Life-cycle cost-effective optimum design of steel bridges considering environmental stressors

This paper presents a practical and realistic LCC methodology for the LCC-effective optimum design of steel bridges considering the time effect of bridge reliability under environmental stressors such as corrosion and heavy truck traffic. The LCC functions considered in the LCC optimization consist of initial cost, expected life-cycle maintenance cost and expected life-cycle rehabilitation costs including repair/replacement costs, loss of contents or fatality and injury losses, road user costs, and indirect socio-economic losses. For the assessment of the life-cycle rehabilitation costs, the annual probability of failure which depends upon the prior and updated load and resistance histories should be accounted for. For the purpose, the Nowak live load model and a corrosion propagation model considering corrosion initiation, corrosion rate, and repainting effect are adopted in this study. The LCC methodology proposed in the paper is applied to the optimum design problem of an actual steel box girder bridge with three continuous spans, and various sensitivity analyses are performed to investigate the effects of various design parameters and conditions on the LCC-effectiveness. From the numerical investigation, it may be positively expected that the proposed methodology can be effectively utilized for the LCC-effective optimum design of steel bridges.