Research of seismic wave time lag on the peak response of vehicle bridge systems

This paper investigates the impact of time lag, defined as the time difference between the arrival of seismic waves and trains at the observation point, on the dynamic response of the vehicle-bridge system (VBS). Firstly, a 9x32 m simply-supported bridge (SSB) model of the high-speed railway (HSR) was modelled using OpenSees, where the wheel-rail interaction was simulated using a self-developed wheel-rail element. Subsequently, fifty seismic waves were selected from the PEER Strong Motion Database using the dual-band ground motion selection method tailored to the site characteristics. A series of numerical simulations were conducted, examining the mutual influence between seismic waves and track irregularity, as well as the influence of the number, intensity, and time lag of seismic waves on the VBS's peak response. The findings reveal that: (1) For a 32 m SSB system, the VBS's dynamic response becomes stable and reliable with more than 35 seismic waves, albeit at the expense of reduced computational efficiency. (2) Higher seismic intensity results in larger peak responses and greater variability in the VBS's seismic response. (3) In most cases, a smaller time lag between seismic waves and trains amplifies the system's dynamic response more. The peak dynamic response is largest when seismic waves and the train arrive at the bridge mid-span simultaneously, posing the most significant risk and requiring increased attention. (4) The system's dynamic response is smaller under positive time lag conditions (where the train arrives first) than under negative time lag conditions. (5) Slower train speeds reduce the dynamic response but do not eliminate the risks associated with the coupling effects of earthquakes and train-induced vibrations. Overall, the number and time lag of seismic waves should be carefully considered in the seismic dynamic analysis of VBS.