Fragility analysis of RC bridges considering spatially varying ground motions and SSI

Long-span structures like bridges experience different movements at the supports because of the wave-passage, incoherence, and site-response effects. In this study, spatially varying ground motions were used to evaluate the seismic vulnerability of different RC bridges. To gain the goal, three prototypes of Caltrans reinforced concrete curve bridges with different column heights and various radii were selected and used for the numerical study. The spatially correlated ground motions were generated by the conditional simulation method and then converted to corresponding displacements time histories to perform non-uniform excitations. The structures were analyzed under generated series and the fragility curves were developed based on the defined limit states. Furthermore, soil-structure interactions and different soil conditions were included in evaluating the non-linear behavior of the bridges. The results show that the damage exceedance probability increased under non-uniform excitations and it is more obvious for long-span bridges. Also, it is found that the effect of soil-structure interactions on the probability of failure of short-span bridges is negligible but for long-span bridges, the effect is significant. Moreover, it is obvious that for long-span structures situated on soft deposits, a combination of spatially varying ground motions in conjunction with soil-structure inter-actions remarkably increases the responses.