuring the second filter. One is the potential for an overlap of criteria amongst perspectives. To address this issue and avoid redundancy, a criterion and its related sub-criteria are assigned to the perspective to which it is most relevant. This requires a judgment as to which perspective will have the greatest impact on sub-criteria performance values. For example, constructability of the design extends over the perspectives of design, production, logistics, and installation. However, it has been assigned to the production perspective where its impact is the greatest. Another example involves the material usage efficiency criterion which is relevant to the design, production, and installation perspectives. It has been assigned to the installation perspective, as the evaluation can be completed only after solution installation. A second challenge arises in maintaining generality and flexibility. Prioritizing and selecting from a comprehensive list of 22 criteria and 94 sub-criteria may lead to a lengthy evaluation process. To solve this issue, not all perspectives/criteria/sub-criteria apply to each and every solution; hence, applicable criteria need to be identified by the evaluator and values estimated.  A third challenge is having sub-criteria that are applicable to only one of the feasible solutions. To address this problem, only sub-criteria applicable to all solutions under consideration are applied. The main reason for this is to avoid biased results by rewarding additional scores to one solution.  Drawing on the performance perspective definitions articulated by Toole (2001), the six evaluation perspectives of interest in our context are defined as follows. Design performance examines solution characteristics relevant to in-use functions, fire safety, structural serviceability, aesthetics, and compatibility with and impacts on other building systems. Production performance treats solution properties such as constructability, production environment, and production characteristics. Logistics performance refers to the characteristics relevant to the supply of material and equipment to the site, site mobilization, and reverse logistics (removal of equipment and material). Installation performance refers to the properties that affect installation environment, installation characteristics, and efficiency of material used. In-use performance refers to the characteristics relevant to end-user expectations that include durability, maintainability, flexibility, and impact on the living environment. Quality performance refers to quality assurance and control plans used for managing a solution’s life-cycle phases in terms of their inputs, transformation processes, and outputs, to achieve the performance objectives. Figure 3-3 depicts in compact form the perspectives, criteria, and sequence of application of the second filter of the evaluation framework. Not shown are the sub-criteria that expand on the criteria shown. Every perspective of the second filter has a role to play. For example, the quality perspective role examines the capabilities of the project team as well as those of the local construction industry for meeting production, installation, and maintenance objectives relevant to project life-cycle phases, namely design, production, logistics, installation, and  88 in-use. The quality perspective treats every phase of the solution’s life cycle as a process that has inputs, a transformation process, outputs, and control mechanisms and assesses whether or not quality requirements can be met throughout every life-cycle phase. The number of life-cycle phases of a solution depends on its production location; for example, if a solution is produced in-situ, this eliminates the off-site production phase. Relevant quality measures are based on quality assurance and control requirements, solution knowledge, temporary and permanent resources required, and required laboratory and field tests. Figure 3-4 reflects the quality perspective role across solution life-cycle processes in terms of managing input, output, and transformation processes.  Figure 3-3 Second filter perspectives, related criteria and their sequence of application Each perspective is defined using a set of criteria and every criterion has a set of sub-criteria for evaluating its performance. Principles for evaluating quality sub-criteria reflect the following four measures outlined by De Toni and Tonchia (2001): (1) produced quality that is represented by the number of defects during any life-cycle phase or in the warranty period; (2) perceived quality as regards customer satisfaction and the technical assistance service performance; (3) input (supply) quality, including the results of controls on certified and non-certified purchasing, and vendor quality rating; and (4) quality costs including the quality system costs and the amount of rework. For example, the sub-criterion, quality of design inputs, sets out quality control measures for design inputs in terms of owner briefing, applicable codes and regulations, tests of used material, solution knowledge, quality assurance and control requirements, inputs from other perspectives, quality of temporary and permanent resources, and required laboratory and field tests. Also, the sub-criterion, quality of design process, measures the capabilities of the local project design team in generating detailed design drawings and a quality assurance and control requirement to avoid redesign actions. The quality of maintenance process sub-criterion sets the standard for maintaining delivered solution quality in the usage phase, considering the capabilities of local operation and maintenance teams, required training, duration of the manufacturer’s warranty, used material, and the operation and maintenance manual. The quality of design outputs sub- 89 criterion measures the anticipated percentage of redesign costs due to incomplete details, errors, or defects. Utilizing the same principles, sub-criteria are assigned to evaluate quality management abilities in both the production and installation phases.   Figure 3-4 Quality perspective role of a solution across skyscraper life cycle phases 3.5.2 Relative weights for perspectives and criteria  In ranking alternative system solutions, consideration must be given to the weights of evaluating perspectives, criteria, and sub-criteria in order to reflect the values of the country involved, the skyscraper context, and the decision-maker’s values. Cole (1998) highlighted that the relative importance of performance evaluation criteria is a crucial part of the decision-making process and criteria weighting should be done to reflect project development objectives and context. Lee et al. (2002) stated that although there is no consensus-based approach or wholly satisfactory method to guide the assignment of weightings, weighting is at the heart of all assessment schemes. Thus, the question arises as to how best weight the different levels in the evaluation hierarchy. This topic is not a primary focus of the work described herein. Rather, a simple approach to weighting has been adopted—one that represents what is commonly done in practice—i.e., weights are elicited directly from those involved in the decision provided that one solution does not dominate all others for the criteria/sub-criteria considered. If there is no dominant solution, the weighting of sub-criteria, criteria, and/or perspectives is required. In that case, consideration should be given to carrying out a sensitivity analysis to assess the robustness of the ranking of solutions (Dodgson et al., 2000). The approach employed to define the relative weights for perspectives and criteria in the case studies is a procedure similar to that outlined in Pahl and Beitz (1996).  This method is transparent, practical, and compatible with the evaluation tree structure and allows for quantitative evaluation of alternatives using weighted factors. Figure 3-5 summarizes the process of calculating relative weights  90 for perspectives and criteria.  Relative weighting is a top-down approach and the sum of all relative weights for all factors equals one. For practicality and simplicity of the calculation process, sub-criteria weighting is excluded, in effect assigning the same weight to each criterion’s sub-criteria.  To clarify the weight calculation process, for illustrative purposes only, see the example shown in Figure 3-5. The relative weights are calculated based on the following assumptions: the weight of each perspective equals the division of the number of its criteria by the total number of all criteria (22) (this assumes that all criteria are relevant to the decision problem at hand), and the criteria related to each perspective are equally important. Based on these assumptions, design perspective has a weight of (0.27) that equals to six divided by 22 and similarly, other perspective weights are calculated: (0.14) for quality, logistics, production, and installation and (0.18) for in-use. Relative and local weights for each perspective are equal. The relative weight for each criterion equals the product of its local weight and relative weight of the perspective to which it belongs. As an example, the production perspective has three criteria. The local weight for each criterion is (0.33), equal to one divided by the total number of related criteria (3). Thus, the relative weight for each criterion is (0.046) which equals its local weight (0.33) multiplied by the relative weight of production perspective (0.14). Relative weights for other criteria can be similarly calculated.  Figure 3-5 Weights calculation example for evaluating perspectives, criteria and sub-criteria 3.5.3 Sub-criteria statuses  Sub-criteria have two statuses as treated in columns two and three of Table 3-2. The first classifies the sub-criteria as applicable or not applicable (Y/N) to the design/construction decision at hand. Numeric values that are given to this 0.27 0.23 0.14 0.14 0.14 0.14 0.14 0.14 0.14 0.14 0.18 0.180.045 0.33 0.045 0.33 0.045 0.33Level 4 Production areaStorage areaRequired workers skills Safety hazardPollution generationInstallation perspective In-use perspectiveAssumptions for this weight calculation example: weight of each perspective equals the division of number of its criteria by sum of all evaluation criteria (22 one), criteria related to each perspective are equally important and sub-criteria weightings are ignored for practicality and simplicity of the tool.Level 3Constructability Production environmentProduction characteristicsLevel 2Design perspectiveQuality perspectiveProduction perspective Logistics perspectiveLevel 1Overall performance weighted value for a solution Sum of relative weights for all evaluation levels equal one. Also, Sum of local weights of relevant evaluation factors at any level equal one.Relative weighting factor  = 1Local weighting factor = 1 91 status are (1/0). Applicable sub-criteria means that they are applicable to all solutions under consideration (not just a subset of them). The main reason for this is to avoid bias in the evaluation process. For example, when one of the solutions is built in-situ and the others are prefabricated, sub-criteria related to the production environment criterion are not applicable to all solutions and are therefore excluded. Although, those sub-criteria are not applied, the advantages of prefabricated solutions are reflected in the sub-criteria of installation perspective. This status enables an early selection of the applicable sub-criteria, which simplifies the evaluation process and narrows the focus of the evaluation team to the applicable ones. The second status classifies the sub-criteria as essential or not essential (Y/N) to the design/construction decision at hand. Numeric values that are given to this status are (1/0). Essential means that the sub-criterion must not receive a failing grade in terms of performance. This step works as a filter for eliminating solutions that do not achieve a minimum required performance threshold. The solution is dismissed when one of its sub-criteria has an essential value of (1) and performance score of (0). 3.5.4 Sub-criteria measuring scales, units, and types Measurement scale units and their type classifications are included in columns four and five of Table 3-2. Absolute scales based on an individual unit of measurement and a measurement scale are used. Three measurement scales are utilized to evaluate the sub-criteria: an ordinal scale for ranking qualitative values in order of preference from the highest to lowest, such as values of technology origin, production location, and production means; an interval scale used for ranking quantitative values such as jointing material life cycle, maintenance cycle, and warrantee period; and a ratio scale used for ranking quantitative values where percentages are required, such as material waste, tower crane usage, and off-site production degree. Two types of measurement units are used in the evaluation process: the majority is quantitative, Q, such as function and structural stability sub-criteria, and the minority is qualitative, q, such as quality of inputs sub-criteria. 3.5.5 Sub-criteria rating questionnaire The rating questionnaire for sub-criteria is included in column six of Table 3-2. To quantitatively evaluate the sub-criteria, a closed-ended questionnaire with defined answers of four-state values has been developed. Users are asked to choose one of these values. The advantages of this approach are that it is less time-consuming to complete and it is easy to compute overall value. Questions are affirmative and short, employ common design and construction terms, and are grouped for every criterion and perspective to simplify the evaluation process (Leung, 2001 Eiselen, 2005). The questions are used to rate the solution from highest to lowest by selecting one of the four ordered state values. Developed measurement scales and their measurement units are based on specific definitions for the four ordered state values using design thresholds, applicable codes, available test results, literature, and commonly used industry values.   92 Table 3-2 Sec. 1 of filter 2 perspectives, criteria, and sub-criteria  Column 1 C2 C3 C4 C5 C6 C7 C8 C9 C10Applicable? Essential? Preferred Acceptable Least preferred FailY/N (1/0) Y/N (1/0) Unit Type 3 2 1 0Design perspectiveFunctionWater tightness Tightness rating Q - water tightness rating. preferred acceptable least preferred failAir tightness Tightness rating Q - air tightness rating. preferred acceptable least preferred failAcoustics Acoustics rating Q - acoustics rating. preferred acceptable least preferred failDaylight Lighted area Q - daylight efficiency considering possible lighting area. preferred acceptable least preferred failThermal resistance U value Q - thermal resistance considering u value. preferred acceptable least preferred failSpatial connectivity Flexibility degree q - flexibility degree in doors and windows locations. preferred acceptable least preferred failFire safetyFire resistance Fire rating Q - fire resistance rating. preferred acceptable least preferred failSmoke development Development classification Q - smoke development classification. preferred acceptable least preferred failFlame spread Spread value Q - flame spread value. preferred acceptable least preferred failCombustibility Combustibility rating Q - combustibility rating. preferred acceptable least preferred failStructural serviceabilityStructural stability Stresses values Q - Tension, compression and shear stresses values. preferred acceptable least preferred failDeformation resistance Deflection value Q- acceptable deflection normal to system length value. preferred acceptable least preferred failSeismic and wind resistanceInterstory drift limit. Q - interstory drift limit. preferred acceptable least preferred failCompatibility with other systemsJointing material Life cycle/years Q- ability to receive and retain jointing material with other building systems considering joint service life in years.>25 25 - 10 <10 failCoating material Life cycle/years Q- ability to receive and retain coating material considering its service life in years.>25 25 - 10 <10 failAccommodation of internal finishes Accommodation% Q- ability to accommodate internal finishes. >60% 30% - 60% <30% failAccommodation of MEP rough in Accommodation% Q - ability to accommodate MEP rough in. >60% 30% - 60% <30% failImpacts on other building systemsUseable floor area Redesign need q - floor area used by the solution. no impact minor impact / no redesign minor redesign failProject aesthetics Redesign need q - project aesthetics considering colour, joint locations and material nature. no impactminor impact / no redesign minor redesign failStructural system Redesign need q - structural system considering solution dead load. no impactminor impact / no redesign minor redesign failEnclosure system Redesign need q- enclosure system considering connection details and transferred structural load.no impact minor impact / no redesign minor redesign failElectrical system Redesign need q - electrical system considering electrical load. no impactminor impact / no redesign minor redesign failMechanical system Redesign need q - mechanical system considering mechanical load. no impactminor impact / no redesign minor redesign failVertical transportation Redesign need q- vertical transportation systems considering impacts on internal finishes, transferred load and MEP.no impact minor impact / no redesign minor redesign failPlease rate the following function measures of the solution in terms of:Please rate the following fire safety measures of the solution in terms of:Please rate the following structural serviceability measures of the solution in terms of:Please rate the following compatibility measures with other building systems of the solution in terms of:Please rate solution impacts on the following systems in terms of redesign need assuming no time impact:Perspectives, criteria and sub-criteriaSub-criteria state values and scoresSub-criteria rating questionnaire and their measurement scalesUnits and types: (Q) quantitative/(q) qualitativeSub-criteria  status 93 Table 3-2 Sec. 2 of filter 2 perspectives, criteria, and sub-criteria  Column 1 C2 C3 C4 C5 C6 C7 C8 C9 C10Applicable? Essential? Preferred Acceptable Least preferred FailY/N (1/0) Y/N (1/0) Unit Type 3 2 1 0AestheticsUnit shape and size No. of options Q - unit shape and size. more than two two option one option failJoint location and size No. of options Q - joint location and size. more than two two option one option failMaterial nature and color No. of options Q - material nature and colour. more than two two option one option failQuality perspective   Quality of inputsDesign inputs Inputs quality q - quality of design inputs. high acceptable low failProduction inputs Inputs quality q - quality of production inputs. high acceptable low failInstallation inputs Inputs quality q - quality of installation inputs. high acceptable low failQuality of transformation processesDesign process Process quality q - quality of design process. high acceptable low failProduction process Process quality q - quality of production process. high acceptable low failInstallation process Process quality q - quality of installation process. high acceptable low failMaintenance process Process quality q- quality of maintenance process to keep the delivered quality. high acceptable low failQuality of outputsDesign outputs Redesign% Q - quality of design outputs. <5% 5% -10%  >10% failProduction outputs Remedial action% Q - quality of production outputs. <5% 5% -10%  >10% failInstallation outputs Remedial action% Q - quality of installation outputs. <5% 5% -10%  >10% failProduction perspective (non workface work)Constructability QComponent standardization Standardization% Q- percentage of component standardization. >60% 30% - 60% <30% failScalability Production volume Q - scalability of standardized components for mass production or purchase.use existing facility built factorygood purchase price failField tolerances Tolerances value Q - field tolerances value of the solution. high acceptable low failJointing material Material type q - type of jointing material between solution sub-systems. none dry material wet material failJointing material with other systems Material type q- type of jointing material between solution and other building systems. none dry material wet material failProduction environmentProduction area Production area Q - required production area considering cost/m2. minor acceptable high failStorage area Storage area Q - required storage area considering cost/m2. minor acceptable high failRequired workers skillsWorker classifications q- classifications of required production workers. unskilled trades skilled tradesspecialist technicians failSafety hazard Hazard degree q- safety hazard considering impact on work continuity of other production activities.no impactminor / other  activities could continueother activities must stop occasionally failPollution generation Pollution volume q- air, water and soil pollution considering impact on work continuity of other production activities.no impactminor / other  activities could continueother activities must stop occasionally failPlease rate the capabilities of project team and local construction industry for managing and producing the required quality inputs measures of the solution considering: quality assurance and control requirements, solution knowledge, quality of temporary and permanent resources and required laboratory and field tests in terms of:Please rate the capabilities of project team and local construction industry for managing the required transformation-process quality measures of the solution considering: quality assurance and control requirements, solution knowledge, quality of temporary and permanent resources and required laboratory and field tests in terms of:Please rate the following  output quality measures of the solution considering anticipated percentage of rework due to incomplete details, errors or defects in terms of:Please rate the following solution constructability measures in terms of:Please rate the following solution production environment measures in terms of:Perspectives, criteria and sub-criteriaSub-criteria  status Units and types: (Q) quantitative/(q) qualitative Sub-criteria rating questionnaire and their measurement scalesSub-criteria state values and scoresPlease rate the following aesthetics measures of the solution considering the number of available options and architectural match degree in terms of: 94 Table 3-2 Sec. 3 of filter 2 perspectives, criteria, and sub-criteria  Column 1 C2 C3 C4 C5 C6 C7 C8 C9 C10Applicable? Essential? Preferred Acceptable Least preferred FailY/N (1/0) Y/N (1/0) Unit Type 3 2 1 0Production process characteristicsTechnology origin Technology origin q - origin of production technology. local national international failProduction location In-situ to off site q - location of production process. on site & not in-situ off site in-situ failProduction means Machine usage degree Q - means used in production process.machine intensive40%-60% machine labour intensive failOff-situ production degree Production% Q - percentage of off-situ production. >60 % 30% - 60% <30% failProduction wastage Waste% Q - percentage of production waste. <5% 5% -10%  >10% failLogistics perspectiveSupply logisticsManagement of information flow Supplier origin q- management of information flow considering solution supplier. local national international failRoad constraints Roads regulation q- roads constraints considering allowable travel timings and associated safety requirements. no restriction specific travel timesspecific safety arrangements failTransportation means Means type Q - proposed means for transportation. light trucks heavy trucks special means failSite inventory area Inventory area Q - required site inventory area <90% 90%-110% >110% failSite logisticsSite access requirement Access requirement q- site access safety and lifting requirements. noneflag people neededspecial lifting requirement failMaterial handling times Handling times Q - site and in-situ handling times. one handling double handling three or more failTower crane usage Cranes usage% Q - usage percentage of tower crane for handling and installing the solution. none <50% ≥50% failIn-situ workforce number Worker number Q- number of in-situ workers considering type of installed structure.volumetric preassemblynon volumetric preassemblycomponent manufacture failDemobilization logisticsWaste disposal Waste% Q - percentage of installation waste to be disposed. <5% 5% -10%  >10% failRejected and unused items disposal Item% Q- percentage of rejected and unused items to be disposed. <5% 5% -10%  >10% failTemporary structures disposal Structure type q- type of in-situ temporary installation structures to be demobilized. mobile scaffold fixed scaffold other structures failInstallation perspective (workface work)Installation environmentInstallation area Installation area Q- required installation area considering impact on work continuity of other building systems.no impactminor / other  activities could continueother activities must stop occasionally failSafety hazard Hazard degree q- safety hazard considering impact on work continuity of other building systems.no impactminor / other  activities could continueother activities must stop occasionally failLabor intensity at workface Worker number Q- number of in-situ workers considering type of installed structure.volumetric preassemblynon volumetric preassemblycomponent manufacture failPollution generation Pollution volume q- air, water and soil pollution considering impact on work continuity of other building systems.no impactminor / other  activities could continueother activities must stop occasionally failPlease rate the following solution demobilization logistics measures in terms of:Please rate the following solution in-situ installation environment measures in terms of:Please rate the following solution site logistics measures in terms of:Please rate the following solution supply logistics measures in terms of:Please rate the following solution production process characteristic measures in terms of:Perspectives, criteria and sub-criteriaSub-criteria  status Units and types: (Q) quantitative/(q) qualitative Sub-criteria rating questionnaire and their measurement scalesSub-criteria state values and scores 95 Table 3-2 Sec. 4 of filter 2 perspectives, criteria, and sub-criteria  Column 1 C2 C3 C4 C5 C6 C7 C8 C9 C10Applicable? Essential? Preferred Acceptable Least preferred FailY/N (1/0) Y/N (1/0) Unit Type 3 2 1 0Installation process characteristicsRequired labor skills Workers classifications q- classifications of installation workers.unskilled trades skilled tradesspecialist technicians failInstallation means Means type Q - type of in-situ installation means. machine intensive40%-60% machine labour intensive failWet trades usage Usage% Q - percentage of wet trades usage. none <50% ≥50% failProductivity Structure types Q- productivity rate considering types of installed structures.volumetric preassemblynon volumetric preassemblycomponent manufacture failMaterial usage efficiencyMaterial origin Material origin q - origin of construction material. local national international failMaterial type Natural to engineered q - type of installation material. engineered mixed natural failSystems designNo. of engineering functions Q- number of engineering functions included in the design. three or more two systems one system failSystem recyclability Recyclability method q- material recyclability method at the end of service life using current available technologies.reuse recycle landfill failIn-use perspectiveDurabilityWear resistance Resistance value. Q - wear resistance value. preferred acceptable least preferred failDeterioration resistance Resistance value. Q - deterioration resistance value. preferred acceptable least preferred failCorrosion resistance Resistance value. Q - corrosion resistance value. preferred acceptable least preferred failDimensional stabilityStrengths/stresses values Q- dimensional stability resistance value  considering swelling and shrinkage impacts.preferred acceptable least preferred failMaintainabilityReliability Warrantee period Q - manufactory warrantee period in years. >10 5 -10 <5 failService life Life/years Q - system service life in years. >50 50 - 25 <25 failMaintenance cycle Cycle / years Q - maintenance cycle of components and sub-systems in years. >10 5 -10 <5 failMaintenance accessibility Ease of access q - maintenance accessibility ways. direct access access panel/s custom access failCleanability Ease of cleaning q - ease of cleaning considering used means. hand tools light machinesheavy machines failRequired labour skillsWorkers classification q- classifications of maintenance workers.unskilled trades skilled tradesspecialist technicians failMaintenance material Supplier origin q - origin of maintenance material. local national international failFlexibilityLayout flexibility Flexibility degree q - architectural layout flexibility degree. flexiblechangeable with minor costinflexible failReplaceability Ease degree q - ease of replacement considering dismantling method.dismantle with no costdismantle with minor costneed demolition failUpgradeability Ease degree q - ease of components and sub-systems upgrading considering used method. add sectionschange sections custom upgrade failIn-use impactsSimplicity of use Difficulty degree q - difficulty degree of solution use.  easy acceptable need a catalogue failIn-door air quality impact Air quality Q- indoor air quality considering fresh air changing rate. no impactminor impact / no redesign minor redesign failEnergy use impact Consumption rate Q - energy consumption rate. no impact minor impact / no redesign minor redesign failWater use impact Consumption rate. Q - water consumption rate. no impact minor impact / no redesign minor redesign failWaste water impact Discharge rate. Q - waste water discharge rate. no impactminor impact / no redesign minor redesign failPerspectives, criteria and sub-criteriaSub-criteria  status Units and types: (Q) quantitative/(q) Sub-criteria rating questionnaire and their measurement scalesSub-criteria state values and scoresPlease rate the following solution material usage efficiency measures in terms of:Please rate the following durability measures of the solution in terms of:Please rate the following solution maintainability measures in terms of:Please rate the following solution flexibility measures in terms of:Please rate the following solution in-use impact measures in terms of:Please rate the following solution in-situ installation process characteristics measures in terms of: 96 3.5.6 Sub-criteria state values and scores Sub-criteria state values and scores are shown in columns seven, eight, nine, and ten of Table 3-2. State values of sub-criteria are quantified using four-state scores: three for preferred, two for acceptable, one for least preferred, and zero for fail. Preferred means that the solution performance falls within the highest possible range of technical performance. Acceptable means that the score of the preferred solution falls in the mid-range of technical performance. Least preferred means that the solution performance equals the least acceptable range of performance. Fail means that the solution fails to meet the minimum threshold of performance required for a sub-criterion, which may or may not be essential. Performance thresholds are defined by the designer, code or regulatory requirements, and/or the client. Fail, as a grade, is applicable only to certain types of sub-criteria (i.e. non-negotiable or must have) that must pass the definite performance thresholds such as function and fire safety sub-criteria. For example, the material usage efficiency sub-criterion has no fail state value. Dismissal of a solution occurs when a sub-criterion has an essential value of (1) and performance score of (0). When a non-essential (i.e. good to have) sub-criterion fails to pass the definite performance threshold, the solution will receive a score of zero. The aim of the scoring scheme as shown in Figures 3-6 and 3-7 is to use dimensionless values, which allow scoring of individual measures to get a meaningful total overall one. Thus, a transformation from a state value definition relevant to a specific sub-criterion to a non-dimensional value must be made. Sub-criteria state values are expressed in terms of a measurement scale and measurement units. Sub-criteria can have continuous or discrete state values with ascending or descending ranges. Figures 3-6 and 3-7 show an example of each. The scoring system involves the use of two axes: the vertical one (the transformed sub-criterion state value) has four non-dimensional score values (0, 1, 2, 3) while the horizontal one treats sub-criterion values in terms of the most relevant quantitative measurement units. As an example of a sub-criterion whose performance is measured in a continuous manner, the service life sub-criterion has three relative state values. The preferred option is the best performance on the horizontal scale, accorded a score of three, which means that the solution service life is more than 50 years. An acceptable option, accorded a score of two, means that the solution service life is between 25 and 50 years. The least preferred option, accorded a score of one, means that the solution service life is less than 25 years. A solution is accorded a zero score if it failed to meet the required service life (e.g., 15 years). A solution with a long service life is preferred as it requires less rehabilitation. Examples of sub-criteria whose performances are measured using discrete scales are the ones related to their impact on other building system criteria. Those are scored based on the need for redesign as follows: preferred option, accorded a score of three—reflects no impact on other building systems; acceptable option, accorded a score of two—implies minor impact without the need for redesign; least preferred option, accorded a score of one—reflects the need for a minor redesign; and fail option, accorded a score of zero—implies the need for a major redesign.  Sub-criteria state values vs. score are shown in Table 3-3 for 12 sub-criteria related to four criteria. These examples reflect development principles, analysis details, and challenges of the proposed quantitative evaluation of choices for a skyscraper system design or construction technology decision. The procedure of evaluating every criterion means that each sub-criterion performance is defined in terms of its measurement scale, unit of measurement, four-state scores, and score evaluation. Examples cited reflect the case study project examined later. As a specific example, evaluation principles of the material usage efficiency criterion and its corresponding sub-criteria are as follows. In our  97 context, material usage efficiency is defined drawing on the work of Longman (2011) and Neely et al. (1995) to mean building a solution as specified using a minimum amount of raw materials, utilizing local material to the maximum, generating the minimum waste, and planning for maximum recyclability of materials at the end of service life.  In terms of sub-criteria evaluation, the material origin sub-criterion is measured based on a preference for local material because of its sustainability benefits—provided that it is cheaper and is of the same quality or better than imported materials. State values for this sub-criterion are: local material is preferred, national material is acceptable, international material is least preferred; there is no fail state value assigned to this sub-criterion. The sub-criterion of material type is measured based on a preference for using engineered materials because of their consistent properties, better performance, and lower cost (Toole, 2001), provided that natural material is not specified as a required solution.  State values specified for this sub-criterion are: engineered materials are preferred, natural material is least preferred, their mix will be acceptable; no fail state value is assigned to this sub-criterion. The systems design sub-criterion is measured based on a preference for maximizing the number of engineering functions incorporated into a solution, as this may offer cost, time, performance, or quality advantages.  For example, structural insulated partitions integrate building structure and insulation subsystems. Engineering functions refer to structural, thermodynamics, fluid dynamics, or material science functions served (Toole, 2001). State values developed for this sub-criterion are: three or more engineering functions are preferred, two are acceptable, one is least preferred; no fail state value is assigned to this sub-criterion. The system recyclability sub-criterion is measured based on a preference for minimizing the environmental impact of a solution through the ability to recycle a solution’s material at the end of its service life using currently available technology. State values for this sub-criterion are: re-use is preferred, recycle is acceptable, landfill disposal is least preferred; no fail state value is assigned to this sub-criterion. Napier (2011) defined these options as follows: re-use is the subsequent use of a material, product, or component upon salvage; recycle is introducing a material into some process for remanufacture into a new product; landfill disposal is depositing materials in a solid waste disposal facility.   Figure 3-6 Scales with continuous values  Figure 3-7 Scales with discrete values 3.5.7 Bottom-up approach for aggregating criteria, perspectives, and solutions’ weighted values  The second filter goal is to rank the feasible design and construction solutions that passed the first filter on the basis of their overall weighted performance values. A bottom-up approach is utilized to calculate these values using the  98 properties shown in Table 3-2 as follows: (1) Prerequisite information for the evaluation process that is relevant to feasible solutions, a skyscraper, stakeholders, and the local construction market as discussed in the next section needs to be identified. (2) Based on the nature of the decision problems, applicable sub-criteria are selected in column C2 and related sub-criteria are accorded values of one. (3) Relevant sub-criteria are classified as essential or not using column C3. Essential sub-criteria are accorded values of one and all others get a value of zero. (4) Sub-criteria performances are computed using the defined state values and are then mapped using the four non-dimensional scoring values described earlier. All solutions that fail to meet the definite performance threshold for the essential sub-criteria are eliminated in this step. (5) For solutions that passed the previous step, scores of the applicable sub-criteria are quantified as set out in Tables 3-2 and 3-3. Criteria scores are the total sum of their applicable sub-criteria as shown in Table 3-5. (6) Test for dominance or near dominance should be done for all criteria scores of alternative solutions.  If one choice fails to dominate all others, then relative weights need to be assigned to the assessing perspectives and criteria by the evaluating team as detailed in Figure 3-5. (7) Criteria weighted values are computed as the product of their relative weights and scores; perspectives weighted values as the sum of their criteria weighted values; and solution overall weighted performance value as the sum of its criteria weighted values. These calculations are detailed in Table 6. (8) The same process is repeated for every feasible solution and solutions are ranked in order of preference. It should be noted that the solution most preferred at the filter 2 level is not necessarily the solution that will ultimately be selected. The most preferred solution is identified at the filter 3 level when monetary, time, and risk performance is assessed in conjunction with technical performance. 3.5.8 Prerequisite information for the performance evaluation of feasible solutions To apply the second filter, related information about system solutions, skyscrapers, stakeholders, and the local construction market is required as follows: (1) a list of feasible system solutions that passed the first filter and their life-cycle performance information; (2) design thresholds and applicable local codes and regulations; (3) stakeholders’ preferred performance objectives and aesthetics; (4) skyscraper characteristics and scope—such as building height, number of floors, and building shape—to figure out the intensity of work activities and solution scope; (5) skyscraper site advantages and constraints, such as location in a busy area, availability and capacity of cranes, and availability of production and storage areas; and (6) local construction industry features such as infrastructure, quality and safety standards, transportation capacities and regulations, and current production facilities and technologies. The function of this step is to define the performance values for applicable sub-criteria for each solution across skyscraper life-cycle phases as set out in Tables 2 and 3.   99 Table 3-3 Sec. 1 of state values analysis for a sample of criteria and sub-criteria on three sections   100 Table 3-3 Sec. 2 of state values analysis for a sample of criteria and sub-criteria   101 Table 3-3 Sec. 3 of state values analysis for a sample of criteria and sub-criteria   102 Table 3-4 Feasible solutions for the three case studies of Abraj Al-Bait Project systems  3.6 Applications of the second filter to three case studies The Abraj Al-Bait project is a monumental skyscraper located in Makkah, Saudi Arabia. This project is a design, build, operate, and transfer skyscraper complex that consists of a 17-floor podium topped by seven skyscrapers ranging in height from 240 m to 601 m, and houses hotels and condominiums. The building holds and has broken several world construction records including: the tallest hotel in the world, the tallest clock tower in the world, and the world’s largest clock face. This project has the world’s largest building floor area of some 1,500,000 m2, and was, at least temporarily, the second tallest building in the world as of its 2012 completion, surpassed only by Dubai’s Burj Khalifa. The project, with a capital cost of $US 15 billion (Wainwright, 2012) can host 100,000 people. A phased construction plan started in 2002 and the project was completed in 2012. The three case studies were selected within this project and provided an opportunity to assess the evaluation tool’s ability to rank the feasible solutions that passed filter one. These three case studies are for building wet areas (washrooms and bathrooms), internal partitions, and cladding systems. A detailed description of these feasible solutions is provided in AboMoslim and Russell (2014). Table 3-4 includes only a summary of these solutions. Case study Solutions DescriptionBlock, plaster& in-situfinishesAlthough, this solution has cultural acceptance in the ArabianGulf Area; it has many disadvantages that include: built in-situusing wet activities; long duration for curing, testing, andcommissioning; low productivity rates; labor intensive;significant work and storage space requirements; high materialwaste; high safety hazard; and, difficult logistics terms for liftingmaterials, equipment, tools and human resources to theworkface.Concrete PodsConcrete Pods are fully prefabricated and internally finishedwashrooms/bathrooms. This solution offers many advantagessuch as: moisture resistance; fire resistance; sound proofing;high quality; high productivity; potential cost and time saving;efficient use of raw materials with no in-situ waste; simplelogistics; and, minimal site manpower and in-situ work scope.Block &plasterThe properties of this solution are as described for theconstruction of wet areas case study.AcotecAcotec involves the use of prefabricated hollow core concretewall panels. This system solution has many advantages: highinstallation rate; moisture resistance; fire resistance; soundresistance; time and cost savings; efficient use of raw materials;and, easy logistics.Stone facedcast in-situconcrete wallsAlthough this solution has gained cultural acceptance in theArabian Gulf Area; it has many disadvantages: built in-situusing wet activities; low production rates; long curing periods;labor intensive; difficult logistics; high waste; heavy self-weight; and, high safety hazard due to the need to work atsignificant heights outside of the building.Upgraded precast systemThis solution offers many advantages: high quality; moistureresistance; fire resistance; soundproofing; material usageefficiency; and, time and cost savings. The main disadvantageof this system is its heavy self-weight.Construction of wet areasConstruction of internalpartitionsConstruction of cladding 103 The professionals working on the Abraj Al-Bait project, assisted by the first author, completed the performance evaluation analysis and calculation. For evaluating the performance of these case studies solutions and to mirror what happened in the actual project, the relative weights of perspectives and criteria were assigned assuming equal importance for all evaluating criteria and calculated using an approach similar to the example shown in Figure 3-6. Although the systems functions for the three case studies are different, the same relative weights are used for simplicity of calculation. 3.6.1 Case study 1: ranking feasible solutions for wet area construction The two potential solutions for building wet areas that successfully passed filter 1 are block and plaster and in-situ finish (the traditional method), and concrete pods (Pods) which involve the off-site production of finished wet area units. The steps for applying the second filter to these solutions, as set out in Tables 3-2 and 3-3, included the following. First, the applicable sub-criteria were selected and accorded values of one (refer to column 2 in Table 3-5) as follows. Given that wet areas are internal systems, sub-criteria relating to the external environmental performance evaluation, such as aesthetics sub-criteria, were excluded. Also, sub-criteria not applicable to any one of the solutions were excluded. For example, production environment sub-criteria are applicable only to Pods as a prefabricated system and not applicable to the block and plaster system; therefore, those sub-criteria were excluded. Essential sub-criteria were defined and accorded values of one (refer to column 3 in Table 3-5) related to criteria of function, fire safety, structural serviceability, compatibility with other systems, constructability, durability, and maintainability. The performance values of all essential sub-criteria passed the definite thresholds such as achieving the requirement of a two-hour fire rating for the fire escape path and a service life of over 50 years.  To assess the scores of sub-criteria, ranking questions were answered by selecting one of the defined state values that represents solution characteristics.  For example, supply logistics sub-criteria scores for both solutions were analyzed as follows: (1) management of information flow scores—the traditional solution, locally available, was assigned a score of three; Pods as a new international solution was assigned a score of one; (2) road constraints scores—the traditional solution with no road restrictions was assigned a score of three and Pods with a requirement for specific safety and traffic arrangements was assigned a score of one; (3) transportation means scores—the traditional solution with usage of light trucks was assigned a score of three and Pods which requires the usage of heavy trucks was assigned a score of two; and (4) site inventory area scores—the traditional solution as an acceptable value was assigned a score of two and Pods which requires less storage area was assigned a score of three. The scores for the supply logistics sub-criteria are 11 for the traditional method and seven for Pods—based on this criterion alone, the traditional method is preferred over the innovative solution. Table 3-3 provides more examples as to how sub-criteria scores are assessed. Presented in Table 3-5 are the criteria and sub-criteria scores for the two feasible solutions examined for building wet areas. All applicable sub-criteria that are non-essential and did not pass the definite thresholds were accorded values of zero.   104 Table 3-5 Scores of perspectives, criteria and sub-criteria for wet areas solutions   Appli-cable?Essen-tial?Traditional solutionConcrete PodsDesign perspectiveFunction 5 7Water tightness 1 1 2 3Air tightness 1 1 2 3Acoustics 0Daylight 0Thermal resistance 0Spatial connectivity 1 1 1 1Fire safety 9 10Fire resistance 1 1 1 2Smoke development 1 1 3 3Flame spread 1 1 3 3Combustibility 1 1 2 2Structural serviceability 6 9Structural stability 1 1 2 3Deformation resistance 1 1 2 3Seismic and wind resistance 1 1 2 3Compatibility with other systems 7 11Jointing material 1 1 3 3Coating material 1 1 2 2Accommodation of internal finishes 1 1 1 3Accommodation of MEP rough in1 1 1 3Impacts on other building systems 11 15Useable floor area 1 1 2 3Project aesthetics 1 1 3 3Structural system 1 1 2 3Enclosure system 0Electrical system 1 1 2 3Mechanical system 1 1 2 3Vertical transportation 0Aesthetics 2 3Unit shape and size 0Joint location and size 0Material nature and color 1 1 2 3Quality perspectiveQuality of inputs 6 8Design inputs 1 0 2 2Production inputs 1 0 2 3Installation inputs 1 0 2 3Transformation processes 8 11Design process 1 0 2 2Production process 1 0 2 3Installation process 1 0 2 3Maintenance process 1 0 2 3Quality of outputs 6 8Design outputs 1 0 2 2Production outputs 1 0 2 3Installation outputs 1 0 2 3Production perspectiveConstructability 6 14Component standardization 1 0 1 3Scalability 1 0 1 3Field tolerances 1 0 2 3Jointing material 1 0 1 3Jointing material with other systems1 0 1 2Production environment 0 0Production area 0Storage area 0Required workers skills 0Safety hazard 0Pollution generation 0Perspectives, criteria and sub-criteriaCriteria/Subs scoresSub-criteria statusAppli-cable?Essen-tial?Traditional solutionConcrete PodsProduction process characteristics6 8Technology origin 1 0 3 1Production location 1 0 1 2Production means 1 0 1 2Off-situ production degree 1 0 1 3Production wastage 0Logistics perspectiveSupply logistics 11 7Management of information flow1 0 3 1Road constraints 1 0 3 1Transportation means 1 0 3 2Site inventory area 1 0 2 3Site logistics 7 10Site access requirement 1 0 3 1Material handling times 1 0 1 3Tower crane usage 1 0 1 3In-situ workforce number 1 0 2 3Demobilization logistics 4 9Waste disposal 1 0 1 3Rejected and unused items disposal1 0 1 3Temporary structures disposal 1 0 2 3Installation perspectiveInstallation environment 7 12Installation area 1 0 1 3Safety hazard 1 0 2 3Labor intensity at workface 1 0 2 3Pollution generation 1 0 2 3Installation process characteristics5 10Required labor skills 1 0 2 2Installation means 1 0 1 2Wet trades usage 1 0 1 3Productivity 1 0 1 3Material usage efficiency 6 10Material origin 1 0 3 3Material type 1 0 1 3Systems design 1 0 1 3System recyclability 1 0 1 1In-use perspectiveDurability 8 12Wear resistance 1 1 2 3Deterioration resistance 1 1 2 3Corrosion resistance 1 1 2 3Dimensional stability 1 1 2 3Maintainability 16 17Reliability 1 1 2 2Service life 1 1 2 3Maintenance cycle 1 1 2 2Maintenance accessibility 1 1 2 2Cleanability 1 0 3 3Required labour skills 1 0 2 2Maintenance material 1 0 3 3Flexibility 4 4Layout flexibility 1 0 1 1Replaceability 1 0 1 1Upgradeability 1 0 2 2In-use impacts 10 11Simplicity of use 1 0 2 2In-door air quality impact 1 0 2 3Energy use impact 1 0 2 2Water use impact 1 0 2 2Waste water impact 1 0 2 2Perspectives, criteria and sub-criteriaSub-criteria status Solutions' scores 105 A summary of criteria scores and the calculation of weighted perspective values and overall performance value for both wet area solutions are presented in Table 3-6. Although one solution dominates in the majority of the criteria scores, weights were assigned as discussed in Figure 3-5 and used to demonstrate the usability of the weighting system. The scoring for each of the evaluation perspectives for Pods resulted in relatively higher values than for traditional methods. The highest differential scores are in the perspectives of design, installation, production, and logistics. Reasons for this include the fact that Pods represents a design and construction technology that offers many benefits: less in-situ work, less waste, less site and reverse logistics, and a high productivity rate, high safety standards, and good quality. On the other hand, Pods has disadvantages including difficult supply logistics, as pods require special transportation means and road safety arrangements; complicated site logistics, as they require special lifting and safety arrangements, and the fact that their heavy self-weight precludes their use for larger public washrooms. Despite these disadvantages, as seen from the results in Table 3-6 the Pods solution dominated the traditional solution for most of the applicable criteria, and thus for each perspective, rendering moot the issue of weighting. 3.6.2 Case study 2: ranking feasible solutions of internal partitions construction The two feasible solutions for building internal partitions are the traditional method of block and plaster, and Acotec, which is partially prefabricated panel. Steps involved in applying the second filter to rank the partition solutions from filter 1 included the following. The applicable sub-criteria were selected and accorded values of one as described. Given that partitions are an internal system, sub-criteria related to in-use energy, water, and waste water impacts were excluded. Also, sub-criteria such as production environment, applicable to only one of the solutions, were excluded. The production environment sub-criteria are applicable only to Acotec as a prefabricated system and not to a block and plaster system; therefore, those sub-criteria were excluded. Essential sub-criteria were defined and accorded values of one that relate to criteria of function, fire safety, structural serviceability, compatibility with other systems, constructability, durability, and maintainability. The performance values of all essential sub-criteria such as structural serviceability and durability passed the performance thresholds. For assessing the scores of the sub-criteria, the questions posed in Table 3-2 were answered by selecting the one defined state value that best described the solution’s characteristics. For example, site logistics sub-criteria scores for both solutions are analyzed as follow: (1) site access requirement scores–the traditional solution with no safety requirements received a score of three, and Acotec with a requirement for flag people received a score of two; (2) material handling time scores— the traditional solution with multiple handling received a score of one, and Acotec with one time handling received a score of three; (3) tower crane usage scores are two for both solutions as they use the tower crane for less than 50% of the time for handling and installation; and (4) in-situ workforce number scores—the traditional solution of a component manufactured concrete block system received a score of one and Acotec as a non-volumetric pre-assembly system received a score of two. Additional examples of sub-criteria score evaluation are included in Table 3-3. All applicable sub-criteria that were non-essential and failed to pass the required performance thresholds were accorded values of zero.   106 Table 3-6 Calculation of overall weighted performance values for wet areas solutions  Only a summary of criteria scores and the calculation of weighted perspective values and overall performance values of these solutions are presented in Table 3-7 due to space constraints. Although Acotec performance trumped performance of the traditional method (i.e. greater than or equal) for all but two criteria, weights were assigned as discussed in Figure 3-5 and used to demonstrate usability of the weighting system. The values for all perspectives of the Acotec solution were higher than for the traditional solution.  The greatest differences lay in the perspectives of design, installation, production, and in-use. This occurred largely because the use of Acotec panels involves less in-situ work, waste, and site and reverse logistics and offers a higher productivity rate, safety standard, quality, and durability. The Acotec solution’s main disadvantages are that when the partition height passes 3.5 m, they need to be built using 14 cm thick Acotec panels in two layers with special connecting details; 14 cm thick Acotec panels must be used to build walls with a two-hour fire rating requirement, such as fire escape pathways, regardless of the height of the partitions; and Acotec cannot be used for building small enclosed areas like mechanical shafts.  Criteria CriteriaCriteria Total Criteria Persp. scores Criteria Persp. scores Criteria Persp.Design perspective 1.00 0.273 1.82 2.50 0.68Function 0.167 0.0455 5 0.23 7 0.32Fire safety 0.167 0.0455 9 0.41 10 0.45Structural serviceability 0.167 0.0455 6 0.27 9 0.41Compatibility with other systems 0.167 0.0455 7 0.32 11 0.50Impacts on other building systems 0.167 0.0455 11 0.50 15 0.68Aesthetics 0.167 0.0455 2 0.09 3 0.14Design perspective total 1.00 0.136 0.91 1.23 0.32Quality of inputs 0.333 0.0455 6 0.27 8 0.36Transformation processes 0.333 0.0455 8 0.36 11 0.50Design outputs 0.333 0.0455 6 0.27 8 0.36Quality perspective total 1.00 0.136 0.55 1.00 0.45Constructability 0.333 0.0455 6 0.27 14 0.64Production environment 0.333 0.0455 0 0.00 0 0.00Production process characteristics 0.333 0.0455 6 0.27 8 0.36Quality perspective 1.00 0.136 1.00 1.18 0.18Supply logistics 0.333 0.0455 11 0.50 7 0.32Site logistics 0.333 0.0455 7 0.32 10 0.45Demobilization logistics 0.333 0.0455 4 0.18 9 0.41Quality perspective 1.00 0.136 0.82 1.45 0.64Installation environment 0.333 0.0455 7 0.32 12 0.55Installation process characteristics 0.333 0.0455 5 0.23 10 0.45Material usage efficiency 0.333 0.0455 6 0.27 10 0.45Installation perspective total 1.00 0.182 1.73 2.00 0.27Durability 0.250 0.0455 8 0.36 12 0.55Maintainability 0.250 0.0455 16 0.73 17 0.77Flexibility 0.250 0.0455 4 0.18 4 0.18In-use impacts 0.250 0.0455 10 0.45 11 0.506.82 9.36 2.552 1Rank of feasible solutionsOverall weighted performance values for feasible solutionsWet areas feasible solutionsTraditional methodWeighted values Weighted valuesPodsPerspective differencesWeightsRelative weightsLocal weightsCriteria 107 Table 3-7 Calculation of overall weighted performance values for internal partition solutions  3.6.3 Case study 3: ranking feasible solutions for exterior enclosure construction The two feasible solutions for the building exterior enclosure were a stone-faced cast-in-situ wall or upgraded fully finished precast panels. The steps in applying the second filter to this decision problem were similar to those applied for the other case studies. In the case at hand, because the cladding system is an external system, all criteria related to the external environmental performance evaluation are included. Sub-criteria not applicable to any one of the solutions are excluded, such as production environment sub-criteria. Essential sub-criteria were defined and accorded values of one. They relate to the criteria of function, fire safety, structural serviceability, compatibility with other systems, constructability, durability, and maintainability. Assessing sub-criteria scores once again requires response to the questions in Table 3-2. For example, the installation process characteristic sub-criteria scores for both solutions are analyzed as follows: (1) required labour skills scores—a value of two was assigned for both solutions as they each use skilled trades; (2) installation means scores—the traditional solution which involves intensive usage of labour was assigned a score of one and precast panels which involve intensive machine usage were assigned a score of three; (3) Criteria CriteriaCriteria Total Criteria Persp. scores Criteria Persp. scores Criteria Persp.Design perspective 1.00 0.273 1.91 2.50 0.59Function 0.167 0.0455 3 0.14 4 0.18Fire safety 0.167 0.0455 9 0.41 10 0.45Structural serviceability 0.167 0.0455 6 0.27 9 0.41Compatibility with other systems 0.167 0.0455 7 0.32 9 0.41Impacts on other building systems 0.167 0.0455 15 0.68 21 0.95Aesthetics 0.167 0.0455 2 0.09 2 0.09Quality perspective 1.00 0.136 0.91 1.23 0.32Quality of inputs 0.333 0.0455 6 0.27 8 0.36Transformation processes 0.333 0.0455 8 0.36 11 0.50Design outputs 0.333 0.0455 6 0.27 8 0.36Production perspective 1.00 0.136 0.55 0.95 0.41Constructability 0.333 0.0455 6 0.27 13 0.59Production environment 0.333 0.0455 0 0.00 0 0.00Production process characteristics 0.333 0.0455 6 0.27 8 0.36Logistics perspective 1.00 0.136 0.95 1.05 0.09Supply logistics 0.333 0.0455 10 0.45 8 0.36Site logistics 0.333 0.0455 7 0.32 9 0.41Demobilization logistics 0.333 0.0455 4 0.18 6 0.27Installation perspective 1.00 0.136 0.82 1.27 0.45Installation environment 0.333 0.0455 7 0.32 11 0.50Installation process characteristics 0.333 0.0455 5 0.23 8 0.36Material usage efficiency 0.333 0.0455 6 0.27 9 0.41In-use perspective 1.00 0.182 1.36 1.55 0.18Durability 0.250 0.0455 8 0.36 11 0.50Maintainability 0.250 0.0455 17 0.77 17 0.77Flexibility 0.250 0.0455 4 0.18 3 0.14In-use impacts 0.250 0.0455 1 0.05 3 0.146.50 8.55 2.052 1Overall weighted performance values for feasible solutionsRank of feasible solutionsPerspective differencesLocal weights Relative weights Weighted values Weighted valuesCriteriaWeightsInternal partitions feasible solutionsTraditional method Acotec 108 wet trades usage scores—the traditional solution with more than 50% usage received a score of one and precast panels with no usage of wet trades received a score of three; and (4) productivity scores—the traditional solution built of manufactured concrete block components received a score of one, and precast panels that are non-volumetric preassembly received a score of two. Additional examples of sub-criteria score evaluation are included in Table 3-3. The performance values of all essential sub-criteria passed the required technical performance thresholds. As seen from Table 3-8, the enhanced precast panel solution dominates for all criteria examined except one. Hence, weights were not applied at the criterion and perspective levels.  Only a summary of the second filter application to the external cladding solutions is provided in Table 3-8 due to space constraints. The perspectives providing the greatest difference in performance are design, installation, production, and quality. This is primarily because the upgraded precast panels involve less in-situ work, waste, and site and reverse logistics, and have a high productivity rate, safety standard, and quality. The main disadvantage of the precast panel solution is its heavy self-weight that has an impact on the size of supporting structural elements.  Table 3-8 Calculation of overall weighted performance values for cladding solutions   Criteria Perpectives Criteria PerpectivesDesign perspective 46 62Function 11 15Fire safety 9 10Structural serviceability 6 9Compatibility with other systems 7 11Impacts on other building systems 11 15Aesthetics 2 2Quality perspective 20 28Quality of inputs 6 8Transformation processes 8 11Design outputs 6 9Production perspective 12 24Constructability 6 14Production environment 0 0Production process characteristics 6 10Logistics perspective 21 27Supply logistics 11 9Site logistics 7 9Demobilization logistics 3 9Installation perspective 18 32Installation environment 7 12Installation process characteristics 5 10Material usage efficiency 6 10In-use perspective 32 38Durability 8 12Maintainability 15 16Flexibility 3 3In-use impacts 6 7Overall solution performance scoreRank of feasible solutions 2 1149 211Enhanced Precast scoreTraditional method scoresPerspective and Criteria 109 3.6.4 Discussion of second filter application results for the examined case studies The application of filter 2 to the three case studies drawn from a major skyscraper project has helped to validate its comprehensiveness, generality, and usability as a performance evaluation tool for skyscraper design and construction solutions. These case studies span external and internal solutions and different kinds of preassembled solutions: volumetric preassembly, non-volumetric preassembly, and component manufacture. The ranking of the solutions examined using filter 2 mirrored that of the actual decision-making on the case study project. The breadth of coverage of the evaluation tool in terms of six primary performance perspectives—22 criteria within these perspectives, and 92 sub-criteria defining the criteria—provides transparent performance information about the solutions.  Ease of use and practicality are achieved through the use of standard state values and a scoring system that simplifies the calculation of an overall performance value. Two types of performance measures were used in the evaluation process: qualitative—judgmental, and quantitative—objective. Scores within solutions for a specific design or construction problem are relative to that problem only—they do not reflect an absolute measurement that can be used to demonstrate the level of achievement of “applicability” in solutions for other design or construction problems. Note that filter 2 does not treat NPV, cost (capital or life-cycle), time or risk performance, but rather just various dimensions of “technical” performance. What it provides is a ranking of feasible solutions, and an indication of the relative technical superiority of one solution over another. This provides guidance as to which solutions should receive priority attention in filter three, where quantitative analysis is conducted on the performance dimensions of NPV, capital and life-cycle cost, time, and risk.  If Pods is more expensive than the traditional system, the latter may be used instead of Pods, depending on the explicit or implicit weighting of technical performance against cost, time, or risk performance. 3.7 Assessment of the performance evaluation tool by three practising professionals Three interviews with construction professionals helped to ensure that the performance evaluation tool provides a structured and comprehensive approach to assessing design and construction alternatives in a manner that is compatible with industry practices.  The practitioners interviewed were: (a) a professional engineer with 29 years of experience who works as a project director for a major skyscraper project in Saudi Arabia; (b) a professional engineer and senior cladding systems specialist with 35 years of experience who works for an international design firm in Vancouver, Canada; and (c) an associate architect with 24 years of experience who works for an international architecture firm in Vancouver, Canada. Each interview lasted approximately two hours and was conducted in two stages. First, an overview of the three-step framework for evaluating skyscraper design and construction technologies was presented, with the main focus being on performance evaluation details (i.e. filter 2). Second, the interviewees were asked four questions: (1) What are the most important criteria to consider when evaluating the performance of various solutions for skyscraper systems? (2) What personal experience have they had in evaluating building systems in general and skyscraper projects in particular? (3) What feedback could they offer about the performance evaluation tool in terms of the contents of its three levels (perspective, criteria, sub-criteria) with regard to completeness, the approach to scoring at the sub-criteria level, and determination, including the weighting of the overall value of a solution? and, (4) Would use of the approach described be a significant improvement over the decision-making process  110 currently used, and why? The responses of the three professionals interviewed are described below. 3.7.1 First practising professional’s feedback The project director indicated that functionality, aesthetics, durability, logistics, production and construction methods, in-situ scope of work, compatibility with and impact on other building systems, productivity, and quality are the most important criteria to be considered in evaluating design and construction solutions for skyscraper projects. The director had personal experience in evaluating the performance of building solutions when evaluating cladding systems for a 40-floor skyscraper project in Saudi Arabia. The solutions under consideration were: in-situ built block walls and finishing versus precast panels. The first option was the locally preferred one and the second the prefabricated one that offered time, cost, and other performance benefits. Two groups of evaluating criteria were considered. The critical group included functionality, durability, compatibility with and impact on other building systems, and quality. The non-critical group included production and construction methods, aesthetics, and usage impact. Weights were assigned by giving more weight to the critical criteria. The main reasons for the use of weighting arose from the limited workforce, required labour skills, and difficult logistics terms. Despite the disadvantages associated with the use of precast panels—namely concrete insert brackets quality management issues, complex logistics due to the project location in a downtown area, and heavy self-weight of the panels—this solution was ranked higher than the traditional solution. A major problem with the traditional solution was the in-situ scope of work for external finishing. With respect to the performance evaluation tool, the director stated that the list of evaluation criteria is holistic and the hierarchical structure helps with understanding the approach.  Also, the use of closed-ended questions with three possible scores is practical and renders the approach feasible in terms of time and cost. The director emphasized the importance of being able to assign weights for perspectives and criteria as this would help to illustrate their degree of importance to the project stakeholders. Finally, he suggested that once the third filter was completed, the evaluation framework would simplify the decision-making process for evaluating the skyscraper design and construction solutions. 3.7.2 Second practising professional’s feedback The cladding specialist emphasized that, in North America, individual firms are hired to provide professional services related to architecture, structural design, code interpretation and compliance advice, enclosure design, and so on, making the decision process for selecting design and construction technology different from that in the Middle East.  For example, the cladding solution screening step is done by the architect, considering the needs of the various stakeholders, including the developer, marketing company, and end-users. The architect then forwards his or her shortlist of solutions to the specialist enclosure consultant for detailed technical performance evaluation and to the contractor and/or the project manager for evaluating production and construction methods. Based on the architect’s evaluation, the consultant advises the architect of his or her technical preference rating for final decision-making by the architect and the client. In terms of criteria that need to be considered as part of the technical performance evaluation of skyscraper cladding systems, he stated that function, structural serviceability, seismic resistance in terms of inter-story drift limit, durability, compatibility with and impact on other building systems, and quality are the primary decision criteria in evaluating technical performance, in addition to construction time and capital cost. Speaking from personal experience in performance evaluation, he evaluated a new glass curtain wall system  111 manufactured in China for a high-rise building in Vancouver. Assessment of quality performance was based on reviewing and approving the following issues: system characteristics should meet or exceed all code requirements; standard technical detail drawings; factory inputs, transformation process steps, and produced products; and a full system mock up sample should pass the required tests. A follow-up step required that after system installation on site, the required field tests were performed to measure the actual installed quality. Durability of the system was evaluated according to the CSA S478-95 (R2007) standard; a key criterion is the existence of a match between system, subsystem, and component service lives and maintenance and rehabilitation cycles. Function, fire safety, and structural serviceability are measured against required performance thresholds. Evaluation of production and construction methods is done by the project manager. With respect to his feedback regarding the performance evaluation tool, he concurred with the hierarchical structure of perspectives, criteria, and sub-criteria and stated that this structure provided a comprehensive list of evaluation criteria. He indicated that the use of closed-ended questions with four scoring values would be efficient to use in terms of time and cost. He also emphasized the importance of using weights, as this will impart the importance of evaluation criteria to the project stakeholders. He stated that the evaluation team assigns weights considering design constraints, project context, and stakeholders’ needs. In his opinion, no standard performance evaluation tool currently exists; at present, decisions are made on a case-by- case basis with no standard evaluation template employed. For large-scale skyscraper projects, he believes that a need exists for such a tool to assist construction professionals in ranking alternative solutions, as the consequences of an incorrect decision can be a major cost.  3.7.3 Third practising professional’s feedback The architect advised that sustainability, functionality, structural stability, aesthetics, fire safety, building integrity, durability, maintainability, and end-user preferences are the most important criteria to be considered in evaluating the performance of skyscraper solutions. In terms of personal experience in evaluating new technologies, she has evaluated many solutions for large-scale low-rise projects. She stated that sustainability needs to be considered in skyscraper projects as they consume a huge amount of material. As there are many new sustainable solutions, she recommended utilizing innovations from a reliable source, as this would contribute to better service after installation, such as training of staff, availability of maintenance material, and technical support. She also highlighted that available solutions are narrowed down by the architect to feasible options, based on an initial evaluation of function efficiency, life-cycle cost, procurement lead time, construction time, and acceptance by the project stakeholders. Detailed performance evaluation is done by specialist consultants. Evaluation of time, life-cycle cost, and associated risk is done by a cost consultant and a project manager. In terms of specific feedback about the framework, she agreed with the gradual evaluation steps, as they mirror what takes place in reality. She also emphasized the importance of evaluating the impact of new technologies on overall project performance, cost, time, and associated risks. She indicated that the steps involved in the performance evaluation are understandable and can be readily applied. She stated that due to the scale of skyscraper projects such a framework with detailed screening and performance evaluation steps is required and when the third step is completed it will provide a comprehensive and systematic tool for the decision-maker.   112 3.8 Conclusion The work described in the paper represents the second step in the development of an assessment framework for skyscraper design and construction solutions and technologies, especially innovative or novel ones. The proposed framework divides the evaluation process into the application of three primary filters. The first filter screens these potential solutions on the basis of their local feasibility and project stakeholder acceptance (AboMoslim and Russell, 2014).  The second filter eliminates any solution that failed to meet essential technical performance thresholds, and ranks the balance of the feasible solutions that passed the filter on the basis of their technical performance evaluation. The third filter assesses the preferred options from filter 2 based on a quantitative assessment of solution NPV, capital and life-cycle cost, project delivery time, and risk.   The objective guiding the development of the second filter was to create a comprehensive tool for assessing the technical performance of skyscraper system solutions that is applicable to a wide range of building systems and components and the off-site and in-situ processes used to produce them. The need for such a tool was observed from a comprehensive review of the literature, discussion with practitioners, and observation of decision-making processes in practice. The structure and content of the tool benefited greatly from a significant number of valuable contributions from previous researchers. An intensive and extensive review of the literature helped to identify a definitive list of technical performance perspectives, criteria, and sub-criteria, with the resulting three-level hierarchy facilitating the task of identifying performance dimensions relevant to the decision task at hand. This list is seen as a significant contribution of the work.  The literature also contributed in terms of how to express questions and value responses at the sub-criterion level. Closed-ended questions were used, along with a four-state value scoring system mapped onto performance achievement levels relevant to the sub-criterion being evaluated (e.g., fire safety rating). Allowance was made for a weighting system at the criteria and perspectives levels of the evaluation hierarchy. However, it is emphasized that prior to invoking a particular weighting approach, consideration should be given to the potential dominance of one solution over all others for the decision problem at hand—this avoids any difficulties that can arise from assigning specific weights. If weighting of criteria and or perspectives is required, then consideration should be given to carrying out a sensitivity analysis in order to assess the robustness of the ranking of solutions. Two actions were pursued for validating the tool in terms of its completeness, practicality/acceptance, and ease of use. First, it was applied to three case studies drawn from a recently completed skyscraper project in Saudi Arabia. These case studies dealt with, respectively, design choices for washroom facilities, internal partitioning, and cladding systems. In each of the case studies, filter 2 captured all relevant technical performance, and the scoring and resultant ranking of solutions mirrored the final choices made for the actual project. Second, the completeness and usefulness of the second filter were assessed through three interviews with senior design and construction professionals. Findings from these interviews and the case studies provide support for the evaluation framework. The novelty of the developed performance evaluation approach lies in its holistic list of treated criteria and sub-criteria, four-state values defined to answer the ranking questions, an elimination scheme for solutions that fail to achieve essential technical performance threshold, a quantification method used for performance evaluation, and its applicability to a wide range of design and construction decision solutions.   113 Future work required for filter 2 includes further testing as to the completeness of criteria, possible refinement of the scoring system at the sub-criterion level, additional work on weighting schema, and additional testing on an even broader range of decision problems in terms of system design solutions and selection of construction technologies and methods. About the third filter, work is in progress on the development of a set of aggregated time and cost (capital, life- cycle) models, inclusive of the treatment of revenue opportunities, cost of financing, inflation, and currency exchange rates which can be integrated into a single quantitative performance model for the economic and risk evaluation of the preferred system solutions from filter 2.  Results from the application of this model in combination with results from filter 2 will provide the basis for the final choice of a preferred solution for the decision problem at hand.     114 Chapter 4 Evaluating Impacts of System’s Solutions on Skyscraper Cash Flow Streams and Their Timelines3 4.1 Introduction  Skyscrapers are very large and complex engineering projects that can be characterized by several features. First, they require large scale investment over long design and construction durations (Watts et al., 2007), which may involve two or more economic cycles with significant exposure to changing inflation, interest, and exchange rates. Second, the mixed-use aspect of such projects leads to multiple intermediate milestones of partial occupancy prior to overall project completion. The speed with which the skyscraper projects) are delivered, including attainment of intermediate milestones, can have a considerable impact on capital expenditures because of the effects of inflation and financing costs, as well as potential revenues and returns on total and equity capital. Third, skyscrapers are characterized by the significant repetition of elements/components for both the vertical and horizontal dimensions of a project (Shaked and Warszawski, 1995), which can on one hand create economies of scale and open up totally new solutions, and on the other hand, require very costly temporary facilities infrastructure. Fourth, a limited in-situ work area creates many challenges in accessing the work-face (Watts et al., 2007) including the utilization of specialized transportation arrangements and means. Fifth, skyscrapers require massive amounts of human, material, and equipment resources and involve the design and construction of both complex conventional and innovative systems which in turn involve the sourcing of technical expertise, material, and equipment from around the globe.  Finally, such projects have very long operating lives with significant operating and maintenance (O&M) and rehabilitation costs (Ali and Armstrong, 2008).  The cost and revenue streams of a project’s life cycle cash flow model can generally be divided into four interrelated phases: capital expenditure, operation and maintenance (O&M), revenue, and financing (Abdel-Aziz and Russell, 2006). Each phase has its own properties (time and logic) and estimation methods. Capital expenditures include direct and indirect costs for systems and subsystems and require treatment of exchange and inflation rates as appropriate, along with some consideration of risk. Direct costs include design, procurement, construction, and testing and commissioning (T&C). Indirect costs include project management, legal, insurance, and general conditions requirements. Operation expenditures include costs for energy, water, security, and other services. Maintenance costs cover ongoing expenditures to keep a project fit for the purpose for which it was built. Disposal expenditures cover costs of dismantling or demolishing and/or recycling a project at the end of its service life. Revenue streams include sales and/or rent/lease values for its commercial, retail, residential, hospitality, etc., functions.  Finance and equity streams include treatment of the funds required for capital expenditures involved, as well as debt servicing streams. The choice of alternative system solutions vis à vis baseline design affects project cash flow stream values and their                                                           3 A version of this chapter is ready for submission to a journal.  115 timing, as follows. The design, production, logistics, installation, and O&M costs for an alternative system solution may differ from a base case system. The costs of other baseline systems may be impacted (both positively and negatively) due to the need for redesign and changes to interfacing details. The design and/or construction duration impact of an alternative system solution could lead to early or late completion of one or more project milestones, which could in turn affect revenues and associated O&M expenditures, financing costs, and other direct and indirect capital costs.  To illustrate the foregoing, consider substitution of a glass curtain wall for a traditional built in-situ block wall and marble finishes cladding. Dead loads associated with the traditional cladding solution are significantly heavier than those associated with a glass curtain wall. Using a glass curtain wall allows the structural system to be redesigned to reflect the reduced dead loads. Further, the interfaces between the structural system and glass curtain wall system will be changed. As the production rate and associated productivity for installing the glass curtain wall system is higher than for the traditional cladding solution, earlier completion of the project may be possible, leading to lowered financing and inflation costs and earlier revenues.  In addition, O&M costs for a curtain wall solution are significantly less than those for a traditional system. Given the availability of many design and construction solutions for building systems, the need exists for development of quantitative evaluation models that are able to measure the impacts of these solutions on capital expenditures, O&M costs, revenues, and financing cash flow streams, in terms of both magnitude and timing. 4.2 Evaluation framework  As discussed in chapters 1, 2, and 3, the proposed evaluation framework for assessing alternative design and construction solutions for systems and components of skyscraper projects involves the application of a three-filter assessment process. As discussed in chapter 2, the first filter is used to screen alternative solutions using a comprehensive checklist of stakeholder acceptance and local feasibility criteria/sub-criteria on a pass-fail basis in order to eliminate the solutions that do not fit with local cultural norms, delivery capabilities, etc. As discussed in chapter 3, the second filter treats criteria related to design, quality, production, logistics, installation, and in-use details for assessing the technical performance of the first filter survivors in order to rank them. The third filter, the focus of this chapter, evaluates the financial performance of a skyscraper over the project life cycle given specific design and construction building system/component choices, and involves treatment of all major cash flow streams (revenues and expenditures) and their timings. Figure 4-1 highlights the characteristics of the evaluation framework and the focus of this chapter.  Challenges in development of models relevant to the third filter include the following. They must be able to represent the scale of investment and complex geometric configuration associated with a skyscraper project. They should have sufficient granularity to handle and justify the range of decision trade-offs involved in selecting building system/component solutions including: capital vs. life cycle costs; direct costs vs. contractor indirect costs and client oversight costs; current dollar cost vs. costs inclusive of financing and potential exchange rate issues; and capital cost inclusive of financing costs vs. earlier receipt of revenue. Models used need to be general, complete, and integrated with each other to allow for the interchange of data.  Performance metrics of interest should correspond to the  116 client/developer perspective, which is the most inclusive perspective. These include scope, time, cash flow, and net present value, both in absolute terms and relative to the current baseline solution. Other perspectives (e.g., contractor) can be treated using a subset of these metrics. Not considered herein is the probabilistic treatment of these metrics, which permits the assessment of risk associated with particular design and construction choices. The treatment of time as a function of system/component choices made is a significant focus in this chapter, as it underpins the structuring of a project’s cash flow representation and the treatment of costs and revenues and any associated trade-offs over the project life cycle.  The third filter incorporates the following integrated set of models: project product models that include a breakdown structure of physical components and their description in terms of a project’s physical parameters describing scale and spatial context; project process models that include work package activities, their sequencing, and their association with product/physical elements; and a cash flow model that covers all phases of a project’s life cycle.  Attention is directed at determining the properties of these models in terms of required generality, completeness, granularity, and interrelationships. Given that filters one and two determine whether an alternative design/construction process is compliant with all technical, regulatory and stakeholder concerns, the choice of a preferred alternative/strategy could be made solely on economic grounds. Alternatively, a weighted multi-criteria evaluation approach could be adopted, especially for cases where the preferred technical solution differs from the compliant best economic solution. This dimension of decision-making is not addressed herein.   Figure 4-1 Framework for evaluating skyscrapers systems’ solutions 4.3 Research methodology Development of cash flow, product, and process models involved several steps. First, an extensive literature review was conducted in the contexts of building projects in general and skyscrapers in particular in an iterative manner on  Solutions Feasible Most Preferred Solutions First Filter Second Filter  Third Filter  First Filter Categories Stakeholder acceptance Local technical feasibility Second Filter Perspectives Design                  Quality Production            Logistics Installation           In-use Third Filter Models Project cash flow model Product models Process models  Focus of This Paper Candidate Skyscraper  Design and  Construction Solutions Screening Recommending  Ranking Ranked Solutions  117 the topics of life cycle cash flow, cost, physical, spatial, elemental, and process models and their properties for both overall project and system levels. The strengths and weaknesses of the related literature were identified and relevant contributions of other researchers (e.g., Lutz et al., 1990; Dell’Isola and Kirk, 1995; Navon, 1995; and Goosen, 2008) incorporated, as appropriate, to formulate the evaluation models and define their properties. Second, general product model scope statements were formulated in terms of physical characteristics inclusive of a hierarchical elemental structure for building systems that comprise a skyscraper project with a mapping onto related work package activities (design / build facility / production / logistics / installation / testing and commissioning (T &C)), and O&M and revenue streams. The function of these statements is to define the required evaluation data and the scope of work for cash flow and process models.  Third, a general project cash flow model was developed which links expenditure and revenue cash flow streams as a function of design, construction, finance, O&M, and revenue generation strategies. The main purpose of this model is to facilitate computation of the difference in net present value between a revised model (i.e. alternative system/component choices) and a base model. Fourth, process models, with emphasis on a flexible time model comprised of major work packages and their constituents, were developed. The function of the time model is to define the delivery milestones and timing and durations of design and construction activities for the cash flow model. Fifth, the responsiveness of the product and time models was assessed through their application to five case studies of a skyscraper project located in Saudi Arabia. The time model is emphasized as it is one of the main determinants of the consequences of an alternative system choice on project performance. Figure 4-2 summarizes the steps of the research methodology. Finally, the developed models were discussed in depth with knowledgeable construction professionals and the received feedback was incorporated resulting in enhanced models’ properties.  Figure 4-2 Research methodology of third filter  118 4.4 Literature review  The literature reviewed in the contexts of general buildings and skyscraper projects focused mainly on project cash flow models, system life cycle cost, physical and elemental classification structures, process (time) models at both the project and building system levels, and the model development process. Researchers have used different levels of detail for both systems and project cash flow and life cycle models. Existing project models are based on: land purchase cost, design and construction cost, finance, revenue, operation cost, and salvage value (Russell and Ranasinghe, 1991); owning, operating, maintaining, and disposal costs (Fuller and Petersen, 1995); capital expenditure, operation and maintenance cost, revenue, and financing (Abdel-Aziz and Russell, 2006); initial and rehabilitation costs (Shohet and Laufer, 1996); and investment and replacement costs, resale value at the end of service life, annual and non-annual O&M costs, and energy costs (Schade, 2007). Current evaluation models for system solutions are based on supply and installation capital costs (Toole, 2001) and usage costs in terms of maintenance and energy (Lutz et al., 1990), energy and water costs and disposal cost (Nelms et al., 2005&2007), and rehabilitation cost (Shohet and Laufer, 1996). Asiedu and Gu (1998) used a bottom-up approach to derive a system cost from its sub-system costs. For estimation of sub-system costs, Park et al. (2005) used labor, temporary and permanent materials and equipment, temporary structures, support infrastructure, and indirect costs. In terms of economic measures, net present value and internal rate of return are commonly used for evaluating project alternatives (Schade, 2007; Blank and Tarquin, 2007), but in practice, net present value is arguably the most widely used measure for project appraisal (Graham and Harvey, 2001; Sandahl and Sjo, 2003; Remmers, 2004; Schade, 2007; Jiménez and Pascual, 2008). Worldwide, many standard elemental structures for buildings in general have been developed (Marshall and Charette (1999)). In the United States, UNIFORMAT II describes a building in terms of foundations, substructure, superstructure, exterior enclosure, roofing, interior construction, conveying systems, mechanical and electrical systems, general conditions and profit, equipment, and site work. In the United Kingdom, the Royal Institution of Chartered Quantity Surveyors describes a building in terms of substructure, superstructure, internal finishes, fittings and furniture, services, and external works. In Canada, the Canadian Institute of Quantity Surveyors classifies the systems of a building as substructure, structure, exterior enclosure, partitions and doors, finishes, fittings and equipment, mechanical, electrical, site work, and ancillary work. In Europe, the elemental format of the International Council of Building Research Studies and Documentation and Construction Economics describes a building using 30 divisions. The Construction Specifications Institute (CSI) MasterFormat TM (1995) is composed of 16 primary divisions for describing a building project: general requirements, site construction, concrete, masonry, metals, wood and plastics, thermal and moisture protection, doors and windows, finishes, specialties, equipment, furnishings, special construction, conveying systems, mechanical, and electrical. Various researchers have used different parameters to describe the scope of work of a building.  Meyer and Burns (1999) utilized function, size, foundation type, exterior closure materials, roof type and material, number of floors, functional space, and utility systems. Chan and Kumaraswamy (1999) used set-up works, piling, pile caps, and rafts including excavation and shoring, superstructure, electrical and mechanical services, finishes, and exterior wall type.  119 Later, Chan and Kumaraswamy (2002) used the number of levels above ground, gross floor area per level, structural frame type, foundation type (shallow or deep), building function, construction cost, and gross volume. Lowe et al. (2006) employed envelope type, building function, gross floor area, total height, quality, shape complexity, number of storeys above ground, number of storeys below ground, and structural system type. Lee et al. (2011) used building height, number of floors, typical floor area, typical core area, rentable floor area, gross floor area, building usage, floor height, hotel area, office area, and structural system features (column type, core type, floor framing system, and lateral load resisting system).  Various researchers have addressed the topic of construction time drivers and the usefulness of linear planning methodology (LP) to explicitly represent some of these drivers and strategies to cope with them.  Critical time drivers identified include project size, building functions, height, complexity, quality, and project location (Thabet and Beliveau, 1997); and total construction cost, type of housing scheme (rental/purchase), presence/absence of precast facades, total building volume, and the ratio of total gross floor area to the number of storeys (Chan and Chan, 2004). Many researchers and developers have employed LP (Russell and Wong, 1993; Thabet and Beliveau, 1994; Chevallier and Russell, 2001; Hegazy, 2002; Yang and Ioannou, 2004; Russell et al, 2009; Kenley and Seppänen, 2010; Russell et al, 2014; and VICO, 2016). It has many advantages including showing production rate and duration information in an easily interpreted graphic format; it provides insights as to where productivity rates should be adjusted to meet targets through one or more system design changes and changes in construction methods; it assists in maintaining work continuity of resources; and it aids in representing the horizontal logic of work in different work zones as well as the vertical logic of work between floors.  The model development process has been addressed by many researchers. Sargent (1981) divided the model development process into three elements: a phenomenon to be modelled to meet a set of well-defined objectives; a conceptual model (mathematical, logical, or graphical representation of this phenomenon); and, a computerized model (implementation of the conceptual model in the form of a computer model). Models need be verified and validated to be useful and successful. Sargent (1991) and Lucko and Rojas (2010) defined the verification process as measuring the technical correctness of a model against its development specifications or requirement – a step which is often performed internally by the researcher. Sargent (2013) defined validation as substantiating that the model within its domain of applicability possesses a satisfactory range of accuracy consistent with the intended application. Lucko and Rojas (2010) defined verification as doing things right and validation as doing the right things. Many related evaluation techniques are discussed in the literature. Sargent (2013) defined operational validation as determining that the model’s outputs have a satisfactory range of accuracy comparable to its domain of applicability. Sargent (2013) defined data validity as ensuring that the data necessary for model building, evaluation and testing, and conducting model experiments to solve a problem are adequate and correct. Leedy and Ormrod (2001) and Lucko and Rojas (2010) defined face validity as seeking the opinion of non-researchers regarding the validity of a model. Sargent (2013) defined predictive validation as forecasting the model’s outcomes, and comparing these outcomes with the real system outcomes to determine whether they are the same. Useful contributions exist in the literature in terms of building elemental structures, process modelling, parametric  120 representation features, driving factors for design and construction time and cost, model development steps, design and construction time modelling and life cycle cash flow streams. Use has been made of these contributions as appropriate in the development third filter models. However, existing models do not adequately treat one or more of the following issues:  Granularity of the evaluation processes: The degree of coarseness that is acceptable in the various models used to represent a design / construction solution needs to be determined by the level of detail necessary to capture any substantive interactions between the physical systems/components impacted by the solution. To assist with the aggregation and disaggregation of data and performance metrics of interest, the constituents of the various models should be structured in a hierarchical manner.  Detailed product model: Such a model should be able to treat the overall project configuration and the scale of all subprojects, major systems, and system components, including temporary facilities. Each system/subsystem needs to be characterized by at least one representative scope measure and possibly more, given that the type(s) of work required to realize a system/subsystem may have to be mapped onto multiple process work packages.  Comprehensive process model: This model needs to define the direct and indirect activities required to design, procure, construct, commission, operate, and maintain all of the physical components of a project, their durations and timing, resource requirements, and sequencing;   Holistic project cost cash flow model: This model is built as a function of the design and construction alternatives being considered and should serve to treat, in current dollar terms, all direct and indirect expenditures associated with the phases of procurement, construction, commissioning, O&M, project financing, project revenue streams, and applicable inflation, exchange, and interest rate(s).   Integrated set of evaluation models: it is important that an integrated approach be used through mapping of the work package, system, and component evaluation models onto one another using shared scope variables and other common time and cost parameters (e.g., productivity and production rates).  In the following section, the development steps for the project: cash flow expenditure and revenue, product, and process models will be presented in detail. 4.5 Development of filter-three models To measure the impact of system solutions on project expenditures and revenues and their timing, the supporting models should have the following features: (i) the ability to reflect properties of skyscraper projects, such as complex geometric configuration, large scale investment, and a large number of sub and superstructure lifts; (ii) usability in terms of clarity of language and explicit representation of items treated; (iii) generality to treat both design and construction innovations and on and off-site production; (iv) granularity in terms of the level of detail necessary to capture any substantive interactions between the solution and other systems; (v) flexibility to disaggregate or aggregate the level of detail required for systems under evaluation or other impacted building systems; (vi) comprehensiveness  121 to treat the impact of a system solution on a project across its life cycle; (vii) completeness of the evaluation process in terms of capturing all impacts of a system choice on project scope, cost, time, and NPV; and (viii) models used need to be integrated or mapped together in order to enable sharing of common data and metric results.   To simplify the discussion and application of the models presented herein, the focus is on single tower projects, and it is assumed that the solutions being examined have successfully passed through filters one and two, and overall feasibility of the project has been determined—i.e. the question is not whether the project should be built, but how best to design and construct it. As elaborated upon in the following sub-sections, the hierarchy of the developed project models is as follows: cash flow model, cost model, product models, and process/time and work package models. The research contribution with respect to these models is the formulation of an integrated set of models relevant to assessing design and construction alternatives in the construction of skyscrapers. 4.5.1 Cash flow model The principles and tests previously elaborated upon guided the effort to develop the cash flow model required for filter 3. In addition, cash flows are treated as being continuous as is their compounding and discounting. The focus is on the deterministic modelling of flows, but the formulation allows easy extension to treat uncertainty in cash flow model parameters/variables, as well as the handling of discrete risk events.  Project cash flow consists of cash in and cash out (Needles et al., 1999; Park et al., 2005). From a client perspective, cash in includes financial arrangements to cover design and construction costs, revenues, and residual project value. Cash out includes capital cost (design and construction cost), other client costs, O&M costs, rehabilitation costs, and debt servicing costs. Subproject/lift revenues are estimated using skyscraper local market sales and/or rental rates that may be driven by low or high seasons or special revenue events. Government tax incentives for utilizing innovative solutions can be an additional source of revenue (Nelms et al., 2005, 2007). Project residual value equates to the market value at time of sale, or the disposal, salvage or scrap cost at the end of service life. Operating and maintenance costs include expenditures for energy, water supply, and other service costs. Rehabilitation cost is incurred at the end of the service life of each system or repurposing of part or all of the built structures, and incorporates the cost of major system retrofits.  Loan repayment costs reflect loan agreement terms and the sculpting of principal and interest payments to reflect the project revenue profile. Building on Russell and Ranasinghe, 1991; Fuller and Petersen, 1995; Shohet and Laufer, 1996; and Abdel-Aziz and Russell, 2006, Figure 4-3 shows a simplified version of the project cash flow model. All flows are expressed in current dollars. Data describing each cash flow component of the overall project cash flow model are derived from the project’s product, cost, and time models. For simplicity of presentation, cash flow shape functions are not shown in Figure 4-3, but any shape function appropriate for a specific cash flow component can be employed. The model incorporates all possible negative and positive cash flow streams for the current baseline solution, plus any adjustments made to reflect an alternative design and/or construction approach inclusive of any interactions with other cash flow components that may be impacted by the choice of a system solution. The nomenclature used in Figure 4-3 is defined as follows. The words substructure and superstructure relate to all systems/components required to produce one or more complete lifts of the project (e.g., structural, electrical, mechanical, enclosure, finishing work). The parameters  122 F, O, and h define the degree of fast-tracking, overlap of T&C with project start-up and revenue generation, and cycle time for major rehabilitation.  To evaluate the impact of a system or component choice (or combination of choices) on the project cash flow model, consideration must be given to the duration and sequencing of expenditure and revenue streams as a function of the design/construction alternatives being considered, their shape, and applicable inflation, exchange, and loan interest rates. The latter requires a context model (not elaborated upon herein) that reflects important characteristics of the natural and man-made environments in which the project is embedded. Evaluation of the desirability of a system/component choice is assessed using NPV.  This performance metric allows trade-offs to be made between various costs/revenues within a given project phase and between project phases.   Figure 4-3 A simplified version of project cost cash flow model 4.5.2 Cost model As indicated earlier, the project will have passed through the feasibility assessment phase and be in either the design phase where system choices are made or in the construction phase when design alternatives may be considered or novel construction methods examined. CSI (2013) divides the design phase into three stages: schematic design, design development, and construction documents. Manfredonia et al. (2010) and Oyedele (2015) recommend a different cost Service life TimeResidual valueSuperstructure O & M cost lift KSub-structure cost lift 1Sub-structure cost lift JSuperstructure cost lift KDesign / tenderingDesign field servicesT & CLoan drawdownIndirect construction costsDirect construction cost including procurementProject management, legal, insurance, etc.Sub-structure O & M cost lift 1Debt servicingSub-structure revenue lift 1Superstructure revenue lift 1Superstructure revenue lift KSub-structure O & M cost lift JProject design and construction durationRehabilitation work carried out every h yearsh hDesign / tendering phaseTesting & commissioning phaseConstruction phaseUsage phase FOAmortization periodSuperstructure cost lift 1Superstructure O & M cost lift 1Sub-structure revenue lift JCapital cost and finance streamsDesign and Construction phaseOperation cost and revenue streams 123 estimate method for each design stage. Estimate types as the level of detail increases are: (i) order of magnitude estimate—employed when the facility is not yet designed, it makes use of cost data of similar facilities built in the past; (ii) conceptual estimate—used in the schematic design phase where major building systems are identified; (iii) detailed estimate—used at the design development stage where the essential features of the facility are identified.  Oyedele (2015) recommended that the capital cost of a product should be broken down to the level appropriate for the purpose of cost estimation and the type of cost estimate. For example, the level of detail required for defining a product is quite coarse for a conceptual estimate and quite fine for a detailed estimate. Bledsoe (2005) recommended using detailed cost estimates for evaluating alternative system solutions. Asiedu and Gu (1998) and Park et al. (2005) highlighted that the cost of a product/system needs to be built up from sub-system costs (bottom-up) and should include consideration of labor, temporary and permanent material and equipment, temporary structure, support infrastructure, and indirect costs. In formulating the relevant cost model for each component of the project life cycle cash flow model as depicted in Figure 4-3, the level of detail required for each project component as a function of available design information can be selected from the hierarchical structure of Tables 4-1(a) and 1(b). Cost model inputs are derived from the product model (scope quantities) and time (process) model (resources and time information). Capital cost consists of indirect and direct costs for design and construction.  Indirect costs extend over the construction duration and cover general condition requirements such as mobilization and material testing. Owner costs extend over design and construction time and cover project management, legal issues, insurance, and marketing costs. Design cost, field design services, indirect construction cost, and owner cost are normally estimated as a fraction of the direct cost. The direct cost of a project is estimated as a function of its systems and equals the total cost of subprojects, and their corresponding work packages and sub-work packages. For example, the services sub-work package cost includes costs associated with plumbing, HVAC (heating, ventilation, and air conditioning), fire protection, electrical, and conveying systems. T&C (testing and commissioning) costs are considered as a part of construction cost and contractor price in accordance with common construction practices. The direct cost of a work package/system choice equals the costs of the design and construction activities. These activities depend on the production location, which could be on or off-site, and include: design, build facility, production and T&C of subsystems, logistics, installation, and T&C of the installed system. Work package activities for solutions produced off-site are summarized in Figure 4-6(d). In terms of cost, the function of the work package model is to analyze the required time and resources of each activity.  Off-site production of a system has many benefits (Blismas et al., 2006; Baldwin et al., 2009; Jaillon et al., 2009; Pan and Gibb, 2009; Li et al., 2011). These benefits include increased service life and higher quality standards, reduced usage of raw materials, reduced installation and T&C times, potentially reduced O&M costs, and an in-situ scope of work and attendant resources that leads to less congestion of site work areas and enhanced site work productivity and production rates. Taking advantage of the economies of scale that a skyscraper project potentially offers, the use of off-site produced systems can lead to: (i) early expenditures to cover the cost of facility design, building/hiring a production facility and equipment, T&C of subsystems, building temporary infrastructure and/or buying/hiring  124 logistics and installation means; (ii) savings in construction and T&C costs as a result of reduced in- situ scope of work; (iii) savings in O&M and rehabilitation costs due to the increased quality and service life cycle; (iv) cost impacts in other building systems that are affected by the solution and required design and/or scope changes; and (v) early delivery of project milestones leading to earlier revenues and changes in finance and inflation costs and other direct and indirect capital costs.  All of these impacts and associated tradeoffs can be captured in the NPV performance metric. A contribution of the cash flow model set out herein deals with the hierarchical structure of cash flow streams, the level of detail used to reflect product and process features and their integration through usage of a common scope measures for determination of cost and duration for a work package / physical product. 4.5.3 Project product models  In additional to the cash flow model features already discussed, the development of project product models requires meeting a number of qualifications. First, models need to be defined in terms of the physical parameters and function/purpose of the systems being considered. A product’s elemental structure needs to be presented in terms of subprojects, work packages, sub-packages, systems, and subsystems.  Second, the level of granularity for defining the scope of each system should be derived from its scope quantities as a function of design and construction activities required. Further, scope variables should be defined to facilitate the definition of cost and process activities and assist in evaluating the reasonableness of estimates made for process component productivity and production rates. And third, compatibility between product, cost, and process models should be achieved at the deepest level of detail to enable the exchange of data. A number of assumptions have been made to simplify the representation of the project product model. The physical parameters that describe a skyscraper scope are divided into three subprojects: foundation, substructure, and superstructure. The substructure and superstructure may be viewed as comprised of multiple work lifts, each lift with one or more levels, and each lift having different physical characteristics, system solutions, and/or different usages. Large floor areas may be viewed as comprised of multiple work zones.  The primary function of the product models is to provide scope measure values for use in the cost and process models required to assess a design and construction solution choice. Depicted in Figure 4-4 is the physical configuration model used in support of the product view. Aspects of this model are further defined in Tables 4-1(a) and (b) with respect to system product models, inclusive of their process and work package models. The contributions claimed for the developed product/process models are a general representation of the vertical and horizontal spatial context of a skyscraper project; the definition of process work packages and sub-packages expressed in terms of physical systems, scope parameters, and values as a function of project spatial characteristics; and an association between work packages and on and off-site activities. These permit an integrated treatment of a project’s product and process dimensions for predicting cost and time performance as a function of system design and construction strategy/method approaches. Elaboration on the features of the product/process model follows. 4.5.3.1 Product model 1: geometric and spatial model As discussed earlier, existing parameter models (Meyer and Burns, 1999; Chan and Kumaraswamy, 2002; Lowe et al., 2006; Lee et al., 2011)) are based on a coarse level of detail. In formulating the spatial and geometric context  125 model described herein, the work of these authors served to help describe a project’s subprojects and lifts. As shown in Figure 4-4, a project is viewed as being comprised of three subprojects: foundations, substructure, and superstructure. The foundation can be of one and possibly two types—deep (piles, pile caps and raft) or shallow (raft and column and wall footings). The substructure and superstructure subprojects can be highly layered with different floor configurations in terms of height, length, width, and shape (circular, elliptical, twisted, etc.).   Figure 4-4 Product model 1: geometric and spatial model To accommodate changes in the vertical direction, consecutive floors with the same configuration or with the same function (parking, retail, residential, commercial, or mixed use) are considered as part of the same lift—the reason being that floors with different areas could involve different capital costs and floors with different usages would likely lead to different O&M costs and revenues. Substructure lifts are assumed from 1 to J and superstructure lifts from 1 to K. A large skyscraper floor plate is assumed to have a number of zones from 1 to M, with horizontal zoning being used to define the logic between sequential trades. This spatial model is linked with the system component product model allowing a complete definition of work scope as a function of system solutions. Inputs required for the product models are related to the project and its subprojects/lifts. Information for each lift includes: usage; number of vertical ` `Average Length, Avg LLift 1Average Width, Avg WShallow FoundationDeep foundationSubstructure lift JSubstructure lift 1UsageUsageUsageLift 1UsageLift KSuperstructure lifts from 1 to KCase study focusLift JSubstructure lifts from 1 to JGround levelSuperstructure lift KSuperstructure lift 1ZMZ1 126 locations; physical characteristics including: inter-storey height, width, length, shape of typical location, height, and exterior roof surface area; number of core areas inclusive of elevators and stairs; and number of work zones/floor. These inputs are used to calculate the scope measures of each system as shown in Tables 4- 1(a) and (b). 4.5.3.2 Product model 2: system components of project hierarchical structure Existing elemental structures devised for a total project and as summarized by Marshall and Charette (1999) are not suitable for evaluating alternative system solutions for skyscraper projects for the following reasons. The multi-functional nature of a skyscraper means that it is normally divided into subprojects, and lifts and system solution(s) would apply only to a specific lift. Thus, the level of detail used in published elemental structures is insufficient to represent the full scope of a skyscraper project or to treat the interaction between system solutions and other building systems as a function of spatial context. Further, such structures focus only on a capital cost estimation and cannot be readily used for process or time modelling. Nevertheless, aspects of existing elemental structures provide a useful starting point for development of a more generalized project representation that integrates both product and process features.  As indicated previously, Tables 4-1(a) and (b) present the hybrid hierarchical structure that combines the product and process models. To represent a building’s features, the model divides a project into six levels: (1) subprojects, (2) packages, (3) sub-packages, (4) systems, (5) design and construction sub-system/activities, and (6) in-use system activities. Foundation, substructure, and superstructure lifts represent the first level of subprojects. The second level identifies the work packages for each subproject. For example, a superstructure lift contains the following possible work packages: structural works, interior finishes, services, and exterior enclosure. The third level treats possible sub-work packages for each work package. For example, sub-packages for Services include plumbing, HVAC (heating, ventilation, and air conditioning), fire protection, electrical, and conveying systems.  The fourth level treats the possible systems for every sub-package including their description, scope variables, and corresponding measurement units.  For example, the dry area is detailed to services rough-in, partitions, rough finishes, and final finishes. System description defines the system type, number of sub-systems, production locations, productivity rates, crew size, and temporary infrastructure and equipment requirements. The fifth level includes activities associated with realizing a system choice. Included are activities related to design, building or acquiring a production facility (factory), system or component production, T&C of system/sub-systems in the factory, logistics, installation, and T&C in situ. The sixth level treats in-use activities of a system and includes O&M, rehabilitation work, and impacts of the system on subproject/lift revenue and on residual project value.  In comparison to the existing elemental structure set out by Marshall and Charette (1999), the developed hierarchical structural has several advantages for design choice and construction technology decision-making. First, in terms of flexibility and comprehensiveness, the user can choose the level of detail from one to six for the subprojects to suit the assessment process. Work package(s) and sub-work package(s) that include the solution(s) under evaluation and other building systems impacted by the solution need to be fully detailed to level six. Other packages and sub-packages not impacted can be summarized to level three or four. For example, to evaluate alternative solutions for a project’s structural system, (e.g., steel, composite of steel and concrete, concrete), the structural package should be detailed up  127 to level six. Also, the building systems that are affected, including cladding and internal partition systems, as a result of changes in connection details and the foundation package due to a change in superstructure weight need to be detailed to level six. Other packages can be summarized to level three or four, as appropriate, for the evaluation process. 4.5.4 Project process model The purpose of the process model is to define the direct and indirect activities required to design, procure, produce, construct, commission, operate, and maintain the systems and related components in terms of their durations, resource inputs, and sequencing. The foregoing permits development of a timeline model which provides the positioning in time of sub-project, packages, and sub-packages as a function of their system solutions. The process model is used to calculate the relative time saving/loss of key project milestones vs. a current base case model. In general terms, time savings in milestone dates can be pursued through the use of one or more of construction innovations (different methods and/or strategies) or the use of other tactical variables (e.g., additional resources, multiple work faces) or investigating the benefits of different design solutions (e.g., modularization and off-site production, substitution of one system type for another).  Tran et al. (2012) and Russell et al. (2014) present strategies for speeding up skyscraper delivery time using a linear planning representation format, as follows: (i) counter-clockwise rotation of activities reflecting a change in production rate (days/location) that can be achieved through one or more of adoption of alternative construction methods, application of additional resources, redefinition of the work week, or substitution of one system type for another.  In this case, all floor activities need to be speeded up— little or no benefit will be gained from speeding up just one activity; (ii) tighter activity sequencing that minimizes the lag time between activities and their spatial separation, thus bringing construction activities closer together through the use of horizontal zoning for large floor plates; and (iii) change in design features that leads to the merging or elimination of some activities, thus shortening the floor cycle time. Figure 4-5 shows a high-level skyscraper process model in linear planning format, possible acceleration strategies, and a project scale in terms of lifts that motivates the pursuit of efforts to achieve earlier project delivery. For example, the use of precast panels as an alternative to a block wall and marble finish cladding system could lead to a saving in construction time because of a faster site installation rate and elimination of many in-situ activities including curing lags. Features required of the process model and related scheduling algorithm for the purpose of exploring multiple design and construction strategies for skyscraper projects include: (i) the ability to quickly formulate a plan inclusive of on and off-site work, and to compute a schedule for any size project; (ii) support of hierarchical planning  so that different levels of granularity for work package modelling can be accommodated, with greater detail accorded to options under consideration and systems impacted; (iii) use of product model geometric and spatial as well as scope data (Table 4-1) and production rate data (the product of productivity and resource usage rate)  to determine activity durations and the location of work; and (v) provision of visual feedback that offers insights on the efficacy of a particular strategy and suggests possible ways to shorten delivery time.    128 Table 4-1(a) Product model 2: project hierarchical structure levels 1 – 4  Level 1 Level 2 Level 3Piles No of piles and depth noPile caps no * area * depth m3Raft Foundation area*depth m3Shoring Perimeter*depth m2Dewatering Area * depth m3Excavation Area * depth m3Backfilling Area * depth m3PlumbingElectricalSpecial serviceColumn & wall footings ∑Areas * depth m3Waterproofing & Insulation Surface area m2Slab on grade Floor area m2Core walls Core walls Columns, walls & stairsSlabsSteel fire Proofing Surface area m2Conveying systemsPlumbingHVACFire ProtectionElectricalServices rough in Subsystems no/specs LSPartitions Partitions areaRough finishesFinal finishesServices rough in Subsystems no/specs LSPartitions Partitions areaRough finishesFinal finishesServices rough in Subsystems no/specs LSPartitions Partitions areaRough finishesFinal finishesWallsInternal rough finishesInternal finishesExternal finishesRoof coveringsOpenings coveringHard landscapeSoft landscapeParking lotsRoadwaysSite utilities Utilities connections No of connections LSLevel 4Subproject Packages Sub-packages Systems Description Scope Measure Units FoundationsDeep foundations Piles worksShallow foundationsShoring worksEarth workFoundationsLump sum, LSWet areas (toilets and  washrooms) m2Ceiling + Wall+ floor areasUnder ground services Subsystems no/specsLump sum, LSLifts of sub-structure from 1 to J and superstructure from 1 to KStructural packageConcrete volume & steel structure weightm3 or tonVerticals and slabsInterior finishesServices Subsystems no/specsDry areas (all other areas of units) m2Ceiling + Wall+ floor areasPublic areas (major lobbies and corridors) m2Ceiling + Wall+ floor areasSite worksSite Improvements Work area m2Exterior enclosureExterior enclosureTypical floor perimeter *height  m2Roofing Roof and openings areas m2 129 Table 4-1(b) Product model 2: project hierarchical structure levels 5 – 6  Level 4Design Build a facility ProductionSubsystemsT & C Logistics InstallationSystem T & CPilesPile capsRaft ShoringDewateringExcavation Backfilling PlumbingElectricalSpecial serviceColumn & wall footings Waterproofing & InsulationSlab on grade Core walls Columns, walls & stairsSlabsSteel fire ProofingConveying systemsPlumbingHVACFire ProtectionElectricalServices rough inPartitionsRough finishesFinal finishesServices rough inPartitionsRough finishesFinal finishesServices rough inPartitionsRough finishesFinal finishesWallsInternal rough finishesInternal finishesExternal finishesRoof coveringsOpenings coveringHard landscapeSoft landscapeParking lotsRoadwaysUtilities connectionsLevel 5: design and construction activities for the systems Level 6: in-use activities for the systemsRevenue per subprojectN/AOn site activitiesO&M Rehabilitation Loan repayment Revenue ResidualsSystemsOff site activitiesN/AN/A 130 To simplify the process modelling task, the following assumptions have been made: (a) learning curve effects are treated by use of average productivity and production rates; (b) no consideration is given to height impacts when estimating production rates; (c) the logic between activities reflects construction practices appropriate to the region in which the project is located—for example, external enclosure work in cold and rainy climates is done after the structural work in order to seal the building before starting interior finishes; in hot climates, interior finishes start after structural works followed by external enclosure to give workers access to fresh air until the air conditioning sy