Effects of Structural Quasi-static Components on Seismic Responses of Train-Track-Bridge System

In order to discuss the effects of structural quasi-static components on the running safety of a train running over a high-speed railway bridge subjected to earthquake action, two dynamic models for a train-track-bridge system subjected to seismic excitation were set up by considering the seismic force boundaries of subgrade and bridge in relative coordinates and absolute coordinates, and the seismic force boundaries were processed respectively by the relative movement method and the large mass method. A rigid-continuous combination beam bridge with spans of 48 m+580 m+48 m was taken as an example, and the effects of structural quasi-static components in different directions on the seismic responses of the train-track-bridge system were analyzed. The research results show that the transversal quasi-static component causes a significant increase in dynamic responses, including the transversal displacements of bridge and rail, derailment coefficient and wheel unloading rate. The longitudinal and vertical quasi-static components have little effect on the seismic responses of the coupling system. When the quasi-static components of all three directions are considered, the derailment coefficient and wheel unloading rate of train increase significantly, their relative errors increase with the raising of train speed and the maximum relative errors can reach 30.5% and 22.2%, respectively. So, if the effects of structural quasi-static components are ignored to a train running through a bridge under earthquake action at a high speed, the dynamic responses of vehicle will be substantially undervalued to lead to an incorrect judgment of the running safety.