Abstract: Based on the finite beam element method, two kinds of whole bridge models of high-speed railway multi-span simply-supported bridge are set up. One is vehicle-bridge model including pile foundation, the dynamic impedances of the layered soil are presented, the improved Penzien model is used to simulate the soil-structure interaction (SSI); the other is vehicle-bridge model where pier bottom is consolidated without considering SSI; the seismic responses of the models are computed at different vehicle speeds, pier heights, earthquake strengths and earthquake waves. The calculation results show that the influence of the SSI on seismic responses of high-speed vehicle-bridge on soft foundation can not be ignored; the lateral displacement and acceleration of the bridge are influenced by low-frequency components, those low-frequency components interact with the earthquake wave incident from bottom side of the piles, which change the spectrum composition of the foundation movement, the frequency components which approach to bridge vibration frequency are strengthened; the lateral displacement and acceleration of bridge increase a lot after considering SSI; the vertical vibration frequency of the bridge changes little while considering SSI; the vertical displacement of the boxing girder increases little with the increase of pier height and vehicle speed; the high-frequency components which are caused mainly by the vehicle load and the track irregularity significantly influenced on the vertical acceleration of the boxing girder

Key words: high-speed railway, vehicle-bridge system, seismic responses, soil-structure interaction