Near-source topographic effect on seismic responses of a multi-span continuous railway bridge crossing a symmetrical V-shaped canyon

Past earthquakes have revealed that topographic features have significant impacts on the characteristics of ground motions, which may cause the amplification and de-amplification of input seismic waves. The topographic effect with the assumption of plane seismic waves on the seismic responses of bridges has been investigated in the existing literature; however, the influence of near-source topographic effects has not been thoroughly understood. The objective of this study is to numerically explore the near-source topographic effects on the seismic behaviors of an existing railway bridge crossing a symmetrical V-shaped canyon. The influence of the source of incident waves is estimated. Numerical results demonstrate that the topographic effects can noticeably amplify the seismic responses of the bridge. Compared to the bridge without crossing a canyon, the peak displacements of the girder, pier, and bearing in the case of the canyon-crossing bridge increase by 15.2%, 2.9%-14.5%, and 24.2%-229.6%, respectively. The piers at the illuminated side of the canyon experience larger seismic responses compared to the piers at the shaded side of the canyon due to the unequal motion amplitudes at each support. As the source-to-canyon distance increases, the seismic responses of the piers show an increasing trend.