Seismic Response of a Bridge Crossing a Canyon to Near-Fault Acceleration-Pulse Ground Motions

Previous seismic events have shown that bridges are more susceptible to severe damage when subjected to near-fault ground motions. Near-fault ground motions usually possess obvious pulse-like features in their velocity time histories. The velocity pulses are further distinguished by either a distinct acceleration pulse (acceleration-pulse) or a succession of high-frequency one-sided acceleration spikes (non-acceleration-pulse). The acceleration-pulse ground motions will probably cause more damage to structures compared with non-acceleration-pulse ground motions. This study will focus on assessing the effects of acceleration-pulse ground motions on the seismic response of a pile-supported bridge at a canyon site. A refined three-dimensional (3D) finite element (FE) model will be developed for the nonlinear time history response analysis of this ground-bridge system, in which enhanced modeling of free field boundary and soil-pile interactions will be considered. To investigate the seismic response of the ground-bridge system, six pairs of acceleration-pulse and non-acceleration-pulse ground motions will be used, and each pair has the same peak ground acceleration (PGA). The seismic response of this ground-bridge system will be subjected to acceleration-pulse and non-acceleration-pulse ground motions and will be fully evaluated considering two aspects. First, the seismic time history responses of the ground-bridge system will be assessed under a single representative acceleration-pulse and non-acceleration-pulse ground motions. Second, the mean of the maximum seismic response of the ground-bridge system under multiple acceleration-pulse and non-acceleration-pulse ground motions will be explored. The results from this study show that compared with the non-acceleration-pulse ground motions, the acceleration-pulse ground motions had a more significant impact on the seismic response of the ground-bridge system. Therefore, special care should be taken on the acceleration-pulse effect of ground motion, because bridge structures are more vulnerable to damage when subjected to acceleration-pulse ground motions.