Seismic Fragility Analysis of Reinforced Concrete Bridges with Chloride Induced Corrosion Subjected to Spatially Varying Ground Motions

This paper studies the time-dependent seismic fragility of reinforced concrete bridges with chloride induced corrosion under spatially varying ground motions. The time-varying characteristic of the chloride corrosion current density and the uncertainties related to the structural, material and corrosion parameters are both considered in the probabilistic finite element modeling of the example RC bridge at different time steps during its life-cycle. Spatially varying ground motions at different bridge supports are stochastically simulated and used as inputs in the fragility analysis. Seismic fragility curves of the corroded RC bridge at different time steps are generated using the probabilistic seismic demand analysis (PSDA) method. Numerical results indicate that both chloride induced corrosion and ground motion spatial variations have a significant effect on the bridge structural seismic fragility. As compared to the intact bridge, the mean peak ground accelerations (PGAs) of the fragility curves of the RC bridge decrease by approximately 40% after 90 years since the initiation of corrosion. Moreover, the effect of ground motion spatial variations changes along with the process of chloride induced corrosion owing to the structural stiffness degradation. Neglecting seismic ground motion spatial variations may not lead to an accurate estimation of the lifetime seismic fragility of RC bridges with chloride induced corrosion.