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

Abstract

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.