ABSTRACT
ABSTRACT: The optimal design considering life cycle cost is performed for a bridge superstructure consisting of steel box girders and concrete deck. Load carrying capacity curves for the steel girder and concrete deck are proposed to calculate life cycle cost. These curves are derived on the basis of bridge diagnostic results and condition grade curves. The service life of the superstructure is determined considering load carrying capacity curves and maintenance histories. The objective function is set to the total life cycle cost including initial cost, damage cost, maintenance cost, user cost, and etc for the service life. Damage cost is calculated based on the damage probabilities to consider the uncertainty of load and resistance and user cost includes traffic operation costs and time delay costs. The optimal design of the superstructure is performed for various service lives. The validity of the proposed method is verified and the effect of user cost is also investigated through the sensitivity analysis.
