Optimal design of a steel box girder bridge considering life cycle cost

Life cycle cost has come to occupy an important position in the design of bridges and many researchers have made an effort to develop cost models to take life cycle cost into account rationally. This paper derived load carrying capacity curves including repair and rehabilitation histories for members of bridge and performed optimal design of a steel box girder bridge consisting of concrete deck, steel box girders and piers considering life cycle cost. Total life cycle cost for the service life is calculated as sum of initial cost, damage cost, maintenance cost, repair and rehabilitation cost, and user cost. The optimization method is applied to the design of bridge members with minimal value. The objective function is set to the annual cost, which is obtained by dividing the total life cycle cost by the service life, and constraints are formulated on the basis of Korean Standards. The optimal design is performed for various service lives and the effect of design factors is investigated. The results suggest that although it is not easy to consider various cost factors accurately, those cost factors which are affected by the various environmental conditions and uncertainties should be considered.