Optimum Life-Cycle Cost Design of Orthotropic Steel Deck Bridges

Abstract

This paper presents an optimum deck and girder system design for minimizing the life-cycle cost (LCC) of orthotropic steel deck bridges. The problem of optimum LCC design of orthotropic steel deck bridges is formulated as that of minimization of the expected total LCC that consists of initial cost, maintenance cost, expected failure cost for strength, deflection, and fatigue. And the performance constraints in the forms of flexural failure, shear failure, serviceability and fatigue failure are based on the Allowable Stress Design (ASD). A multi-level (M/L) optimization design algorithm is introduced in which the specific features of orthotropic steel deck bridges are considered. For the efficiency of the optimum design, various techniques such as effective reanalysis technique, sensitivity analysis using an automatic differentiation (AD), and variable linking are utilized for the multi-level optimization design algorithm. And to optimize discrete member design, the genetic algorithm (GA) is used in orthotropic steel deck optimization. To demonstrate the effect of LCC optimum design of orthotropic steel deck, a real example which has four continuous spans is used. From the numerical investigations, it may be positively stated that the optimum design of orthotropic steel deck bridges based on LCC approach proposed in this study will lead to more rational, economical and safer design compared with conventional initial cost optimum design