Effect of Ground Motion Spatial Variations on Pounding Response of High-Pier Railway Bridge

The authors present a theoretical analysis for a typical HPRB under synchronous and asynchronous excitations, using nonlinear dynamic analysis based on OpenSees, to investigate the effect of ground motion spatial variations (GMSVs) on the pounding response of high-pier railway bridges (HPRBs). The Hertz-damp model was adopted to simulate energy dissipation and the change in stiffness during pounding. In accordance with the Chinese seismic code of bridges, actual ground motion records were selected for each site condition by using the spectrum match method, and then, a comparative analysis was conducted considering both the wave-path and local site effects. The results show that GMSVs not only increases the seismic responses of the bridge structure but also increases the amplitude and non-synchronous vibration of adjacent structures, which will result in more pounding. Therefore, special attention should be paid on the effect of GMSVs on the seismic design of high-pier bridges. Otherwise, the responses of the bridge structure will be incorrectly estimated. Moreover, the wave-path effect may become more evident for beam-beam pounding by changing the phase angle of ground motions, especially, for a lower apparent velocity, while the local site effect may become more evident for beam-abutment pounding by increasing the amplitude of ground motions. It is suggested that both GMSVs and the leading cause of pounding at different locations should be considered for adopting an appropriate seismic design method and measures to mitigate or prevent pounding.