Failure cost design of structural systems

A systematic design approach based on applying weights to modes of failure is proposed. Representative individual failure modes are identified on the limit state surface using a nonlinear structural analysis program. Modal failure probabilities are computed in load space (in which randomness in structural resistance is included), and linearized around mean plastic moment capacities. Single- and multi-objective formulations with objectives of failure cost and initial cost, and with mean plastic moment capacities of structural members as decision variables are used. An iterative procedure with successively tighter bounds on the decision variables is employed. The procedure is applied to a simple frame for which optimum plastic moment capacities (single-objective case) and a trade-off curve between future (failure) cost and initial cost (multi-objective case) are found.