Seismic response sensitivity of a V-shaped canyon-crossing bridge considering the near-source canyon topographic effects

Abstract

Past seismic events have shown that the canyon-crossing bridges are more vulnerable due to the canyon topographic effects. The seismic responses of such bridges are affected by various influential factors, including source-to-canyon distance, depth-to-half-width ratio of the canyon, incident angle of the ground motion, and shear wave velocity. This study numerically examines the impacts of these factors on the seismic responses of a typical bridge across a V-shaped canyon, which are not adequately investigated in the existing literature. To represent the canyon topographic effects, the ground motions at each bridge pier location are synthesized by the scattering and diffraction models of seismic waves induced by the V-shaped canyon. The accuracy of the analytical model in describing the effect of the source location has been validated. A detailed parametric analysis is conducted to evaluate the importance of the main influential factors in the seismic design of the bridge. The results demonstrated that the incident angle and depth-to-half-width ratio result in significant effects on the bridge responses. When the incident angle is larger than 45°, the topographic amplification effect on the bridge responses should be considered in the seismic design of the bridge. The source location and soil property show certain influences on the seismic responses of the piers. The deep canyon can cause much higher bridge responses than the shallow canyon. When the depth-to-half-width ratio is larger than 0.4, the topographic irregularities can cause noticeable amplifications on the pier responses at the illuminated canyon side. After the earthquake events, the bearings experience noticeable residual deformations under the seismic waves with unequal amplitudes and phases induced by the local topography.