Effect of V-shape canyon topography on seismic response of deep-water rigid-frame bridge based on simulated ground motions

Deep-water bridges located in a V-shape canyon may suffer from spatially varying ground motions due to the canyon topography. This paper focused on the effect of canyon topography on the seismic responses of a deepwater continuous rigid-frame bridge that crosses a V-shape canyon. The ground motions in three example sites with different topography conditions were simulated by the numerical spectral element method. A database with one hundred point-sources considering the uncertainties of seismic magnitude and source location was sampled and adopted to simulate the seismic waves propagating from the source to the bridge site. Nonlinear seismic response analyses of the example deep-water bridge were performed under the simulated spatially varying ground motions considering the hydrodynamic added mass on the piers. The effects of the canyon topography on the seismic wave field, peak ground acceleration at bridge foundations, and seismic responses of the bridge were analyzed. According to the example studies, the canyon topography induces a significant spatial variation of the ground motions for the bridge in the canyon. Compared with the canyon topography, the influence of water within the canyon on the ground motion is slight. Neglecting the effect of canyon topography leads to the inappropriate assessment of the seismic fragility of the deep-water bridge in both component and system levels.