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UBC Theses and Dissertations

A contribution to risk evaluation of fabricator/erector during production and installation of steel structures Jalayer, Mehdi


Risk assessment is an important aspect of making informed decisions for civil engineering projects. Managers and engineers in charge of projects must often make critical decisions under lack of access to perfect information and many uncertainties. More specifically, steel fabricators and erectors are faced with various decisions during the initial stages of a project. Such decisions could range from choosing a fabrication/erection scheme to design of a particular false work component. These decisions can have significant impacts on the job in terms of cost and duration. This thesis attempts to provide a detailed overview of risk assessment methods for fabrication and installation of steel structures. Before identifying risks, it is important to understand how problem variables influence each other in framework of structural steel projects, as presented in this thesis. Realization of a steel structure, whether simple or complex involves participation of several parties including those that are directly involved such as the owner, designer and the fabricator and those that are indirectly involved such as equipment and material suppliers. Each participant has its own specific variables which influence the project on different scales. Although projects vary in terms of complexity, they share a common trait: interaction between project participants and their associated variables. Identifying the appropriate critical project variables and their relationships is crucial for assessing risks. Today many information technology tools are available, which enable the decision maker to account for uncertainties involved in a decision. An overview of decision science principles and tools are presented, which lead to utilization of three methods of risk assessment: the Expected Monetary Value (EMV) approach, the Monte Carlo Simulation and the First Order Reliability Method (FORM). The latter is applied to fabrication tolerance analysis problems as a tool in order to guide the engineer in specifying fabrication and erection tolerances for geometrically complex steel structures. Application of the FORM on a roller coaster fabrication problem is presented as an example. With regards to risk assessment in construction of steel structures, a cost model is created on DecisionPro. Using the Monte Carlo simulation, this general cost model enables a manager to determine profit margins and corresponding probabilities of breaking even or financial loss for erecting a steel structure. Lastly, the EMV approach is applied to the cost model as a risk assessment method for installation of structural steel. This method uses subjective probabilities from expert opinion with regards to different scenarios during the installation phase. Application of the EMV approach illustrated by its application to a bridge project.

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