Fuzzy Sets Model for Evaluation of Bridge Projects

by John O. Sobanjo, California Dept of Transportation, Los Angeles, United States,

Document Type: Proceeding Paper

Part of: Infrastructure: Planning and Management


This paper presents the formulation of a computerized decision support system that would aid the bridge engineer in long range planning of bridge funding needs, specially, to select the best set of strategies (projects) for bridge rehabilitation and replacement on a highway network. Considering single or multiple bridges on a multi-period basis, the proposed methodology recognizes the following aspects of the decision problem faced by the bridge engineer when evaluating a set of feasible alternative strategies for bridge engineer when evaluating a set of feasible alternative strategies for bridge rehabilitation and replacement: (1) multiple attribute nature of bridge deficiencies; (2) risk impact of the predicted deterioration of the bridge; and (3) uncertainty due to the subjectively estimated decision variables. Based on a systems approach, the decision theory concepts of Multiple Criteria Decision Making (MCDM), Utility Theory, and Decision Making Under Risk (DMUR) are used in formulating a decision support system while the estimates of the decision variables are represented as fuzzy numbers. Modeling the predicted deteriorated state (condition) of the bridge as state fuzzy probability vectors, the feasible strategies for bridge rehabilitation and replacement are evaluated under each probable state of the bridge. The benefit associated with each feasible strategy is computed as expected fuzzy utilities. Based on the possibility distributions of the fuzzy utilities, the strategies are then compared and the best ones chosen.

Subject Headings: Highway bridges | Risk management | Deterioration | Bridge tests | Decision making | Construction management | Computer aided operations | Fuzzy sets

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