As the high-speed railway is developing rapidly both in China and abroad at present,it is necessary to deeply analyze the dynamic responses of high-speed railway bridges under seismic action. In this paper,a wholebridge model of a multi-span simply-supported high-speed railway bridge with round-ended piers is set up with the finite element software,and the natural vibration properties of the structure are analyzed. Then,different speeds,strong motion records,pier heights,earthquake accelerations and earthquake load combinations in various directions are respectively input to calculate the elastic seismic responses of the bridge. Finally,by applying the moment-curvature relationship to the nonlinear beam element,the elastoplastic seismic responses of the round-ended piers with and without train loads are calculated. The results show that,under the designed earthquake,the bridge is in the elastic stage and the seismic responses increase with the train speed and pier height,while under severe
earthquakes,the pier bottom steps into the elastoplastic stage,the impact of train loads on the seismic responses of the round-ended piers is relatively slight,and plastic hinges occur at the pier bottom,so that some countermeasures should be taken to ensure the security of the plastic hinge region.