Effect of sedimentary V-shaped canyon on bridge seismic response considering fault dynamic rupture

Past earthquakes have shown that the canyon topography and sedimentary soil covering canyons directly influence the features of seismic waves and make the canyon-crossing bridge more fragile. The impacts of canyon topography on the seismic behaviors of these bridges have been numerically investigated using plane waves as excitations in existing literature; however, there are very limited studies on how both the canyon topography and sedimentary soil affect their seismic performance. This study focuses on the seismic performance of a three-span continuous bridge situated in a sedimentary V-shaped canyon considering the fault dynamic rupture. For this purpose, an entire physical model is established to simulate the fault dynamic rupture, attenuation in the propagation, and site effect by the Spectral Element Method (SEM). Three cases are simulated including flat land (FL), V-shaped canyon (VC), and sedimentary V-shaped canyon (SVC). The temporal and spatial distribution characteristics of ground motions in the case of the SVC are thoroughly investigated. Seismic responses of the bridge located in FL, VC, and SVC are analyzed and compared. The results showed that a higher initial shear stress results in a larger stress drop, which can enlarge the released energy of fault rupture. The SVC can cause significant spatial variation of ground motions. Both V-shaped canyon and sedimentary soil can amplify the amplitudes of velocity pulse. Compared with the VC, the sedimentary soil covering the canyon results in larger amplitude of velocity pulse. The seismic responses of the canyon-crossing bridge could be considerably increased by SVC. The maximum acceleration of the girder, bearings deformations, and pier base shear in the case of SVC increased by 55.5 %, 61.4 %-239 %, and 4 %-15 % compared to VC, respectively. The sedimentary V-shaped canyon effect in the seismic design of bridges can not be neglected.