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A contribution to a practical approach to corrosion protection and coating maintenance of steel bridge… Chan, Phyllis 2005

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A CONTRIBUTION TO A PRACTICAL APPROACH TO CORROSION PROTECTION AND COATING MAINTENANCE OF STEEL BRIDGE STRUCTURES by PHYLLIS CHAN B.A.Sc., The University of British Columbia, 2003 A THESIS SUBMITTED IN PARTIAL F U L F I L L M E N T OF THE REQUIREMENTS FOR THE DEGREE OF M A S T E R OF APPLIED SCIENCE in THE F A C U L T Y OF G R A D U A T E STUDIES Civil Engineering THE UNIVERSITY OF BRITISH C O L U M B I A April 2005 © Phyllis Chan, 2005 Abstract This report summarizes the state-of-the-art practices in corrosion protection coating maintenance in British Columbia and worldwide. Details regarding maintenance policies, maintenance strategies, and maintenance materials are outlined. A computer-based decision making tool used to minimize the cost of coating maintenance for steel bridges is presented in this report. Variations of the model, adapted for specific use, are presented. A maintenance approach with the lowest equivalent uniform annual cost is recommended for each analysis using the model. The analysis may be performed for one bridge structure using deterministic or probabilistic input values or for all bridge structures of a certain inventory using deterministic input values. The variation of the model allowing analysis of the entire bridge inventory will provide an estimation of the annual budgetary requirements for the coating maintenance in a region and will facilitate the prioritization of these coating maintenance projects. From preliminary analyses using the Steel Bridge Coating Maintenance Evaluation Model, it is observed that the most cost efficient approach to coating maintenance is touch-up painting. However, the coating condition of the bridge must be kept high in order for this maintenance strategy to be applicable. Therefore, it might be necessary to temporarily increase the coating maintenance budget in order to improve the average condition. This will allow for a lower annual maintenance cost in the future, resulting in reduction of the total costs over the life-time of the bridges. n Table of Contents Abstract ii List of Figures vii List of Tables ix Acknowledgements x Chapter 1. Introduction 1 Chapter 2. Objectives 5 Chapter 3. Past Studies and Literature Review 7 Chapter 4. Corrosion Basics 11 4.1. Mechanism of Corrosion 11 4.2. Types of Corrosion 12 4.2.1. Uniform Corrosion 12 4.2.2. Galvanic Corrosion 13 4.2.3. Concentration Cell Corrosion 13 4.2.4. Pitting Corrosion 13 4.2.5. Crevice Corrosion 13 4.2.6. Filiform Corrosion 14 4.2.7. Intergranular Corrosion 14 4.2.8. Stress Corrosion Cracking 14 4.2.9. Corrosion Fatigue 14 4.2.10. Fretting Corrosion 15 4.2.11. Erosion Corrosion 15 4.2.12. Dealloying 15 4.2.13. Hydrogen Damage 15 4.2.14. Corrosion in Concrete 15 4.2.15. Microbial Corrosion 16 Chapter 5. Crevice Corrosion 17 5.1. Crevice Corrosion Basics 18 5.1.1. Mechanism of Crevice Corrosion 18 5.1.2. Causes of Crevice Corrosion 20 5.1.3. Factors Crucial to Crevice Corrosion 22 5.1.3.1. Electrolyte 22 5.1.3.2. Role of Geometrical Factor 22 5.1.4. Model and Rate of Crevice Corrosion 23 5.1.5. Difficulties with Experimentation on Crevice Corrosion 24 5.2. Design and Prevention of Crevice Corrosion 25 5.2.1. Selection of Materials Resistant to Crevice Corrosion 26 5.2.2. Rational Methods of Design 27 5.2.2.1. Consideration of Macroclimates 27 5.2.2.2. Consideration of Microclimates 27 5.2.2.3. Joints 28 5.2.2.4. Link Plates and Pin Connections 29 5.2.2.5. Girders 29 5.2.2.6. Truss Members 29 ii i 5.2.2.7. Bolted Connections 30 5.2.2.8. Access for Maintenance 31 5.2.3. Painting 31 5.2.4. Metallic Coating 31 5.2.4.1. Hot-Dip Galvanizing 32 5.2.4.2. Thermal Spray Coatings 32 5.3. Maintenance and Rehabilitation of Crevice Corrosion 32 5.3.1. Inspection 32 5.3.2. Corrosion Detection Technology 33 5.3.3. Maintenance 35 5.3.4. Rehabilitation 36 5.3.4.1. Selection of Paints 36 5.3.4.2. Surface Preparation 36 5.3.4.3. Coating Faying Surfaces and Connections 37 Chapter 6. Corrosion Maintenance Strategies 38 6.1. Coating Maintenance Policies 38 6.1.1. Corrective Maintenance 38 6.1.2. Preventative Maintenance 39 6.1.3. Predictive Maintenance 39 6.2. Coating Maintenance Strategies 39 6.2.1. Touch-up Painting 40 6.2.2. Overcoating 40 6.2.3. Recoating 41 6.2.4. "Do-Nothing"... 41 6.3. Types of Corrosion Protection Materials 42 6.3.1. Paint Systems 42 6.3.2. Hot-Dip Galvanizing 43 6.3.3. Cold Galvanizing 43 6.3.4. Thermal Spray Coatings 44 6.3.5. Weathering Steel .' 44 Chapter 7. Current Corrosion Maintenance Practice in British Columbia 46 7.1. Coating Maintenance Project Procedure 46 7.2. Previously Implemented Bridge Coating Rating System 49 7.3. Current Bridge Inspection Report 51 7.4. Examples of Maintenance Projects in British Columbia 53 7.1.1. Stanley Park Equestrian Overpass 54 7.1.2. Porteau Cove Emergency Docking Facilities 56 Chapter 8. Current Corrosion Maintenance Practice in the United States and Worldwide 59 8.1. Corrosion Protection Materials used in the United States 60 8.2. Strategies and Surface Preparation Methods used in the United States 62 8.3. United States Experience with Durability of Coatings and Strategies 63 8.4. United States Experience with Maintenance Considerations 68 8.5. Corrosion Maintenance Practice in Europe 73 Chapter 9. Steel Bridge Coating Maintenance Evaluation Model based on Life-Cycle Costs 75 iv 9.1. Model Layout /:> 9.1.1. Model Constraints 76 9.1.2. Model Formulation 77 9.2. Variations of the Model 81 9.2.1. Overall Bridge Condition Rating, Deterministic Input 82 9.2.2. Bridge Component Condition Rating, Deterministic Input 82 9.2.3. Overall Bridge Condition Rating, Probabilistic Input 83 9.2.4. Bridge Component Condition Rating, Probabilistic Input 84 9.2.5. Bridge Inventory, using Overall Bridge Condition Rating, Deterministic Input 85 9.3. Model Input 86 9.3.1. Input Parameters 87 9.3.1.1. Input for Overall Bridge Condition Rating, Deterministic Input 87 9.3.1.2. Input for Bridge Components Condition Rating, Deterministic Input.... 88 9.3.1.3. Input for Overall Bridge Condition Rating, Probabilistic Input 89 9.3.1.4. Input for Bridge Components Condition Rating, Probabilistic Input 90 9.3.1.5. Input for Bridge Inventory, using Overall Bridge Condition Rating, Deterministic Input 91 9.3.2. Discussion of Input Values 92 9.4. Model Output 107 9.4.1. Output Parameters 107 9.4.1.1. Output from Overall Bridge Condition Rating, Deterministic Input 108 9.4.1.2. Output from Bridge Components Condition Rating, Deterministic Input 109 9.4.1.3. Output from Overall Bridge Condition Rating, Probabilistic Input 109 9.4.1.4. Output from Bridge Components Condition Rating, Probabilistic Input 110 9.4.1.5. Output from Bridge Inventory, using Overall Bridge Condition Rating, Deterministic Input -. I l l 9.4.2. Sensitivity Analysis Plots 112 9.5. Examples using the Steel Bridge Coating Maintenance Evaluation Model 113 9.5.1. Example using Overall Bridge Condition Rating, Deterministic Input 113 9.5.2. Example using Bridge Components Condition Rating, Deterministic Input 114 9.5.3. Example using Overall Bridge Condition Rating, Probabilistic Input 116 9.5.4. Example using Bridge Components Condition Rating, Probabilistic Input .119 9.5.5. Example using Bridge Inventory, using Overall Bridge Condition Rating, Deterministic Input 122 9.6. Model Summary 124 Chapter 10. Conclusions and Implications Derived from the Model 126 10.1. Comparison of Corrosion Protection Coating Maintenance Strategies 126 10.2. Sensitivity of Costs to Varying Escalation and Interest Rates 128 10.3. Sensitivity of Costs to Varying Coating Durability 129 10.4. Allowable Premium for Increased Coating Durability 130 10.5. Input Parameter Componentization 130 Chapter 11. Recommendations 132 11.1. Bridge Coating Condition Data Collection 132 v 11.2. Increase Average Rating of Bridge Inventory 133 Chapter 12. Future Developments 135 References 137 Appendix A. Logs of Site Visits 140 Appendix B. Sample Specification Content of Large Maintenance Projects in British Columbia 147 Appendix C. Sample Bridge Coating Rating System Coating Inspection Report 154 Appendix D. Sample British Columbia Ministry of Transportation Bridge Inspection Report and Definition of Condition Rating Categories 156 Appendix E-I. Steel Bridge Coating Maintenance Evaluation Model 163 Appendix E. Overall Bridge Condition Rating, using Deterministic Input Values 164 Appendix F. Bridge Components Condition Rating, using Deterministic Input Values 170 Appendix G. Overall Bridge Condition Rating, using Probabilistic Input Values 176 Appendix H. Bridge Components Condition Rating, using Probabilistic Input Values 182 Appendix I. Bridge Inventory: Estimation of Funding and Prioritization of Projects using Overall Bridge Condition Rating and Deterministic Input Values 188 vi List of Figures Figure 1 - Corrosion Mechanism in Steel 12 Figure 2 - Crevice Corrosion Mechanism in Steel 19 Figure 3 - Typical Structure of a Crevice Corrosion Model 24 Figure 4 - British Columbia Ministry of Transportation Coating Maintenance Project Procedure 48 Figure 5 - Stanley Park Equestrian Overpass Vertical Support Leg Prior to Maintenance 55 Figure 6 - Stanley Park Equestrian Overpass Vertical Support Leg Following Maintenance 56 Figure 7 - Porteau Cove Emergency Docking Facilities Following Maintenance 58 Figure 8 - Failure Ranges of Various Coating Materials and Maintenance Strategies 64 Figure 9 - Durability of Paint 64 Figure 10 - Durability of Repaint 65 Figure 11 - Durability of Overcoat 65 Figure 12 - Durability of Metallizing 66 Figure 13 - Durability of Galvanizing 66 Figure 14 - Durability of Weathering Steel 67 Figure 15 - Durability of Concrete 67 Figure 16 - Levels of Concern Regarding General Maintenance Issues 71 Figure 17 - Levels of Concern Regarding Structure Conditions 71 Figure 18 - Levels of Concern Regarding Mitigation Factors 72 Figure 19 - Steel Bridge Coating Maintenance Evaluation Model General Layout 76 Figure 20 - Steel Bridge Coating Maintenance Evaluation Model Constraints 77 Figure 21 - General Layout of the First and Third Model 82 Figure 22 - General Layout of the Second and Fourth Models 83 Figure 23 - General Layout of Funding Calculations in the Fifth Model 86 Figure 24 - General Layout of Benefit-to-Cost Ratio Calculations in the Fifth Model.... 86 Figure 25 - Input Table for the First Model 87 Figure 26 - Corrosion Rating Input Value Distribution 94 Figure 27 - Corrosion Curve Input Value Distribution 95 Figure 28 - Escalation Input Value Distribution 96 Figure 29 - Interest Input Value Distribution 97 Figure 30 - Life Input Value Distribution 99 Figure 31 - Touch-Up Durability Input Value Distribution 100 Figure 32 - Touch-Up Unit Cost Input Value Distribution 101 Figure 33 - Overcoat Durability Input Value Distribution 102 Figure 34 - Overcoat Unit Cost Input Value Distribution 103 Figure 35 - Recoat Durability Input Value Distribution 104 Figure 36 - Recoat Unit Cost Input Value Distribution 105 Figure 37 - Replace Cost Input Value Distribution 106 Figure 38 - Model Variation 3 - E U A C Frequency Distribution 117 Figure 39 - Model Variation 3 - E U A C Cumulative Distribution 117 Figure 40 - Sensitivity Analysis Plot of Financial Factors 118 vii Figure 41 - Sensitivity Analysis Plot of Coating Durability 119 Figure 42 - Model Variation 4 - E U A C Frequency Distribution 121 Figure 43 - Model Variation 4 - E U A C Cumulative Distribution 122 viii List of Tables Table 1 - Primary NDI Technologies 34 Table 2 - Trends of NDI Technologies 34 Table 3 - Maintenance Policies Practiced by Agencies 69 Table 4 - Input Parameters for the First Variation of the Model 88 Table 5 - Input Parameters for the Second Variation of the Model 89 Table 6 - Input Parameters for the Third Variation of the Model 90 Table 7 - Input Parameters for the Fourth Variation of the Model 91 Table 8 - Input Parameters for the Fifth Variation of the Model 92 Table 9 - Input Values for the First Variation of the Model 114 Table 10 - Input Values for the Second Variation of the Model 115 Table 11 - Input Values for the Third Variation of the Model 116 Table 12 - Input Value for the Fourth Variation of the Model 120 Table 13 - General Input Values for the Fifth Variation of the Model 123 Table 14 - Bridge Specific Input Values for the Fifth Variation of the Model 123 Table 15 - Output Values for the Fifth Variation of the Model 123 Table 16 - Summary of the Bridge Coating Maintenance Evaluation Model 124 ix Acknowledgements I would like to thank members of the Ministry of Transportation of British Columbia: Kevin Baskin - Chief Bridge Engineer, Sharlie Huffman - Bridge Seismic Engineer, Zbigniew Radzimowski - Area Managers - Bridges, and Peter Chiu - Bridge Project Supervisor; for their interest and support in this project. I would also like to thank Doug Jensen of Mainroad Contracting Ltd., Russell Raine of Trans Canada Coatings Consultants Ltd., and Helmut Tepper of Coast Pacific Coating and Consultants Ltd. for their assistance. I would like to acknowledge fellow students who have participated in this project: Nicolas Marcouiller, Jason Wang, and Vignesh Ramadhas. I would also like to extend my thank you to my mentor, Dr. S. F. Stiemer, for his constant guidance and wisdom over the past years. A special thank you goes to my dear mother, my father, and my sister for their continual support in all that I do. Chapter 1. Introduction Steel structures subject to the natural environment will have to be protected against corrosion. In general, corrosion protection requires maintenance during the life-span of the steel structure. Currently this constitutes a large portion of the maintenance costs of steel structures. Globally, corrosion failures in metallic materials amount to billions of dollars every year. Therefore, the prevention of corrosion is not only essential to the safety of the users of the structures, but also focal to the economic well-being of the owners of the structures. The Province of British Columbia owns over 700 steel structures, mostly bridges which are located throughout the province. The Ministry of Transportation of British Columbia (MoT) is responsible for maintaining and improving the highway system, which includes the numerous steel bridges. Corrosion is initiated by the presence of oxygen and moisture, amongst other factors. In British Columbia, especially in the coastal regions where moisture in the atmosphere is abundant, corrosion in steel structures is more likely and occurs more rapidly. Various methods can be employed in order to protect the steel from corroding. These methods include protective paint coatings, hot-dip galvanizing, cold galvanizing, thermal sprays, and other state-of-the-art corrosion protection procedures. Most of the steel bridges in British Columbia have been painted with protective coatings, as this is often the simplest and most economical procedure. In order to prevent corrosion from causing section loss in the structural steel, the integrity of the protective coating must be ensured. This requires inspections, evaluations, and maintenance of the protective coating on steel bridges on a regular basis 1 or when necessary. It is desirable to determine the most cost efficient approach to the coating maintenance. MoT, in conjunction with the University of British Columbia, is involved in a project developing a strategy to address the above-mentioned issues. The objectives of the project are: to gather and assemble information regarding the maintenance strategies practiced locally and worldwide, and their associated costs, benefits and risks; to produce a decision making tool to aid in the selection of the maintenance strategies for remediation of observed corrosion on bridge structures throughout their lives; and to observe the effects of probabilistic factors in the decision making process and to evaluate the implications derived from the decision making model. This report will serve to document the results from this project. Over the past decade, MoT has conducted several studies on coating maintenance and corrosion prevention and remediation for steel bridges in the province. In 1994, Tam outlined the basics of bridge protective coatings, and presented a bridge corrosion cost model and a bridge coating maintenance model (Tam, 1994). These models performed life-cycle cost analysis based on deterministic input values using dynamic programming for optimizing coating maintenance approaches. From 1995 to 2001, Raine developed a bridge coating rating system in order to collect and log valuable data on the current condition of protective coatings on steel bridge structures throughout British Columbia (Raine, 2001). The bridge coating rating system included a bridge inspection report and a bridge coating condition database. The bridge inspection report facilitated the collection of detailed information regarding the condition of the corrosion protection coating on the 2 bridge structures. Unfortunately, the funding for the development of coating maintenance optimization was interrupted and the studies were stopped temporarily. In 2003, MoT approached the coating maintenance issue with renewed interest. During Phase I of Rehabilitation and Maintenance Strategies: Applied Methods for Remediation of Corrosion of Bridge Structures, Marcouiller produced reports on the subjects of corrosion of steel, corrosion protection of steel, fatigue analysis, and thermal spray protection (Marcouiller, 2003, 1-3). Wang conducted a study on crevice corrosion as part of Phase II of Rehabilitation and Maintenance Strategies: Applied Methods for Remediation of Corrosion of Bridge Structures (Wang, 2004). The results from the Wang study may be found in Section 5 of this report. The project documented in this report, also as a part of Phase II of Rehabilitation and Maintenance Strategies: Applied Methods for Remediation of Corrosion of Bridge Structures, summarizes the current corrosion maintenance practice in British Columbia, as well as the current corrosion maintenance practice in the United States. Several steel bridge coating maintenance evaluation models based on life-cycle cost analyses were developed by the author of this report. A simplified model with minimal input requirements was developed for use with the limited data available in the current British Columbia Bridge Maintenance Information System database. This model was created using a commercial software (DecisionPro) to allow clear visual presentation of the procedures and their relationships (Vanguard, 2002). A second slightly more complex model was also created in DecisionPro for allowing the possibility of selecting different coating maintenance approaches for different components of the bridge; such as structural steel components, bearings, expansion joints, and non-structural components. 3 Variations of both models (a third and fourth model) were created in both DecisionPro and Microsoft Excel for the evaluation of the problem with probabilistic input values (Microsoft, 2001). This allowed for a more realistic model of the real world situation and a better insight into the implications derived from the model. Finally, a fifth model was developed using DecisionPro to evaluate the amount of moneys that should be ideally allocated by MoT to a coating maintenance program for the maintenance of steel bridge protective coatings on an annual basis. Using these models, a comparison of corrosion maintenance coating alternatives may be made for steel bridges at different stages of their lives, based on life-cycle cost analysis. This method is a more comprehensive method than comparisons based on simple single-time costs. However, it is crucial that the data collected for the input of the models be representative of the values in the real world. A sensitivity study of the cost to varying escalation and interest rates may be performed with these models. By evaluating the sensitivities, it may be apparent that forecast models for escalation and interest are required to be developed. It is important to predict these values for the materials and labour in the coating maintenance sector in particular. The sensitivity of the cost to varying coating durability may also be derived from the models and the allowable premium for more-durable coatings may be calculated. 4 Chapter 2. Objectives The primary objective of this project is to develop tools to aid in the decisions for remediation of the corrosion observed in steel bridge structures. Maintenance strategies available for the protective coatings are evaluated and the most cost effective approach detected. Various maintenance strategies as used locally and worldwide are documented. Costs, benefits, and risks associated with each strategy are outlined. The information is compiled in the form of a report. A computer-based decision making tool is to be developed in order to aid in the selection of the best approach to perform coating maintenance on bridge structures. The decision making tool will allow for the modelling of the current coating maintenance practice in British Columbia as well as possible alternate maintenance strategies. Different external factors such as environmental and financial characteristics may also be modelled. This project will evaluate and compare the various events and outcomes. Implications derived from the decision making tool will be summarized. In previous studies, the life cycle cost analysis of coating maintenance strategies were performed using deterministic values as the input data (Tam, 1994). However, it is obvious that in real world situations, representing input parameters as deterministic values is not always adequate. Therefore, in this project, the life cycle cost analysis of coating maintenance strategies will be performed using probabilistic distributions for applicable input data. The effects of the probabilistic values in the analysis will be observed. 5 In an effort to determine the annual funding requirements for the corrosion protection coating maintenance projects in British Columbia, a variation of the decision model will be created allowing input of the entire steel bridge inventory. This model wi calculate the annual costs associated with the routine maintenance of all the steel bridge structures, as well as suggest a prioritization for the projects. 6 Chapter 3. Past Studies and Literature Review Several studies have been conducted by the British Columbia Ministry of Transportation, in conjunction with the University of British Columbia, on the topic of corrosion maintenance for steel structures. In 1994, Tam from the University of British Columbia conducted a study of bridge coating maintenance (Tam, 1994). Tam described the basics of bridge protective coatings, and presented a bridge corrosion cost model and a bridge coating maintenance model. These models performed simple life-cycle cost analysis on deterministic input values and used dynamic programming for optimizing coating maintenance approaches. Tam concluded that the most cost effective approach for bridge coating maintenance is spot repair, since only corrosion-damaged areas of the bridge structure is required to be maintained by this approach. However, spot repair is not a suitable strategy if the steel structure is severely corroded. Tam recommended that a comprehensive database on rehabilitation costs and deterioration rates of coating systems is necessary in order to optimize the coating maintenance strategies. From 1995 to 2001, Raine, with the British Columbia Ministry of Transportation, developed a bridge coating rating system for use as a catalog of the steel bridge structures (Raine, 2001). The bridge coating rating system recorded the inspections of the bridge structures and the condition of the coatings at the time of the inspections. A weighting system was used to determine the overall condition of the coating on the bridges in order to prioritize coating maintenance projects. Details of the bridge coating rating system developed by Raine are outlined in Section 7.2 of this report. 7 In 2003 (Phase I of Rehabilitation and Maintenance Strategies: Applied Methods for Remediation of Corrosion of Bridge Structures), Marcouiller, working with the University of British Columbia, documented the subjects of corrosion of steel, corrosion protection of steel, fatigue analysis, and thermal spray protection (Marcouiller, 2003, 1-3). His report provided classifications of atmospheric environments. These environments include: mild, moderate, tropical, industrial, marine, severe marine, immersion, and buried. Marcouiller also described the types of coatings available for the corrosion protection of steel, including details on protective paint systems and their application requirements, hot-dip galvanizing, cold galvanizing, and thermal spray coatings. Marcouiller listed the factors affecting the choice of the corrosion protection coating for steel structures as follows: the expected life of the structure and the feasibility of maintenance; the environment to which the steel structure is subjected; the size and shape of the members; the site conditions and accessibility; and the funding available for maintenance. The selection of the coating will affect the decision on the method of surface preparation, the method of application, and the number of coats and the thickness of each coat to be used. Marcouiller also documented a marine corrosion test series performed by the Japan Association of Corrosion Control on thermal sprayed zinc, aluminum, and zinc-aluminum coatings on steel pipes. The Japanese study found that after 7 years of exposure, the zinc coatings were suffering degradation in the immersed portions of the structure while the aluminum and zinc-aluminum coatings did not suffer any observable damage. In 2004, as part of Phase II of Rehabilitation and Maintenance Strategies: Applied Methods for Remediation of Corrosion of Bridge Structures, Wang conducted a study on 8 crevice corrosion on steel bridges (Wang, 2004). Wang's study included the topics of basics of crevice corrosion, design and prevention of crevice corrosion, and maintenance and rehabilitation of crevice corrosion. A summary of the Wang study is provided in Section 5 of this report. A large part of the literature review for this project stems from research performed in the United States. The U.S. Department of Transportation Federal Highway Administration and the Transportation Research Board of the National Research Council have produced several reports on the topic of steel bridge corrosion protection and bridge coating maintenance. In 1984, the Transportation Research Board National Cooperative Highway Research Program produced a report on the Performance of Weathering Steel in Bridges (Albrecht and Naeemi, 1984). The report outlines the behaviour of steel structures in various conditions, including various environments and service conditions. The report also provides a comparison of the effects of applying paint to new bridges of weathering steel versus new bridges of carbon steel. In 1988, Kayser conducted a research on The Effects of Corrosion on the Reliability of Steel Girder Bridges (Kayser, 1988). Kayser's report included corrosion patterns obtained from practitioners and observed in field inspections. Kayser also proposed the use of an equation by Komp for the rate of corrosion (Komp, 1987). The Federal Highway Administration Bridge Coatings Technology Outreach Team released a Bridge Coatings Technical Note in 1997 that outlined the approximate unit cost for an overcoating procedure of a steel bridge structure versus the approximate unit cost of the full removal and replacement of the paint of a steel bridge structure 9 (Federal Highway Administration, 1997). This report suggested that the feasibility of a coating maintenance strategy should be based on the cost, the relative potential performance of the strategy, and the risk with potential early failure of the strategy. This report found that using life cycle analysis, the most cost effective maintenance strategy is full removal and replacement of the coating, especially for steel structures in marine environments or in areas exposed to de-icing salt. The Federal Highway Administration also published an article on Steel Bridge Coatings Research in the magazine Public Roads in 1997 (Kogler and Chong, 1997). This article stated that the cost of paint material is insignificant compared to the overall cost of a coating maintenance project. Therefore, it was recommended that a more-durable coating material be selected since the benefit of durability far outweighs the higher initial costs. In 1998, the Transportation Research Board National Cooperative Highway Research Program produced a report on Maintenance Issues and Alternate Corrosion Protection Methods for Exposed Bridge Steel (Neal, 1998). The information for this report was obtained by surveying state transportation agencies. It described the current practice in the United States regarding maintenance and protection strategies for exposed structural steel on existing bridges. A summary of the current corrosion maintenance practice in the United States is included as Section 8 of this report. 10 Chapter 4. Corrosion Basics Corrosion is an electrochemical procedure that occurs in metals exposed to oxygen, and is favoured in the presence of water. The metal deteriorates by oxidation. In the case of iron and steel, corrosion is often referred to as rusting. Corrosion may occur in many forms. 4.1. Mechanism of Corrosion Corrosion is a type of electrochemical reaction known as a reduction-oxidation reaction. The reduction-oxidation reaction involves the flow of electrons from an anode to a cathode. Material from the anode dissolves into solution and its ions migrates towards the cathode. A medium, usually water, is required for the exchange of ions between the cathode and the anode. In a corrosion reaction, the material acts as both the cathode and the anode. Metals are highly susceptible to corrosion since they are electric conductors. In steel, corrosion produces rust from the degradation of the steel substrate. In the presence of oxygen and water, the major component of steel, iron, loses electrons and become positively charged, while oxygen, water, and electrons combine to produce hydroxide ions. The positive iron ions then combine with the negative hydroxide ions to produce iron hydroxide. The iron hydroxide then reacts with the dissolved oxygen in water to produce hydrated iron oxide, rust. The rust will be deposited at the cathode while loss of material occurs at the anode. The rust may eventually result in a protective coating on the metal surface, decreasing the rate of further corrosion in the metal. 11 Figure 1 shows the corrosion mechanism in steel. 0 2 Air Water Droplet \ ^ / f Fe 2 + / Rust (Fe 2 0 3 H 2 0) Anode Region Fe — • Fe 2 + + 2e" e" y Cathode Region 0 2 + 4 H + + 4e" — • 2 H 2 0 Iron Metal Figure 1 - Corrosion Mechanism in Steel 4.2. Types of Corrosion The many types of corrosion include uniform corrosion, galvanic corrosion, concentration cell corrosion, pitting corrosion, crevice corrosion, filiform corrosion, intergranular corrosion, stress corrosion cracking, corrosion fatigue, fretting corrosion, erosion corrosion, dealloying, hydrogen damage, corrosion in concrete, and microbial corrosion. 4.2.1. Uniform Corrosion Uniform corrosion is also known as general corrosion. Uniform corrosion is the most common type of corrosion found in metallic surfaces. In uniform corrosion, there is a uniform etching of the metal. Uniform corrosion is common in direct chemical attacks. The general loss of surface material will lead to the gradual thinning of members and a risk of structural failure. 12 4.2.2. Galvanic Corrosion Galvanic corrosion is the result of the electrochemical action of two dissimilar metals in the presence of an electrolyte and an electron conductive path. Galvanic corrosion may occur when two dissimilar metals are electrochemically coupled at bolted or welded connections. 4.2.3. Concentration Cell Corrosion Concentration cell corrosion occurs when two or more areas of the metal surface is in contact with different concentrations of the same solution. This may occur on steel piers and tower legs that are submerged in seawater. 4.2.4. Pitting Corrosion Pitting corrosion is localized corrosion that occurs at microscopic defects on the metal surface. Pitting corrosion is usually restricted to a very small area but may be dangerous since pit extensions into the metal may be difficult to detect. Pitting corrosion is a cause for concern especially in high stress regions of the structure since they cause local stress concentrations. 4.2.5. Crevice Corrosion Crevice corrosion is also known as contact corrosion. Crevice corrosion occurs at regions of contact of metals with metals or metals with non-metals. Crevice corrosion is common on steel bridge structures at bolted connections and joints. A steel structure may be protected from crevice corrosion i f the connections are snug or a sealant is applied to the crevices. Details on crevice corrosion and protection methods are included as Section 5 of this report. 13 4.2.6. Filiform Corrosion Filiform corrosion occurs on painted or plated surfaces when moisture penetrates the coating. Filiform corrosion results in long branching filaments of corrosion product extending from the original corrosion pit and causes degradation of the protective coating. This type of corrosion will occur on coated steel bridge structures i f the coating has not been applied properly. 4.2.7. Intergranular Corrosion Intergranular corrosion is the corrosion attack on or adjacent to the grain boundaries of a metal or an alloy. 4.2.8. Stress Corrosion Cracking Stress corrosion cracking is the simultaneous effects of tensile stress and specific corrosive environment on a member. Stress corrosion is usually negligible in mild carbon steel bridges in ordinary environments. 4.2.9. Corrosion Fatigue Corrosion fatigue is a special case of stress corrosion. Corrosion fatigue occurs when cyclic stress and corrosion are present in a member. Corrosion fatigue may be further aggravated by pitting or crevice corrosion. Corrosion fatigue reduces the fatigue life of the metal. 14 4.2.10. Fretting Corrosion Fretting corrosion is a rapid form of corrosion. Fretting corrosion occurs at the interface between contacting, highly loaded metal surfaces subject to slight vibratory motions. 4.2.11. Erosion Corrosion Erosion corrosion occurs as a result of a combination of an aggressive chemical environment and high fluid-surface velocities. 4.2.12. Dealloying Dealloying is a rare form of corrosion. Dealloying occurs in copper alloys, gray cast iron, and some other alloys. Dealloying occurs when the alloy loses the active component of the metal and retains the more corrosion resistant component. This results in a porous sponge-like texture on the metal surface. 4.2.13. Hydrogen Damage Hydrogen damage is also known as hydrogen embrittlement. Hydrogen damage occurs in high strength steels, titanium, and some other metals. Hydrogen damage may be controlled by eliminating hydrogen from the environment or by using resistant alloys. 4.2.14. Corrosion in Concrete Steel encased in concrete is also subject to corrosion. Due to cracks in the concrete, reinforcing steel bars embedded in the concrete may be corroded. The reinforcing steel in concrete should be protected in order to ensure the integrity of the concrete members. 15 4.2.15. Microbial Corros ion Microbial corrosion is also known as microbiologically-influenced corrosion. Microbial corrosion is caused by the presence and the activities of microbes. Microbial corrosion can take many forms. Microbial corrosion may be controlled by biocides or conventional corrosion control methods. 16 Chapter 5. Crevice Corrosion Localized corrosion is a form of corrosion that occurs over only a small percentage of the total surface area of the metal. Although the area where the corrosion occurs is small in localized corrosion, the regions where corrosion occurs experience extremely high corrosion rates. Crevice corrosion is a form of localized corrosion. Crevice corrosion distinguishes itself from other forms of localized corrosion, such as pitting, in that it occurs specifically in a region where a crevice has been formed. Crevice on steel structures are typically formed when a metal or non-metal is in close enough proximity to the surface of the metal substrate to create a geometry such that the environment inside the crevice is restricted from freely interacting and mixing with the bulk environment. An example of a possible region where crevice corrosion may occur is between two steel plates held together by bolts. A crevice is formed between the contact surfaces, and accelerated corrosion occurs in this region. Since the corrosion occurs between the two steel plates, it is difficult to identify the crevice corrosion by visual inspections. During the design process, engineers can design structures to resist crevice corrosion by selecting proper materials and finishes and using drainage, sealants, and corrosion inhibitors. Throughout the service life of the steel structure, a crevice corrosion control program should be employed. Crevice corrosion should be identified and corrected before it becomes severely damaging. 17 5.1. Crevice Corrosion Basics Localized corrosion is an insidious process in which there is an intense attack at localized sites on the surface of a structure, while the rest of the surface is corroding at a much lower rate. The corrosion protection coating on the main surface of a structure may be in satisfactory condition, while the coating may have been deteriorated at localized areas and corrosion has been initiated. Crevice corrosion is a particularly damaging form of localized corrosion. Crevice corrosion is difficult to predict and difficult to detect. Undetected crevice corrosion may lead to structural damage of the component, which may jeopardize the ability of the steel structure to carry its intended design loads. 5.1.1. Mechanism of Crevice Corrosion Crevice corrosion occurs as the main surface of a steel structure is shielded by another metal or non-metal component, resulting in limited access to the surrounding environment for the shielded portion of the main structure. The environment surrounding the crevice often contains damaging corrosion species, such as chloride ions. Corrosion occurs in the crevice, quickly expending the available oxygen. Due to the limited access to the surrounding environment, the oxygen in the crevice cannot be replenished. The entrance to the crevice becomes cathodic, since it can satisfy the oxygen-demanding cathode reaction. The tip of the crevice becomes a localized anode and high corrosion rates occur at this point. Figure 2 shows the crevice corrosion mechanism in steel. 18 Figure 2 - Crevice Corrosion Mechanism in Steel The depth of the crevice corrosion attack varies within the crevice. Minimal attack occurs near the mouth of the crevice. With increasing distance into the crevice, the amount of crevice corrosion attack increases until a peak is reached, at which point the amount of crevice corrosion decreases. The differing amount of attack along the crevice indicates that the conditions within the crevice are not uniform. The pH level, electrolyte composition, and potential may vary greatly within the crevice. There is an initiation time between the formation of the crevice and the start of the corrosion attack. Once the crevice has been initiated, propagation of the crevice occurs. Initiation is the generation of conditions that are sufficient to attack the metal. Propagation depends on sustaining those conditions. Changes in geometry, such as the widening of the mouth of a crevice due to rapid corrosion, may deem the damaging electrical or chemical conditions unsustainable and therefore halt the crevice corrosion process. 19 5.1.2. Causes of Crevice Corrosion Crevice corrosion occurs as a result of a locally aggressive environment having been developed within a crevice. The conditions within the crevice become locally more aggressive than the surrounding bulk environment as a result of a combination of chemical and electrical changes inside the shielded area. Two main theories have been adopted by researchers to explain the initiation of crevice corrosion. The Critical Crevice Solution (CCS) model assigns primacy to the chemical changes in a crevice, while the Critical IR Drop (IR) model assigns primacy to the electrical changes in a crevice. Most modern models employ a combination of elements from both the CCS and IR models. The CCS model explains the initiation of crevice corrosion in terms of the crevice acting as a barrier to chemical transport. The basic process of the CCS model for the initiation of crevice corrosion on steel is as follows: • Deoxygenation of the crevice • Anodic dissolution of metal inside the crevice supported by cathodic reactions on the boldly exposed surface • Hydrolysis of the resulting metal cations lowering the pH • Ingress of chloride ions to balance the charge of the more slowly moving metal cations According to the CCS model, the conditions inside the crevice are the result of an interaction between the generation of chemical species inside the crevice and their transport out of it. A lag in the removal of the dissolution products, such as that resulting from the formation of a crevice, will allow the metal cations to accumulate. The cations 20 then hydrolyze and form metal hydroxides, lowering the pH of the solution. Simultaneously, negatively charged anions, such as chlorides, migrate into the crevice to balance the excess positive charge from the metal cation. The net result is an acidic chloride solution that is more aggressive than the initial solution. The dissolution rate increases as a result of the change in chemistry. Therefore, the crevice corrosion process is autocatalytic. The CCS model provides adequate explanation for several aspects of crevice corrosion. The unaffected region at the mouth of the crevice is a result of the mass transport out of the crevice, preventing the development of a sufficiently aggressive solution. The time delay of the initiation of crevice corrosion is a result of the time required to develop a concentrated electrolyte for the process. The resulting solution from the CCS model is the expected acidic chloride solution for crevice corrosion. However, the CCS model does not serve to explain the lack of corrosion attack at the greatest depths of the crevice. The IR model explains the initiation of crevice corrosion in terms of the crevice acting as a barrier to electrical transport. The basic process of the IR model for the initiation of crevice corrosion on steel is as follows: • Deoxygenation of the crevice • Localized anodic and cathodic reactions occur in the crevice interior and on the boldly exposed surface respectively • Net current flow from the crevice interior out to the boldly exposed surface • Current crosses the electrically resistive crevice electrolyte, potential drop due toIR 21 • Rapid attack due to lowered potential of the metal from the bulk potential to the active nose of the metal According to the IR model, the conditions in the crevice are determined by the interplay between current generation and crevice resistance, which is a product of geometry and conductivity. The IR model provides adequate explanation for several aspects of crevice corrosion. The uncorroded areas at the mouth of the crevice are a result of the inadequate potential drop in these areas. The uncorroded areas at the depths of the crevice are a result of a lack of driving force to corrode at a rate greater than the corrosion current in these areas. However, the IR model does not serve to explain the time delay before the initiation of crevice corrosion. 5.1.3. Factors Crucia l to Crev ice Corros ion Two factors which are important to the occurrence of crevice corrosion are the electrolyte within the crevice, and the role of geometrical factors. 5.1.3.1. Electrolyte Stagnant solution plays an important role in crevice corrosion. The stagnant solution facilitates the set up of highly corrosive microenvironments inside crevices. A metallic material tends to assume a more anodic character within the stagnant crevice corrosion than on the exposed bulk surface. 5.1.3.2. Role of Geometrical Factor Geometrical factors also play an important role in crevice corrosion. The width and depth ofa crevice determine the access to oxygen, the change in the composition of 22 the electrolyte, the distribution of the potential, and the effectiveness of the performance of the macro elements. Crevices that promote crevice corrosion must be of a sufficient width to permit entry of the corrodent, while at the same time must be sufficiently narrow to ensure that the corrodent remains stagnant. It has been observed that as the width of the crevice diminishes, the rate of corrosion rises, and the intensity of the corrosion likewise changes. The intensity of the corrosion increases up to a maximum value as the width of the crevice is diminished, then decreases as the width of the crevice is further diminished. This phenomenon is due to the change in the character of corrosion of the metal in the crevice. As the width of the crevice diminishes, corrosion acquires a local character, and the passive state is disturbed over the surface of the crevice. As a result, the intensity of the corrosion decreases, while the total corrosion increases. Crevice corrosion usually occurs in gaps that are a few micrometers wide, and is not found in crevices in which circulation of the corrodent is possible. Crevices can be formed during design and fabrication by design detailing and welding, or after erection by surface debris. 5.1.4. Model and Rate of Crevice Corrosion Crevice corrosion is generally governed by generation and transport. The reaction rate at any interface is determined by the local conditions. The local chemistry, the local electrochemical potential, the temperature, and the absolute pressure may be used to determine the reaction rate on any given surface. Models for crevice corrosion typically consist of four main conceptual areas. The four areas are: crevice properties, material/chemical properties, governing equations, and 23 mathematical solution. The governing equations regarding the chemical and electrical transport are central and common to all crevice corrosion problems. By identifying the input values for crevice properties and material/chemical properties specific to the crevice studied, a mathematical solution for the crevice corrosion behaviour may be obtained. Crevice corrosion models may use analytical approaches or numerical approaches to solve the differential equations involved. Figure 3 shows the typical structure of a crevice corrosion model. Crevice Properties Material/Chemical Properties Geometry Material Chemistry Present Temperature, Pressure Material Behaviour Corrosion Rate Species Behaviour Transport Properties Governing Equations Electrical Transport Chemical Transport Mathematical Solution Potential Field Concentration Field Figure 3 - Typical Structure of a Crevice Corrosion Model Data source: Wang, 2004. 5.1.5. Difficulties with Experimentation on Crevice Corrosion It is difficult to obtain information about the chemical and electrical distributions inside a crevice. The microscopic crevices do not allow the insertion of sensors or probes 24 for data collection. Also, the insertion of sensors or probes may influence the corrosion process. Scaling factors are difficult to be applied for experimentation with crevices large enough to allow easy access for data collection. It is not clear which characters of the crevices are required to be scaled. Also, it is difficult to prevent subcrevices in the large-scale crevices to form and dominate the corrosion process. It has been found that there is a lot of variability in the behaviour of crevice corrosion. Nominally identical crevices on the same piece of metal subjected simultaneously to the same environment will not necessarily have the same resistance to crevice corrosion. It is also very difficult to deduce the interactions of the numerous variables affecting crevice corrosion. Therefore, it is difficult to experimentally vary a single parameter for measurement. Although it is difficult to perform measurements within a crevice, it is possible to obtain measurements for the crevice as a whole. Measurements that may be taken include the net anodic current from the crevice, the overall pH, and the initiation time. 5.2. Design and Prevention of Crevice Corrosion Crevice corrosion has been found to be the largest contributor to section loss in steel structures. The crevices formed between back-to-back angles, intermittently welded members, and between link plates and the web at expansion joints are highly vulnerable to crevice corrosion. The best remedy for prevention of crevice corrosion is to totally and permanently isolate the metal from any kind of oxidizing environment. However, this approach is expensive and impractical for large structures such as bridges. Generally, engineers adopt other measures to maintain the corrosion at an economically tolerable 25 level. Several methods employed to control crevice corrosion include selection of materials resistant to crevice corrosion, rational methods of design, painting, galvanized coating, and caulking of crevices with sealant. 5.2.1. Selection of Materials Resistant to Crevice Corrosion Crevice corrosion occurs as a result of acidification of the medium in the crevice and on account of anodic polarization. Therefore, materials that are resistant to crevice corrosion will have no passivation current or a positive activation potential. According to laboratory experiments, the only materials found to be completely resistant to crevice corrosion are stainless steels which contain molybdenum as well as chromium. However, steel is the only metal found to exhibit acceptable mechanical properties and conform to the overall economics in bridge construction. Structural steels are typically classified into three categories: carbon steels containing less than 0.02% copper, copper-bearing steels containing at least 0.20% copper, and weathering steels containing about 2% copper, nickel, chromium, and silicon. Carbon steels offer very little resistant to atmospheric corrosion. Copper-bearing steels have moderate atmospheric corrosion resistance. Weathering steels develop a protective oxide film that inhibits continuous atmospheric corrosion in the steel. However, weathering steels should not be used in connections and details susceptible to crevice corrosion. The shortage of oxygen in the crevice will prevent the formation of a protective oxide film in the crevices. The usage of weathering steel is further discussed in Section 6.3.5 of this report. 26 5.2.2. Rational Methods of Design The design of details to enhance crevice corrosion resistance is important to the long-term performance of steel bridge structures. Improper design details may result in crevice corrosion problems that require periodic maintenance. The benefit gained from limiting crevice corrosion on a structure far outweighs the initial cost of ensuring a better design. Therefore, every effort must be made to avoid section geometries and design details that may result in future crevice corrosion. 5.2.2.1. Consideration of Macroclimates Although crevice corrosion is a form of localized corrosion, the ambient environment is still an important factor in the severity of the corrosion attack. General factors for atmospheric corrosion include relative humidity, average temperature and temperature range, pollutant concentration, suspended dust particles, and total time of wetness. These factors should be taken into consideration at the design stage as they cannot be controlled. 5.2.2.2. Consideration of Microclimates The severity of crevice corrosion is also affected by the nature of the conditions to which the crevice is exposed. Factors that affect the microclimates of the crevice include shelter, orientation, and airborne contaminants. Shelter may affect crevice corrosion on a steel structure in either a beneficial or an adverse manner. In some instances, sheltering may prevent the deposition of corrosive contaminants on to the structure. Alternately, sheltering may prevent rain from washing corrosive contaminants from the surface of a steel structure. Sheltering may also raise or 27 lower the time-of-wetness experienced by the structure. Therefore, it is not possible to determine whether sheltering will have a positive or negative effect on crevice corrosion processes. However, it has been observed that sheltered steel bridge structures contaminated with salt and subjected to periods of condensation or high humidity will corrode at unacceptably high rates. The orientation of a structure or component may affect its rate of corrosion. Generally, surfaces exposed to the ground will experience a higher rate of corrosion than members exposed to the sky. Similarly, surfaces exposed to the north will experience a higher rate of corrosion than members exposed to the south. This phenomenon is attributed to the longer time-of-wetness for the groundward and northward orientations. Contamination by airborne chlorides and sulfur compounds increases the corrosion rate of steel structures. These and other contaminants may originate from a variety of sources, including fumes from chemical process plants, vapours from polluted waterways, splash from roadway water containing de-icing salts, and acid rain. 5.2.2.3. Joints The most severe and common cause of corrosion problem in steel bridges is leaking joints. Runoff water leaking through deck joints will wet the bearings, flanges, web, stiffeners, and diaphragms in the vicinity of the joint. Runoff water may also wick about 150mm up along the web. In order to prevent corrosion due to leaking joints, the steel superstructure on either side of a joint should be painted over a length equal to two beam depths or 3.0m, whichever is greater. The painting should include girder ends, diaphragms, and lateral 28 bracing within the specified distance. Painted deflector (drip) plates should be welded to the bottom flange at the end of each painted section. 5.2.2.4. Link Plates and Pin Connections Water leaking through open deck joints may leak over the link plate and pin connection at cantilever expansion joints of steel girders. At these locations, the steel may be severely attacked by crevice corrosion in the gap between the girder web and the link plates. The crevices will eventually become tightly packed with rust, causing the expansion join to freeze. The thermal expansion and contraction of the girders will then damage the fixed bearings and abutments. 5.2.2.5. Girders Locations that are most susceptible to crevice corrosion in I-girder bridge members include bottom flanges, gusset plates for horizontal bracing, longitudinal stiffeners, bolted splice of horizontal and sloped member, and intersections of bearing and intermediate stiffeners with flanges and gusset plates. In order to avoid water ponding and debris accumulation, the design should minimize the number of horizontal surfaces on which water can pond and debris can accumulate, minimize the number of re-entrant corners that prevent drainage and entrap debris and windblown dust, and provide details for self cleaning and easy discharge of water. When possible, girders should be sloped longitudinally. 5.2.2.6. Truss Members Trough-like truss chords that may be subjected to water ponding and debris accumulation should be sloped longitudinally. An adequate number of 50mm diameter 29 drainage holes should be drilled through the web of the truss. Lateral bracing members should be arranged in an inverted position and should be connected to the underside of gusset plates. 5.2.2.7. Bolted Connections Crevice corrosion in bolted joints is caused by accumulation of water and corrosive components from the atmosphere during condensation and rain periods. The formation of corrosion product within the joint leads to expansive forces, which can deform the plates between adjacent bolts, life the plate edges, and cause large tensile loads on the bolts. Crevice corrosion in bolted joints can be prevented by initially tensioning the bolts to 70 percent of their tensile strength. The design must also specify a plate thickness and bolt spacing to provide adequate stiffness. The bolted steel parts must fit solidly through the joint after the bolts are tightened. The surfaces of bolted parts in contact with the bolt head or nut must be normal to the bolts axis, as sloped parts may permit moisture to intrude beneath the tilted bolt head or nut. In weathering steel bridge structures, bolts made of dissimilar metals, such as stainless steel, may be used if the bolt metal is nobler than the weathering steel. Zinc and cadmium coated bolts should not be used due to the fact that the coating will be sacrificed over time, leaving an exposed carbon steel bolt less resistant to atmospheric corrosion than weathering steel. Load indicator washers may be susceptible to crevice corrosion due to the gap maintained by the flattened protrusions on the washer. When the use of load indicator 30 washers is inevitable, it is recommended that the bolts be tightened to nil gaps to eliminate the crevice created by the washer. 5.2.2.8. Access for Maintenance It is important to provide access for inspection and maintenance in order to ensure the structural integrity of bridge structures by preventing and correcting crevice corrosion. Good design and detailing is critical for ease of inspections, which is necessary to identify possible occurrences of crevice corrosion. Upon identification of crevice corrosion, maintenance actions must be performed, which is only possible i f adequate maintenance access has been provided. Therefore, inspection and maintenance requirements should be incorporated into the design of a steel bridge structure. 5.2.3. Painting Steel structures that are not inherently corrosion resistant are painted to protect the metal. The usage of paint will be discussed further in Section 6.3.1 of this report. 5.2.4. Metallic Coat ing Galvanizing, or applying a zinc coating, provides corrosion protection for steel members. In general, there are six methods used in coating steel members: hot-dipping, zinc electroplating, mechanical coating, sherardizing, thermal spraying, and coating incorporating zinc dust or flakes. Of the six methods available, hot-dip galvanizing is most often used for structural components of steel bridges. 31 5.2.4.1. Hot-Dip Galvanizing Hot-dip galvanizing is the most common form of metallic coating used for the corrosion protection of steel bridge structures. The usage of hot-dip galvanizing will be discussed further in Section 6.3.2 of this report. 5.2.4.2. Thermal Spray Coatings Another form of metallic coating used for the corrosion protection of steel bridge structures is thermal spray coatings. The usage of thermal spray coatings will be discussed further in Section 6.3.4 of this report. 5.3. Maintenance and Rehabilitation of Crevice Corrosion Crevice corrosion can only be prevented by coupling crevice corrosion design with planned long-term maintenance schemes. Maintenance typically involves inspection, corrosion detection, corrosion evaluation, and rehabilitation. 5.3.1. Inspection One of the most important tasks in ensuring the prevention of crevice corrosion is inspection. Experience and technical expertise is required in order to expedite an inspection in a methodical and systematic way. Therefore, inspections should be performed by, or at least supervised by, a very competent and qualified person. Inspections serve as a means to measure the condition of the protective coating system of a steel bridge structure. The results of an inspection must be accurately and fully recorded. The cause of any defect should be identified and rectified to prevent further deterioration. 32 Prior to an inspection, the inspector should have access to the design drawings of the steel bridge structure in order to thoroughly review them for critical details. Locations on the structure prone to crevice corrosion should be identified. These locations should receive careful attention during the inspection. The inspection of weathering steel bridges is more difficult and thus more costly. The inspector must distinguish between a protective and non-protective oxide coating. In addition, it is necessary to inspect the structure at a close proximity (l-3m) in order to be able to detect non-protective oxide coatings. 5.3.2. Corrosion Detection Technology A number of types of Non-Destructive Inspection (NDI) technologies are available for use in corrosion detection. However, no single means of corrosion detection is either ideal or suitable for all forms of corrosion. Table 1 summarizes the primary NDI technologies and their advantages and disadvantages. 33 Table 1 - Primary NDI Technologies Data source: Wang, 2004. Technology Advantages Disadvantages Primarily Detects Visual - Relatively inexpensive - Large area coverage - Portability - Highly subjective - Measurements not precise - Limited to surface inspection - Labour intensive Surface, exfoliation, pitting, and intergranular corrosion Enhanced Visual - Large area coverage - Very fast - Very sensitive to lap joint corrosion - Multi-layer - Quantification difficult - Subjective - requires experience - Requires surface preparation Same as visual except enhanced through magnification or accessibility Eddy Current - Relatively inexpensive - Good resolution - Multiple layer capability - Portability - Low throughput - Interpretation of output - Operator training - Human factors (tedium) Surface and subsurface flaws such as cracks, exfoliation corrosion around fasteners and corrosion thinning Ultrasonic - Good resolution - Can detect material loss and thickness - Single-sided - Requires couplant - Cannot assess multiple layers - Low throughput Corrosion loss and delaminations, voids in laminated structures Radiography - Best resolution (approx.1%) - Image interpretation - Expensive - Radiation safety - Bulky equipment Surface and subsurface corrosion flaws Thermography - Large area scan - Relatively high throughput - "Macro view" of structures - Complex equipment - Layered structures are a problem - Precision of measurements Surface corrosion Robotics and Automation - Potential productivity improvements - Quality assurance - Reliability Various There are also novel N D I technologies in various developmental stages. Table 2 summarizes the trends and directions of various N D I technologies. Table 2 - Trends of NDI Technologies Data source: Wang, 2004. Technology Trends Enhanced Visual - Quantification of corrosion automation of image interpretation - Film highlighters for temporary surface modification - Scanner-based systems Eddy Current - More sophisticated signal and data processing (pulsed eddy current, C-scan imaging) - More sophisticated sensors (multi-frequency) Ultrasonic - More efficient scanning methods (dripless bubbler, gantrys, etc.) - Dry couplants (including laser stimulation) - A i r coupled ultrasonics Radiography - Single-sided methods (backscatter) - Three-dimensional image processing (computed tomography) Thermography - Time domain analysis (thermal wave imaging) - Multi-spectral (dual-band infrared) - Three-dimensional image processing (computed tomography) Robotics and Automation - Attached computer-controlled positioning mechanisms - Gantrys (multi-axis) - Crawlers (including vertical and inverted surfaces) Data Fusion - Image processing (color coding, three dimensional, etc.) - Image correlation (C-scan, etc.) - Multi-mode NDI Sensor Fusion - Currently only attempted within a single technology (e.g., eddy current, infrared) - No observation of research into combining two different sensors into a single probe for simultaneous measurements 34 5.3.3. Maintenance Maintenance of steel bridge structures is necessary to prevent crevice corrosion. Highway bridges can accumulate debris, get wet from condensation, leaky joints, and traffic spray, and are exposed to salts and atmospheric pollutants. Crevice corrosion may be caused by a combination of these aggressive conditions. Therefore, proper maintenance of a steel bridge structure is vital to its structural integrity. Various maintenance actions that may be required are as follows: • Remove loose debris with a jet of compressed air or vacuum cleaning equipment • Scrape off sheets of rust • High-pressure hose wet debris and aggressive agents from the steel surfaces, particularly where the surfaces are contaminated with salt • Trace leaks to their sources by inspecting the bridge on rainy days or by hosing the top of the deck near expansion joints and observing drainage lines. Repair all leaky joints • Install drainage systems, drip plates, and deflector plates that divert runoff water away from the superstructure and abutments • Clean drains and downspouts • Epoxy inject or seal weld all crevices such as those occurring at widely spaced bolt patterns and discontinuous welds • Remedially paint areas of excessive corrosion Through regular maintenance, the bridge structure may be kept debris-free, and any sign of corrosion may be easily identified and rectified. 35 5.3.4. Rehabilitation Crevice corrosion may generally be treated in one of three ways, depending on the type of detail and degree of corrosion: disassemble, blast clean, paint the contact surfaces, and reassemble; epoxy inject the crevice and epoxy caulk all edges; and seal weld all edges. For this rehabilitation method, care must be exercised in the selection of paints, the surface preparation, and the coating of faying surfaces and connections. 5.3.4.1. Selection of Paints The selection of a suitable coating system will ensure effective and cost efficient crevice corrosion control. The first step of the coating selection process is to evaluate the structure and its environment. Factors that should be considered include age, type, size of the bridge, traffic characteristics, factors that lead to crevice corrosion, environmental conditions that contribute to the corrosion process such as time-of-wetness, salt contamination, proximity to a body of water, and expected service life of the coating system. The second step of the selection process is to match the properties of a coating system to the condition of the bridge. The properties of a coating system may be derived from field experience, laboratory testing, and/or theory. 5.3.4.2. Surface Preparation Surface preparation is necessary prior to the remedial painting of the structure. The surface of the bridge structure often has a high roughness, with numerous pits containing chemical contaminants and corrosion products. Different maintenance strategies require different levels of surface preparation. 36 Surface preparation methods used in the United States will be discussed further in Section 8.2 of this report. 5.3.4.3. Coating Faying Surfaces and Connections Faying surfaces should be coated to prevent crevice corrosion. The procedures used in coating faying surfaces and connections are as follows: • Disassemble bolted connections • Blast clean the components separately • Prime, and cure, the components • Vacuum the connection prior to reassembly • Scrub the surface with a commercial detergent and thoroughly rinse with water if the surface is not clean enough for bolting • Reassemble the connection by fully tightening the bolts using the turn-of-nut method For slip critical connections, faying surfaces must be coated in accordance with the requirements for this class of connections. 37 Chapter 6. Corrosion Maintenance Strategies Maintenance projects may fall under the category of corrective maintenance, preventive maintenance, or predictive maintenance. There are also a number of maintenance strategies such as touch-up painting, overcoating, recoating, or even a "do-nothing" approach. With each coating strategy, different coatings may be used, with their associated preparation and application procedures. 6.1. Coating Maintenance Policies There are three types of coating maintenance: corrective maintenance, preventive maintenance, and predictive maintenance. Corrosion monitor plays a different role in each of these strategies. 6.1.1. Correct ive Maintenance Corrective maintenance is the most common type of coating maintenance policy. Corrective maintenance is reactive, with maintenance projects scheduled after the observation of corrosion on a steel structure. With this policy, corrosion monitoring is at a minimum. The emphasis of a corrective maintenance program is on repairs. This policy is widely used since coating maintenance projects are delayed to the latest instance possibly with this policy; however, this policy may be cost ineffective since repairs will tend to become more costly as corrosion continues to degrade the structure over time. In addition, the average reliability of the structure will be decreased. 38 6.1.2. Preventative Maintenance In preventative maintenance, coating maintenance projects occur prior to failure of a coating. Corrosion monitoring plays an important role in preventative maintenance. Corrosion monitoring enables the scheduling of a maintenance project prior to the event of significant corrosion damage otherwise. Preventative maintenance ensures that the condition of the protective coating is good throughout the life of the steel structure. 6.1.3. Predictive Maintenance Predictive maintenance follows a complex program, with maintenance projects scheduled based on the actual condition of the coating, rather than on a predicted fixed schedule. High-level corrosion monitoring, typically via sensors and other electronic devices, is essential to the success of a predictive maintenance program, with the focus on obtaining information on the actual condition of the coating at all times. Predictive maintenance minimizes human inspection and maintenance activities by identifying when coating maintenance projects are actually required. 6.2. Coating Maintenance Strategies The various coating maintenance strategies that may be adopted for each maintenance project include touch-up painting, overcoating, recoating, or the "do-nothing" approach. The "do-nothing" approach does not require any monetary input; however, it will decrease the service life of the structure. When comparing the three maintenance strategies, touch-up painting turns out to be the least expensive on a single-event basis, and recoating is the most expensive. However, the total cost over the service 39 life of the structure of each maintenance strategy will have to be compared using a life cycle cost analysis. 6.2.1. Touch-up Painting Touch-up painting involves cleaning and recoating only areas of the structure where significant corrosion has occurred. Areas with minor corrosion can be ignored until the condition deteriorates to a more severe level. Touch-up painting is only applicable for structures with limited corrosion and adequate adhesion. The American Society for Testing and Materials (ASTM) has published a guideline regarding the evaluation of the degree of rusting on painted steel surfaces (American Society for Testing and Materials, 2001). In the A S T M Standard D610, corrosion grades are assigned based on percentage of the total surface area rusted observed on the structure. The touch-up painting requirements correspond to the A S T M D610 corrosion grade 7 and above, with less than 0.1 percent of the total surface area rusted. Since surface preparation and application of new coating is only required on deteriorated areas of the structure, the associated preparation and application cost would be low compared to other coating maintenance strategies. However, crew and equipment mobilization and set-up costs, as well as indirect costs, per unit area would be high since the total area maintained is small. 6.2.2. Overcoat ing Overcoating involves cleaning and preparation of all areas of the structure where corrosion has occurred. A new coating is then applied to the entire structure, over the bare metal in the cleaned areas and over the existing coating in non-corroded areas. It is 40 important that the new coating selected be compatible with the existing coating, such that proper adhesion between the two coatings is obtained. For overcoating, it is recommended that the coating condition of the structure be at least the level corresponding to A S T M D610 corrosion grade 5 and above, with less than 1.0 percent of the total surface area rusted. Overcoating is more cost effective than recoating when the existing coating is a lead-based paint or another environmentally harmful coating, since removal of such systems requires full containment. 6.2.3. Recoat ing Recoating involves cleaning, surface preparation, and coating application to the entire structure. The coating was allowed to deteriorate to a level where coating maintenance became imminent. Although this strategy is more costly due to the labour and material required for cleaning and coating the entire structure, the coating condition will be restored to its initial condition. 6.2.4. "Do-Noth ing " The "do-nothing" approach means that no maintenance action is performed on the coating even when severe corrosion is observed. The "do-nothing" approach is usually only selected when the structure is nearing its service life, since unchecked corrosion may result in section loss of members and structural failure. If the life of the coating can be estimated at past the service life of the structure, the "do-nothing" approach may be feasible and cost-effective. If the life of the coating is estimated at less than the service life of the structure, the "do-nothing" approach will lead to the premature failure of the structure. 41 6.3. Types of Corrosion Protection Materials Common coating types used in corrosion protection and maintenance include paint systems, hot-dip galvanizing, cold galvanizing, and thermal spray coatings. Weathering steel is also used in some structures to prevent undesirable corrosion. Each type of coating requires specific application procedures and conditions. 6.3.1. Paint Systems There are three general types of paint systems: (1) inhibitive primers, (2) sacrificial primers, and (3) barrier coats. Each of these systems uses a different mechanism to control corrosion. A combination of these systems may be used in the corrosion protection of a steel structure, provided that compatibility between the systems is achieved. (1) Inhibitive primers control corrosion the decreasing the potential difference between the anode and the cathode and/or increasing the electrical resistance across the corrosive cell. (2) Sacrificial primers protect the steel from corrosion by becoming anodic. Sacrificial primers will oxidize in place of the steel, thereby preventing the steel from corrosion damage. (3) Barrier coatings prevent the corrosion of the steel structure by minimizing the penetration of water and oxygen through the coating to the steel substrate. Paint systems are generally applied by brush, by roller, or by spray. Due to the relative simplicity of its application procedure and its relative low costs, paint systems ar< often the preferred strategy for corrosion protection of steel bridges. 42 6.3.2. Hot-Dip Galvaniz ing Hot-dip galvanizing is the most common form of corrosion protection via metallic coating. Hot-dip galvanizing involves coating the surface of the steel structure with a layer of zinc. After proper surface preparation, the steel structure is dipped into a bath of molten zinc. Upon removal from the bath, a layer of relatively pure zinc is deposited on the surface of the steel structure. The size of the members to be hot-dip galvanized is limited by the size of the bath used in the procedure. Hot-dip galvanizing is usually used in the initial fabrication procedure to protect the steel structure from corrosion. If hot-dip galvanizing is to be used for maintenance action, the structure must be disassembled and transported to a fabrication shop where the hot-dip galvanizing can occur. This results in the temporary closure of the bridge, and therefore is rarely considered as a maintenance option. 6.3.3. Co ld Galvaniz ing Cold galvanizing produces similar results as hot-dip galvanizing. A layer of zinc is applied to the surface of the steel structure. The surface preparation required for cold galvanizing is less extensive than that for hot-dip galvanizing. For galvanized surfaces or surfaces with rust, loss particles need to be removed and the surface needs to be degreased. For painted surfaces, the surface needs to be cleaned by grit blasting, ultra high water jetting, or any chemical technique. Cold galvanizing may be applied on-site. The application of cold galvanizing is possible even on damp surfaces in moist conditions. Cold galvanizing may be brushed, rolled, or sprayed, much like a paint system. 43 6.3.4. Thermal Spray Coatings Thermal spray coatings involve applying a layer of metal, zinc or aluminum, to the surface of a steel structure. The zinc or aluminum, in powder or wire form, is fed through a special spray gun containing a heat source. Molten globules of the metal are blown by compressed air jet onto the steel surface. Metallizing is a form of thermal spraying. Metallizing is the spray application of a coat or layer of molten metal onto a prepared surface. Metallizing contains zero volatile organic compounds (VOC). Powder coating is another form of thermal application of protective material. Powder coating is the application of a fine, dry powder to a substrate that is heated to make the powder form a continuous film. Powder coating is capable of being used in the field but is limited by the ability to preheat the metal to be coated. Thermal spray coatings are applied by flame spray or arc spray. High-deposition electric arc guns are faster than flame guns but may result in a rougher surface. 6.3.5. Weathering Steel Weathering steel may be used in steel structures for corrosion protection. Weathering steel produces an oxidized steel layer on the surface of the structure that inhibits further corrosion of the steel. In order for weathering steel to produce a protective film, several conditions have to exist: no prolonged wetting, a wet/dry cycle is required; no heavy concentrations of corrosive pollutants, especially de-icing salts; exposed surfaces must be periodically washed by rain water; good design detailing so that corrosion producing dirt, debris, and 44 moisture are not trapped. It is advised that weathering steel expansion joint areas be painted for protection. The use of weathering steel in place of conventional steel must be determined prior to the fabrication of the structure. If the corrosion maintenance of a structure requires the replacement of the corroded structure with a structure constructed with weathering steel, the existing structure must be disassembled and removed and a new weathering steel structure must be fabricated and erected in its place. This procedure may be costly but long-term savings may be possible due to the low maintenance requirements of a weathering steel structure. 45 Chapter 7. Current Corrosion Maintenance Practice in British Columbia In 2004, MoT is gathering information regarding current corrosion protection coating maintenance practices. In this study, a model is developed to facilitate the decision making process for corrosion maintenance projects. In order to develop a knowledge base regarding the current corrosion protection maintenance practice, this report was developed with interaction with the Ministry of Transportation. Logs of site visits may be found in Appendix A of this report. This section of the report outlines the current procedure employed by MoT for coating maintenance projects. The processes formerly and presently used in obtaining information regarding the current condition of steel bridge structure are described. Examples of current small-scale maintenance projects are provided. 7.1. Coating Maintenance Project Procedure Currently, the procedure for determining the maintenance strategy to be applied to a steel bridge structure follows a series of processes. Initially, the need for maintenance has to be recognized. Bridge inspectors perform routine inspections on steel bridge structures. During these inspections, the inspectors note the current condition of the structure, the protective coating and the amount of corrosion present. The current condition of the bridge structure will determine whether a maintenance project is necessary. Once a need for repair has been identified, the decision maker requires information regarding the bridge in question in order to decide upon a course of action 46 for the maintenance. Information to be assembled includes the condition of the coating, the size of the bridge, the type of construction used for the bridge, the location of the bridge and its usage level, the accessibility of the area to be maintained, etc. At this stage of the decision making process, the decision maker, usually an area manager and a maintenance contractor for MoT, will decide on the scope and priority of the maintenance project to be undertaken. This decision will be based on the coating condition of the bridge, the importance of the aesthetics of the bridge, the size of the maintenance required including the scope and costs, and last but not least, the availability of funds. The maintenance project will then be classified as (a) a large maintenance project, (b) a small maintenance project, or (c) a "do-riothing" project. (a) A large maintenance project is a project that will be handled in B.C. by the Region Highways. This type of project typically involves the overcoating or complete recoating of the corroded structure. A structure will typically fall into this category if the A S T M D610 corrosion rating received is grade 7 or lower. In a large project, the specifications used in the maintenance are developed by MoT specifically for each project, and are derived from the Society for Protective Coatings (SSPC, formerly known as the Steel Structures Painting Council) Standards (Society for Protective Coatings, 2005). An example of the contents of the specifications for a large maintenance project in British Columbia may be found in Appendix B of this report. (b) A small maintenance project, also known as a "fire-fighting" project, is a regular low-level maintenance project. In this type of project, small corroded areas on the structure are maintained as they appear. Small maintenance projects are typically handled by MoT Maintenance Contractors. Small maintenance projects follow less 47 rigorous specifications, and the paint material and application procedures are typically decided by the maintenance contractors. The coating material most often used in B.C. for small maintenance project is marine-grade enamel. (c) The decision makers may find that some structures should not receive maintenance due to economic reasons. The structure may be nearing its design life and there would be no benefit in prolonging the life of its corrosion protection coating. It may also be possible that the structure will require replacement in the near future due to increased usage demand. In these situations, no maintenance will be performed on the structure, and the corrosion protection coating on the structure will be allowed to continue to deteriorate until the structure is decommissioned or replaced. Figure 4 shows the coating maintenance project procedure followed by the British Columbia Ministry of Transportation. I THIS IS W H E R E I T H E M O D E L I FITS IN Proiect Inout Condition of Coating Size of Bridge Type of Bridge Location of Bridge (Usage Level) Accessibility (Inspection Report) Evaluate Prioritv/ScoDe (Zbigniew, Doug) • Aesthetics • Coating Condition • Size of Project o Scope o Costs o Funds available W -Do Nothing'' Region Highways Large Maintenance Projects Allow Coating to Continue to Deteriorate Using MoT Specifications (Derived from SSPC Standard) MoT Maintenance Touch-up Contractors Painting Marine-grade Regular Low-Level W Maintenance Enamel Using Less Rigorous Specifications Figure 4 - British Columbia Ministry of Transportation Coating Maintenance Project Procedure 48 The decision making model developed in this study will facilitate in the decision making process as currently handled by the British Columbia Ministry of Transportation area manager and maintenance contractor as shown in Figure 4. 7.2. Previously Implemented Bridge Coating Rating System From 1995 to 2001, Raine developed a bridge coating rating system for use by the Ministry of Transportation to collect and log data on the current condition of protective coatings on steel bridge structures throughout British Columbia. The program developed by Raine was called the Bridge Coating Rating System (Raine, 2001). The Bridge Coating Rating System is primarily comprised of two parts: data collection and data management. The data collection is done by inspectors in the field, using a standardized data collection form. The data management is then performed by recording the data collected into the computer program. This section of the report will summarize the type of data collected on the data collection form. The data collection form, known as the Bridge Inspection Report, contains basic information about the bridge structure. Basic information includes structure identification number, structure name, span type, number of spans, year built, bridge length, and span length. The Bridge Inspection Report also included location data such as latitude, longitude, highway, nearest town, distance to nearest town, and direction from nearest town. Previous coating information includes year last painted overall, bearings, splash zone, fascia, and protected area, and bridge coating system and colour of primer, midcoat, second midcoat, and topcoat. 49 The Bridge Inspection Report then records date of inspection, inspection team, environment type, roadway approaches type, ambient humidity, weather, air temperature, steel temperature, R H % , and dew point. The data recorded on the condition of the coating is recorded individually for each component, such as west fascia, west protected area, etc. The information recorded includes component name, location tested, percentage of each A S T M D6I0 corrosion rating grade, average A S T M D610 corrosion rating grade, soluble salts present, adhesion, coatability, etc. The average A S T M D610 corrosion rating grade is calculated from the percentage of each A S T M D610 corrosion rating grade as follows: 10 avg _ grade = ^ grade x % grade grade=0 If the component contained 50% A S T M D610 corrosion rating grade 10 and 50% A S T M D610 corrosion rating grade 5, the average A S T M D610 corrosion rating grade would be 10 x 0.5 + 5 x 0.5 = 7.5. The average A S T M D610 corrosion rating for the entire bridge may be found by combining the average A S T M D610 corrosion rating for each component. The rating for each component may be weighted according to their importance (i.e. the weighting for bearings would be higher than the weighting for non-structural components). The detailed information gathered in this Bridge Inspection Report is highly valuable to developing a database for the decision making process regarding scope definition and prioritization of corrosion protection coating maintenance projects in British Columbia. 50 A copy of the Bridge Inspection Report used in the Bridge Coating Rating System may be found in Appendix C of this report. 7.3. Current Bridge Inspection Report Currently, the MoT area manager and maintenance contractor uses a Bridge Management Information System to record data regarding the condition of steel bridge structures in the province. The data collection is performed by the area managers and maintenance contractors using a Condition Inspection Report. The Condition Inspection Report includes basic information regarding the steel bridge structure including region, district, contract area, structure number, status, road number, and features crossed. Also included are the year the structure was built, the length of the structure, the main span length, the main span type, and the number of spans. The inspection type is noted; the most typical inspection type being a routine condition inspection. The inspector name and the date of the inspection are recorded. Various components of the bridge are inspected and their conditions are noted. The categories used for the condition are excellent, good, fair, poor, very poor, cannot inspect, and not applicable. The percentage of each component falling under each condition category is noted in the inspection report. Excellent condition corresponds to an as new condition. Good condition corresponds to a normal wear and deterioration not requiring maintenance or repair, such as chalking or checking of the paint. Fair condition corresponds to minor defects or deterioration, or light corrosion or minor pitting. Poor condition corresponds to advance deterioration that requires damage, such as medium corrosion with less than 15% section 51 loss. Very poor condition corresponds to serious defects or deterioration, such as heavy corrosion with more than 15% section loss. When there are components or parts of components that can not be inspected, a brief description of the reason needs to be specified. When a component is not present on the structure being inspected, the not applicable rating is used. The components of a steel bridge structure that need to be inspected are divided into component groups. These component groups include channel, substructure, superstructure, deck, and approaches. In the channel component group, the components inspected include debris risk, bank/bed scour/buildup, and dolphins/fenders. In the substructure component group, the components inspected include foundation movement, abutments, wing/retaining walls, footings/piling, pier columns/walls/cribs, bearings, caps, and corbels. In the superstructure component group, the components inspected include floor beams/transoms, stringers, girders, portals, bracing diaphragms, truss chords/arch ribs, arch ties, truss diagonals, truss rods/verticals, cables, panels, pins/bolts/rivets, camber/sag, vibration due to live load, and coating of the structure. In the deck component group, the components inspected include sub deck/cross ties, wearing surface, deck joints, curbs/wheelguards, sidewalks, railings/parapets, median barrier, drains/pipes, and coating of the railings. In the approaches component group, the components inspected include signing/lighting, roadway approaches, and roadway flares. 52 Because the Condition Inspection Report is used to note the total condition of the steel bridge structure and is not designed specifically for the inspection of the condition of the coatings, there are only two inspection items related directly to the coating condition: coating of the structure and coating of the railings. However, other components may indirectly relate to the condition of the bridge since deterioration in the coating may result in structural damage of various components such as stringers, girders, bracing, pins, and railings. The inspector will also take notes regarding certain items or maintenance work required as he/she sees fit. These notes will often contain information on the corrosion condition of various components of the structure. The urgency of the work required for the structure, the BCI rating, and the adjusted BCI rating are also noted on the Condition Inspection Report. A copy of the Condition Inspection Report currently used in the Bridge Management Information System may be found in Appendix D of this report. The description of the condition ratings used by the Condition Inspection Report is also included in Appendix D of this report. 7.4. Examples of Maintenance Projects in British Columbia Two of the corrosion protection coating maintenance projects that have been undertaken recently are the Stanley Park Equestrian Overpass maintenance project and the Porteau Cove Emergency Docking Facilities maintenance project. Both of these projects are categorized as small maintenance projects. 53 7.4.1. Stanley Park Equestrian Overpass The Stanley Park Equestrian Overpass is located in Stanley Park, over the Stanley Park Causeway. Built in 1970, the overpass is 78.5m long, with 6 spans. The main span is a stringer type span, with a span length of 9.14m. The overpass allowed equestrian and cyclist traffic to safely pass over the Stanley Park Causeway. The overpass is divided along its length into two equal lanes, one for the equestrian traffic and one for the cyclist traffic. Over the years, the equestrian traffic has worn down the protective covering for the steel in the span, and the exposed steel was displaying signs of corrosion. Prior to the maintenance of the Stanley Park Equestrian Overpass, Radzimowski, a British Columbia Ministry of Transportation area manager, conducted a condition inspection of the overpass on December 10, 2002. In the Condition Inspection Report, the girder was noted as 75% excellent, 20% good, and 5% fair. The coating of the structure was noted as 50% good and 50% poor. The railings and parapets were noted as 99% excellent and 1% fair. The coating of the railings was noted as 25% good, 65% fair, and 10% poor. The west pier bottom section was noted as displaying light corrosion. The bearings were also noted as displaying light corrosion. The girders were noted as displaying light to medium flaking corrosion along the edges and on the underside. The coating of the structure was noted as displaying light rust and rust stains on the sub deck. The railings were noted as displaying light to medium corrosion at the connections. The coating of the railings was noted as displaying spots of rust. A copy of the Condition Inspection Report for the Stanley Park Equestrian Overpass may be found in Appendix D of this report. 54 For the Stanley Park Equestrian Overpass maintenance project, the paint system used was marine enamel suitable for primed interior and exterior surfaces. The product' described as a highly durable alkyd vehicle combined with highly opaque and light-fast pigments. The primer used was a plastic primer. The coating system was applied using the brush application method. Figure 5 shows the condition of one of the vertical support legs of the Stanley Park Equestrian Overpass prior to maintenance. Figure 6 shows the vertical support leg following maintenance. Figure 5 - Stanley Park Equestrian Overpass Vertical Support Leg Prior to Maintenance Source: Jensen, 2004, 1. 5 5 Figure 6 - Stanley Park Equestrian Overpass Vertical Support Leg Following Maintenance Source: Radzimowski, 2004, 1. 7.4.2. Porteau Cove Emergency Docking Facilities The Porteau Cove Emergency Docking Facilities, built in 2001, are located in Porteau Cove, and are intended for use as an emergency docking facility when other docking facilities are out of service. During times when emergency docking facilities are not required, the Porteau Cove Emergency Docking Facilities are used as a recreational area. The Porteau Cove Emergency Docking Facilities include various non-structural steel components such as railings and lamp posts, many of which are irregular in geometry. Due to the nature of the docking facilities (located over water), access to the maintenance areas is limited and often requires special equipment and arrangements. Prior to the maintenance of the Porteau Cove Emergency Docking Facilities, 56 Radzimowski, a British Columbia Ministry of Transportation area manager, conducted a condition inspection of the facilities on June 28, 2004. In the Condition Inspection Report, the railings and parapets were noted as 10% excellent, 75% good, 10% fair, and 5% poor. The coating of the railings was noted as 85%) good and 15% poor. The piles were noted as displaying light corrosion on exposed surfaces, and medium corrosion with flaking rust and less than 15% section loss at the top sections. The railings were noted as displaying light to medium corrosion for the steel components, and heavy corrosion locally with perforation and section loss for the railing steel mesh. The coating of the railings was noted as displaying aging paint and local coating failure. A copy of the Condition Inspection Report for the Porteau Cove Emergency Docking Facilities may be found in Appendix D of this report. For the Porteau Cove Emergency Docking Facilities maintenance project, the paint system used was marine enamel suitable for primed interior and exterior surfaces. The product is described as a highly durable alkyd vehicle combined with highly opaque and light-fast pigments. The primer used was a plastic primer. The coating system was applied using the brush application method. Figure 7 shows the Porteau Cove Emergency Docking Facilities following maintenance. 57 Figure 7 - Porteau Cove Emergency Docking Facilities Following Maintenance Source: Radzimowski, 2004, 2. 58 Chapter 8. Current Corrosion Maintenance Practice in the United States and Worldwide In 1998, the United States National Research Council Transportation Research Board National Cooperative Highway Research Program (NCHRP) commissioned a synthesis study, Synthesis 257, on Maintenance Issues and Alternate Corrosion Protection Methods for Exposed Bridge Steel (Neal, 1998). Synthesis 257 reviewed the current state of the practice regarding the maintenance and protection strategies for exposed structural bridge steel in the United States. The report served as a summary of the information available in the United States regarding corrosion protection and maintenance. A comprehensive questionnaire was developed and distributed amongst transportation agencies in the United States, Canada, the District of Columbia, and Puerto Rico. The questionnaire addressed issues such as the materials used in corrosion protection and the logic used in arriving at a maintenance decision. Eighty-five percent of the agencies responded to the questionnaire. The synthesis report outlines material selection for corrosion protection maintenance, as well as surface preparation and application requirements for various corrosion protection maintenance strategies. Responses to the questionnaire were used to tabulate the United States experience with durability of corrosion protection coatings and maintenance strategies. Maintenance considerations were identified, along with the maintenance management systems being used by the various transportation agencies. The synthesis report includes some information on corrosion protection maintenance strategies practiced in various European countries. 59 This section of the report outlines the findings of Synthesis 257. 8.1. Corrosion Protection Materials used in the United States In the United States, various methods are used for the corrosion protection and maintenance of exposed steel structures. The protective materials include paint, metallizing, hot-dip galvanizing, powder coating, weathering steel, and other materials. The corrosion protection material that has been used longest and most often is paint. The paint system most widely used in the past had been a lead pigment in an oil or oil/alkyd resin. Due to environmental concerns, lead-based paints are no longer used and have been replaced primarily by inorganic zinc rich paints (IOZ) and organic zinc rich paints (OZ). Inorganic zinc rich paints are chosen more often due to its ability to provide friction for slip critical connections. As a result of the volatile organic compound (VOC) restrictions, the topcoat for a zinc rich primer has moved from a vinyl coating to epoxy and polyurethanes or water-borne acrylics. For maintenance painting of existing structures, it is important to control the cure times between coats and to take into account compatibility and surface contamination issues. The survey found that for new construction of steel bridge structures, about ninety percent of the transportation agencies use a zinc rich system, and both IOZ and OZ paints were used. The type and number of intermediate and/or topcoats used differed between the agencies, ranging from none to two coats. The most common intermediate and topcoat system used was an epoxy polyamide and polyurethane system. For maintenance painting, one-fourth of the agencies used a zinc rich system when a total removal of the existing system was required. Other systems used include 60 non-leaded alkyd systems, water-borne acrylic systems, epoxy mastic systems, and polyurethane resin systems. Protective pigments, other than zinc, used includes aluminum, red iron oxide/zinc oxide, calcium sulfonate, and zinc hydroxy phosphite. Lead-based coatings are no longer being used. Metallizing is not widely used in the United States. When a bridge structure is metallized, a thick metallizing layer (200-300 microns) is applied, with topcoats mainly applied for aesthetic purposes only. For new steel bridge construction, the survey indicated that metallizing of beams and girders are used by seven agencies for a total of 36 structures. Metallizing of bearings and expansion devices are used by 16 agencies The average price for field application of metallizing, including the cost of lead-based paint removal, was found to be $182.25/m2 (US dollars). The use of hot-dip galvanizing for new construction has been reported by nine agencies in the United States, for a total of 178 structures. Galvanizing of bearings, insert plates, and cross frames are used by twenty-one agencies. The number of galvanized steel bridge structures in the United States is very low compared to the number of galvanized steel bridge structures in Canada. Powder coatings are rarely used in the United States, with only two agencies reporting the use of powder coatings for beams and girders of steel bridge structures. Powder coatings for cross frames or diaphragms are used by five agencies. Weathering steel bridge structures are quite common in the United States. Weathering steel is used by forty-eight agencies for a total of 4,301 weathering steel bridge structures. Different states adopt different positions regarding the use of 61 unpainted weathering steel bridges. Some states have banned the use of unpainted weathering steel bridges in the highway system, some states advocate the painting of weathering steel bridges for aesthetic purposes, and some states continue the construction of unpainted weathering steel bridges. Other materials are also used for bridge construction in the United States. Stainless steel has been used for pin-and-hanger assemblies in conjunction with steel members. Some aluminum bridges are also in use. In total, steel structures comprise about 40 percent of the bridges over 6m long in the United States. According to the survey, half of the agencies determine the type of material to be used'based on policy. One-tenth of the agencies allowed the designer to make the decision regarding the material to be used. One-tenth indicated that a combination of policy and designer decision is used in the material selection process. About 60 percent of the agencies considered future maintenance costs during the up-front design of the structures. 8.2. Strategies and Surface Preparation Methods used in the United States The primary corrosion protection maintenance strategies used in the United States include touch-up painting, overcoating, and recoating. Touch-up painting requires the cleaning of and coating application for areas of the existing coating damaged by corrosion. Overcoating requires the cleaning and priming of areas of the existing coating damaged by corrosion, followed by the coating application for the entire bridge structure. Repainting requires the full removal of the existing coating, followed by the coating application for the entire bridge structure. 62 Surface preparation for touch-up painting and overcoating may be performed using a variety of surface preparation methods, ranging from power washing to spot blasting. Recoating requires the use of either commercial blast cleaning (SSPC-SP6), near-white blast cleaning (SSPC-SP10), or power tool cleaning to bare metal (SSPC-SP11) (Society for Protective Coatings, 2005). Application of the coatings is performed using the brush, roller, or spray application methods, as recommended by the manufacturer of the coatings. 8.3. United States Experience with Durability of Coatings and Strategies The durability of a corrosion protection system is directly related to its quality of environmental exposure. Factors that contribute to the rate of corrosion includes temperature, pH of the environment, humidity, and metallurgical and electrolyte composition. Figure 8 shows a summary of the United States experience with the durability of various coating materials and maintenance strategies. The coating materials compared includes concrete covering, powder coating, weathering steel, galvanizing, metallizing, and paint. The maintenance strategies compared includes overcoating, recoating, and new paint application. Figures 9-15 show the break down of the survey responses for each coating material and each maintenance strategy. 63 Repaint Overcoat Metallizing Galvanizing Weathering Steel Powder Coating Figure 8 - Failure Ranges of Various Coating Materials and Maintenance Strategies Data source: Neal, 1998. Figure 9 - Durability of Paint Data source: Neal, 1998. 64 25 30 35 40 45 50 55 60 65 70 75 80 Years Figure 10 - Durability of Repaint Data source: Neal, 1998. r 15 20 25 30 35 40 45 50 55 60 70 80 Years Figure 11 - Durability of Overcoat Data source: Neal, 1998. 65 25 30 35 40 45 50 55 Years Figure 12 - Durability of Metallizing Data source: Neal, 1998. 25 30 35 40 45 50 55 Years Figure 13 - Durability of Galvanizing Data source: Neal, 1998. 66 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 Years Figure 14 - Durability of Weathering Steel Data source: Neal, 1998. 12 • 5 1 0 1 5 20 25 30 35 40 45 50 55 60 65 70 Years Figure 15 - Durability of Concrete Data source: Neal, 1998. 67 It is observed that the durability of concrete covering and weathering steel approach the design life of the steel bridge structures. The coating that is expected to have the highest durability is galvanizing. Overcoating has the lowest durability due to possible cleaning and adhesion issues. The durability of recoating is considered to be similar to the durability of paint application on new steel structure construction. 8.4. United States Experience with Maintenance Considerations Due to the budgetary limitations for the maintenance of corrosion protection coatings, it is necessary to perform analyses to determine the priority of the maintenance work that is needed. Considerations for the prioritization of the maintenance work can be divided into two categories: condition analysis and priority assessment. In condition analysis, considerations include: current coating system type, thickness and number of coats, and whether the structure has been repainted; condition of the substrate under the existing coating and the extent of substrate rehabilitation necessary; configuration of the surface; degree of flexing anticipated in the steel surface; variability in temperature; overall condition of the existing coat, including the adhesion, eroded paint film, corrosion pattern, pitting and percent of rusted service area; presence of ionic or non-ionic contaminants, such as chlorides, sulfates, bird droppings, grease, heavy dirt; and surface preparation history. In priority assessment, considerations include: type of member; expected service life of the structure; expected life of the coating to be applied; whether the overcoatability of the applied coating is to be a significant factor; cost and logistics of structural replacement; available or allowable application methods; emission limitations regarding air, water, soil; future maintenance costs of applied coatings; limitations on surface 68 preparation methods; degree to which a coating failure can be tolerated; cost of overcoating as a percentage of the cost of abatement; urgency of the action; necessity of structural preservation; and other costs such as traffic control and mobilization costs. With the above-mentioned considerations addressed, the agency can arrive at a course of action for the corrosion protection coating maintenance work. Table 3 lists the types of maintenance policies practiced by the various agencies participating in the survey. Preventative maintenance is maintenance that is targeted at preventing a failure from occurring. Routine maintenance is maintenance that occurs at specific time intervals. Deferred maintenance refers to non-critical maintenance that is deferred due to a lack of funding. Conditional based maintenance is maintenance that is performed based and ranked on the actual condition of the structures. Replacement is the replacement of existing structures with new structures. Rehabilitation is the restoration of replacement of certain components of the structure. Prioritization involves using life-cycle costs to determine the order in which maintenance work is to be performed on the various structures. Major maintenance is maintenance that involves the repair of the defective areas of the coatings. Table 3 - Maintenance Policies Practiced by Agencies Data source: Neal, 1998. Types Responses Preventative 37 Routine 41 Deferred 46 Conditional Based 53 Replacement 33 Rehabilitation 44 Prioritization 27 Major Maintenance 50 69 It is observed that all the agencies participating in the survey indicate the use of conditional based maintenance. It can then be said that most agencies prioritize the maintenance work based only on the current condition of the steel bridge structure rather than the life-cycle costs of the maintenance. Although deferral is presumed to be an economic benefit based on the assumption that a benefit will be derived from doing a higher valued project, deferral of maintenance work generally increases its life-cycle cost. The structure will continue to degrade or deteriorate due to corrosion. Deferral may result in a severe level of corrosion which will limit or restrict the choices for maintenance. Figure 16 shows the agencies' levels of concern regarding general maintenance issues. Figure 17 shows the agencies' levels of concern regarding structure conditions of the structures. Figure 18 shows the agencies' levels of concern regarding mitigation factors. 70 X 0 Levels of Concern Figure 16 - Levels of Concern Regarding General Maintenance Issues Data source: Neal, 1998. Levels of Concern Figure 17 - Levels of Concern Regarding Structure Conditions Data source: Neal, 1998. 71 Levels of Concern Figure 18 - Levels of Concern Regarding Mitigation Factors Data source: Neal, 1998. The focal issue of concern deals with economics. This is mainly due to the budget generally allocated for maintenance of steel bridge structures. The primary concern regarding the structure condition is the adhesion of the existing coating. The adhesion is of great importance since it dictates the coating approach that the engineer may select. The largest concerns regarding mitigation factors are the expected life of the structure and the expected life of the coating to be applied. A structure nearing its design life will not require the application of a highly durable protective coating, and in some instances, may not require the application of any coating at all. In order to facilitate the decision making regarding the maintenance of corrosion protection coatings of steel bridges, a bridge management system should be developed and used. In the United States, a bridge management expert system (Pontis) has been developed by the Federal Highway Administration (FHWA). When the bridge 72 management systems are fully implemented, they can provide condition assessment sufficiency ratings, as well as prioritization, deterioration rates, life-cycle costing, and optimization. A bridge management system should simplify recordkeeping once it is implemented by the agencies. It is important to note that an essential part of any bridge management system is an extensive database. According to the survey, forty agencies indicated that a bridge management system is available, with thirty-four agencies indicating that the bridge management system is implemented. Nine agencies indicated that they do not have a bridge management system. In terms of the decision regarding corrosion protection coating maintenance, forty agencies indicated that the use of a rating system to determine the need for maintenance painting. A l l forty agencies evaluate the amount of corrosion product present, whereas only twenty-five agencies evaluate the adhesion of the existing coating. No agency evaluated the amount of contaminant present. When the need for maintenance is determined, half of the agencies indicate the use of a system to prioritize the structures. 8.5. Corrosion Maintenance Practice in Europe In Europe, the focus regarding maintenance painting of steel bridges is on "applying a high-durability paint system onto a properly prepared surface early in the failure cycle of the existing bridge coating in order to avoid any significant metal loss" (U.S. Department of Transportation, 1997). Therefore, the predominant form of coating maintenance is recoating. Maintenance strategies such as touch-up painting and overcoating are generally not used. 73 For the painting of steel bridges in Europe, micaceous iron oxide (MIO) is widely used as a pigment in the intermediate and topcoats. In Switzerland, Germany, and the Netherlands, multi-coat paint systems are used, with primers containing zinc-phosphate. In Switzerland, the primer used for protection and maintenance on existing structures is a two-component epoxy-combination of low solvent content. The topcoat used is a modified synthetic resin combination with active corrosion-protection pigments. The surface preparation typically specified for protection and maintenance on existing structures in European countries is near-white blast cleaning (SSPC-SP10), in order to allow for recoating. In some countries in Europe, thermal spraying of steel bridge structures is rather common. In the United Kingdom, 80 to 90 percent of shop fabricated bridge steel is metallized. Arc-sprayed aluminum is used as the primer for metallizing. A thin film (100 microns) is applied followed by subsequent inhibitive topcoats of epoxy, urethane, or silicone alkyd for additional corrosion protection. 74 Chapter 9. Steel Bridge Coating Maintenance Evaluation Model based on Life-Cycle Costs A Steel Bridge Coating Maintenance Evaluation Model has been developed by the author to facilitate in the decision making process regarding corrosion protection coating maintenance strategies for steel bridge structures in British Columbia. The decision making tool was created using the computer software DecisionPro (Vanguard, 2002). 9.1. Model Layout The Steel Bridge Coating Maintenance Evaluation Model proposes a maintenance strategy to be implemented for the duration of the life of the steel structure. The strategy proposed would be repeated throughout the design life of the structure as necessary, based on the durability of the strategy chosen. Only one type of maintenance strategy is assumed to be applied throughout the life of the structure. This assumption is deemed to suffice for the model since the structure may be re-evaluated during the course of its life if a different strategy is desired or i f circumstances surrounding the decision are changed. However, it should be noted that the actual number of times that a strategy may be repeated will depend on the adhesion of the existing coating, which is affected by previous maintenance actions performed on the structure. The decision maker should be aware of previous maintenance activities and select a strategy accordingly. The general layout of the Steel Bridge Coating Maintenance Evaluation Model involves arriving at a proposed maintenance strategy given the coating condition of a steel bridge structure. The coating condition of a structure may be divided into three 75 categories: minor damage, fair damage, and severe damage. When the coating has experienced minor damage, the maintenance strategies that may be selected include touch-up painting, overcoating, recoating, and "do-nothing". When the coating has experienced fair damage, the maintenance strategies that may be selected include overcoating, recoating, and "do-nothing". When the coating is severely deteriorated, the maintenance strategies that may be selected are limited to recoating and "do-nothing". The strategy with the lowest equivalent uniform annual cost in the applicable coating condition category will be selected. Figure 19 shows the general layout of the Steel Bridge Coating Maintenance Evaluation Model. strategy H corr rate minor_damage H do nothing_EUAC |-» touchupEUAC]-> overcoat E U A C p -H recoat EUAC h> H fair_damage do_nothing_EUAC overcoat EUAC ^ L t H recoat EUAC l i H severe_damageH do_nothing_EUAC L i L i H recoat EUAC Figure 19 - Steel Bridge Coating Maintenance Evaluation Model General Layout 9.1.1. Model Constra ints The strategies that are available for selection are based on the coating condition of the steel bridge structure. The coating condition may be classified using A S T M D610 Standards. According to coating expert, the condition of the bridge may be classified as 76 minor damage, fair damage, and severe damage based on the A S T M D610 ratings (Raine, 2005, 1). A coating that received an A S T M D610 corrosion rating of 8 or above is classified as having experienced minor damage, and the maintenance strategies that may be selected for this coating include touch-up painting, overcoating, recoating, and "do-nothing". A coating that received an A S T M D610 corrosion rating of 5 or above is classified as having experienced fair damage, and the maintenance strategies that may be selected for this coating include overcoating, recoating, and "do-nothing". A coating that received an A S T M D610 corrosion rating below 5 is classified as having experienced severe damage, and the maintenance strategies that may be selected for this coating include recoating and "do-nothing". Figure 20 shows the Steel Bridge Coating Maintenance Evaluation Model constraints. r—<^  corr_rate | minor_damage minor damaqe := MlN( do nothinq E U A C , touch up E U A C , overcoat E U A C , recoat E U A C strategy strategy:1 1 IF(corr ra te iB , minor damaqe, IF( corr rate^5,fair damage, severe damage) fair_damage fair damaqe :» MIN( do nothinq E U A C , overcoat E U A C , recoat E U A C ) severe_damage severe damage := MIN(do nothinq E U A C , recoat E U A C ) Figure 20 - Steel Bridge Coating Maintenance Evaluation Model Constraints 9.1.2. Model Formulation The selection of the maintenance strategy to be applied to the steel bridge structure is based on the equivalent uniform annual costs of the various strategies. The equivalent uniform annual costs of the strategies are calculated using economic principles applied to the coating maintenance cash flows throughout the life of the structure. The 77 equivalent uniform annual costs are calculated from the present value of the costs using the following formula: strategy _TPV x interest x (1 + interest)11'" (1 + interest)1*" -1 strategy_EUAC = / t . . ..,/,/, where strategy_EUAC = equivalent uniform annual cost of the strategy strategy_TPV = total present value of the strategy interest = interest rate (rate of return) life = remaining design life of the structure In turn, the total present value of each maintenance strategy is calculated by summing the cash flows throughout the life of the structure, and discounting to their present worth by taking into account the time value of money. The expected cash flows in the future for each strategy are calculated by applying an escalation rate to the initial cost of each strategy at present. The formula for touch-up painting, overcoating, and recoating is as follows: ™ eye* strategy _ I C x ( 1 + escalation)x^ra,csy-durab""y) strategy _1PV - ^ 'i + interesty1"^-*"*"™ where strategy_IC = initial cost of the strategy (cost at present) escalation = escalation rate strategy_durability = durability of the strategy (time interval between maintenance) touch_up_cycles = number of maintenance projects required throughout the remaining life of the structure 78 The initial cost of each strategy is calculated from the unit cost of the strategy and the maintenance area for the strategy. The equation is as follows: strategy _IC = strategy _ unit _ cost x strategy _ maintenance _ area The maintenance area for touch-up painting is taken as twenty-five times the corroded area of the bridge. The factor of twenty-five is applied since the corroded area for touch-up painting is usually very small, and it is highly likely that an area surrounding the corroded area will be included in the maintenance as a result. Therefore, assuming the radius of the maintenance area to be five times larger than the radius of the corrosion, the maintenance area will be twenty-five times larger than the area of the corrosion. The maintenance area for both the overcoating and recoating is taken as the total surface area of the bridge structure. This is due to the fact that in both procedures, the entire bridge structure will be coated. For the "do-nothing" strategy, the present value of the strategy cost is calculated as the difference between the present value of the cost of replacing the structure at the end of its design life and the cost of replacing the structure at the end of its coating life, plus the present value of any additional costs associated with the replacement of the structure. These additional costs include costs resulting from the premature decommissioning of the bridge, social and political costs, and possibly benefits from replacing the structure with a new structure requiring less maintenance. The formulae are as follows: replace _ cost x (1 + escalation) (1 + inter est)!lJe life replace _ end _of _ life __PV replace _ end _of _ coating _PV replace _ cost x (1 + escalation) (\ +inter estyoa,i"s-79 replace _ add cost x (1 + escalation)c""m'-"Jc (1 + interest)1 replace _ add _ cost _PV = 7T7^'t Ac™/«„g _m where replace_end_of_life_PV = present value of the cost of replacing the structure at the end of its design life replace_end_of_coating_PV = present value of the cost of replacing the structure at the end of its coating life replace_add_cost_PV = present value of the additional costs associated with the replacement of the structure replace_cost = cost of replacing the structure (cost at present) replace_add_cost = additional costs associated with replacing the structure (cost at present) coating_life = remaining life of the coating The remaining life of the coating is calculated from the current condition of the coating. The formula is as follows: ,. r 100 -corr rating coating _hje = = corr_ curve where corr_rating = percentage of the total area of the structure corroded based on the A S T M D610 corrosion rating of the structure corr_curve = corrosion curve of the structure (rate at which corrosion occurs) The corrosion curve of the structure is assumed to be linear due to the fact that there is insufficient data regarding the actual corrosion behaviour of bridge structures in British Columbia. As more information is available, the model may be updated to reflect a non-linear corrosion curve. 80 9.2. Variations of the Model Several variations of the model have been developed for various amount of input data available and for various purposes. The five variations of the model are: (1) Overall bridge condition rating, using deterministic input values (2) Bridge component condition rating, using deterministic input values (3) Overall bridge condition rating, using probabilistic input values (4) Bridge component condition rating, using probabilistic input values (5) Bridge inventory, using overall bridge condition rating, deterministic input values The first four models reflect different levels of condition inspection required. For using the model with an overall bridge condition rating, only one input value is required for the A S T M D610 corrosion rating, as is available from the current Bridge Management Information System used by the MoT. For using the model with the bridge component condition ratings, an A S T M D610 corrosion rating is required for each component of the bridge, and a detailed inspection, similar to the Bridge Coating Rating System developed by Raine, is necessary (Raine, 2001). Deterministic or probabilistic values may be used for the input parameters of the model, as determined by the decision maker. Probabilistic input values may better reflect the actual values, and will result in probabilistic output values, providing a guide to the likelihood and confidence of the solution. The fifth variation of the model involves the inventory of the steel bridge structures in British Columbia. By using this variation of the model, the funding that should be allotted annually for the coating maintenance of steel bridge can be calculated, 81 and a prioritization of the maintenance projects may be possible. In this model, an overall bridge condition rating input for each bridge structure in the inventory is required. Deterministic values are used for the input parameters of the model. 9.2.1. Overall Bridge Condition Rating, Deterministic Input The first variation of the model is used when only one A S T M D610 corrosion rating is available for the entire bridge structure, and when deterministic input and output values are desirable. In this variation, the proposed maintenance strategy is calculated using the above-mentioned model formulation. Figure 21 shows the general layout of this variation of the evaluation model. | strategy minor_damage minor_damage := MIN(.do_nothing_EUAC, touch_up_EUAC, overcoat E U A C , recoat_EUAC ) I do nothing E U A C h> | touch_up_EUAC . h> I overcoat_EUAC [* \ recoat_EUAC~r> fair_damage fair damage := MIN( do nothing._EUAC, overcoat E U A C , recoat_EUAC ; I do nothing. E U A C P | overcoat_EUAC recoat E U A C severe_damage severe_damage := MIN( do_nothing._EUAC, recoat_EUAC ) hi do._nothing. E U A C | - ^ recoat_EUAC Figure 21 - General Layout of the First and Third Model The complete first model may be found in Appendix E of this report. 9.2.2. Bridge Component Condition Rating, Deterministic Input The second variation of the model is used when a separate A S T M D610 corrosion rating is available for each component of the bridge structure, and when deterministic input and output values are desirable. 82 The components of the bridge structure identified in this variation of the model are major structural components, bearings, expansion joints, and non-structural components. A maintenance strategy is proposed for each bridge component identified, and the overall cost is calculated as the lower of the equivalent uniform annual maintenance cost of the four components combined, or the equivalent uniform annual cost of the "do-nothing" strategy for the entire bridge structure. However, the decision maker must note that the model does not include a discount for the reduced mobilization and overhead costs for the case when the same strategy is adopted for two or more of the components of the bridge. Therefore, when the same strategy is proposed for two or more of the bridge components, the actual equivalent annual cost of the maintenance will be lower than the calculated equivalent annual cost of the maintenance. Figure 22 shows the general layout of this variation of the evaluation model. | overall._Sttalegy ;= MlN( overall maintenance_EUAC, do nothing_EUAC ) | rH struct. Strategy ""}-» | overall_maintenance_EUAC "~ |_ H l overall_maintenance_ EUAC := struct strategy + bear strategy * exp joints_strategy + non struct_strategy | 1 do nothing_EUAC h» - \ bear_strategy . j-* - | expjoints strategy r* -H non_struct_strategy f-> Figure 22 - General Layout of the Second and Fourth Models The complete second model may be found in Appendix F of this report. 9.2.3. Overall Bridge Condition Rating, Probabilistic Input The third variation of the model is used when only one A S T M D610 corrosion rating is available for the entire bridge structure, and when probabilistic input and output values are desirable. In this variation, the proposed maintenance strategy is calculated similarly to the first variation. However, the distribution of the output, due to the combined effects of the 83 distribution of the inputs as described in Section 9.3.2, is calculated using Monte Carlo simulations. In order to obtain the output using Monte Carlo simulations in DecisionPro, the user needs to access the "Tool" menu in the toolbar, and select "Monte Carlo", "Run Simulation". A dialog box will then appear. The user should verify that the output node name is correct, and select the checkboxes for "Frequency distribution graph" and "Cumulative distribution graph". A frequency distribution graph and a cumulative distribution graph will then be created as separate sheets in the DecisionPro file. Figure 21 shows the general layout of this variation of the evaluation model. The complete third model may be found in Appendix G of this report. 9.2.4. Br idge C o m p o n e n t Condit ion Rating, Probabi l ist ic Input The fourth variation of the model is used when a separate A S T M D610 corrosion rating is available for each component of the bridge structure, and when probabilistic input and output values are desirable. The components of the bridge structure identified in this variation of the model are major structural components, bearings, expansion joints, and non-structural components. In this variation, the proposed maintenance strategy is calculated similarly to the second variation. However, the distribution of the output, due to the combined effects of the distribution of the inputs as described in Section 9.3.2, is calculated using Monte Carlo simulations. Figure 22 shows the general layout of this variation of the evaluation model. The complete fourth model may be found in Appendix H of this report. 84 9.2.5. Bridge Inventory, us ing Overall Bridge Condit ion Rating, Deterministic Input The fifth variation of the model is used to calculate the required budget for the coating maintenance program for the steel bridge structures in British Columbia. This variation of the model can also be used to facilitate in the prioritization of the maintenance projects. This variation requires only one A S T M D610 corrosion rating for each steel bridge structure, and deterministic input and output values are used. In this variation, the proposed maintenance strategy for each bridge structure is calculated similarly to the first variation. In order to calculate the annual funding requirement of the coating maintenance program, the equivalent uniform annual maintenance cost of each bridge structure is summed. To facilitate in the prioritization of the maintenance projects, the benefit-cost ratio of each bridge structure is calculated. The formula is as follows: do nothing EUAC - strategy cost benefit _ cost _ ratio = —= = strategy _ cost where benefit_cost_ratio = benefit-cost ratio of each maintenance project do_nothing_EUAC = equivalent uniform annual cost of the "do-nothing" strategy for each bridge structure strategy_cost = equivalent uniform annual cost of the selected strategy for each bridge structure In this formulation, the benefit gained from the maintenance project is taken as the difference between the cost of "do-nothing" and the cost of applying the selected maintenance strategy. 85 Figures 23 and 24 show the general layout of this variation of the evaluation model. funding funding := SUM( strategy_costfl ) strategy_cost := [] IF( corr_rate[x] k 8, minor_damageIxl, IF( corr_rate[x] £ 5. fair_damagelx), severe_damagetx) H corr..ra"te"i-» -j minor_damage \ * \ fair_damage Y+ \ severe_damage }*• Figure 23 - General Layout of Funding Calculations in the Fifth Model benefit_cost_ratio number • benefit_cost_ratio = 1 1 x := 0 benefit[x] strategy_cost[x] benefit number -1 benefit := [] do_nothing_EUAC [x] - strategy_cost[x] x :=0 | do_nothing EUAC ~r> _ > | strategy_cost . number I strategy_cost | -^ | number |-^ Figure 24 - General Layout of Benefit-to-Cost Ratio Calculations in the Fifth Model The complete fifth model may be found in Appendix I of this report. 9.3. Model Input The input parameters used in the model includes the A S T M D610 corrosion rating of the overall structure, the A S T M D610 corrosion rating of the bridge components, the corrosion curve of the structure, the escalation rate, the interest rate, the total surface area of the structure, the surface area of the bridge components, the remaining design life of the structure, the durability and unit cost of each maintenance strategy, the replacement cost of the structure, and the additional costs associated with the replacement of the structure. The input parameters assume deterministic values in the first, third, and fifth variations of the model, and probabilistic values in the second and fourth variations of the model. 86 9.3.1. Input Parameters The input for the first, second, third, and fourth model are entered directly into DecisionPro. The user may enter the input directly into a table displayed in the upper-left corner of the DecisionPro sheet (in the sheet "decision" or "overall^decision"). Figure 25 shows the input table for the first model. Inputs: corr rate 8 corr curve 5 escalation 0.025 interest 0.03 total bridqe surface area 3500 life 70 touch up durability 12.5 touch up unit cost 450 overcoat durability 20 overcoat unit cost 130 recoat durability 25 recoat unit cost 200 replace cost 20000000 replace add cost 0 Figure 25 - Input Table for the First Model The input for the fifth model is entered into a Microsoft Excel worksheet, and this worksheet must be opened first in order for the DecisionPro model to run. The model is formatted to process an inventory of 1 to 800 steel bridge structures. The input values for each steel bridge structure may be entered in the appropriate column for each input value, in the row corresponding to its bridge number. The analysis requires the bridges to be numbered consecutively with no skipped numbers, starting from bridge number one. 9.3.1.1. Input for Overall Bridge Condition Rating, Deterministic Input The input parameters required for the first variation of the model are summarized in Table 4. 87 Table 4 - Input Parameters for the First Variation of the Model INPUT PARAMETER NAME INPUT PARAMETER DESCRIPTION corr rate ASTM D610 corrosion rating for the overall bridge structure corr curve corrosion curve of the bridge coating escalation escalation rate interest interest rate total bridge surface_area total surface area of the bridge structure life remaining design life of the bridge structure touch up durability durability of the touch-up painting strategy (time interval between maintenance) touch up unit cost unit cost (per unit area) of the touch-up painting strategy overcoat_durability durability of the overcoat strategy (time interval between maintenance) overcoat unit cost unit cost (per unit area) of the overcoat strategy recoat durability durability of the recoat strategy (time interval between maintenance) recoat unit cost unit cost (per unit area) of the recoat strategy replace cost cost of replacing the bridge structure replace add cost additional costs associated with replacing the bridge structure The input values are deterministic for this variation of the model; therefore, only the expected value for each parameter is required to be entered. 9.3.1.2. Input for Bridge Components Condition Rating, Deterministic Input The input parameters required for the second variation of the model are summarized in Table 5. 88 Table 5 - Input Parameters for the Second Variation of the Model INPUT PARAMETER NAME INPUT PARAMETER DESCRIPTION struct corr rate ASTM D610 corrosion rating for the main structural components bear corr rate ASTM D610 corrosion rating for the bearings expJoints_corr_rate ASTM D610 corrosion rating for the expansion joints non struct corr rate ASTM D610 corrosion rating for the non-structural components corr curve corrosion curve of the bridge coating escalation escalation rate interest interest rate struct surface area surface area of the main structural components bear surface area surface area of the bearings expJoints_surface_area surface area of the expansion joints non struct surface area surface area of the non-structural components life remaining design life of the bridge structure touch up durability durability of the touch-up painting strategy (time interval between maintenance) touch_up_unit_cost unit cost (per unit area) of the touch-up painting strategy overcoat_durability durability of the overcoat strategy (time interval between maintenance) overcoat unit cost unit cost (per unit area) of the overcoat strategy recoat_durability durability of the recoat strategy (time interval between maintenance) recoat unit cost unit cost (per unit area) of the recoat strategy replace_cost cost of replacing the bridge structure replace_add_cost additional costs associated with replacing the bridge structure The input values are probabilistic for this variation of the model; therefore, a distribution type and the associated statistical inputs for each parameter are required to be entered. The distribution types available for use in DecisionPro include uniform distribution, normal distribution, and lognormal distribution. Uniform distributions are entered as randilowerJimit, upper Jimif). Normal distributions are entered as nrand(mean,std_dev). Lognormal distributions are entered as lrand(mean,std_dev). 9.3.1.3. Input for Overall Bridge Condition Rating, Probabilistic Input The input parameters required for the third variation of the model are summarized in Table 6. 89 Table 6 - Input Parameters for the Third Variation of the Model INPUT PARAMETER NAME INPUT PARAMETER DESCRIPTION corr rate ASTM D610 corrosion rating for the overall bridge structure corr curve corrosion curve of the bridge coating escalation escalation rate interest interest rate total bridge surface area total surface area of the bridge structure life remaininq design life of the bridge structure touch up durability durability of the touch-up painting strategy (time interval between maintenance) touch up unit_cost unit cost (per unit area) of the touch-up painting strategy overcoat durability durability of the overcoat strategy (time interval between maintenance) overcoat unit cost unit cost (per unit area) of the overcoat strategy recoat durability durability of the recoat strategy (time interval between maintenance) recoat unit cost unit cost (per unit area) of the recoat strategy replace cost cost of replacing the bridge structure replace add cost additional costs associated with replacing the bridge structure The input values are deterministic for this variation of the model; therefore, only the expected value for each parameter is required to be entered. 9.3.1.4. Input for Bridge Components Condition Rating, Probabilistic Input The input parameters required for the fourth variation of the model are summarized in Table 7. 90 Table 7 - Input Parameters for the Fourth Variation of the Model INPUT PARAMETER NAME INPUT PARAMETER DESCRIPTION struct corr rate ASTM D610 corrosion rating for the main structural components bear corr rate ASTM D610 corrosion rating for the bearings expjoints corr rate ASTM D610 corrosion ratinq for the expansion joints non struct corr rate ASTM D610 corrosion rating for the non-structural components corr curve corrosion curve of the bridge coating escalation escalation rate _ interest interest rate . struct surface area surface area of the main structural components bear surface area surface area of the bearings expjoints surface area surface area of the expansion joints non struct surface area surface area of the non-structural components life remaininq design life of the bridge structure touch up durability durability of the touch-up painting strategy (time interval between maintenance) touch up unit cost unit cost (per unit area) of the touch-up painting strategy overcoat durability durability of the overcoat strategy (time interval between maintenance) overcoat unit cost unit cost (per unit area) of the overcoat strategy recoat durability durability of the recoat strateqy (time interval between maintenance) recoat unit cost unit cost (per unit area) of the recoat strategy replace cost cost of replacing the bridge structure replace add cost additional costs associated with replacing the bridge structure The input values are probabilistic for this variation of the model; therefore, a distribution type and the associated statistical inputs for each parameter are required to entered. 9.3.1.5. Input for Bridge Inventory, using Overall Bridge Condition Rating, Deterministic Input The input parameters required for the fifth variation of the model are summarized in Table 8. 91 Table 8 - Input Parameters for the Fifth Variation of the Model INPUT PARAMETER NAME INPUT PARAMETER DESCRIPTION number number of steel bridqe structures in the inventory corr rate — A S T M D610 corrosion rating for the overall bridge structure (1 for each bridge) corr curve corrosion curve of the bridge coating (1 for each bridge) escalation escalation rate interest interest rate total bridge surface area total surface area of the bridge structure (1 for each bridge) life remaining design life of the bridge structure (1 for each bridge) touch up durability durability of the touch-up painting strategy (time interval between maintenance) touch up unit cost unit cost (per unit area) of the touch-up painting strategy overcoat durability durability of the overcoat strategy (time interval between maintenance) overcoat unit cost unit cost (per unit area) of the overcoat strategy recoat durability durability of the recoat strategy (time interval between maintenance) recoat unit cost unit cost (per unit area) of the recoat strategy replace cost cost of replacing the bridge structure (1 for each bridge) replace add cost additional costs associated with replacing the bridge structure (1 for each bridge) The input values are deterministic for this variation of the model; therefore, only the expected value for each parameter is required to be entered. The input values will be entered into the Microsoft Excel worksheet inventory_input_data.xls, which is linked to the DecisionPro worksheet. Note that the Microsoft Excel worksheet must be opened before the DecisionPro model in order to perform the analysis. The values from the Microsoft Excel worksheet will be imported into the DecisionPro worksheet as a matrix for each input parameter. The matrix for each input parameter will contain the input value for each bridge structure in the inventory. 9.3.2. D i scus s ion of Input Values The input values used for the variations of the model will be discussed in this section of the report. A description of each input parameter, the factors affecting the value of each input parameter, the suggested value of each input parameter, and the justification of the suggested value of each input parameter will be summarized. 92 corr_rate - the A S T M D610 corrosion rating for the bridge structure is a reflection of the condition of the coating as evaluated by bridge coating inspectors on the site. Because the corrosion rating is determined by visual inspection of individual inspectors, this value is subjective and may differ from inspector to inspector. However, coating inspectors are typically trained experts in their field; therefore, the variation in the results should be minimal. In addition, it is general practice that inspectors calibrated their inspection techniques in common training sessions on a regular basis. The corrosion rating number input is bridge specific, but the variation of the input may be suggested. It is assumed that the bridge coating inspectors are correct in their determination of the corrosion rating 90% of the time, with error of one rating number high or low 5% of the time each. Therefore, in the variations of the model requiring probabilistic input, the input value for the corrosion rating is a discrete distribution, with a 90% chance of being the observed corrosion rating, and a 5% chance each of being the observed corrosion rating plus or minus one. The corrosion rating for individual components of the bridge follows a similar distribution. Figure 26 shows the distribution of the corrosion rating input value using a discrete distribution, with an observed A S T M D610 corrosion rating of 8. 93 Frequency Distribution 800 600 111 i, ,, - J --.*'.:*>; EP i t .-* * E5Z3 , , , . , . K g i—i—i—i—i—i—•—i—1 i ' i 1 i ' i 7 7.2 7.4 7.6 7.8 8 8.2 8.4 8.6 8.8 9 — corrjating Figure 26 - Corrosion Rating Input Value Distribution corr_curve - the corrosion curve of the bridge structure reflects the corrosion behaviour of the coating based on field observations, and is expressed in units of % area corroded / year. Due to the lack of field observation data for steel bridge structures in British Columbia, the corrosion curve for the steel bridges are currently assumed as linear. This assumption is incorrect and will require update as more data is available for the construction of a corrosion curve that is more representative of the real behaviour of the coating corrosion. According to Raine, the factors affecting the value of the corrosion curve are the size of the corroded area, the coatings used, the microclimate of the site, and the macroclimate of the site (Raine, 2005, 3). Raine suggested that the likely distribution of the actual corrosion curve would be the normal distribution since the distributions of all the factors would blend to result in a normal distribution overall. The 94 corrosion curve input for the model is bridge specific, and the distribution suggested is a normal distribution with a standard deviation of 25% of the mean. With a standard deviation of 25% of the mean, it is assured that the value of the corrosion curve will not result in the negative range, and the distribution will result in possible values at 200% of the mean, which is representative of the high variability of this input parameter. Figure 27 shows the distribution of the corrosion curve input value using a normal distribution, with a mean value of 5%/year, and a standard deviation of 1.25%/year. Frequency Distribution 200 -| • 1 Figure 27 - Corrosion Curve Input Value Distribution escalation - the escalation rate is an economic input to the model used to calculate the future costs of each maintenance strategy due to inflation. Many factors affect the value of the escalation rate, including supply-demand ratio, price trend of raw materials, and trend of labour compensation. According to Russell, the current prediction 95 of the escalation rate in Canada is 2.5% (Russell, 2005). He expects the distribution of the escalation rate to follow a lognormal distribution, since he believes that Canada is in a low economic cycle presently, and the distribution of the escalation should definitely be skewed right. Russell suggests a standard deviation of approximately 0.3%. Figure 28 shows the distribution of the escalation input value using a lognormal distribution, with a mean value of 2.5%, and a standard deviation of 0.3%. Frequency Distribution 250 200 0.016 0.018 0.034 0.036 0.038 Figure 28 - Escalation Input Value Distribution interest - the interest rate is an economic input to the model used to calculate the equivalent uniform annual cost of each strategy for comparison, accounting for the time value of money. The interest rate is also referred to as the rate of return, and is an economic input used to represent the expected return (profit) of the investment of a sum of money. Factors affecting the value of the interest rate include the amount of funding 96 available, and the total number and value of the projects currently undertaken. According to Russell, the current prediction of the interest rate is 3%, with a lognormal distribution and a standard deviation of approximately 0.3% (Russell, 2005). Russell believes that Canada is in a low economic cycle presently, and that the distribution of the interest should definitely be skewed right. Figure 29 shows the distribution of the interest input value using a lognormal distribution, with a mean value of 3%, and a standard deviation of 0.3%. Frequency Distribution —I 1 r I i ' " 1 1 0.026 0 .028 0 .03 0.032 0 .034 0 .036 0 .038 H interest Figure 29 - Interest Input Value Distribution total_bridge_surface_area - the total surface area of a bridge may be calculated from the design drawings and specifications for the bridge. This value is taken as a deterministic input value. Although there are tolerance allowances for the total surface area, these minor deviations are considered negligible for this application. The total 97 bridge surface area input is bridge specific. The surface areas for individual components of the bridge are also taken as deterministic input values. life - the remaining design life of a steel bridge structure is affected by many factors. Factors may include the structural condition of the bridge, the forecasted usage level of the bridge, the usage capacity of the bridge, the aesthetic importance of the bridge, as well as various social and political factors. Bridges are typically designed with a safety margin, and it is highly unlikely that a bridge will fail before the end of its design life. In fact, many bridges have survived well past 200% of their design life. Therefore, the remaining design life input value used in the model is suggested to follow a lognormal distribution with a shift in the mean. The remaining design life input value is bridge specific. However, the standard deviation suggest is 30% of the mean for all bridge structures, with a shift of 60% of the mean. For example, if the remaining design life of a structure is 70 years, the input to the DecisionPro model will be lrand(70,21)+42. Figure 30 shows the distribution of the life input value using a lognormal distribution, with a mean value of 70 years, a standard deviation of 21 years, and a shift of 42 years. 98 Frequency Distribution Figure 30 - Life Input Value Distribution touch_up_durability - the durability of the touch-up painting strategy reflects the time interval between maintenance projects required. The factors affecting the durability of the touch-up painting strategy include environmental exposure, paint system used, application procedures, condition during application and curing, and expertise of maintenance crew. The distribution for the durability of touch-up painting will likely follow a lognormal distribution, as a factor of safety is normally applied and the durability of the system will surpass its stated durability. According to Raine, the expected durability of touch-up painting is 12.5 years, with a standard deviation of 2.5 years (Raine, 2005, 3). Figure 31 shows the distribution of the touch-up durability input value using a lognormal distribution, with a mean value of 12.5 years, and a standard deviation of 2.5 years. 99 Frequency Distribution touch_up_durability Figure 31 - Touch-Up Durability Input Value Distribution touch_up_unit_cost - the cost per unit area of the touch-up painting strategy is made up of material costs, labour costs (removal, preparation, and application), cost of temporary structures, mobilization costs, traffic control costs, environmental costs, social costs, etc. Factors affecting the touch-up painting unit cost include type of construction used for the structure, supply distance, accommodation for crew, and accessibility of the maintenance area. The unit cost for touch-up painting will typically be 1.5 to 3 times the unit cost for a complete recoat, but the maintenance area will be much smaller, resulting in a lower total cost overall. Raine suggests a uniform distribution for the touch-up painting unit cost input value, with a lower limit of $300/m2 and an upper limit of $600/m2 (Raine, 2005, 2). For the variations of the model where a deterministic input value is desired, the value of the touch-up painting unit cost is taken as $450/m2. Figure 100 32 shows the distribution of the touch-up unit cost input value using a uniform distribution, with a lower limit of $300/m2, and an upper limit of $600/m2. Frequency Distribution touch_up_unit_cost Figure 32 - Touch-Up Unit Cost Input Value Distribution overcoat_durability - the durability of the overcoating strategy reflects the time interval between maintenance projects required. The factors affecting the durability of the overcoating strategy include environmental exposure, paint system used, application procedures, condition during application and curing, and expertise of maintenance crew. The distribution for the durability of overcoating will likely follow a lognormal distribution, as a factor of safety is normally applied and the durability of the system will surpass its stated durability. According to Raine, the expected durability of overcoating is 20 years, with a standard deviation of 5 years (Raine, 2005, 3). Figure 33 shows the 101 distribution of the overcoat durability input value using a lognormal distribution, with a mean value of 20 years, and a standard deviation of 5 years. Frequency Distribution 200 -, • ' Figure 33 - Overcoat Durability Input Value Distribution overcoat_unit_cost - the cost per unit area of the overcoating strategy is made up of material costs, labour costs (removal, preparation, and application), cost of temporary structures, mobilization costs, traffic control costs, environmental costs, social costs, etc. Factors affecting the overcoating unit cost include type of construction used for the structure, supply distance, accommodation for crew, and accessibility of the maintenance area. The unit cost for overcoating will typically be 0.5 to 0.8 times the unit cost for a complete recoat. Raine suggests a uniform distribution for the overcoating unit cost input value, with a lower limit of $100/m2 and an upper limit of $160/m2 (Raine, 2005, 2). For the variations of the model where a deterministic input value is desired, the value of the 102 overcoating unit cost is taken as $130/m2. Figure 34 shows the distribution of the overcoat unit cost input value using a uniform distribution, with a lower limit of $100/m2, and an upper limit of $ 1607m . Frequency Distribution Figure 34 - Overcoat Unit Cost Input Value Distribution recoat_durability - the durability of the recoating strategy reflects the time interval between maintenance projects required. The factors affecting the durability of the recoating strategy include environmental exposure, paint system used, application procedures, condition during application and curing, and expertise of maintenance crew. The distribution for the durability of recoating will likely follow a lognormal distribution, as a factor of safety is normally applied and the durability of the system will surpass its stated durability. According to Raine, the expected durability of recoating is 25 years, with a standard deviation of 5 years (Raine, 2005, 3). Figure 35 shows the distribution of 103 the recoat durability input value using a lognormal distribution, with a mean value of 25 years, and a standard deviation of 5 years. Frequency Distribution 200 -] Figure 35 - Recoat Durability Input Value Distribution recoat_unit_cost - the cost per unit area of the recoating strategy is made up of material costs, labour costs (removal, preparation, and application), cost of temporary structures, mobilization costs, traffic control costs, environmental costs, social costs, etc. Factors affecting the recoating unit cost include type of construction used for the structure, supply distance, accommodation for crew, and accessibility of the maintenance area. Raine suggests a uniform distribution for the recoating unit cost input value, with a lower limit of $ 1507m2 and an upper limit of $250/m2 (Raine, 2005, 2). For the variations of the model where a deterministic input value is desired, the value of the recoating unit cost is taken as $200/m2. Figure 36 shows the distribution of the recoat unit cost input 104 value using a uniform distribution, with a lower limit of $ 1507m2, and an upper limit of $250/m2 Frequency Distribution 150 155 160 165 170 175 180 185 190 195 200 205 210 215 220 225 230 235 240 245 250 H H | recoat unit cost Figure 36 - Recoat Unit Cost Input Value Distribution replace_cost - the cost of the replacement of the bridge structure consists of many components, including design costs, fabrication costs, erection costs, environmental costs, and social costs. Due to the fact that the replacement of a bridge structure is a construction project, the variation in the actual costs incurred will be relatively large. Factors affecting the replacement cost of a bridge structure include delay in schedule, availability of labour crews, the number of construction projects occurring in the same time frame, and unforeseen costs arising from claims. It is suggested that a lognormal distribution with a shift be used for the replacement cost input value. The replacement cost input value is bridge specific; however, a standard deviation of 50% of 105 the mean and a shift of 50% of the mean is suggested for all bridge structures. The large standard deviation and shift is representative of the high uncertainties associated with construction projects. Figure 37 shows the distribution of the replacement cost input value using a lognormal distribution, with a mean value of $20,000,000, a standard deviation of $10,000,000, and a shift of $10,000,000. Frequency Distribution 300 -, 1 1.5e+7 2e+7 2.5e+7 3e+7 3.5e+7 4e+7 4.5e+7 5e+7 5.5e+7 6e+7 6.5e+7 7e+7 7.5e+7 8e+7 8.5e+7 9e+7 9.5e+7 replace_cost Figure 37 - Replace Cost Input Value Distribution replace_add_cost - the additional costs associated with the replacement of a steel bridge structure include all the costs that are not encompassed by the replacement cost input parameter. The additional costs associated with the replacement of a bridge structure may include the cost of the reduced life span of a bridge, social costs such as duration of closures, and political costs. The additional costs may also assume a negative value, for possible benefits such as increased tourism activity. The additional costs are 106 assumed to follow a normal distribution, with a standard deviation of 20% of the mean. The additional costs of the replacement of a bridge are bridge specific. 9.4. Model Output The model outputs obtained from the variations of the model include the maintenance strategy selected, the equivalent uniform annual cost associated with the selected maintenance strategy, the benefit-cost ratio for each bridge structure in the inventory, and the recommended annual budget for maintenance. The output values are deterministic in the first, third, and fifth variations of the model. Probabilistic distributions for the output may be displayed in the second and fourth variations of the model. 9.4.1. Output Parameters The strategy selected for the life-cycle maintenance of a steel bridge structure and its associated equivalent uniform annual cost is an indication of the minimum amount of funding that should be allocated annually to the corrosion protection coating maintenance of that particular steel bridge structure. However, it should be noted that the equivalent uniform annual cost is only an economic equivalent to the actual cash flows of the maintenance to be performed; the actual cash flows of the maintenance will be larger than the equivalent uniform annual cost, and will be spaced in time intervals equal to the durability of the strategy selected. The actual cash flows of the maintenance may be found in the model contained within the node "strategy_PV" for the various strategies. The benefit-cost ratio for each bridge structure (calculated in the fifth variation of the model), may be used in facilitating the prioritization of the maintenance projects for 107 the steel bridge structures in the British Columbia inventory. The benefit-cost ratio is calculated by comparing the benefit obtained by performing the suggested maintenance strategy as opposed to adopting the "do-nothing" strategy, to the cost of performing the suggested maintenance strategy. The various maintenance projects may then be prioritized by arranging the projects in order of decreasing benefit-cost ratio, with the project associated with the highest benefit-cost ratio having the highest priority. The recommended annual budget for maintenance is calculated by summing the equivalent uniform annual costs associated with the maintenance of each steel bridge structure in the British Columbia inventory. In combination with the prioritization of the maintenance projects using the benefit-cost ratio, the recommended annual funding may be used to adequately maintain the corrosion protection coating of the steel bridge structures in the British Columbia inventory. 9.4.1.1. Output from Overall Bridge Condition Rating, Deterministic Input In the first variation of the model, the output node "strategy" (in the sheet "decision") contains the equivalent uniform annual cost associated with the selected maintenance strategy. The selected maintenance strategy may then be identified by matching the displayed equivalent uniform annual cost to the equivalent uniform annual costs of each of the strategies. The equivalent uniform annual cost calculated by this variation of the model is a deterministic value. 108 9.4.1.2. Output from Bridge Components Condition Rating, Deterministic Input In the second variation of the model, the output node "over all_strategy" (in the sheet"'overall _decision") contains the equivalent uniform annual cost associated with the selected maintenance strategy, which is chosen as the minimum of the sum of the maintenance strategies for the individual components or a "do-nothing" strategy for the entire bridge structure. The equivalent uniform annual cost associated with the selected maintenance strategy for each individual component may be found in the node "'component^strategy" (in the sheets "'struct_decision", "bear _decision", "expJointsjdecision", and "non_structjdecision") for each component. The selected maintenance strategy may then be identified by matching the displayed equivalent uniform annual cost to the equivalent uniform annual costs of each of the strategies. The equivalent uniform annual costs calculated by this variation of the model are deterministic values. 9.4.1.3. Output from Overall Bridge Condition Rating, Probabilistic Input In the third variation of the model, the output node "strategy" (in the sheet "decision") contains the equivalent uniform annual cost associated with the selected maintenance strategy. The selected maintenance strategy may then be identified by matching the displayed equivalent uniform annual cost to the equivalent uniform annual costs of each of the strategies. This variation of the model may calculate the frequency distribution of the equivalent uniform annual cost. To display the frequency distribution of the output, the user needs to access the "Tools" menu from the toolbar, and select "Monte Carlo", "Run 109 Simulation". A dialog box will then appear. The user should verify that the output node name is correct (in this case, "strategy"), and select the checkboxes for "Frequency distribution graph" and "Cumulative distribution graph". A frequency distribution graph and a cumulative distribution graph will then be created as separate work or tree sheets in the DecisionPro file. The sample size used for the Monte Carlo simulations may also be selected by the user. The frequency distribution of the equivalent uniform annual cost may be used to predict the likelihood of expected costs associated with the maintenance strategy selected. 9.4.1.4. Output from Bridge Components Condition Rating, Probabilistic Input In the fourth variation of the model, the output node "overalljstrategy" (in the sheet "overalljdecision") contains the equivalent uniform annual cost associated with the selected maintenance strategy, which is chosen as the minimum of the sum of the maintenance strategies for the individual components or a "do-nothing" strategy for the entire bridge structure. The equivalent uniform annual cost associated with the selected maintenance strategy for each individual component may be found in the node "componentjstrategy" (in the sheets "structjdecision", "bearjdecision", "exp Joints jdecision", and "non jstructjdecision") for each component. The selected maintenance strategy may then be identified by matching the displayed equivalent uniform annual cost to the equivalent uniform annual costs of each of the strategies. This variation of the model may calculate the frequency distributions of the equivalent uniform annual costs. In order to display the frequency distributions of the outputs, the user needs to access the "Tools" menu from the toolbar, and select "Monte 110 Carlo", "Run Simulation". A dialog box will then appear. The user needs to verify that the output node name is correct (in this case, "strategy" or " component_strategy"), and select the checkboxes for "Frequency distribution graph" and "Cumulative distribution graph". A frequency distribution graph and a cumulative distribution graph will then be created as separate sheets in the DecisionPro file. The sample size used for the Monte Carlo simulations may also be selected by the user. The frequency distributions of the equivalent uniform annual costs may be used to predict the likelihood of expected costs associated with the maintenance strategies selected. 9.4.1.5. Output from Bridge Inventory, using Overall Bridge Condition Rating, Deterministic Input In the fifth variation of the model, the output node "output" (in the sheet "summary") summarizes the bridge number, maintenance strategy selected and associated equivalent uniform annual cost, and benefit-cost ratio of each bridge in the British Columbia steel bridge inventory. To facilitate the display of the output and the prioritization of the maintenance projects, the output of the DecisionPro model may be displayed in a Microsoft Excel worksheet. In order to display the output in the Microsoft Excel worksheet, the user needs to right-click and copy the contents of the output node "output" in the DecisionPro model, and paste the contents into cell "AT" of the Microsoft Excel worksheet inventory_output.xls. In the Microsoft Excel worksheet, the bridge numbers of the bridge structures analyzed will be displayed in column A of the worksheet, the maintenance strategies proposed will be displayed in column B of the worksheet, the equivalent uniform annual costs of the maintenance strategies proposed will be displayed in column 111 C of the worksheet, and the benefit-cost ratios will be displayed in column D of the worksheet. The output data for the bridge structures analyzed may then be sorted according to their benefit-cost ratio to facilitate the prioritization of the maintenance projects. The proposed annual funding allotment for the coating maintenance program is displayed in the output node "funding" (in the sheet "program funding") of the DecisionPro model. This output value is also displayed in cell " G J " of the Microsoft Excel worksheet. 9.4.2. Sensitivity Ana lys i s Plots The effects of the various input parameters on the equivalent uniform annual cost for the selected strategy may be displayed using sensitivity analysis plots. In order to create a sensitivity plot in the DecisionPro model, the user needs to access the "Tools" menu from the toolbar, and select "Sensitivity Analysis", "Sensitivity Graph". A dialog box will then appear. The "graph node" should be set as the output node containing the equivalent uniform annual cost for the selected strategy, and the "specific nodes" option should be selected for the "while changing" box. The range of the varying parameter whose effects are to be studied may be changed according to the user's needs. By clicking "OK", a new dialog box will appear. The name of the varying parameter whose effects are to be studied should be entered into the dialog box. By clicking " O K " once again, a sensitivity analysis plot of the effects of the varying parameter on the equivalent uniform annual cost will be created as a separate work or tree sheet in the DecisionPro model. 112 9.5. Examples using the Steel Bridge Coating Maintenance Evaluation Model Each variation of the Steel Bridge Coating Maintenance Evaluation Model was used with example input data to generate example output values. In the first and third variations of the model, the value of the equivalent uniform annual cost of the maintenance strategy is deterministic. In the second and fourth variations of the model, the frequency distribution of the value of the equivalent uniform annual cost of the maintenance strategy is calculated. In the fifth variation of the model, data from five steel bridge structures are analyzed and their recommended maintenance strategies and associated equivalent uniform annual costs are calculated. The benefit-cost ratios of the five bridges are also calculated, as well as a recommended annual funding requirement for the maintenance program of the bridges. 9.5.1. Example us ing Overal l Bridge Condit ion Rating, Deterministic Input The input values used in the example using the first variation of the model are outlined in Table 9. 113 Table 9 - Input Values for the First Variation of the Model INPUT PARAMETER NAME INPUT PARAMETER VALUE INPUT PARAMETER UNIT corr rate 8 corr curve 5 % area / year escalation 2.5 % interest 3 % total bridge_surface_area 3500 mA2 life 70 years touch_up_durability 12.5 years touch_up_unit_cost 450 $ / m A 2 overcoat_durability 20 years overcoat unit cost 130 $ / m A 2 recoat durability 25 years recoat unit cost 200 $ / mA2 replace_cost 20000000 $ replace add_cost 0 $ The maintenance strategy proposed for this structure is touch-up painting, with an equivalent uniform annual cost of approximately $7,005. A copy of this example may be found in Appendix E of this report. 9.5.2. Example us ing Br idge Component s Condi t ion Rating, Deterministic Input The input values used in the example using the second variation of the model are outlined in Table 10. 114 Table 10 - Input Values for the Second Variation of the Model INPUT PARAMETER NAME INPUT PARAMETER VALUE INPUT PARAMETER UNIT struct corr rate 8 bear corr rate 5 exp joints corr_rate 5 non struct corr rate 7 corr curve 5 % area / year escalation 2.5 % interest 3 % struct surface area 3000 mA2 bear surface area 1 mA2 expjoints surface area 4 mA2 non struct surface area 495 mA2 life 70 years touch up durability 12.5 years touch up_unit_cost 450 $ / mA 2 overcoat durability 20 years overcoat unit cost 130 $ / mA 2 recoat durability 25 years recoat unit cost 200 $ / mA 2 replace cost 20000000 $ replace add cost 0 $ The maintenance strategy proposed for the main structural components of this structure is touch-up painting, with an equivalent uniform annual cost of approximately $6,005. The maintenance strategy proposed for the bearings of this structure is overcoating, with an equivalent uniform annual cost of approximately $16. The maintenance strategy proposed for the expansion joints of this structure is overcoating, with an equivalent uniform annual cost of approximately $62. The maintenance strategy proposed for the non-structural components of this structure is overcoating, with an equivalent uniform annual cost of approximately $7,683. The total equivalent uniform annual cost of the maintenance of the entire bridge structure is approximately $13,765. A copy of this example may be found in Appendix F of this report. 115 9.5.3. Example us ing Overal l Bridge Condit ion Rating, Probabil ist ic Input The input values used in the example using the third variation of the model are outlined in Table 11. Table 11 - Input Values for the Third Variation of the Model INPUT PARAMETER NAME INPUT PARAMETER VALUE INPUT PARAMETER UNIT Distribution Mean Std.Dev. / Lower Limit Shift / Upper Limit corr rate discrete 8 r ' corr curve normal 5 1.25 % area / year escalation lognormal 2.5 0.3 % interest lognormal 3 0.3 % total bridge surface_area deterministic 3500 mA2 life lognormal 70 21 42 years touch up durability lognormal 12.5 2.5 years touch up unit cost uniform 300 ' 600 $ / mA 2 overcoat durability lognormal 20 5 years overcoat unit cost uniform ||jjJi!E3i(f: 100 160 $ /m A 2 recoat durability lognormal 25 5 years recoat unit cost uniform 150 250 $ /mA 2 replace cost lognormal 20000000 10000000 10000000 $ replace add cost normal 0 0 $ The maintenance strategy proposed for this structure is touch-up painting, with an equivalent uniform annual cost of approximately $7,703. The frequency distribution and the cumulative distribution of the expected equivalent uniform annual cost are shown in Figure 38 and Figure 39. 116 Frequency Distribution 110 368 848 1,011 788 481 259 ^ 115 | 4^2 | 1|S | j | | | | f | 0 10000 20000 30000 40000 50000 60000 70000 80000 90000 100000 110000 120000 130000 140000 150000 160000 H strategy Figure 38 - Model Variation 3 - EUAC Frequency Distribution Figure 39 - Model Variation 3 - EUAC Cumulative Distribution 117 The sensitivity analysis plot of the effects of the financial factors, escalation and interest, on the equivalent uniform annual cost is shown in Figure 40. It is shown that a 10% increase in the escalation rate will result in a 11.9% increase in the equivalent uniform annual cost of the maintenance strategy. Also, a 10% increase in the interest rate will result in a 4.1% decrease in the equivalent uniform annual cost of the maintenance strategy. Therefore, the equivalent uniform annual cost of the maintenance strategy is highly sensitive to the financial input values. Input Sensitivity Graph 10,000 7,500 -\ H —\ 1 1 -10 -5 0 5 1( % Change in Input —a— escalation X interest Figure 40 - Sensitivity Analysis Plot of Financial Factors The sensitivity analysis plot of the effects of the durability of the coating on the equivalent uniform annual cost is shown in Figure 41. It is shown that a 20% increase in the durability of the coating will result in a 12% decrease in the equivalent uniform annual cost of the maintenance strategy, corresponding to an annual savings of $1,055. 118 Therefore, a premium equivalent to 12% of the current equivalent uniform annual cost is allowed for obtaining a coating with a 20% increased durability. Input Sensitivity Graph 12,000 -| • • • 7,000 -| t - 1 H 1 1 1 1 1 -20 -10 0 10 20 % Change in Input touch_up_durability Figure 41 - Sensitivity Analysis Plot of Coating Durability A copy of this example may be found in Appendix G of this report. 9.5.4. Example us ing Br idge Component s Condi t ion Rating, Probabil istic Input The input values used in the example using the fourth variation of the model are outlined in Table 12. 119 Table 12 - Input Value for the Fourth Variation of the Model INPUT P A R A M E T E R N A M E INPUT P A R A M E T E R V A L U E INPUT P A R A M E T E R UNIT Distr ibut ion Mean Std.Dev. / Lower Limit Shift / U p p e r Limit struct corr rate discrete 8 bear corr rate discrete 5 expjoints corr rate discrete 5 non struct corr rate discrete 7 corr curve normal 5 1.25 % area / year escalation lognormal 2.5 0.3 % interest lognormal 3 0.3 % struct surface area deterministic 3000 mA2 bear surface area deterministic 1 mA2 expjoints surface_area deterministic 4 mA2 non struct surface_area deterministic 495 mA2 life lognormal 70 21 42 years touch up durability lognormal 12.5 2.5 years touch up unit_cost uniform 300 600 $ / mA2 overcoat durability lognormal 20 5 years overcoat unit_cost uniform 100 160 $ /mA 2 recoat durability lognormal 25 5 years recoat unit cost uniform 150 250 $ / mA 2 replace cost lognormal 20000000 10000000 10000000 $ replace add cost normal 0 0 $ The maintenance strategy proposed for the main structural components of this structure is touch-up painting, with an equivalent uniform annual cost of approximately $7,507. The maintenance strategy proposed for the bearings of this structure is overcoating, with an equivalent uniform annual cost of approximately $19. The maintenance strategy proposed for the expansion joints of this structure is overcoating, with an equivalent uniform annual cost of approximately $77. The maintenance strategy proposed for the non-structural components of this structure is overcoating, with an equivalent uniform annual cost of approximately $9,556. The total equivalent uniform annual cost of the maintenance o f the entire bridge structure is approximately $17,159. 120 The frequency distribution and the cumulative distribution of the expected total equivalent uniform annual cost of the maintenance of the entire bridge structure are shown in Figure 42 and Figure 43. Frequency Distribution 300 0 10000 20000 30000 40000 50000 60000 70000 80000 90000 100000 110000 | overall_strategy Figure 42 - Model Variation 4 - EUAC Frequency Distribution 121 Cumulative Distribution 100% 80% 60% >* 40% 20% 0 % 0 20000 40000 60000 80000 100000 120000 overall_strategy Figure 43 - Model Variation 4 - EUAC Cumulative Distribution A copy of this example may be found in Appendix H of this report. 9.5.5. Example using Bridge Inventory, using Overall Bridge Condition Rating, Deterministic Input The input values used in the example using the fifth variation of the model are outlined in Table 13 and Table 14. 122 Table 13 - General Input Values for the Fifth Variation of the Model INPUT PARAMETER NAME INPUT PARAMETER VALUE INPUT PARAMETER UNIT number 5 corr rate bridge specific corr curve bridge specific % area / year escalation 2.5 % interest 3 % total bridge surface_area bridge specific mA2 life bridge specific years touch up durability 12.5 years touch up unit_cost 450 $ /m A 2 overcoat_durability 20 years overcoat unit cost 130 $ /m A 2 recoat durability 25 years recoat unit cost 200 $ /m A 2 replace cost bridge specific $ replace add cost bridge specific $ Table 14 - Bridge Specific Input Values for the Fifth Variation of the Model Bridge Number Remaining Design Life Total Surface Area ASTM D610 Corrosion Rating Corrosion Curve Replacement Cost Replacement Additional Costs (years) (mA2) (%area/year) ($) ($) 1 70 3500 8 5 20000000 0 2 55 550 7 4 5000000 1000 3 40 5000 6 3 50000000 5000 4 65 1250 5 10 10000000 3000 5 75 7000 9 8 100000000 10000 The output values obtained from the analysis are summarized in Table 15. Table IS - Output Values for the Fifth Variation of the Model Bridge Number Maintenance Strategy Proposed Cost of Maintenance Strategy Proposed ($/year) Benefit-Cost Ratio 1 touch up 7005 18.22 2 overcoat 7291 2.09 3 do nothing 61879 0.00 4 overcoat 19859 2.99 5 touch up 4674 176.85 123 According to the benefit-cost ratios calculated for the maintenance projects associated with each bridge structure in the bridge inventory, the priority of the maintenance projects may be ordered as (beginning with the highest priority) Bridge 5, Bridge 1, Bridge 4, then Bridge 2. It is observed that there is no benefit from performing maintenance on Bridge 3, since the most cost effective strategy proposed for Bridge 3 is "do-nothing". The recommended annual funding requirement for the maintenance program of the five bridge structures in the inventory is $100,708. A copy of this example may be found in Appendix I of this report. 9.6. Model Summary Table 16 shows a summary of the Bridge Coating Maintenance Evaluation Model. Table 16 - Summary of the Bridge Coating Maintenance Evaluation Model Model Usage Input Parameters Output Parameters Location of Number Example 1 For determining the corr_rate overall maintenance Appendix E best maintenance corr_curve strategy proposed strategy and its escalation associated cost over the interest cost of overall life of a bridge, using total bridge surface area maintenance strategy an overall bridge life proposed condition rating, and touch_up_durability deterministic input touch_up_unit_cost parameters. overcoat_durability overcoat unit cost recoat_durability recoat_unit_cost replace_cost replace add cost 2 For determining the struct_corr_rate overall maintenance Appendix F best maintenance bear corr rate strategy proposed strategy and its e x P _j 0 ints_corr_rate associated cost over the non_struct_corr_rate cost of overall life of a bridge, using a corr_curve maintenance strategy condition rating for escalation proposed each component group interest of the bridge, and struct_surface_area maintenance strategy for deterministic input bear_surface_area each component parameters. expJoints_surface_area non struct surface_area life touch up durability cost of maintenance strategy for each component 124 touch_up_unit_cost overcoat_durability overcoat_unit_cost recoat_durability recoat_unit_cost replace_cost replace add cost 3 For determining the corr_rate overall maintenance Appendix G best maintenance corr_curve strategy proposed strategy and its escalation associated cost over the interest cost of overall life of a bridge, using total bridge surface area maintenance strategy an overall bridge life proposed condition rating, and touch_up_durability probabilistic input touch_up_unit_cost parameters. overcoat durability overcoat unit_cost recoat_durability recoat_unit_cost replace_cost replace add cost 4 For determining the struct_corr_rate overall maintenance Appendix H best maintenance bear_corr_rate strategy proposed strategy and its exp J o ints_corr_rate associated cost over the non_struct_corr_rate cost of overall life of a bridge, using a corr_curve maintenance strategy condition rating for escalation proposed each component group interest of the bridge, and struct_surface_area maintenance strategy for probabilistic input bear_surface_area each component parameters. exp_joints_surface_area non struct surface area cost of maintenance life strategy for each touch_up_durability component touch_up_unit_cost overcoat_durability overcoat unit_cost recoat_durability recoat_unit_cost replace_cost replace add cost 5 For determining the number maintenance strategy Appendix I budget requirements for corr_rate proposed for each bridge a steel bridge coating corr curve maintenance program, escalation cost of maintenance and for prioritizing the interest strategy proposed for each maintenance projects total bridge surface area bridge within the program. life touch_up_durability benefit-cost ratio for each touch_up_unit_cost bridge overcoat_durability overcoat_unit_cost overall budget for recoat_durability maintenance program recoat_unit_cost replace_cost replace add cost 125 Chapter 10. Conclusions and Implications Derived from the Model The Steel Bridge Coating Maintenance Evaluation Model provides many insights into the considerations surrounding the decision process of selecting a life-cycle coating maintenance strategy for a steel bridge. The model may be used to recommend a maintenance strategy for one steel bridge, a maintenance strategy for each component of a steel bridge, or a maintenance program for a group of steel bridges. The model may also be applied to calculate an approximate annual budgetary requirement for a maintenance program for steel bridges. The maintenance projects within the maintenance program may be prioritized and the funds may be allocated accordingly. Other implications may also be derived from the Steel Bridge Coating Maintenance Evaluation Model. These include the comparison of various corrosion protection coating maintenance strategies, the sensitivity of the maintenance cost to varying financial factors, the sensitivity of the maintenance cost to varying coating system durability, and the allowable premium for more-durable coating systems. In order to facilitate the update of the model when changes occur in the input parameters, it may be beneficial to further componentize the model structure. 10.1. Comparison of Corrosion Protection Coating Maintenance Strategies As observed from the Steel Bridge Coating Maintenance Evaluation Model, the most cost effective corrosion protection coating maintenance strategy is touch-up painting. The annual uniform equivalent cost of the touch-up painting strategy is often more cost effective than the next maintenance strategy, overcoating, by a factor of 10 to 126 20. This is due to the lower level of surface preparation required for the touch-up painting strategy. Also, a smaller maintenance crew with less expertise is required for touch-up painting. However, the touch-up painting strategy may only be applied on bridges with a coating condition of A S T M D610 corrosion rating 8 or above. Also, the applicability of the touch-up painting strategy is dependent on the adhesion level of the coating. From the model, it is also observed that the overcoating maintenance strategy is more cost effective than the recoating strategy by a factor 1.1 to 1.5. This is due to the fact that extensive cleaning is not required for overcoating. Extensive cleaning may be costly, especially in the case where the existing coating is a lead-based paint, and environmental measures have to be put in place. However, the overcoating strategy may only be applied on bridges with a coating condition of A S T M D610 corrosion rating 5 or above. Also, the applicability of the overcoating strategy is dependent on the adhesion level of the coating. Therefore, for a structure with a coating condition of corrosion rating 8 or above and adequate adhesion, the recommended maintenance strategy is touch-up painting. For a structure with a coating level between corrosion rating 5 and 7 and adequate adhesion, the recommended maintenance strategy is overcoating. The recoating strategy is only recommended for structures with coating levels below 5, or with poor adhesion. The "do-nothing" strategy is typically recommended for structures nearing the end of its design life. The "do-nothing" strategy may be most cost-effective for structures with a remaining coating life greater than or approximately equal to their remaining design life. The "do-nothing" strategy may also be selected for structures 127 scheduled for replacement in the near future due to increased usage demand. The replacement of a structure may also provide the added benefit of a lower maintenance requirement in the future due to a better design and the use of more advanced corrosion resistant or corrosion protection materials in the structure. 10.2. Sensitivity of Costs to Varying Escalation and Interest Rates The effects of varying financial factors on the equivalent uniform annual costs of the maintenance strategies may be determined by performing sensitivity analysis on the varying parameter. From Figure 40, it can be seen that the equivalent uniform annual cost of the proposed maintenance strategy is highly sensitive to the financial input factors, especially the escalation rate. It is shown that a 10% increase in the escalation rate will result in a 11.9% increase in the equivalent uniform annual cost of the maintenance strategy. Also, a 10%) increase in the interest rate will result in a 4.1% decrease in the equivalent uniform annual cost of the maintenance strategy. It can be observed that the percent change in the equivalent uniform annual cost varies linearly with the percent change in the financial input values. The linear sensitivity will facilitate extrapolation of the value of the expected equivalent uniform annual cost when the deviations in the financial input values are known. In the case of the escalation rate, the percent change in the equivalent uniform annual cost is greater than the percent change in the escalation rate. This type of sensitivity is known in economic terms as "elastic behaviour". Elastic behaviour will result in the "multiplier effect"; in other words, an error or deviation in the prediction of 128 the escalation rate will result in a larger error or deviation in the prediction of the equivalent uniform annual cost. This effect is highly undesirable. In addition, the historical trends for financial factors such as escalation rate and interest rate are highly undefined, with predictions for future trends often incorrect. The combination of the undesirable multiplier effect and the erratic future trends of financial factors warrant the development of forecast models for the escalation rate and interest rate used as input for the Steel Bridge Coating Maintenance Evaluation Model. Economic experts should be employed to provide a better prediction of the escalation rate and interest rate. The financial inputs to the model should be updated regularly and an analysis should be performed to reflect changes in the economic trends experienced in B.C. This will allow a better prediction of the equivalent uniform annual cost of the proposed maintenance strategy at different points in time. 10.3. Sensitivity of Costs to Varying Coating Durability The effects of varying coating durability on the equivalent uniform annual costs of the maintenance strategies may be determined by performing sensitivity analysis on the varying parameter. From Figure 41, it can be seen that the equivalent uniform annual cost of the proposed maintenance strategy is mildly sensitive to the coating durability. It is shown that a 20% increase in the coating durability will result in a 12% decrease in the equivalent uniform annual cost of the maintenance strategy. It can be seen that the percent change in the equivalent uniform annual cost varies with the percent change in the coating durability following a step function. This step function results from the fact that the increased coating durability will increase the time 129 interval between maintenance projects, and thereby decrease the number of maintenance projects required throughout the remaining design life of the structure. As the coating durability is changed, the equivalent uniform annual cost will remain unchanged until a large enough change in the coating durability value results in the increase or decrease of one whole maintenance cycle for the structure; at which point the equivalent uniform annual cost will increase or decrease accordingly. 10.4. Allowable Premium for Increased Coating Durability From section 10.3, the sensitivity of the equivalent uniform annual cost to the coating durability of a maintenance system can be observed. It can then be reasoned that an allowable premium equal to 12% of the equivalent uniform annual cost may be expended in obtaining a coating system with a 20% increased durability. It is the experience of many transportation agencies that the benefits resulting from the selection of a more-durable coating system far outweighs the additional costs incurred by employing the superior coating system. Therefore, it is worthwhile for an agency such as the MoT to actively seek out more-durable coatings that may be utilized in maintenance projects for a small added premium. 10.5. Input Parameter Componentization Input parameters for the Steel Bridge Coating Maintenance Evaluation Model should be componentized to allow for a better representation of the real value of each parameter. For example, the unit cost of each maintenance strategy should be componentized into material costs, labour costs (which may further be componentized 130 into removal costs, surface preparation costs, and application costs), costs of temporary structures, mobilization costs, traffic control costs, environmental costs, and social costs The componentization of the input parameters will also facilitate updates to the model inputs reflecting revision regarding specific components. For example, during a construction boom, the labour costs may be inflated due to the shortage of work crews, but the other costs contributing to the unit cost of the maintenance strategy will remain unchanged. With the model input parameter componentization, the unit cost may be updated by changing the labour cost component, and may be reset with ease once the construction boom has passed. 131 Chapter 11. Recommendations The focal recommendations resulting from this project are: • A Bridge Coating Condition Data Collection System is needed • Increase Average A S T M D610 Corrosion Rating of Bridge Inventory The details of the recommendations are outlined in the following sections. 11.1. Bridge Coating Condition Data Collection One of the most important aspects of coating maintenance is to maintain a good database on the current coating condition of the inventory of bridge structures in British Columbia. In order to obtain up-to-date information regarding the coating condition of all the bridge structures located in the province, it is necessary to employ coating inspectors to perform routine coating inspections at regular intervals (preferably short intervals in time). To facilitate and expedite the inspection process, a detailed bridge coating inspection report should be developed. The bridge coating inspection report should include data regarding the coating condition, as evaluated using A S T M D610 Standards, of each individual component of the bridge (or at least each major component of the bridge). Adhesion information should also be collected for the coating of each component of the bridge. With information gathered from frequent coating inspections, an accurate corrosion curve may be developed for the deterioration of the coating system on each bridge structure. 132 In addition to a database of the coating condition of the inventory of bridge structures, a database should also be developed for costs and durability information pertaining to various maintenance strategies. It is only with good data that an accurate prediction of the costs associated with each maintenance strategy may be made, and a maintenance strategy may be proposed. Furthermore, good data will allow for better prediction of the budgetary requirements for the maintenance program of steel bridges. 11.2. Increase Average Rating of Bridge Inventory The Steel Bridge Coating Maintenance Evaluation Model has shown that the most cost effective maintenance strategy is touch-up painting, often by a factor of 10 to 20. However, touch-up painting may only be applied to structures with an A S T M D610 corrosion rating of 8 and above. Therefore, in order to lower the funding requirements of a maintenance program for steel bridges, it is desirable to increase the coating conditions of all bridge structures in the inventory to an A S T M D610 corrosion rating of 8 and above. To increase the average coating condition of the steel bridge inventory, it is necessary to invest a large sum of money upfront. However, the savings obtained from the following low-level maintenance as opposed to the costly maintenance required by severely corroded structures will far outweigh the initial cost of upgrading the condition of the bridges. It is important to upgrade the existing bridges in a timely fashion, as delays in the upgrade will lead to the continual degradation of the coating systems resulting in more severe corrosion of the structure and a higher maintenance cost. 133 An added benefit in upgrading the steel bridges to an A S T M D610 corrosion rating of 8 and above is the increase in the average corrosion rating of each bridge structure throughout its service life. The higher average corrosion rating will result in a more aesthetically-pleasing structure. In addition, it will decrease the chance of section loss due to corrosion experienced by the structure and therefore increase the safety of the structure. 134 Chapter 12. Future Developments A study of the costs involved in the maintenance strategies may be conducted. For the purpose of analysis using the Steel Bridge Coating Maintenance Evaluation Model, it is desirable to catalog and quantify social cost inputs such as the cost of reduced aesthetic value, costs related to closures, benefit of increased tourism activity, costs associated with public reaction to reduced life span of structure, etc. Corrosion curves for individual bridge structures should be developed for more accurate input into the evaluation model. In order to develop corrosion curves for the bridge structures, it may be necessary to install corrosion test patches at various locations in the province, representative of the various site conditions present at the location of the bridges. Regular inspection of the test patches over a prolonged period may provide data on the deterioration behaviour of the coating systems applied using the various maintenance strategies. A higher level of interaction between the components of the bridge may be developed in the model. For example, a discount for mobilization costs may be applied if the same maintenance strategy is selected for more than one component. The analysis used in this project selects an optimal maintenance strategy by calculating the life-cycle costs of a strategy repeated throughout the remaining design life of a steel bridge structure. This is a logical analysis procedure since it simplifies the problem and the analysis procedure may be re-applied at any time throughout the life of the structure i f there is a change in the conditions. However, the next step may be to employ dynamic programming or another analysis technique to evaluate maintenance approaches involving a combination of different maintenance strategies throughout the 135 life of the structure. Previous maintenance data should be included to calculate the coating condition and adhesion level at different points in the life of the structure. This optimization will be a better representation of the real problem since certain maintenance strategies may only be practically repeated a limited number of times. 136 References Albrecht, P., Naeemi, A . H . Performance of Weathering Steel in Bridges. National Cooperative Highway Research Program Report 272, Transportation Research Board, 1984. American Society for Testing and Materials. "Standard Test Method for Evaluating Degree of Rusting on Painted Steel Surfaces". ASTM International Standard D610-07,2001. CAN/CSA-S6-00. Canadian Highway Bridge Design Code. Clause 10.6, Tables 10.6.3, 10.6.4. Chong, Shuang-Ling. "Preventing Corrosion in Steel Bridges." Public Roads, Volume 68, No.2, September/October 2004. < http://www.tflirc.gov/pubrds/04sep/08.htm > Federal Highway Administration, Bridge Coatings Technology Outreach Team. Bridge Coatings Technical Note: "Overcoating (Maintenance Painting). Jan. 1, 1997. < http.V/www.tfhrc.gov/hnr20/bridge/overct.htm > Gedig, Michael, and Stiemer, Siegfried F. "Decision Making Tools for Steel Structures Engineering." Jensen, Doug. Picture 007.jpg [Photo]. 2004. Jensen, Doug. Meeting with Phyllis Chan. Nov. 16, 2004. Jensen, Doug. Site Visit with Phyllis Chan. Dec. 3, 2004. Jensen, Doug. "RE: questions regarding unit costs". Mar. 14, 2005. E-mail to Phyllis Chan. Kayser, Jack R. The Effects of Corrosion on the Reliability of Steel Girder Bridges. Doctor of Philosophy Dissertation (Civil Engineering), The University of Michigan, 1988. Kogler, Robert A . Jr., Chong, Shuang-Ling. "Steel Bridge Coatings Research." Public Roads, Volume 61, N o . l , July/August 1997. < http://www.tmrc.gov/pubrds/iuly97/brdgct.htm > Komp, M.E. "Atmospheric Corrosion Ratings of Weathering Steels - Calculations and Significance", Materials Performance, Vol . 26, No. 7, July 1987, pp. 42-44. 137 Marcouiller, Nicolas. "Corrosion of Steel." 2003. http.V/sigi.civil.ubc.ca/mot/reports/corrosionproiectyWebHelp/corrosionproject.htm Marcouiller, Nicolas. "Corrosion Protection of Steel." 2003. http://sigi.civil.ubc.ca/mot/reports/coatingsteels/WebHelp/coatingproiect.htm Marcouiller, Nicolas. "Thermalspray Protection." 2003. http://sigi.civil.ubc.ca/mot/reports/thermalspravproiect/WebHelp/thermalsprayproie ct.htm Meade, Bobby W., and Hopwood, Ted. "Long-term Evaluation of Experimental Overcoating Projects in Kentucky." 2004 International Bridge Conference, June 14-16, 2004, Pittsburgh, United States. Microsoft Excel 2002 [Computer Software]. Microsoft Corporation, 1985-2001. Neal, Tom W, Jr. Maintenance Issues and Alternative Corrosion Protection Methods for Exposed Bridge Steel. National Cooperative Highway Research Program Synthesis Reports #257, Transportation Research Board, National Academy Press, Washington D.C., 1998. Radzimowski, Zbigniew. 2304 Paint Job 05.jpg [Photo]. 2004. Radzimowski, Zbigniew. p0002860.jpg [Photo]. 2004. Radzimowski, Zbigniew. Meeting with Phyllis Chan. Nov. 16, 2004. Radzimowski, Zbigniew. Site Visit with Phyllis Chan. Dec. 3, 2004. Raine, Russell. Bridge Coating Rating System [Computer Software]. Ministry of Transportation of British Columbia, British Columbia, Canada, 2001. Raine, Russell. Meeting with Phyllis Chan. Jan. 18, 2005. Raine, Russell. "RE: questions regarding unit costs". Mar. 14,2005. E-mail to Phyllis Chan. Raine, Russell. "RE: questions regarding unit costs". Mar. 15, 2005. E-mail to Phyllis Chan. Raine, Russell. "RE: questions regarding unit costs". Mar. 17, 2005. E-mail to Phyllis Chan. Russell, Alan D. CIVL 522 Class Notes, University of British Columbia, 2004. Russell, Alan D. Meeting with Phyllis Chan. Mar. 15,2005. 138 Society for Protective Coatings. "SSPC Standards Titles and Scopes". Society for Protective Coatings, Pittsburgh, PA, 1995-2005. < http://www.sspc.org/standards/scopes.html > Tam, Chun Kwok. A Study of Bridge Coating Maintenance. Masters of Applied Science Thesis (Civil Engineering), The University of British Columbia, 1994. Tam, Chun Kwok., and Stiemer, Siegfried F. "Development of Bridge Corrosion Cost Model for Coating Maintenance." Journal of Performance of Constructed Facilities, May 1996, 47-56. Vanguard DecisionPro for Windows Version 4.0.4. [Computer Software]. Vanguard Software Corporation, 1992-2002. Wang, Jason. Crevice Corrosion: Basics, Design and Prevention, Maintenance and Rehabilitation. 2004. Web-based references: Corus Group. "Corus Construction Centre: Corrosion Protection of Steel Bridges". < http://www.corusconstruction.com/page 9009.htm > InterCorr International. "Starter Topic - Bridge Coating Maintenance Cost Models -CorrosionSource.com Discussion Boards". < http://www.corrosionsoui"ce.com/discuss2/ubb/Forum46/HTML/000001 .html > Kingston Technical Software Co. "Corrosion Science and Engineering Information Hub". < http://www.corrosion-doctors.org/ > National Aeronautics and Space Administration. "Kennedy Space Center Corrosion Technology Testbed". < http://corrosion.ksc.nasa.gov/html/corr_forms.htm > Tullmin Consulting. "Corrosion Monitoring at Corrosion Club". Ontario, Canada. < http://www.corrosion-club.com > U.S. Department of Transportation. "Federal Highway Administration Home Page". < http://www.thwa.dot.gov/ > U.S. Department of Transportation. "FHWA Study Tour for Bridge Maintenance Coatings: FHWA's Scanning Program". 1997. < http://iti.acns.nwu.edu/publications/bernecki/fst/ > Zinga. "ZINGA Cold Galvanizing System". < http://www.zingacanada.com/ > 139 Appendix A. Logs of Site Visits 140 Site Visit Log Site Visited: Lions Gate Bridge Date Visited: October 27, 2004 Party Present: Helmut Tepper (Painting Inspector), Ron Lowther (BC MoT West Kootenay District), Greg (BC MoT West Kootenay District) Intent of Visit: • To understand the procedures involved in a major corrosion maintenance project • To obtain information from an experienced painting inspector Description of Visit: The visit involved a tour of the maintenance area, namely North Viaduct bents. The North Tower was also visited and the group climbed a small portion of the tower for visual inspection. The underside of the bridge girders were also observed by the group. The tour was followed by a discussion with painting inspector Helmut Tepper. Background Information on the Project: • Lions Gate Bridge Maintenance Project Specifications o Steel Field System SF2: Organic zinc primer, epoxy intermediate coat, polyurethane finish coat, in accordance with SS308 o Dry film thickness • Primer 75-125um • Intermediate stripe coat 65-90pm • Full intermediate coat 100-150pm • Finish coat 50-65pm o Penetrating epoxy sealer to all crevices, seams, intersections (all areas to be washed, blast-cleaned, recoated) o Caulk vertical seams/intersections, top horizontal seams of tower; bottom not caulked to provide drainage o Immersion coating for sump area Observations from the Visit: • Basic procedure for a maintenance job is: wash, clean, overcoat (with some areas recoated) • Specifications used by the Lions Gate Bridge maintenance project is: Steel Structure Painting Council (SSPC) - The Society for Protective Coatings • Class 1A containment structure o Negative pressure o Temperature regulated o Filter units o Crew and visitors require respirators • (Superintendent on the job - Tony from Washington State) 141 • Procedure: build containment, blast, paint • Hard to predict duration of maintenance o Probability of cost variation o Hard to predict even with experienced blasters • Lions Gate Bridge maintenance project is behind schedule • Sometimes when the job is started, conditions are found to be worse than anticipated (e.g. section loss); may need to lower loading capacity • Cost of scaffolding is substantial (scaffolding tiered for easy access by workers) • Visual inspection is most important during work (check for any substance coming out of containment) • Areas with pack rust o Pack rust washed and sealant injected o Pack rust distorts steel work (cannot be fixed, just clean and seal) o E.g. Lions Gate Bridge Bent 23 W - plate highly distorted • 5-15% Blastox (Portland Cement) binds to lead during sandblasting to contain and prevent leeching • Some bridges are "metallized" instead of painted • Golden rule of bridge painting: Cannot paint steel that is 3°C/5°F above dewpoint or below 7°C Questions Asked and Answers: • Do you have unit prices for cleaning/coating procedures? o Schedule 7 of the Specifications contain the unit prices for the job. The Lions Gate Bridge Project cost is $20.5M for the painting job, including scaffolding, cleaning, painting, etc. The scaffolding component accounts for approximately 1/3 of the contract, with a typical 12-worker scaffolding crew versus a 24-worker painting crew. The contingency fund for overlooks for the Lions Gate Bridge maintenance project is $300,000. • How would you describe social/environmental concerns? (quantity as $ possible?) o The social concerns are primary associated with closures (see question below). The environmental concerns include noise control and contamination control. The Lions Gate Bridge maintenance project involves the removal of red lead, and therefore full containment must be used. • Is the entire bridge being recoated? How was this "maintenance area" [scope] decided? o Lions Gate Bridge is the most famous bridge in the province. Ever since the suspended spans were replaced, the towers, viaduct, and cables looked out-of-place aesthetically. Pack rust on such light steel work may pose structural hazards. Re-painting the bridge was mostly a timing issue, and the time is right now. • How would you quantify the costs associated with closures? o Contractors should be innovative enough to not require full closures. Lane closures are acceptable. 142 • Why are certain paint systems selected? What is the basis? o Coating systems are tested in labs. Coating is most effective (25% savings) when compared with galvanizing or metallizing. While metallizing is durable for 30-40 years, this coating is durable for 25-30 years. This system has been tested and determined to perform best in the BC climate (high moisture); it is more reliable. The Lions Gate Bridge maintenance project involves spray coating with touch-up by brush; this is a typical procedure, and therefore a "better" job is performed. • Are surface preparations usually dictated by manufacturers of coating systems? o The Province of BC sets the standards for cleaning procedures. These procedures are guided by the SSPC. SP6 - Commercial Blast with 33.3% Stain is used for the Lions Gate Bridge project. • Can you provide contacts of manufacturers for further questions? o (Question not asked/No answer provided) Further Questions: • (none) Follow-up Actions Required: • Obtain Schedule 7 of the Specifications from Kevin Baskin o November 16, 2004: Unit prices are protected information from contractors; perhaps Kevin Baskin may provide an average of the bids submitted • Return to Lions Gate Bridge site for tour inside the containment structures when the Lions Gate Bridge office acquires respirators for visitors, provided that the weather is mild 143 Site Vis i t L o g Site Vis i ted: Stanley Park Pedestrian Overpass, Porteau Cove Emergency Docking Facility, Eagleridge Overpass, Middle Arm Bridge Date Vis i ted: December 3, 2004 Party Present: Zbigniew Radzimowski (BC MoT), Doug Jensen (Mainroad Contracting Ltd.) Intent of Vis i t : • To understand the procedures involved in a "large" minor corrosion maintenance project • To relate the "product" of the maintenance procedures with the bridge inspection reports prior to the maintenance Description of Vis i t : The visit involved an on-foot tour of the three sites. The Stanley Park Pedestrian Overpass and the Porteau Cove Emergency Docking Facility have undergone corrosion maintenance painting in the recent past, while the Eagleridge Overpass is scheduled to receive corrosion maintenance painting in the near future. The Porteau Cove Emergency Docking Facility maintenance project involved painting of numerous non-structural components specific only to the site; therefore is an example of the difficulty in the unit pricing approach of maintenance projects. Background Information on the Project: • Cost of a maintenance project dependent on o Access (e.g. Middle Arm Bridge) o Details involved (e.g. Porteau Cove) o Night time closures over traffic (e.g. Stanley Park Causeway) • Traffic control people required, etc. • There is really no unit cost for this type of work (too many factors involved, "not like painting a wall on the ground") • The preparation cost entails 50%+ of the total cost of the maintenance project • Typical minor maintenance jobs o Painting procedures involve • Anti-corrosion primer • No sandblasting required o Lower environmental concerns o Lower effort required • Marine-grade enamel o System requires less rigorous preparation o System is quite durable (although there is no quantitative data available for the durability of the system) • Bridge inspection reports and paint systems used are available for most of these maintenance projects 144 Observations from the Visit: • Stanley Park Pedestrian Overpass o Maintenance painting in some areas are done by using scaffolding on wheels o Paint was applied at night • Outdoor • Shady • Not in the vicinity of the dewpoint but cannot be helped o Piers were dug out, cleaned, and recoated o Railings, underside of the overpass were painted with brush and roller o Substance was added in paint to obtain to correct consistency in order to prevent streaking while also avoiding "dripping" o Paving on the overpass was worn down to the steel by horses • Possible section loss o Containment of the site and regulation of temperature and humidity was not possible; therefore, high-quality paint must be used o Observation of algae growing on newly painted surfaces • Not aesthetically pleasing • Cleaning required o "Regions will not spend the money on such small projects." -Z .R. o "If we can spend 1/10 of the money [cost of major maintenance project] to quickly touch-up, we can do it 10 times as often!" -D.J . • Porteau Cove Emergency Docking Facility o Environmental concerns of high importance • Maintenance site is over open-water o Access is difficult over water o Detailsand design are specific to this site only • Unit pricing for each type of component is not possible • Eagleridge Overpass o Overpass scheduled to be painted, extent of corrosion visible o Steel girder, concrete deck type overpass o Marine water spray from cars and wind caused corrosion on the steel components o Steel structure "badly rusted" in one direction (possibly in the direction of the prevailing wind) o Entire structure will be painted regardless of the condition • The entire structure will maintain the same color • Prolong the interval before a second maintenance job is required o Painting must occur over traffic • Lane closures in sections are required • Lane closures will occur at night time • No day closures will be allowed • Middle Arm Bridge o The visit to the Middle Arm Bridge was cancelled due to poor and degrading weather conditions 145 Questions Asked and Answers: • (none) Further Questions: • (none) Follow-up Actions Required: • Obtain approximate unit cost breakdown of maintenance project from Doug Jensen • Obtain bridge inspection report for Eagleridge Overpass from Zbigniew Radzimowski 146 Appendix B. Sample Specification Content of Large Maintenance Projects in British Columbia 147 P R O J E C T NO. 11696-0002 LIONS' GATE BRIDGE NO. 1481 STRUCTURAL STEEL COATING SUSPENSION BRIDGE AND NORTH APPROACH VIADUCT SCHEDULE 3 - SPECIAL PROVISIONS AND APPENDICES TABLE OF CONTENTS SECTION 1 - GENERAL 1.1 CLARIFICATION 1 1.2 INTERPRETATION 1 1.3 APPLICABLE AGREEMENT - GENERAL CONDITIONS 1 1.4 LIMITED FISCAL FUNDS 2 1.5 PRIME CONTRACTOR AND SPECIFIED AREA 2 1.6 PRE-TENDER MEETING 2 1.7 REFERENCE DOCUMENTS 3 1.7.1 Contract Specific Reference Documents 3 17 1.1 General 3 1.7.1.2 Information on Existing Lions Gate Bridge 3 1.7.2 General Reference Documents 4 1.8 AVAILABILITY OF RELEVANT PUBLICATIONS 4 1.9 LOCATION OF THE WORK SITE 5 1.10 SCOPE OF WORK 5 1.10.1 Suspension Bridge 5 1.10.1.1 General 5 1.10.1.2 Items to be Protected from Damage 7 1.10.2 North Approach Viaduct 7 1.10.2.1 General 7 1.10.2.2 Items to be Protected from Damage 8 1.10.2.3 Existing Chain Link Fencing 8 1.10.2.4 Pedestrian/Cyclist Fences 9 1.11 HOURS OF WORK 9 1.12 AVAILABILITY OF SITE AND SITE A C C E S S 9 1.12.1 General 9 1.12.2 Vancouver Port Authority (VPA) Project Permit 9 1.12.3 Contractor Responsibilities 10 1.12.4 Stanley Park 10 1.12.5 Access to Base of South Tower 10 1 12.5.1 Water Access 10 1.12.5.2 Seawall Access 11 1.12.6 Removal and Replacement of Security Locks 11 1.12.7 Areas That Cannot Be Used for Storage 11 1.12.8 Areas That May Be Used for Temporary Storage 11 1.12.9 Recertification of "Man-Safe" Fall Arrest System 12 1.12.10 Use of Maintenance Travelers 12 P R O J E C T No. 11696-0002 148 1.12.10.1 Suspended Span 12 1 12.10.2 North Approach Viaduct 12 1.13 PROTECTION OF EXISTING BRIDGE COMPONENTS 12 1.13.1 Existing Sidewalk Paving 12 1.13.2 Existing Suspended Span Deck 13 1.13.3 Suspension Bridge Miscellaneous Components 13 1.14 WORK BY OTHERS IN PROJECT AREA 13 1.15 CONSTRUCTION SCHEDULE AND CASH FLOW PROJECTION SCHEDULE 14 1.16 QUALITY MANAGEMENT 16 1.16.1 General 16 1.16.2 Access of Ministry Representative 17 1.16.3 Quality Control Plan (QC Plan).. 17 1.16.3.1 QC Plan General Requirements 17 1.16.3.2 QC Plan Quality Control Staff and Equipment Submission Requirements ... 18 1.16.3.3 QC Plan Contract-Specific Work Submission Requirements 19 1.16.4 Quality Assurance Plan 20 1.16.5 Quality Audit 21 1.16.6 Non-Conformance 21 1.16.7 Appeal 21 1.16.8 Payment 22 1.17 TRAFFIC MANAGEMENT 23 1.17.1 General 23 1.17.2 Speed Limits for Public Traffic and Safe Passage through the Work 23 1.17.3 Provisions for Traffic During Construction 23 1.17.4 General Requirements 24 1.17.5 Traffic Control Specifications 24 1.17.5.1 General Traffic Requirements 24 1.17.6 Contractor's Deliverables 24 1.17.6.1 Traffic Management Plan 24 1.17.6.2 Traffic Control Supervisor 24 1.17.6.3 General Traffic Control Plan 24 1.17.6.4 Specific Traffic Control Plans 25 1.17.6.5 Site Documents 25 1.17.7 Ministry's Responsibilities 25 1.17.8 General Requirements 26 1.17.8.1 Traffic Control Supervisor 26 1.17.9 Incident Management Plan 26 1.17.9.1 Incident Management Plan - First Narrows 26 1 17 9 2 Incident Management Plan - Ironworker's Memorial Second Narrows Bridge 26 1.17 10 Closures to Traffic 26 1.17.10.1 Bridge Road & Welch Street - North Shore 28 1.17.11 Accesses to Neighbouring Properties 28 1.17.12 Pedestrians and Cyclists 28 1.17.12.1 General 28 1.17.12.2 Sidewalk Closures 28 1.17.13 Turnarounds for Construction Traffic at South End of Bridge 29 1.17.14 Location and Storage of Materials and Equipment 29 1.17.15 Temporary Signing 29 1.17.15.1 General 29 1.17.15.2 Payment - 29 1.17.16 Obstruction of Traffic 29 1.17.17 Lane Control Systems 3 0 P R O J E C T No. 11696-0002 149 1.17.17.1 General 30 1.17.17.2 Lane Closures During Construction 30 1.17.18 Payment 30 1.18 MAINTENANCE OF ROADWAYS WITHIN PROJECT LIMITS 30 1.18.1 Contractor's Responsibilities 30 1.18.2 Ministry's Responsibilities 31 1.18.3 The Protection of Roads 31 1.18.4 Use of Existing Traffic Control Personnel 31 1.18.5 Payment 32 1.19 MATERIALS SUPPLIED BY THE MINISTRY..... 32 1.20 PROTECTION OF THE ENVIRONMENT 32 1.20.1 General 32 1.20.2 Roles and Responsibilities 32 1.20.2.1 Contractor Responsibilities 33 1.20.2.2 Ministry Responsibilities 34 1.20.3 Regulatory Requirements 34 1.20.3.1 Vancouver Port Authority 34 1.20.3.2 Other Environmental Requirements 34 1.20.4 Government Agency Notification 34 1.20.5 Environmental Criteria 34 1.20.5.1 General Requirements 35 1.20.5.2 Specific Environmental Criteria 35 1.20.6 Environmental Management Plan 39 1.20.6.1 Sediment and Drainage Management Plan 40 1.20.6.2 Environmental Emergency Response Plan 40 1.20.6.3 Noise Mitigation Plan 40 1.20.6.4 Hazardous Materials Containment, Storage, Transportation, and Disposal Plan 41 1.20.7 Environmental Quality Management 41 1.20.8 Communications 41 1.20.9 Contractor's Environmental Monitor 41 1.20.10 Payment 42 1.21 PROTECTION OF RAILWAY PROPERTY/ACCOMMODATION OF RAILWAY TRAFFIC 43 1.22 PROTECTION (AND RELOCATION, IF REQUIRED) OF UTILITIES 44 1.22.1 General 44 1.22.2 Existing Utility Descriptions 45 1 22 2.1 MoT Lane Control System 45 1.22.2 2 MoT Street Lighting 45 1.22.2.3 Navigation Aids 45 1 22.2.4 Telus Utilities 45 1.22.2.5 MoT Ornamental Lights 45 1.22.2.6 MoT Bridge Security System 45 1.22.2.7 MoT Air/Water Line 46 1.22.2.8 MoT Maintenance Travelers 46 1.22.2.9 BC Hydro Power Line 46 1.22.2.10 Power Line to Lighthouse at Prospect Point 46 1.23 INSURANCE 46 1.24 COMPLETION OF "LIST OF DESIGNATED SUBCONTRACTORS AND DESIGNATED SUPPLIERS" 46 1.25 PROJECT SIGNS 46 1.26 VALUE ENGINEERING PROPOSALS 47 PROJECT No. 11696-0002 150 1.27 FREEDOM OF INFORMATION AND PROTECTION OF PRIVACY ACT 47 1.28 BC21 SOCIAL AND ECONOMIC OBJECTIVES.... 47 1.29 AS-BUILT DRAWINGS 47 1.30 FIRST NATIONS RELATIONS 47 1.31 PUBLIC SAFETY DURING CONSTRUCTION 48 1.32 MARINE TRAFFIC AND FIRST NARROWS 49 1.32.1 General 49 1.32.2 Contractor's Marine Operation Plan 49 1.32.3 Communication System 49 1.32.4 Marine Navigation Aids 50 1.32.5 Contact Persons 50 1.32.6 Restrictions on Contractor's Operations Affecting Navigation at First Narrows 50 1 32.7 Payment 50 1.33 AIR TRAFFIC PROVISIONS 50 1.33.1 General 50 1.33.2 Air Navigation Aids 50 1.33.3 Air Traffic Issues 51 1.34 OCCUPATIONAL HEALTH AND SAFETY PROGRAM 51 1.35 OCCUPATIONAL HEALTH AND SAFETY REGULATIONS 51 1.35.1 WCB Fall Protection Regulations 51 1.35.2 Toxic or Hazardous Substances 51 1.35.3 Other Known Hazards 52 1.36 COMMUNICATIONS PLAN 52 1.36.1 General...; 52 1.36.2 Roles and Responsibilities 52 1.36.3 Communications Resources 53 1.36.4 Communications Objectives 53 1.36.5 Audiences 53 1.36.6 Media Relations 53 1.36.7 Messaging 53 1.36.8 Milestone Announcements 53 1.36.9 Advertising 53 1.36.10 Critical Issues Management 54 1.36.11 Agency Communications Strategy 54 1.36.12 Communications During Construction 54 1.36.12.1 Communication of Traffic Conditions During Construction 54 1.36.12.2 Public Information During Construction 55 1.36.13 Payment 55 1.37 PAINTING CONTRACTOR QUALIFICATIONS 55 1.37.1 General 55 1.37.2 SSPC Certification • 56 1.37.2.1 QP1 Certification 56 1 37 2.2 QP2 Certification 56 1.38 SCAFFOLDING AND SHROUDING EXTENTS 56 1.38.1 Top-Down Work Procedure 56 1.38.2 Protection of Motorist, Cyclists, and Pedestrians 56 1.38.3 Allowable Scaffolding Extents 56 1.38.3.1 Suspension Bridge 56 1.38.3.2 North Approach Viaduct 57 1.38.4 Temporary Connection to the Bridge 57 PROJECT No. 11696-0002 151 1 38.4.1 General 57 1.38.4.2 Suspension Bridge 57 1 38.4.3 North Approach Viaduct 57 2.1 GENERAL 58 2.1.1 Payment Criteria 58 2.1.2 Existing Dimensions 58 2.1.3 Fall Protection 58 2.1.4 Mobilization .-. 58 2.1.5 Ministry Site Office 58 2.1.6 Safety Criteria for Removal of Existing Coating , 58 2.1.6.1 Protection of the Environment 58 2.1.6.2 Occupational Health and Safety Regulations 59 2.1.7 Pre-Construction Meetings 59 2.1.8 Hierarchy of Specifications 59 2.1.9 Supply of Materials 59 2.1.9.1 Coating System for Structural Steel 59 2.1.9.2 Coating Dry Film Thicknesses 59 2.1.9 3 Colour of Top Coat 59 2.1.9.4 Penetrating Epoxy Sealer and/or Caulking 60 2.1.9.5 Coating for Exposed Main Cables and Anchor Assemblies in Anchor Chambers 60 2.1.9.6 Immersion Coating for the Zone 4 Sump Area 60 2.1.10 Definition of Abrasive Blast Cleaning 60 2.1.11 Crevice Corrosion '. 60 2.2 SUSPENSION BRIDGE WASHING, CLEANING, AND COATING 61 2.2.1 General 61 2.2.2 Suspension System 61 2.2.2.1 General 61 2.2.2.2 Exposed Main Cable Strands on Saddles at Tops of Tower Legs 61 2.2.2.3 Interior of Main Cable Saddle Housing at the Top of the Towers 62 2.2.2.4 Wrapping Wires of Main Cables 62 2.2.2.5 Main Cable Hanger Bands (Including Main Cable Hand Strand Support Brackets) : 63 2.2.2.6 Exposed Main Cable Strands and Anchor Assemblies in Anchor Chambers63 2.2.2.7 Tie-back Cables Between North Cable Bent and North Anchorage 64 2.2.2.8 Hangers 64 2.2.2.9 Hanger Sockets and Hanger Connection Plates to Deck 65 2 2.2 10 Traction Rods 65 2.2.2.11 Basis of Payment '. 66 2.2.3 Exterior Surfaces of Main Tower Legs and Bracing Between Tower Legs 66 2.2.3.1 General 66 2.2.3.2 Tower Leg Zones Above and Below Splash Zones and Bracing and Horizontal Struts Between Tower Legs Above and Below Splash Zones 66 2.2.3.3 Tower Legs at Splash Zones 68 2.2.3.4 Basis of Payment 68 2.2.4 Interior Surfaces of Main Tower Legs 69 2.2.4.1 General 69 2.2.4.2 WCB Confined Space Designation 69 2.2.4.3 Extents of Painting 69 2.2.4.4 Zone 1: Above Deck to Tops of Towers 69 2.2.4.5 Zone 2: Below Deck to 3 m Above Top of Foundation 70 2.2.4.6 Zone 3: 3m Above Top of Foundation to, but not including ,the Plate Above the Sump at the Bottom of Tower Legs 70 2.2.4.7 Zone 4: The Plate Above the Sump at the Bottom of the Tower Legs and All Sump Surfaces to the Foundation 70 PROJECT No. 11696-0002 152 2.2.4.8 Basis of Payment 2.2.5 North Cable Bent and South Cable Post 2.2.5.1 General 2.2.5.2 Washing, Cleaning, Penetrating Epoxy Sealer, and Coating 2.2.5.3 Basis of Payment 2.3 NORTH APPROACH VIADUCT WASHING, CLEANING, AND COATING 2.3.1 General 2.3.2 Seismic Retrofit and Sidewalk Widening Steelwork 2.3.2.1 General 2.3.2.2 Option 1 - Washing, Cleaning, and Protecting from Overblast Damage 2.3.2.3 Option 2 - Abrasive Blasting of All Steel and Recoating 2.3.2.4 Basis of Payment 2.3.3 Original Structural Steelwork (All Steelwork Other Than Seismic Retrofit and Sidewalk Widening Steelwork) 75 2.3.3.1 General 75 2.3.3.2 Washing, Cleaning, Penetrating Epoxy Sealer, and Recoating 75 2.3.3.3 Basis of Payment 76 2.4 PROVISIONAL SUM FOR MODIFICATIONS ON SITE 76 APPENDICES A Sample Traffic Management Forms B Reference Documents B.1 General B.2 Original Design Drawings B.3 Original Shop Drawings B.4 Modifications to the Bridge Since Original Construction B.5 Electrical and Mechanical Drawings of Existing Bridge B.6 Air/Water Line Drawings B.7 North Approach Viaduct Deck Replacement Drawings (1975) B.8 Suspension Bridge Deck Replacement Drawings (1999-2001) B.9 North Approach Viaduct Sidewalk Widening Drawings (1999-2001) B.10 North Approach Viaduct Seismic Rehabilitation Drawings (1999-2001) B.11 Suspension Bridge and North Approach Viaduct Street Light As-Builts (2002) B.12 Environmental Reports Painting of Transportation Infrastructure D Communication between Ministry of Transportation and Vancouver Board of Parks and Recreation Regarding Use of Stanley Park E Lane Closure Costs Provided by Mainroad (Howe Sound) Contracting Ltd. (Ministry of Transportation Maintenance Contractor) F Project Review Application to Vancouver Port Authority G Quality Control Program for Coating of Steelwork H Survey Layout Services and Products Appendix BC 21 - Tender and Contract Language PROJECT No. 11696-0002 153 Appendix C. Sample Bridge Coating Rating Sysfc Coating Inspection Report 154 BRIDGE INSPECTION REPORT Appendix D. Sample British Columbia Ministry of Transportation Bridge Inspection Report and Definition of Condition Rating Categories 156 BRITISH COLUMBIA MINISTRY OF TRANSPORTATION BRIDGE MANAGEMENT INFORMATION SYSTEM Condition Inspection Report Cr i te r ia : St ructure No = 2304 R e g i o n : 1 - South Coas t S t ruc ture No : 2304 - E Q U E S T . P E D O/P R o a d N o : 1 - S T A N PK C S W Y Dist r ic t : 1 - Lower Mainland S ta tus : Open/In Use Con t rac t A r e a : 4 - Howe Sound Inspect ion T y p e : Routine Cond Fea tu res C r o s s e d : S T A N P K C S W Y S T A N L E Y P A R K P/O A P P R O A C H E S Bui l t : 1970 Main Span Leng th : 9.140 U r g e n c y : 2 Inspector / Inspected B y : Z B . R A D Z I M O W S K I Leng th (m): 78.500 Ma in Span Type : S T R I N G E R BCI Ra t ing : 1.1 O n 2002/12/10 A m e n d e d B y : C o m p o n e n t G r o u p / C o m p o n e n t E G F P V X N/A C H A N N E L ; 1. [Debris Risk Y 2. |Bank /Bed Scour /Bui ldup Y 3. | Dolphins/Fenders 1 1 v S U B S T R U C T U R E ; 4. | Foundat ion Movement 100 N 5. | Abutments 100 N 6. [Wing/Retaining Walls Y 7. [Footings/Pil ing 99 1 N a. | Pier Columns/Wal ls /Cr ibs 99 1 | N 9. j Bearings [ 90 10 N 10. | C a p s I Y 11. | Corbels Y S U P E R S T R U C T U R E : 12. (Floor Beams/Transoms Y 13. | Stringers Y 14. | Girders 75 20 5 N 15. [Portals Y 16. |Bracing Diaphragms Y 17. | Truss C h o r d s / A r c h Ribs Y 18. | Arch Ties Y 19. [Truss Diagonals Y 20. (Truss Rods/Vert icals Y 21. | Cables Y 22. [Panels Y 23. [ Pins/Bolts/Rivets Y 24. I Camber /Sag 100 1 N | 25. JLive Load Vibration 100 1 N | 26. |Coating (Structure) 50 50 1 N j D E C K ; 27. | Sub Deck /Cross Ties 1 y 1 28. [Wearing Surface 75 15 10 N 29. |Deck Joints 100 N 30. [curbs/Wheelquards Y 31. [sidewalk(S) Y 32. [Railings/Parapets 99 | 1 N 33. | Median Barrier Y 34. jOrams/Pipes Y 35. [Coating (Railings) 25 65 10 N Isigning/lightinq 1 95 5 N I Roadway Approaches 100 [ N | Roadway Flares 1 1 1 Y S p a n s : 6 Ad jus ted BCI R a t i n g : 1.17 O n Foo t i ngs /P i l i ng W E S T P IER F O U N D A T I O N : S - E C O R N E R : - med ium crack . P ie r C o l u m n s/Wal ls/Cr ir . W E S T P I E R : 157 BiSH70oo BRITISH COLUMBIA MINISTRY OF TRANSPORTATION BRIDGE MANAGEMENT INFORMATION SYSTEM Condition Inspection Report Criteria: Structure No = 2304 District: 1 - Lower Mainland Contract Area: 4 - Howe Sound Status: Open/In Use Inspection Type: Routine Cond BOTTOM SECTION: - light corrosion. 9 . Bearings - Light corrosion. 14 . Girders - Light to medium flaking corrosion along the edges and on the underside. 26 . Coating (Structure) - Light rust and rust stains on sub deck. 28 . Wearing Surface EQUESTRIAN BOUND: - worn out areas of anti-skid surface. Region: 1 - South Coast Structure No: 2304 - EQUEST. PED O/P 32 . Railings/Parapets HORIZONTAL RAILS: - light to medium corrosion @ connections. 35 . Coating (Railings) - New paint flaking and peeling in various locations. - Spots of rust. 36 . Signing/Lighting - Paint damaged. - Green stain. - West sign damaged. Inspection Notes: Maintenance Work Notes - Paint sub deck & railings. - Restore non-skid coat where worn out. - Clean & recoat beraings. - Replace damaged sign. Rehab Work Notes JULY 1995: - joints sealed with Dow-Corning, - railings, parapets & pier columns painted. 158 BRITISH COLUMBIA MINISTRY OF TRANSPORTATION BRIDGE MANAGEMENT INFORMATION SYSTEM Condition Inspection Report C r i t e r i a : S t r u c t u r e N o = 7 9 8 4 R e g i o n : 1 - S o u t h C o a s t S t r u c t u r e N o : 7984 - P O R T E A U C O V E P I E R R o a d N o : D i s t r i c t : 1 - L o w e r M a i n l a n d S t a t u s : Open / In U s e F e a t u r e s C r o s s e d : C o n t r a c t A r e a : 4 - H o w e S o u n d I n s p e c t i o n T y p e : Rout ine C o n d C o m p o n e n t G r o u p / C o m p o n e n t C H A N N E L : E G F P V X N/A 1- |Oebris Risk I Y 2. |Bank /Bed Scour /Bui ldup I Y 3. | Dolphins/Fenders I Y S U B S T R U C T U R E ; S U P E R S T R U C T U R E ; (Foundation Movement Y | Abutments Y [ Wing/Retaining Walls Y , | Footings/Pi l ing 98 2 N | Pier Columns/Walts /Cr ibs Y j Bearings Y 99 1 1 N [Corbels Y [Floor Beams/Transoms Y Y [stringers ] Girders Y | Portals Y [Bracing Diaphragms * Y | Truss Chords /Arch Ribs Y | Arch T ies Y [Truss Diagonals Y (Truss Rods/Vert icals Y | Cables Y [Panels Y (pins/Bolts/Rtvets Y | Camber /Sag Y I Live Load Vibration Y |Coat ing (Structure) Y [Sub Deck /Cross Ties i y (Wearing Surface I Y [Deck Joints Y j Curbs/Wheel guard s- 95 5 N Ssidewa(k(S) Y | Rail ings/Parapets 10 75 10 5 N [Median Barrier Y [Drains/Pipes Y [Coating (Railings) 85 r 15 N A P P R O A C H E S : {Signing/Lighting i Y (Roadway Approaches i Y [Roadway Flares i Y B u i l t 2001 M a i n S p a n L e n g t h : U r g e n c y : 1 I n s p e c t o r / I n s p e c t e d B y : Z B . R A D Z I M O W S K I L e n g t h (m): .000 M a i n S p a n T y p e : B C I R a t i n g : 1.34 O n 2004 /06 /28 A m e n d e d B y : S p a n s : A d j u s t e d B C I R a t i n g : 1.89 O n Item N o t e s : 7 . F o o t i n g s / P i l i n g - m o s t l e n g t h o f t h e p i l e s c o v e r e d wi th s h e l l s , - l ight c o r r o s i o n o n e x p o s e d s u r f a c e s , - m e d i u m c o r r o s i o n w i t h f l a k i n g r u s t & <15% s e c t i o n l o s s @ t o p s e c t i o n s . 159 BRITISH COLUMBIA MINISTRY OF TRANSPORTATION BRIDGE MANAGEMENT INFORMATION SYSTEM Condition Inspection Report Criteria: Structure No = 7984 Region: 1 - South Coast Structure No: 7984 - PORTEAU COVE PIER District: 1 - Lower Mainland Status: Open/In Use Contract Area: 4 - Howe Sound Inspection Type: Routine Cond Caps 1st PIER: - UNDERSIDE @ SOUTH PILE: - spall with rusted rebar exposed. 7th PIER ( LAST PIER OF CONCRETE STRUCTURE) • diagonal cracks sealed with epoxy. 30 . CurbsAVheetguards ON CONCRETE STRUCTURE: - weathering & checking. ON MOVABLE RAMP; - checking, - minor to significant rot - damp & soft wood with <25% section loss localy. Railings/Parapets - Weathering & checking for timber componenets. - Light to medium corrosion for steel components. - Heavy corrosion localy with perforation & section loss for railing steel mash. Coating (Ratlings) - Paint aging. - Coat failing localy. Inspection Notes: Maintenance Work Notes - Replace wheelguard sections where rotten. - Repair railing mash where section loss. - Touch-up paint railing. 160 Inspection of Steel Superst ructures Condition Rating , S T E E L S U P E R S T R U C T U R E 25.9 In order to complete the Bridge Inspection Card, each component must be assessed to determine what percentage of each component is in each condition state (total 100%). The following guidelines are provided to assist you in identifying the condition state of each component. Conventions for calculating percentages of Component Condition State are contained in 18.4.2 Condition State Description Excellent Condition - as new condition Good Condition - normal wear and deterioration not requiring maintenance or repair - chalking/checking of paint * - weathering steel* - oxide is purple brown in colour and tightly adhered or light brown and dusty Fair Condition - minor defects, deterioration or collision damage; generally requires maintenance or repair - light corrosion/minor pitting with no measurable section loss - collision damage - surface scrapes only with no bending or buckling - cracking/peeling of paint * - weathering steel * - oxide is black and granular in a few areas Poor Condition - advanced deterioration; significant defects or collision damage; repair required - medium corrosion - with less than 15% section loss - hinges and pin connections frozen from corrosion - cracks present in non-critical areas * - any bending of members (may be upgraded upon inspection by Regional Bridge Engineer) - loose or missing fasteners - less than 20% of the connection - paint system has failed * - weathering steel * - oxide is black with flakes or sheets of rust 161 Condition State Description Very Poor Condition - serious defects, deterioration or collision damage; imminent failure of component requiring immediate repair or replacement and/or load restriction - heavy corrosion with more than 15% section loss - cracked welds or cracks present in a major structural element * - collision damage - members buckled or badly bent - loose connections; missing fasteners - more than 20% of the connection Not Applicable - use only when that component is not present on the structure Cannot Inspect - include a brief description or reason why the component cannot be inspected, e.g. inspection requires specialized access equipment. * Notes: - A l l cracks in steel must be reported to the Regional Bridge Engineer - Descriptions relating to paint and weathering steel are intended to produce condition codes for "coatings" and not the steelwork itself. For additional information on weathering steel, see Section 25.8.2. 162 Appendix E - I . Steel Bridge Coating Maintenance Evaluation Model 163 Appendix E. Overall Bridge Condition Rating, using Deterministic Input Values 164 Inputs: corr rate 8 corr curve 5 escalation 0.025 interest 0.03 total_bridge_surface_area 3500 life 70 touch_up_durability 12.5 touch up unit_cost 450 overcoatdurability 20 overcoat unit cost 130 recoatdurability 25 recoat unit cost 200 replace_cost 20000000 replace_add_cost 0 strategy strategy := IF( corr_rate £ 8, minor_damage, IF( corr_rate > 5, fair_damage, severe_damage)) [-| 7005.31 corr_rate corr rate := 8 t o u c h u p E U A C |- | touch_up_EUAC: 7005.31 minor_damage minor_damage := MIN( do_nothing_EUAC, touch_up_EUAC, overcoat_EUAC, recoat_EUAC) |-j 7005.31 d o n o t h i n g E U A C r-| do_nothing_EUAC := 134620.71 -0 replace_end_of_coating_PV - replace_end_of_life_PV • replace_add_cost_PV) * interest * (1 + interest) > (replace_end_of_coating_PV (1 + interest) -1 touch_up_TPV * interest * (1 • interest) (1 + interest )' l ,e -1 touch_up_TPV touch_up_TPV := SUM( touch_up_PV[0]n ) 204018.73 interest interest := 0.03 v 0 .03 life life := 70 70 overcoat. EUAC overcoat_ EUAC overcoat T P V * interest * (1 + interest ) W e (1 + interest) -1 54324.5 overcoat_TPV overcoat_TPV := SUM( overcoat_PV[0]D ) 1582115.44 interest recoat_EUAC H recoat_EUAC := 64162.72 recoat_TPV * interest * (1 + interest) (1 + interest )' l ,e -1 recoat_TPV recoat_TPV := SUM( recoat_PV[0]Q ) 1868638 \ interest fair_damage fair_damage := MIN( do_nothing_EUAC, overcoat_EUAC, recoat_EUAC ] 54324.5 | do_nothing_EUAC |-^ | overcoat_EUAC |-^ | recoat_EUAC~l-* severe_damage severe_damage := MIN( do_nothing_EUAC, recoat_EUAC ) Unevaluated H do_nothing_EUAC |-^ H recoat_EUAC IfoS do_nothing_EUAC do_nothing_EUAC: 134620.71 (replace_end_of_coating_PV - replace_end_of_lrfe_PV + replace_add_cost_PV) * interest * (1 + interest) > ^ (replace_end_of_coating_PV| ( 1 + interest) - 1 replace_end_of_coating_PV I . . „ w replace cost * (1 + escalation ) H replace_end_oLcoating_PV~ = — ., 6 (1 + interest) 18147009.92 < replace_cost 20000000 escalation 0.025 coating_life corrosion rating[1][0] - corrosion rating(1][corr rate] coating life := corrcurve 19.98 interest interest := 0.03 0.03 corrosion rating K0,1,2l3,4,5,6,7,8.9,1O].[10O.5O,33,16.7,1Q,3,1,0.3,0.1,0.03,...]] corr_rate corr_rate := 8 8 corrcurve 5 replace_end_of_life_PV |—| replace_end_of_life_PV := 14226394.37 _ replace_cost * (1 + escalation ) (1 + interest }life \ replace_cost [-^  | escalation]-^ K lrfe life := 70 70 replace_add_cost_PV replace_add_cost_PV:: 0 replace_add_cost * (1 + escalation ) (1 + interest) coatingjife [—| interest"}-^  lifel replace_add_cost replace_add_cost := 0 0 | coatingjife}-^ \ interest touch_up_TPV touch_up_TPV := SUM( touch_up_PV[0]Q ) 204018.73 touch_up_PV touch_up_PV: touch_up_cycles -1 x • t 0 U c h up durability touch_up_IC (1 + escalation ) Z-^—L LJ , . . . touch up durability x : = o (1 + interest) ~ [39375,37051.31066,34864.75229,32807.23221,30871.1353,29049.29586] touch_up_IC touch_up_IC := touch_up_unit_cost * maintenance_area 39375 escalation 0.025 touch_up_unit_cost 450 maintenance_area 87.5 touch_up_durability 12.5 corrosion rating [[0,1,2,3,4,5,6,7,8,9,10],[100,50,33,16.7,10,3,1,0.3,0.1,0.03,...]] corr_rate corr_rate := 8 8 K total_bridge_surface_area 3500 interest interest := 0.03 0.03 touch_up_cycles touch_up_cycles := MAX( touch_up[0]Q ] 6 touch_up n_touch_up touch_up := [] y [1,2,3,4,5,6] y:=1 n_touch_up n_touch 6.6 i_up := ^ life touch_up_durability life life := 70 .70 [ touch_up_durability"|-^ overcoat_TPV overcoatTPV: 1582115.44 = SUM( overcoat_PV[0]Q ) overcoat_PV overcoat PV overcoat_cycles -1 [] ... ,a * overcoat durability overcoatJC * (1 + escalation ) ~ . .a * overcoat durability o (1 + interest) [455000,412804.298,374521.73285,339789.40882] overcoatJC H overcoatJC: 455000 : overcoat_unit_cost * totalJ>ridge_surface_areH K overcoat_unit_cost i30 escalation 0.025 totalj3ridge_surface_area 3500 overcoat_durability 20 interest interest := 0.03 .0.03 overcoat_cycles overcoat_cycles := MAX( overcoat[0]D ) 4 overcoat n_overcoat overcoat := [] b b:=1 [1,2,3,4] n_overcoat n_overcoat 4.5 life overcoat durabilii overcoat_durability"]-^ recoat_TPV recoat_TPV := SUM( recoat_PV[0]Q ) 1868638 recoat_PV recoat_cycles -1 . . . ,c * recoat durability • _., r , recoat IC (1 + escalation ) recoat_PV := [] = — — • recoat d u r a b i l i l y c : = o (1 + interest) [700000,619817.81852,548820.18308] recoatJC r-| recoatJC := recoat_unit_cost * total J>ridge_surface_area 700000 escalation . 0.025 recoat_durability 25 interest interest := 0.03 . 0.03 recoat_cycles L - | recoat_cycles := MAX( recoat[0][|) 3 recoat n_recoat recoat := [] d d:=1 [1.2,3] recoat_unit_cost 200 total J)ridge_surface_area 3500 n_recoat n_recoat: 3.8 life recoat_durability recoat_durability |-^ Appendix F. Bridge Components Condition Rating, using Deterministic Input Values 170 corr rate 5 struct corr rate 8 bear con* rate 5 expjoints corr rate 5 non struct corr rate 7 corr curve 5 escalation 0.025 interest 0.03 struct surface area 3000 bear surface area 1 expjoints surface area 4 non struct surface area 495 life 70 touch up durability 12.5 touch up unit cost 450 overcoat durability 20 overcoat unit cost 130 recoat durability 25 recoat unit cost 200 replace cost 20000000 replace add cost 0 H bear_strategy bear_strategy := IF( b e a r c o r r r a t e a 8, bear_minor_damage, IF( bear_corr_rate z 5, bear_fair_damage, bear_severe_damage )) -15.52129 overall_strategy overall_strategy := MIN( overall_maintenance_EUAC, do_nothingJEUAC ) 13765.19882 overall_maintenance_ overaII_maintenance 13765.19882 E U A C E U A C := struct_strategy + be a ^ strategy + expJoints_strategy + non_struct_strategy h-j struct_strategy [—J struct_strategy := IF( struct_corr_rate £ 8, struct_minor_damage, IF( struct_corr_rate 2 5, structJair_damage, struct_severB_damage ) 6004.5553 struct__corr_rate struct corr rate := 8 struct_mrnor_damage struct_minor_damage := MIN( struct_touch_upJEUA(} 6004.5553 strucMou ch_up_E U A C 6004.5553 struct_overcoatJ=UAC 46563.86116 struct_recoatJ=UAC 54996.61926 struct_fair_damage struct_fair_damage := MIN( struct_overcoatJEUAC, slf Unevaluated Hi struct_oyercoatJEUAC J-^  struct^recoat^EUAC f-^ struct_severe_damage struct_severe_damage := stru ct_recoat_E UAC Unevaluated \ strucWecoarEUAC J-^  bear_corr_rate bear_corr_rate := 5 bear_minor_damage bear_minor_damage := MIN( bear_touch_upJEUAC, 2.00152 j bear jouch_up j=UAC 2.00152 bear_overcoatJEUAC 15.52129 bear_recoat_EUAC 18.33221 bear_fair_damage bear_fair_damage : - MIN( bear_overcoatJ=UAC, bea|-) 15.52129 { b e a r o v e r c o a t E U A C [-^ \ bear_recoat_EUAC bear_severe_damage bear_severe_damage := bear_recoatJEUAC Unevaluated \ bear_recoat_EUAC j - ^ KexpJoints_corr_rate expJoints__corr__rate : : 5 '-expJoints_Strategy expJoints_strategy := IF( expJoints_corr_rate ^ 8, expjoints_minor_damage, IF( expjoints_corr_rate 2 5, expJoints_fair_damage, expJoints_severe_damagi 62.08515 expJoints_minor_damage exp_joints_minor_damage := MIN( e x p j o i n t s j o u c h 8.00607 I exp jo in tsJouch_upj= U A C K 1 - 1 8 . 0 0 6 0 7 ^ expJoints_overcoat_EUAC I 62.08515 ^ expJoints_recoat_EUAC I 73.32883 ^ expJointsJair_damage expJointsJair_damage := MIN( expJoints_overcoat 62.08515 | expjoints. o v e r c o a t E U A C | expJoints_recoat E U A C f-^ expJoints_severe_damage . expJoints_severe_damage := expJoints_recoat_EUf l—| expJoints_recoat_EUAC | - J Unevaluated non_struct_strategy non_struct_strategy := IF( non_struct_corr_rate £ 8, non_struct_minor_damage, IF( non_struct_corr_rate £ 5, non_struct_fair_damage, non_struct_severe_dama[ 7683.03709 K reptace_cost rep!ace_cost := 20000000 20000000 do_nothing_EUAC do_nothing_EUAC := 136381.84 -( (replace_end_of_coatingJ : > V - replace_end_ofJife^PV + replace_add_cost_PV) * interest * (1 + interest) (1 + interest )' l fa -1 replace_end_of_coatingJ : ,V replace_end_of_coating_PV := 18198300.2 replace_cost * (1 + escalation ) < escalation escalation := 0.025 0.025 non_struct_corr_rate non_struct_corr_ratB := 7 7 non_struct_minor_damage n o n s t r u c t m i n o r d a m a g e := MIN( non_strucMouch 990.75162 non_stru ct_touch_up_E U A C 990.75162 non_struct_overcoatj=UAC 7683.03709 non_struct_recoatJEUAC 9074.44218 non_struct_fair_damage non_struct_fair_damage := MIN( non_struct_overcoat| 7683.03709 non_struct__severe_damage non_struct_severe_damage := non_struct_reooat_EU] Unevaluated ^ n o n s t r u c t o v e r c o a t J E U A C j - ^ \ non_struct_recoat^EUAC | -^ •] non'_struct_recoat . E U A C | -^ coatingjife coating life — c o r r o s ' o n rating[1)[0] - corrosion rating[| 19.4 corr curve interest interest :=0.03 0.03 corrosion rating corrosion rating ;= [[0,1,2,3,4,5,6,7,8,9,10l,[100,50,33,16.7,10,3,1,0.3,0.1,0.03,...ll corr_rate corr_rate := MIN( struct_corr_rate, bear_corr_rate, t 5 corr_curve corr^curve := 5 \ struct corr^rate ] bear_corr_rate p ] expJoints_corr_ratel-^ \ non i_struct_corr_raie~t-^ replace_end_ofJife_PV rep lace_end_ofJ i fe j °V := 14226394.37 replace cost * (1 + escalation ) (1 + interest )' I ,B | replace_cost |-^ I escalation")-^  life life := 70 70 | interest |-^ replace_add_( replace_add_( replace_add_cost * (1 + escalation ) c o a l i n 9- l i t e = (^interest)""'"0-1" rep!ace_add_cost repiace_add_cost := 0 0 ) escalation}-^ | c c ^ t i n g j i f B ~ | - ^ | interest ni struct_minor_damage struct_minor_damage := MIN( struct_touch_up_EUAC]-| 6004.5553 struct_touch_u p_E UAC struct_touch_up_EUAC := 6004.5553 struct_touchjjpJTPV * irtq (1 + intere struct_touch_up__TPV struct_touch_up_TPV := SUM( struct_touch_up_PV[( 174873.19398 I interest \ struct_tou ch_u p_P V touch_up_cycles -1 struct_touch_up_PV := [] =— x:=0 [33750,31758.26628,29884.07339,28120.48475,2643 struct_touch_ ."P. JC struct touch .UP-JC := touch_up_unit_cost * struct_m 33750 Ktouch_u p_un it_cost touch_up_unit_cost := 450 escalation escalation := 0.025 0.025 struct_maintenance_area struct_maintenance_area := corrosion rating[1][struct 75 corrosion rating corrosion rating := [T0,1,2,3,4,5,6,7,a,9,10],[100,50,33,16.7.10,3,1,0.3,0.1,0.03,-]3 struct_corr_rate struct corr rate := 8 touch_up__durability touch_up_durability := 12.5 12.5 struct_surfa ce_area struct_surface_area := 3000 3000 interest interest := 0.03 0.03 touch_up_cycles touch_up_cycles := MAX( touch_up[0][]) 6 touch_up n touch up touch_up := " o" y y:=1 [1,2,3,4,5,6] n_touch_up n_touch_up : 6.6 life k touch_up_durability H life life := 70 70 | touchupdurabilityl-^ struct_overcoat_E U AC struct_overcoat_EUAC := 46563.86116 struct overcoat TPV * inta ( 1 + interest struct__ove rcoat_TPV struct_overcoat_TPV := SUM( struct_overcoat_PV[0]J 1356098.94828 interest \ struct overcoat PV overcxjatcydes -1 struct_overcoat_PV := a:=0 ( [390000,353832.25543,321018.62815,291248.0647] struct_overcoat_l C struct_overcoat_IC := overcoat_unit_cost * struct_surH 390000 overcoat_unit_cost overcoat_unit_cost := 130 130 \ escalatioTT}-^  | struct_surface_area~|~^ < overcoat_durabi!ity overcoat_durability := 20 20 | interest \ overcoat_cycles overcoat_cycles := MAX( overcoat[0]Q ) 4 overcoat n__overcoat overcoat := [] b I—j b:= 1 [1,2,3,4] n_overcoat n_overcoat: 4.5 life ^ overcoat_durability life \ overcoat^durability struct_recoat_EUAC struct_recoat_EUAC := 54996.61926 struct recoat TPV * interest ( 1 + interest) struct_recoat_TPV r-| struct_recoat_TPV := SUfv1( stnjct_recoat_PV[0][]) 1601689.71566 interest [ struct_recoat_PV recoat_cyd struct_recoat_PV := [] c:=0 [600000,531272.41588,470417.29978] struct recoat IC struct_recoat_IC struct_recoat_IC recoat_unit_cost * struct_surface 600000 / recoat_unit_cost recoat_unit_cost := 200 M \ 2 o o \ escalation")-^ < | struct_surface_area"j-^ recoat_durability recoat_durability := 25 25 interest recoat_cycles recoat_cycles := MAX( recoat[0]Q ) 3 recoat nrecoat recoat := [] d I—j d := 1 HA3L n_recoat nrecoat: 3.8 life A | recoat_durability J life} recoat_durability f-^ \1Z bear_minor_damage bear_minor_damage := MIN( bear_touch_up_EUAC, 2.00152 bea r_touch_u p_EUAC bear touch up TPV * inter! bear_touch_up_EUAC := = 1 2.00152 (1 + interest! bea r_overcoat_E U AC bear_overcoat_EUAC := 15.52129 bear overcoat TPV * intere (1 + interest bear_recoat_ EUAC bear_recoat_ 18.33221 EUAC bear recoat TPV * interest * ( (1 + interest ) l i f e bear__touch_up_TPV bear_touch_up_TPV - SUM( bear_touch_up_PV[0][]| 58.29106 interest r bear_overcoat_TPV bearovercoatTPV := SUM( bear_overcoat_PV[0]fl 452.03298 interest life] bear_recoat_TPV bear_recoat_TPV := SUM( bear_recoat_PV[0]FJ ) 533.89657 interest"!-^ bea r_touch_u p_PV bear_touch_up_PV touch_up cycles -1 ; " rj x:=0 bear touch J [11.25,10.58609,9.96136,9.37349,8.82032,8.2998] bear_toucn_up_IC bear_touch_up_JC := touch_up_unit_cost * bear_mairj-| 11.25 touch_u p_unit_cost touch_up_unit_cost := 450 450 escalation escalation := 0.025 0.025 bear_maintenance_area bear_maintenance_area := corrosion rating[1][bear_c| 0.025 corrosion rating corrosion rating [[0,1,2,3,4,5,6,7,8,9,10],[100,50,33,16.7,10,3,1,0.3,0.1,0.03,...]] bear_corr_rate bear_corr_rate := 5 5 touch_up_durability touch_up_durability := 12.5 12.5 bearsurfa cearea bear surface area := 1 interest interest := 0.03 touch_up touch_up_cycles n touch up touch up cycles 6 := MAX( touch_up[0][]) touch_up := " [ ] " y y:=1 [1,2,3,4,5,6] n_touch_up n_touch 6.6 1 uh* i_up := ^ life touch_up_durability -life life := 70 70 | touch^updurabiiity"]-^ bear_overcoat_PV overcoat_cycles -1 bear_overcoat_PV := [] a:=0 [130,117.94409,107.00621,97.08269] bear overcoat] (1 bear_overcoat_l C bearovercoatlC := overcoat_unit_cost * bear_surfaiH 130 overcoat_un it_cost overcoat_unit_cost := 130 130 | escalation"]-^ | bear_surface_area j - ^ < overcoatdurability overcoatdurability := 20 20 interest \ overcoat_cycles overcoat_cycles := MAX( overcoat[0][] ] 4 overcoat n overcoat overcoat := "[ ] » b:= 1 [1,2,3,4] n overcoat := — — r r — H - ^ overcoat_durability J overcoat durabili bear_recoat_PV rBCoat_cyde! bear_recoat_PV := [] c:=0 [200,177.09081,156.80577] bear_recoat_IC * ( ( 1 + intd bear_ _recoat_ JC bear recoat_ IC := recoatunitcost * bear_surfaoe_a 200 " recoat_unit_cost recoat_unit_cost := 200 200 | escalation]-^ | bear_surface_area |-^ < recoat_durability recoat_durability := 25 25 1 interest t recoat_cycles recoat_cycles := MAX( recoat[0]Q ) 3 n_recoat recoat := d P.2.3] nrecoat n_recoat 3.8 life recoat_durability life} recoat_durability f-^  IIS expJoints_minor_damage expJoints_minor_damage := MIN( expjoints touch_|—j 8.00607 expJoints_touch_up_EUAC • • . . - i . C I I A / * expjoints touch up expjointsJouch_up_EUAC := — — = ^ - ^ (1 8.00607 expJointsJouch_up_TPV expJoints_touch_up_TPV :; 233.16426 SUM( expjointsjouch I interest \ expJointsJouch_up_PV touch_up_cydes -1 expJointsJouch_up_PV := [] e*PJo x:=0 [45,42.34436,39.84543,37.49398,35.2B13,33.1992] exp JointsJouch_upJC expJointsJouchjjpJC := touch_up_unit_cost * exp K tou ch_up_un it_cost touch_up_unit_cost := 450 450 escalation escalation := 0.025 0.025 expJoints_maintenance_area L-j expJoints_maintenance_area := corrosion rating[1][e] 0.1 corrosion rating prj corrosion rating := nO,1,2,3,4t5.6,7,B,9,10),[100,50,33.16.7,10,3,1,0.3,0.1.0.03.-ll exp j oi nts_corr_rate expJoints_corr_rate := 5 5 touch_up_dura bility touch_up_durability := 12.5 12.5 exp J oi nts_surfa ce_area expJoints_surface_area := 4 4 interest interest := 0.03 0.03 touch_up_cycles •-"I touch_up_cycles := MAX( touch_up[0][]) 6 touch_up n_touch_up touch_up :- [] y I—I [1,2,3,4,5,6] y : « 1 n_touch_up njouch 6.6 Lup := ^ life touch_up_dura bility life life := 70 70 | touch_up_dura bility*}-^ expJoints_overcoat_EUAC • . , r i l . « expjoints overcoat n expjoints_overcoat_EUAC := — — =- =f 62.08515 (1 -expJoints_overcoat_TPV expJoints_overcoat_TPV := SUM( expjoints_o 1808.13193 interest expJoints_overcoat_PV overcoat_cydes -1 expJoints_overcoat_PV := a :=0 [520,471.77634,428.02484,388.33075] expjoinf expJointsovercoatJC expJoints_overcoatJC := overcoat_unit_cost * expj| 520 / overcoat_unit_cost r-^ overcoat_unit_cost: JJ \ 1 3 0 | escalation"}-^  | expJoints-surface_area < ove rcoat_dura bility overcoat_durability := 20 20 interest overcoat_cycles overcoat_cycles := MAX( overcoat[0]Q ) 4 overcoat n overcoat overcoat := "[] " b:= 1 [1,2,3,4] n_overcoat n_overcoat := ^ overcoatdurability J 4.5 *—\ overco overcoat_durability |-^ expJoints_recoat_EUAC expJoints_recoat_EUAC := 73.32883 expJoints_recoat_TPV ( 1 + intd expJoints_recoat_TPV expJoints_recoat_TPV := SUM( expJoints_recoat_P| 2135.58629 f interest \ expJoints_recoat_PV recoat_cydes expJoints_recoat_PV := [] c:=0 [800,708.36322,627.22307] expJoints_ra expJoi nts_recoat_lC expJoints_recoatJC := recoat_unit_cost * expjoints] 800 recoatunitcost recoatunitcost := 200 200 ] escalatioTTr-^  \ expJoints_surface_area |-^ < recoat_durability recoat_durability := 25 25 recoat recoat_cycles n_re -Oat recoat cycles 3 = MAX( recoat[0]rj) recoat := [ d:= d 1 [1,2,3] n_recoat njecoat: 3.8 life recoat_durability _ lifer recoat_durability |-^ non_struct_minor_damage non_suTJct_rninor_damage := MIN( non_struct_touch 990.75162 n on_struct_tou ch_u p_ EUAC non_struct_touch_up_ EUAC non_struct_touch_up (1 990.75162 non_struct_tou ch_up_PV non_structJouch_up_TPV I I touchjjp_cydes -1 non_struct_touch_up_TPV := SUM( non_struct_touch|— non_struct_touch_up_PV := [] 28854.07701 interest L GIr i [5568.75,5240.11394,4930.87211.4639.87998.4366.(3 non_struct_touch_ _up_ JC non struct touch. JC := touch_up_unit_cost * non 5568.75 Ktouch_up_unit_cost touch_up_unit_cost := 450 450 escalation escalation := 0.025 0.025 non_struct_maintenance_area non_struct_maintenance_area := corrosion rating[1][r 12.375 corrosion rating corrosion rating := aO,1,2,3,4,5,6,7,B,9,10],[100,50,33,16.7,10,3,1,0.3,0.1,0.03„. non_struct_corr_rate non_struct_corr_rate := 7 7 < touch_up_durability touch_up_durability := 12.5 12.5 non_struct_surface_area non_struct_surface_area := 495 495 interest interest := 0.03 0.03 touch_up_cycles touch_up_cycles := MAX< touch_up[0][]) 6 touch_up n. touch up touch_up := " []" y y:=1 [1,2,3,4,5,6] n_touch_up ntouchup life touch_up_durability ^ life life := 70 70 | touchupdurability"}-^ non_struct_overcoat_EUAC H non_struct_overcoat_EUAC : 7683.03709 non struct overcoat (1 non_stnjct_overcoat_TPV non_struct_overcoat_TPV := SUM{ non_struct_overci 223756.32647 \ interest non struct overcoat PV Qvercoat_cycles -1 non_struct_overcoat_PV := = a:=o [84350,58382.32215,52968.07365,48055.93068] non_stnjct_ overcoat. IC non struct overcoat. JC = overcoat_unit_cost * non_ 64350 overcoat_un it_cost overcoat_unit_cost := 130 130 | escalation"!-^ | non_struct_surface_area < overcoat_durability overcoat_durability := 20 20 | interest |-^ overcoatcycles overcoat_cycles := MAX{ overcoat[0]Q ) 4 overcoat n_overcoat overcoat := [] b b:= 1 [1,2,3,4] n_overcoat novercoat 4.5 overcoat durabili i t y ) ' life} overcoat_durability j - ^ n on_struct_recoat_E UAC non_struct_recoat_EUAC : 9074.44218 non struct recoat TPV (1 + inU non_struct_recoat_TPV p j non_struct_recoat_TPV := SUM( non_struct_recoat_ 264278.80308 interest |-^ life} non struct recoat PV recoat_cydes -1 non_struct_recoat_PV := [] c :=0 [99000,87659.94862,77618.85446] non_struct_recoat_l C nonstructrecoatJC := recoatunitcost * non_struc(—| 99000 K recoat_unit_cost recoat_unit_cost := 200 200 | escalation"]-^ \ non_struct_surface area j - ^ recoat_durability recoat_durability := 25 25 interest t recoat_cycles recoat_cycles := MAX( recoat[0][]) 3 n_recoat n_recoat 3.8 life recoat_durability Hfe] recoat_durability [-^  ITS Appendix G. Overall Bridge Condition Rating using Probabilistic Input Values 176 Inputs: corr rate 8 corr curve 5 escalation 0.025 interest 0.03 total bridge surface are a 3500 life 112 touch_up durability 12.5 touch up unit cost 450 overcoat durability 20 overcoat unit cost 130 recoat durability 25 recoat unit cost 200 replace cost 30000000 replace add cost 0 strategy strategy := IF( corrjrating z 8, minor_damage, IF( corr_rating 2 5, fair_damage, severe_damaj—| 8758 corT_rating 8 corr_rate corr_rate := 8 8 minor_damage minor_damage := MIN( do_nothing_EUAC,.touch_up_EUAC, overcoat_EUAC, recoat_EUAf-| 8758 do_nothing_EUAC r-| do_nothing_EUAC 305929.59 (replace_end_of_coating_PV - replace_end_of_life_PV + replace_add_cost_PV) * interest * (1 + interest) (1 + interest fe -1 (replace_end_of_coating_PV - replace_end_of tife_ { 1 + int touch_ " P . _EUAC touch. up_ _EUAC _ touch_up_TPV * interest * (1 + interest ) l l f e (1 + interest)' e -1 8758 touch_up_TPV touch_up_TPV := SUM( touch_up_PV[0][J ) 281279.37 interest interest := lrand( 0.03, 0.003 ) .0.03 touch_up_PV touch_up_cycles-1 ,x • touch up durability touch up P V - ri touch_up_IC-(1+escalation) »_ , ^ 0 (1 + i n t e r e s t ) x ' l o u , ; h - u p - a o r a b i l i ' y [39375,37051.31066.34864.75229,32807.23221,30871.1353,29049.29586,...] life life := lrand( 70, 21 ) + 42 112 overcoat_EUAC overcoat_EUAC: 67568.37 overcoat_TPV * interest * ( 1 + interest) ( 1 + interest )W e -1 overcoat_TPV overcoat_TPV := SUM( overcoat_PV[0]fJ ) 2170082.57 I interest overcoat_PV overcoat PV overcoat_cyctes-1 .a • overcoat durability ^ overcoatJC (1 + escalation ) - ' a:=0 .a * overcaal_durability (1 + interest) [455000,412804.298,374521.73285,339789.40882,308278.08434,279689.05097] recoat_EUAC recoatEUAC: 86711.02 recoat_TPV * interest * (1 + interest) (1 + i n t e r e s t - 1 recoat_TPV recoat_TPV := SUM( recoat_PV[0][]) 2784883.89 \ interest [ recoat_PV recoat P V : recoat_cycles-1 .c • recoat durability „ recoatJC (1 * escalation ) ' LJ , „ . . ,c * recoat_durability (1 + interest) [700000,619817.81852,548820.18308,485955.04091,430290.847651 fair_damage fair_damage := MIN( do_nothing_EUAC, overcoat_EUAC, recoat_EUAC 0 ^ do_nothing EUAC |-^ { re raaT f i jAC] - * severe_damage severedamage := MIN( donothingJEUAC, recoat_EUAC| Unevaluated \ do_nothing_EUAC p {recoir|uAc]-* 1-77 d o_noth ing_E UAC do_nothing_EUAC := 305929.59 - ( ( replace^ (1 + interest) -1 ( 1 + int replace_end_of_coating_PV „ . replace cost • (1 + escalation )C 0 8 t i nfl- , i t a replace end of coating PV := — = 1 - — ~ r — — — , . . . , . .coating life (1 + interest) *~ 27220514.88 < replace_cost 30000000 escalation 0.025 coatingjife [-j coatingjife : 19.98 corrosion rating[1][0] - corrosion rating[1][corr_rating) | [ | corT_rating corr_curve interest interest := lrand( 0.03, 0.003 ) 0.03 replace_end_of_life_PV |—| replace_end_of_life_PV : : 17395023.17 replace_cost * (1 + escalation ) {1 + interest ) i l f e \ replace^ cost |-^  \ escalatiorT}-^  < life := lrand( 70, 21 ) + 42 112 replace_add_cost_PV |—| replace_add_cost_PV; 0 _ replace_add_cost * { 1 + escalation ^ c o a t i n 9 - l l f e (1 + interest) replace_a dd_cost replace_add_cost := nrand( 0, 0 ) 0 [ coatingjife j - ^ j interest f-^  J corrosion rating [t0,1,2,3,4,5,6,7,8,9,10],(100,50,33,16.7,10,3,1,0.3,0.1,0.03,...]] corr_rate corr rate := 8 corr_curve v5 touch_up_PV touch_up_PV := touch_up_cycles -1 , , touch_up_IC * (1 + escalation ) * touch_up_durability x : = 0 ( 1 + interest) - ' _ [39375,37051.31066,34864.75229,32807.23221,30871.1353,29049.29586 touch_up_durability touch_up_IC touch_up_IC := touch_up_unit_cost * maintenance_area 39375 ' escalation v 0.025 touch_up_durability . 12.5 interest interest := lrand( 0.03, 0.003 ) 0.03 touch_up_cycles touch_up_cycles := MAX( touch_up[0][]) 9 K touch_up_unit_cost 450 maintenance_area maintenance_area := corrosion rating[1][corr_rating] * 0.01 * total_bridge_surface_area * 2!f 87.5 touch_up n_touch_up touch_up := [] y y:=1 [1,2,3,4,5,6,7,8,9] __| corrosion rating [[0,1,2,3,4,5,6,7,8,9,10],[100,50,33,16.7,10,3,1,0.3,0.1,0.03,...]] corr_rating 8 corr_rate corr_rate := 8 8 K total_bridge_surface_area 3500 n_touch_up n_touch 9.96 i_up := ^ life touch_up_durability life life := lrand( 70, 21 ) + 42 112 touch_up_durability j - ^ overcoat_PV overcoat_cycles -1 , .. .a * overcoat durability x „ , , r , overcoat IC (1 + escalation ) overcoat_PV := [] =—— . o v e r c o a t d u r a b i | i t y a ._ o (1 + interest) [455000,412804.298,374521.73285,339789.40882,308278.08434,279689.05097] overcoat_IC H overcoat_IC: 455000 : overcoat_unit_cost * total_bridge_surface_area escalation . 0.025 overcoat_durability .20 interest interest := lrand( 0.03, 0.003 ) 0.03 overcoat_cycles overcoat_cycles := MAX( overcoat[0]Q ) 6 K overcoat_unit_cost 130 total_bridge_surface_area 3500 overcoat n_overcoat overcoat := [] b b := 1 [1,2,3,4,5,6] n_overcoat n_overcoat 6.6 - { ! « 2 V i " \_ overcoat_durability J life life := lrand( 70, 21 ) + 42 112 | overcoat_durability~|-^ ISO recoat_PV recoat_cycles -1 , ,.. ,c * recoat durability ^ _,, r i recoat IC (1 + escalation ) recoat PV := f l = 1 : ^-r—rrz — LJ . . . ,c recoat durability c : = o (1 + interest) [700000,619817.81852,548820.18308,485955.04091,430290.84765] recoatJC |—| recoat_IC := recoat_unit_cost * total_bridge_surface_area 700000 escalation . 0.025 recoat_durability .25 interest . interest := lrand( 0.03, 0.003 ) recoat recoat_cycles n_recoat recoat_cycles := MAX( recoat[0]Q ) 5 recoat := [] d d := 1 [1,2,3,4,5] IB recoat_unit_cost 200 total_bridge_surface_area 3500 n_recoat n_recoat: 5.48 life recoat_durability ) + 1 life life := lrand( 70, 21 ) + 42 112 j recoat_durability |-^ Appendix H. Bridge Components Condition Rating using Probabilistic Input Values 182 struct corr rate 8 bear corr rate 5 exo Joints corr rate 5 non struct corr rate 7 corr curve 5 escalation 0.025 interest 0.03 struct surface area 3000 bear surface area 1 exp joints surface area 4 non struct surface area 495 life 112 touch up durability 12.5 touch up unit cost 450 overcoat durability 20 overcoat unit cost 130 recoat durability 25 recoat unit cost 200 replace cost 30000000 replace add cost 0 overallstrategy overafl_strategy:; 17159.48377 MINf overall_maIntenanceJEUAC, do_nothing_EUAC) H overall_maintenance_E UAC overatl_maintenance EUAC := struct_strategy + bear_strategy + expjoints strategy + non_stnjct_strateoj—j 17159.48377 struct_strategy struct_strategy := IF( struct_corr rating z 8, struct minor damage, IF{ struct corr_rating 2 5, struct fair_damage, struct_severe_damage)) 7506.85941 ~ ~ ~ ~ stru ct_con_ra ti ng struct_corr_rating := IF( nrandf struct_corr_rate, 0.6 ) struct_corr_rate struct_corr_rate := 8 struct_minor_damage struct_minor damage := MIN( structJouch_upJEUAfi 7506.85941~ structJouch_up_EUAC 7506.B5941 struct_overcoatJEUAC 57915.7461B struct_recoat_EUAC 74323.72868 struct_fair_damage struct_fair_damage := MIN( stru ct_overcoat_E UAC. 57915.74618 ~ Hi stjuct_overcoat_ EUAC~|-^ struct_recoat_EUAC [-^  stru ct_sey e re_d a mag e struct__severe_damage := struct_recoat_EUAC 74323.72868 ~ H struct_recoat_EUAC |-^ bear_strategy bear_strategy := IF( b 19.30525 r_ratinga8, bear_minor_damage, iF( bear_corr_rating25, bearjair_damage, bear_severe_damage)) H bear_corr_rating bear_corr_ratlng := IF( nrand( bear_corrj,ate, 0.6) s I bear_corr_rate bear_corr_rate := 5 bear_minor_damage bear_minor_damage := MINf bear_touch_up_EUAC, 2.50229 " bearjouch_up_EUAC L 2.50229 " bear_overeoat_EUAC 19.30525 bear_recoat_EUAC 24.77458 ~ bear_fair_damage bear_fatr_damage := MINf bear_overcoat EUAC, bei 19.30525 ft bear. overcoat_EUAC~l-^ bear_recoat_EUAC bear_severe__damage bear_severe_damage := bear_recoat_EUAC 20.24162 ~ H bear_recoat_EUAC \ ^ a xpJo ints_strategy H expJoints_strategy := IF( expjoint5_corr_rating i 8. expJoints_minor_damage, IF( expjoints_corr_rating2 5, expJointsJair_damage, expjoints severe_damage 77.22099 ~ expjofnts_corr_rating expjolnts_corr_rating := IF( nrandf expJoints_corr_ expJoints_corr_rate exp Join ts_corr_rate := 5 expJoints_minor_damage expJolnts_rninor_damage:= MINf expjointsjouch 10.00915' " I expjointsjouch upJEUAC 10.00915 expJoints_overcoat_EUAC 77.22099 expJoints_recoat_EUAC L 99.0983 exp J o I nts_fa ir_damage expJointsJair_damage := MINf expjolnts_overcoat 77.22099 ~ " Hi expJoints_overcoat_EUAC (-^  expJolnts_recoat._EUAC expJolnts_severe_damage . expjoints severe damage := expJoints_recoat_EUfl—| expJoints_recoat_EUAC \ - * 80.96647 ~ non_struct_strategy non_struct_strategy := IF( non_struct_corr_rating z 8, non_stnjct_mirtor_damage, IF( non_stnjct_corr_ratlng z 5, non__stmctJair_damage, non_stnjct_severe_damag|—I 9556.09812 non_struct_corr_rating non_struct_corr_rating := IF{ nrandf non_stnjct_corr_ non_stru ct_corr_ra te non struct corr rate := non_stnjct_minor_damage non_struct_minor_damage := MIN( non_structJouch 3456.27721 " non_struct_touch up_EUAC L 3456.27721 ^ non_struct_overcoat_EUAC 9556.09812 no n_struct_recoat_EU AC 12263.41523 non_structJair_damage I—I non_structJair_damage := MIN( non_struct_overcoatl 9556.09812 non_struct_severe_damage non_struct_severe_damage := non_struct_recoat_EU] Unevaluated non stjuct overcoat_EUAC~r~^ non_stnjct_recoat_EUAC )-^ i—i non_stnjcl_recoat. EUAC Hi do_nothing_EUAC do_nothing_EUAC := 308325.07 replace_end_of_coating_PV - replace_end_ot_IBe_PV + replace_add_cost_PV) * interest * (1 + interest) {1 + interest f*e -1 replace_end_of_coating_ replace_end_of_coating_ 27297450.31 _ replace_cost * {1 + escalation) • ~'° (1 interest ) t ° * " , B - " ' • replace_cost replacejxst := lrand( 20000000, 10000000 ) + 10000J 30000000 escalation escalation := Irandf 0.025, 0.003 ) 0.025 coatingjlfe J-| coatingjife : : 19.4 corrosion rating[1][0) - corrosion rating]] corr_c4jrve interest interest := lrand( 0.03, 0.003 ; 0.03 corrosion rating corrosion rating := [[0,1,2,3,4,5,6,7,8,9,10], [100,50,33,16.7,10,3,1,0.3,0.1,0.03,-]] corr_ra te corr_ra e := MINf struct_corr_rating, be ar_corr_rating. 5 corr_curve corrcurve := nrandf 5,1.25 } r_rating bear. corT_rating"r-^ H expJoint5_corr_^ratina - | nonMistruct_corr_rating replace_end_ofJife_PV | - | replace_end_ofJile_PV := 17395023.17 replace_cost * (1 + escalation ) (1 + interest )W" replace cost r life := Irandf 70. 21)+ 42 replace_add_cost_PV H replace_add_cx>st_PV := replace add_cost * (1 + escalation j 0 0 3 0 " 8 - ' 1 ' " . .coating We (1 + interest) H interest"!-^ -TJEErJ' replace_add_cost replace_add_cost := nrandl | coatingjife"!-^ | interest j - ^ struct_minor_damage struct_minor_damage := MIN( struct_touch_up_EUA(J-| 7506.85941 struct_touch_ -UP. EUAC struct_touch_ _up_ .EUAC _ struct__touch_up_TPV" int {1 + tntere: 7506.85941 struct_touch_up_TPV struct_touch_up_TPV := SUM( struct_touch_up_PVT0 241096.60588 _ _ _ _ _ struct_touch_u p_PV touchupcycles -1 struct_touch_up_PV := [] =— x:=0 [33750,31756.26628,29864.07339,28120.48475.264^ stnjct_touch_ . "P . JC struct_touch_ . "P . JC := touch_jp_uni t_cost" structjll 33750 K touch_up_uni t_cost touch_up_unit_cost := rand( 300, 600 ) 450 escalation escalation := lrand( 0.025, 0.003 ) 0.025 struct_maintenance_area struct_maintenance_area := corrosion rating[1][struct 75 corrosion rating p-| corrosion rating := [[0,1,2,3,4,5,6,7,8,9,10],I100,50,33,16.7,1Q,3,1,0.3,0.1,0.03,...]1 struct_corr_rating stnjct__corr_rating := IF( nrand( stnjct_corr_rate, 0.6 struct_corr_rate struct_corr_rate := 8 8 <touch_up_durability touch_up_durability := lrand( 12.5, 2.5 ) 12.5 K struct_su rface_area struct_surface_area := 3000 3000 interest interest := lrand( 0.03, 0.003 ) touch_up touchupcycles touch up touch_up_cycles 9 = MAX( touch_up[0]fj) touch_up := [] i y:=1 [1,2,3,4,5,6,7,* ,9] n_touch_up njouchup 9.96 -( ss V i -^ touch__up__durability J life := lrand( 70, 21 ) + 42 112 \ touch_up_durabilityV^  struc t_overcoat_E UAC struct_overcoat_EUAC := 57915.74618 struct overcoat TPV * intei (1 + interest struct_overcoat_TPV struct_overcoat_TPV := SUM( struc t_overcoat_PV[0][j 1860070.77855 1 | interest [-^  riifTT struct overcoat PV overcoatcydes -1 struct_overcoi struct_overcoat_PV := [] a := 0 ( [390000,353B32.25543,321018.62815,291248.0647,; struct_overcoat_IC struct_overcoat_IC := overcoat_unit_cost* struct_surfj-| 390000 Kovercoat_unit_cost overcoat_unit_cost := rand( 100,160 ) _30 struct surface area \ escalation"}-^ <overcoatdurability overcoatdurability := lrand( 20, 5 ) _20 interest overcoat_cycles overcoat_cycles := MAX{ overcoat[0][j) 6 overcoat novercoat overcoat := [] b I—I b:= 1 [1,2,3,4,5,6] n_overcoat n_overcoat 6.6 life overcoat_durability ^ life I-overcoat_durability f-^ struct_recoat_l struct_recoat_l 74323.72868 struc t_recoat_TPV * interest (1 + interest) stnj ct_recoat_TPV struct_recoat_TPV := SUM( struct_recoat_PV[0]D ) 2387043.33442 | interest V struct recoat PV recoat_cyctes -1 struct_recoat_PV := [] c:=0 struct_recoat IC < 1 + inl [600000,531272.41588,470417.29978,416532.89221 M escalation structrecoa t_IC stnjct_recoat_IC := recoat_unit__cost* struct_surface 600000 " recoat_unit_cost recoat_unit_cost := rand( 150, 250 ] 200 [ struct surface area \ < recoat_durability recoat_durability:= lrand( 25, 5 ) 25 1 interest [ recoat_cycles •-I recoat_cycles := MAX( recoat[0][]) 5 recoat n_recoat |—| recoat := [] ct | j d:= 1 [1,2,3,4,5] n_recoat n_recoat:; 5.48 f !!£ ^ \^  recoat_durability J life} recoaMlura bility i84 bear_minor_damage bearjminorjjarnage := MIN( beartouch_up_EUAC|-| 2.50229 bear_touch_up_EUAC bearJouch_up_EUAC : 2.50229 bear_touchjjp_TPV * inter] (1 + interest bea r_touch_up_TPV bear_touch_up_TPV := SUM( bear_touch_up_PV[0]D 80.36554 interest bear_touch_up_PV touch_up_cyclBs -1 bear_touch_up_PV := [] x:=0 bear touch uf [11.25,10.58609,9.96136,9.37349,8.82032,8.2998,7.a; bear_touch_up_IC bear_touch_up_IC := touch_up_unit_cost * bear_mair[—| 11.25 touch_up_unit_cost touch_up_unit_cost := rand( 300, 600 ) 450 K < escalation escalation := lrand( 0.025, 0.003 ) 0.025 bear_maintenance_area bear_maintenance_area := corrosion rating[1][bear_c 0.025 corrosion rating corrosion rating := t[0,1,2,3,4,5,6,7,8,9,10],[100,50,33,16.7,10,3,1,0.3,0.1,0.03,...I] bear_co*T_rating bear_co*r_rating := IF( nrand( bear_corr_rate, 0.6 ) s 5 bear_corr_rate bear_corr_rate := 5 5 touch_up_durability touch_up_durability := lrand( 12.5, 2.5 ) 12.5 Kbear_surface_area bear_surface_area := 1 j interest interest := trand( 0.03, 0.003 ) 0.03 touch_up_cycles touch_up_cycles := MAX( touch_up[0]Q ) 9 touch_up n_louch_up touchup := [] y y:=1 [1,2,3,4,5,6,7,8,9) n_touch_up n_touch_up 9.96 - ( life touch_up_durability _ life := irand( 70, 21 ) + 42 112 | touch_up_durability~|~^ bearovercoatEUAC bear_overcoat_EUAC := 19.30525 bear overcoat TPV * intere (1 + interest bear_overcoat_TPV bear_overcoat_TPV := SUM£ bear_overcoat_PV[0]0 620.02359 interest bearovercoatPV overcoat^ cydes -1 bear overcoat bear_overcoat_PV := ["] [130,117.94409,107.00621,97.08269,88.07945,79.91 bear_overcoat_IC bear_overcoat_IC := overcoat_unit_cost" bear_surfaf-j 130 overcoat_unit_cost overcoat_unit_cost := rand( 100,160 ) 130 | bear surface_area"t--^  \ escalation \ < overcoat_durability overcoat_durability := lrand( 20, 5 ) 20 1 interest \ overcoat_cycles overcoat_cycles := MAX( overcoat[0]fj ) 6 overcoat n overcoat overcoat := " [ ] b b := 1 [1,2,3,4,5,6] n_overcoat f life A n_overcoat := +1 ^ overcoat_durabtlity J 6.6 life h overcoat_durabiiity |-^ bear_recoat_ EUAC bear_recoat_ EUAC bear recoat TPV * interest * ( (1 + . .life interest) 24.77458 bear_recoat_T PV |-j bear_recoat_TPV := SUM( bear_recoat_PV[0]D ) 795.68111 interest \ bear recoat PV recoal_cydBS -1 bear_recoat_PV := [] c:=0 bearjecoatJC * ( (1 + intej [200,177.09081,156.80577,138.8443,122.94024] bear. _recoat_ JC bear _recoat_ IC := recoat_unit_cost * bear_surface_a 200 recoat_unit_cost recoat_unit_cost := rand( 150, 250 ) 200 | bear_surface_area"f-^ recoat_durability recoat_durability := lrand( 25, 5 ) 25 | interest recoatcycles recoat_cycles := MAX( recoat[0]D ) [—| recoat := [] d j—j i [1,2,3,4,5] nrecoat nrecoat 5.48 J—as—V ^ recoat_durability J life} recoat_durability |-^ IBS' HexpJoints_touch_up_IC expjoints Jouch_upJC := touch_up_unit__cost * exp 45 expJoints_minor_damage expJoints_minor_damage 10.00915 _____ = MIN( expjointsjouchj expJoints_touch_up_EUAC exp JointsJouch_up_EU AC := -^P^° i n t -?-^° u ?.^rT. u ,^ ; (1 10.00915 expJoints_touch_up_TPV expJoints_touch_up_TPV := SUM( expjointsjouch 321.46214 expJoints_touch_u p_PV expJoints_touch_up_PV : touch_up_cycles -1 [] [45,42.34436,39.84543,37.49398,35.2813,33.1992,31 touch_up_unit_cost touch_up__unit_cost := rand( 300, 600 ) 450 escalation escalation := lrand( 0.025, 0.003 ] 0.025 expJoints_maintenance_area expJoints_maintenance_area := corrosion rating[1][e; 0.1 corrosion rating j—| corrosion rating := expJoints_con_ratin g expjoints_corr_rating := IF{ nrand( expJoints_corr_i 5 touch_up_durabtlity touch_up_durability := lrand( 12.5, 2.5 } 12.5 expJoints_su rface_area expJoints_surface_area := 4 interest interest := lrand( 0.03, 0.003 ) 0.03 toucti__up_cycles I touch_up_cycles := MAX( touch_up[0]Q ) touch_up n_touch_up touch_up := [] y y:=1 [1,2,3,4,5,6.7,8,9] n_touch_up njouch 9.96 i_up := ^ touch_up_du rabi lity H life := lrand{ 70. 21 ) + 42 112 | touch_up_.durabilityr-^ expJoints_ove rcoat_E UAC exp_Joints__overcoat_EUAC := 77.22099 expJoints^ overcoatU (1 -exp_joints_overcoat_PV expJoin tS_OVercoat_TPV I I overcoal_cydes -1 expJoints_overcoat_TPV := SUM( e x p j o i n t s _ o v e r c o [ — ] expJoints_overcoat_PV := [] 2480.09437 I interest h expjointi [520.471.77634,428.02484,388.33075,352.31781,319, expJoints_overcoat_l C |-j expJoints_overcoat_IC := overcoat_unit_cost * expjj-j 520 overcoat__unit_cost overooat_unit_cost := rand( 100,160 ) 130 | expjoints_surface_area |-^ [ escalation I overcoat_durability overcoatdurability := lrand( 20, 5 ) 20 overcoatcycles overcoatcycles := MAX( overcoat[0]D ) n_overcoai overcoat:= [] b [1,2.3.4,5.6] n_overcoat r rfe A n_overcoat := ] • 1 ^ overcoat durability J 6.6 lffe> overcoatdurabi l i ty expJoints_ | expJoints_ 99.0983 . , - . e x p j o i n t s recoat TPV recoat EUAC := — = = (1 + inte expJoints_recoat_TPV r-| expJoints_recoat_TPV := SUM( expJoints_recoat_P| 3182.72445 interest t expJoints_recoat_PV expJoints_recoatPV := expJoints_re f800.708.36322,627.22307,555.37719,491.76097] expJoints_recoatJC expJoints_recoat_IC := recoat_unit_cost * expjoints] 800 recoatunitcost recoat_unit_cost := rand( 150, 250 ) 200 | escalation"]-^ ^ expJoints_surface__area |-^ recoat_durability recoat_durability := lrand( 25, 5 ) 25 j interest [ recoat_cycles recoat_cycles := MAX( recoat[0]fj) 5 recoat n_recoat recoat := [] d d := 1 [1,2,3,4,5] njrecoat n_recoat 5.48 •= f life < \^ recoat_durability J life r recoatdurability expjoints_corr_rate expJoints_corr_rate := 5 5 non_struct__minor_da mage non_struct_nino r_damage := MIN( non_strucMouchj—| 3456.27721 non__struct_t ouch_u p_E U AC non_struct_toucri_up_EUAC := 3456.27721 non_struct_touch__upJ (1 non_struct_overcoat__EUAC non_struct_overcoat_EUAC : 9556.09812 non struct overcoat non_struct_recoat_EUAC H non_struct_recoat_EUAC := 12263.41523 non struct recoat TPV ( 1 + intd non_struct_touch_up_PV non_struct_touch_up_TPV I I touch_up_cycies -1 non_struct_touch_up_TPV := SUM( non_struct_touchl non_struct_touch_up_PV := [] 122000.4916 1 1 interest life} [16617.24391,15755.20253,14937.88069,14162.9584 Kescalation escalation := lrand{ 0.025, 0.003 ) 0.025 non_struct__touch_up_IC non_struct_touch_up_IC :- touch_up_unit_cost * non 16617.24391 K touch_u p_unit_cost touch_up_unit_cost := rand( 300, 600 ) £50 non__struct_maintenance_area non_stnjct_maintenance_area := corrosion rating[1][r 37.125 corrosion rating corrosion rating := [[0,1 ^.3.4.5.6.7 A9.101,[100.50,33,16.7,10,3,1,0.3,0.1,0.03,...H no n_stru ct_corr_ rat i n g non__struct_corr_rating := 1F( nrand( non_struct_corr_ 7 n on_struct_corr_rate non_stnjct_corr_rate := 7 7 touch_up_dura bility touch_up_durability := lrand( 12.5, 2.5 ) 12.5 n on_struct_surface_area non_struct_surface_area := 495 495 interest interest := lrand( 0.03, 0.003 ) touch_up touch_up_cycles touch up touch_up_cycles 9 = MAX{ touch_up[0]D ) touch_up := y:=1 [1,2,3,4,5,6,7, i.9l n_touch_up n_touch_up 9.96 - ( life touch_up_durability J K life := lrand( 70, 21 ) + 42 112 I touch_up_durability"r-^  non_struct_overcoat_TPV p-j non_struct_overcoa t_TPV := SUM( non_struct_overct|—j 306911.67846 4js_r* non_struct_overcoat_PV non struct overcoat PV : overcoat_cycles -1 [] [64350,58382.32215,52968.07365,48055.93068,4359; non_struct_overcoat_IC non__struc t_overcoat_IC := overcoat_unit_cost * non_H 64350 Kovercoat_unit_cost overcoat_unit_cost := rand( 100,160 ) _30 I escalation"}-^ | non_struct_surface_area < overcoat_durability overcoatdurability := lrand( 20, 5 ) 20 [ interest \ overcoatcycles overcoatcycles := MAX( overcoat[0][j) 6 overcoat n_overco< [—j overcoat := [] b |—| b:= 1 [1,2,3,4,5,61 n_overcoat n overcoat overcoat durabili overcoatdurability f-^  non_struct_recoat_TPV non_struct_recoatTPV := SUM( non_stnjct_recoat_ 393862.15018 [ interest \ non struct recoat PV recoat_cycles -1 non_struct_recoat_PV := [] non struct rq [99000,87659.94862,77618.85446,68727.92721,608j non_struct_recoatJC non_struct_recoat_ C := recoat_unit_cost * non_stnjc|—J 99000 recoat_unit_cost recoat_unit_cost := rand( 150, 250 ) 200 | non_structsurface_area escalation h < recoat_durabiiity recoat_durability := lrand( 25, 5 ) 25 interest \ recoat_cycles recoat_cycles := MAX( recoat[0]Q ) 5 recoat n_re< wat recoat ;= [' d := [1,2,3,4,51 1 n_recoat n_recoat 5.48 recoat_durability J life} recoatdurability |-^ 187 Appendix I. Bridge Inventory: Estimation of Funding and Priorization of Projects using Overall Bridge Condition Rating and Deterministic Input Values 188 output number -1 " output := [] [x + 1, strategy^], strategy_cost[x], benefit_cost_ratio[x] ] x:=0 [[l.touch up,7005.31451,18.21694],[2,overcoat,7291.38507,2.09317],...] -| strategy_cost |-^  strategy number -1 strategy := [] IF( strategy_cost[x] == touch_up_EUAC[x], "touch up", IF( strategy_cost[x] == overcoat_EUAC[x], "overcoat", IF( strategy_cost[x] == recoat_EUAC[x], "recoat", "do nothing") x:=0 [touch up.overcoat.do nothing.overcoat.touch up] benefit cost ratio H benefit cost ratio : [] benefit[x] strategy_cost[x] [18.21694,2.09317,0,2.98806,176.8485] benefit number -1 benefit := [] do_nothing_EUAC[x] - strategy_cost[x] x:=0 [127615.3915,15262.13759,0,59339.35754,826505.84435] I do_nothing_EUAC [134620.71,22553.52,61879.35,79198.19,831179.37] [ strategy_cost |-^  | number |-^  number [ strategy^cost | number |-^  strategy_cost [7005.31,7291.39,61879.35,19858.83,4673.52] touch_up_EUAC [7005.31,3080.76,89057.64,76825.76,4673.52] overcoat_EUAC [54324.5,7291.39,76779.97,19858.83,106533.21 ] recoat_EUAC [64162.72,10967.3,81569.22,23455.29,158548.7] number number := 5 5 strategy_cost number -1 strategy_cost := [] IF( corr_rate[x] > 8, minor_damage[x], IF( corr_rate[x] > 5, fair_damage[x], severe_damage[x] )|—| x :=0 [7005.31,7291.39,61879.35,19858.83,4673.52] corr_rate corr_rate := data[2][] [8,7,6,5,9 ] minordamage number -1 minor_damage := [] MIN( do_nothing_EUAC[x], touch_up_EUAC[x], overcoat_EUAC[x], recoat_EUAC[x] x :=0 [7005.31,3080.76,61879.35,19858.83,4673.52] ) J touch_up_EUAC [7005.31,3080.76,89057.64,76825.76,4673.52] do_nothing_EUAC [134620.71,22553.52,61879.35,79198.19,831179.37] overcoat_EUAC [54324.5,7291.39,76779.97,19858.83,106533.21] recoat_EUAC [64162.72,10967.3,81569.22,23455.29,158548.7] number number := 5 .5 fair_damage number -1 fair_damage := [] MIN( donothingEUAQx], overcoat_EUAC[x], recoat_EUAC[x]) x:=0 Unevaluated severe_damage number -1 severe_damage := [] MIN( do_nothing_EUAC[x], recoat_EUAC[x]) x:=0 Unevaluated do_nothing_EUAC \-* overcoat_EUAC |-^ recoat_EUAC |-^ number |-^ do_nothing_EUAC recoat_EUAC~r-^ number |-^ number 1^ 0 do_nothing_EUAC * \ do_nothing_EUAC : [] (replace_end_of_coating_PV[x] - replace_end_of_life_PV[x] + replace_add_cost_PV[x]) * interest * (1 + interest) (1 + interest) life[x] - 1 [134620.71,22553.52,61879.35,79198.19,831179.371 K escalation escalation := 0.025 0.025 re place_end _pf_ life_PV I—I replace__end_of_life_PV; replace_e nd_of_coati ng_PV number-1 .coaling life[x] . . , r . replace cost[x] * ( 1 + esca ation ) replace end of coating PV := f l — = L J _ 1 r—rnri K _ _ _ a_ LJ . .coating ifefx x : = o (1 + interest) *- " [18147009.92,4428886.22,42582303.11,9538946.54,94100283.9] replace_cost replace_cost := data[4]Q [20000000,5000000,50000000,10000000,100000000,, coatingjife coatingjife [19.98,24.925,33,9.7,12.49625] r i corrosion rating[1][0] - corrosion rating[1][corr_rate[x]] L-l corr_curve[x] K interest interest := 0.03 0.03 corrosion rating corrosion rating := [[0,1,2,3,4,5,6,7,8,9,10],[100,50,33,16.7,10,3,1,0.3,0.1,0.03,...]] corr_rate corr_rate := data[2][] [8,7,6,5,9 ] corr_curve corr_curve := data[3][] [5,4,3,10,8,,,,,] [] replacecostjx] * ( 1 + escalation ) (1 + interest) life[x] [14226394.37,3825914.34,41156234.38,7288390.69,69422148.7] \ number")-^  \ replace_cost \ escalatiorTl-^  number number := 5 5 \-\-\ life := data[0]D * [70,55,40,65,75 ] replace_add_cost_PV I—I replace_add_cost_PV: r l replace__add_cost[x] * {1 + escalation ) LJ , _ . .coatingjifejx] ( 1 + interest) [0,885.78,4258.23,2861.6B.9410.03] - \ interest"}-^ replace_add_cost [-j replace_add_cost := data[5]Q [0,1000,5000,3000,10000,,,,,] j escalation f-* | coatingjife |-^ | interest [-^  | number |-^ H number]-^  touch_up_EUAC number -1 .-. n touch up TPVTx] * interest *( 1 + interest) x . l Q ( 1 + interest) -[7005.31,3060.76,89057.64,76825.76,4673.52] touch_up_TPV number • 1 p j touch_up_TPV := [] SUM( touch_up_PV>;][)) x:=0 [204018.73,B2485.59,2058547.07,2185914.92,13881; number -1 touch_up_cycles(x] -1 touchjjp_IC[x] ' (1 + escalation )' touch_up__PV touch_up_PV := x " o yVo ( 1 + interest)' [[39375,37051.31066,34864.75229,32807.23221,30B71.1353.29049.295B6],...) y" touch_up_durability y ' toueti_up_doraWliiy < < | number f-^ number")-^ touch_up_IC number -1 touch_up_IC := [] touch_up_unit_cost * maintenance_area[x] x:=0 139375,18562.5.562500,421B75,23625] escalation escalation := 0.025 0.025 touch_up_unit_cost touch up_unit_cost := 450 450 maintenance_area number -1 maintenance_area := [] corrosion rating[1][corr_ratelxJ]' 0.01" total_bridge_surface_area|x] * 2| [87.5,41.25,1250,937.5,52.5] H number}-^ corrosion rating corrosion rating := [[0,1,2,3,4,5,6,7,8,9,10],[100,50,33,16.7,10,3,1.0.3,0.1,0.03,...]] corr_rate corr_rate := data[2]G f * [8,7,6.5,9 ] : total_bridge_surface_area total_bridge_surface_area := data[1][j [3500,550,5000,1250,7000 ] ' touch_up_durability touch_up_durability := 1 12.5 Knumber number := 5 1 K interest interest := 0.03 0.03 touch_up_cycies number -1 touch_up_cycles := [] MAX( touch jjp[x]Q ) x:*0 [6.5,4,6,7] number |-^ touch_up number -1 n_toucti_up(x] touch_up := D " [1 > x:.0 y:-1 [[1,2,3.4,5,6 ,ri.2.3.4.5l.|1.2.3.4].|1.2.3.4.5,6!.n.2.3.4,5... H n__touch_up number -1 -n_touch_up := [] I x= n [6.6,5.4,4.2,6.2,71 touch_up_durability j | - | life := data[0]Q f * [70,55,40,65,75,,, | number |-^ | tour^_up_durability~r~^ | number J-^  I number | -^ overcoat E U A C o v e r c o a t _ E U A C := [ ] x:=0 number • 1 lifelxl overcoat_TPV[x l * interest * (1 + interest) (1 " [54324.5,7291.39,76779.97,19658.83,106533.21] < o v e r c o a t _ T P V number -1 o v e r c o a t _ T P V := [] S U M ( overcoat_PV[x][]) x:=0 [1562115.44,195222.66,1774751.47,565041.23,3164230.8^ overcoat P V := number-1 overcoat_cycleslx] -1 .a "overcoat durability ^ r i overcoat_IC[x] (1 + escalation ) [] a:=0 a * overcoat_durability (1 + interest) [[455000,412604.298,374521.73285,339789.40882],[71500,64869.24683,...], . . .] H number"]-^ o v e r c o a t J C number -1 r-j o v e r c o a t J C := [] overcoat_unit_cost* total_bridge_surface_area| x:=0 [455000,71500,650000,162500,910000] escalation escalation := 0.025 0.025 overcoat_unit_cost overcoat_unit_cost := 130 130 totat_bridge_su rfa c e _ a r e a total_bridge_surface_area := data[1]fj| [3500,550,5000,1250,7000 ] number number ;= 5 5 overcoat_durability overcoat_durability := 20 20 interest interest := 0.03 0.03 overcoat_cycles [-] overcoat_cycles " [4,3,3,4,4] number } -^ [] M A X ( overcoat[x][]; number -1 n_ j-\ overcoat := [] overcoat[x] [] y [f1,2,3,4),|1,2,31,(1,2,31,|1,2,3,41,[1,2,3,411 n_overcoat number • 1 n overcoat := H ( *V K T Vi - U x:=0 \_ overcoat_durability J [4.5,3.75,3,4.25,4.75] | - | life := dala[0]D * [70,55,40,65,75 ] \ overcoat durabili [ number f-^ recoa t_EUAC recoat EUAC : number -1 |jferxi ^ recoat_TPV[x] * interest * (1 + interest) x := 0 (1 + interest )l i f e W -1 [64162.72,10967.3,81569.22,23455.29,158548.71 Kescalation escalation := 0.025 0.025 recoat_TPV number - 1 recoat__TPV:= [] SUM( recoat_PVlx]D) x := 0 [1868638,293643.11,1885454.03,667370.71,4709186.09] recoat_PV number -1 recoat_cyclesfx] -1 . i . # - . »• ^ * r e c o a t durability 4 _., r _ r , recoat IC x] (1 + escaation } recoat PV:= H f l - 1 1 y : — ^ -— LJ LJ . . . , . .c * recoat durability x := o c := o (1 + interest) [[700000,619817.81852,548820.18308],[110000,97399.94291,86243.17163],...] H number life \ number [-^  recoatJC number -1 recoatJC := [] recoat_unit_cost * totalj3ridge_surface_area[x] x:=0 [700000,110000,1000000,250000,1400000] recoat_durabi!ity recoat_durability := 25 25 interest interest := 0.03 0.03 recoat_cycles number -1 recoat_cycles := [] MAX( recoat_x]Q ) |—| [3,3,2,3,4] recoat recoat: : recoat_u nit_cost recoat_unit_cost := 200 200 totalJ3ridge_su rface_area tota_bridge_surface_area := data[1]Q [3500,550,5000,1250,7000 ] ; number number: 5 number -1 [] recoat[x] [] d [[1,2,3].[1,2,3],[1,2],[1,2.3].[1,2,3.4]] mber -1 . lite[x] recoat_durability -[3.8,3.2,2.6,3.6,4] H numbeTj-^  life life := data[0]D -i [70,55,40,65,75 ] | recoat_durability \ number \ number benefit_cost_ratio benefit cost ratio: number -1 [] x:=0 benefit[x] strategy_cost[x] [18.21694,2.09317,0,2.98806,176.8485] benefit number -1 benefit := [] do_nothing_EUAC[x] - strategy_cost[x] | x :=0 [127615.3915,15262.13759,0,59339.35754,826505.84435] | strategy_cost |-^ | number |-^ do_nothing_EUAC number -1 f |if , , - do nothina EUAC - n IF I (replace_end_of_coating_PV[x] - replace_end_pf_life_PV[x] + replace_add_cost_PVTx]) * interest * (1 + interest) 1 J ^Jo V ( 1 + i n t e r e s t f e M - 1 [134620.71,22553.52,61879.35,79198.19,831179.37] strategy_cost number -1 strategy_cost := [] IF( corr_rate[x] > 8, minor_damage[x], IF( corr_rate[x] > 5, fair_damage[x], severe_damage[x] )| x :=0 [7005.31,7291.39,61879.35,19858.83,4673.52] number number := 5 .5 

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