Effects of track structure on seismic responses of medium-speed maglev vehicle-bridge system

In order to investigate the effects of track structure on the coupling vibration of the medium-speed maglev vehicle-bridge system under seismic action, two numerical models have been built for calculating seismic responses of the maglev vehicle-bridge system with and without track structure. The vehicle model is simulated as a multi-rigid body with 45 degrees of freedom (DOFs), and the bridge model is established in an absolute coordinate system by the finite element method (FEM). The maglev vehicle-track coupling relationship is built based on the proportional-integral–differential (PID) active controller. Through a case study, the effect law of track structure on the vibration responses of the vehicle and bridge system under seismic action is analyzed in both time and frequency domains, and the effect of equivalent under-rail stiffness on the seismic responses of the system is discussed. The results show that the overall stiffness of the bridge structure will increase after considering the track structure, which will reduce the system’s seismic responses, especially in the lateral motion. The frequency domain responses of the maglev vehicle-bridge system under seismic action are closely related to the natural frequencies of the structure and the characteristic frequencies generated by the running vehicle. Compared with the girder’s vibration, the F-rail’s vibration mainly occurs in the high-frequency band (greater than 50 Hz), while the F-rail’s high-frequency local vibration also leads to increasing the girder’s vibration responses in the high-frequency band. Under seismic action, the vertical displacement amplitude of the girder is insensitive to the variation of vertical equivalent under-rail stiffness, while the lateral displacement amplitude of the girder and the vertical and lateral displacement amplitude of the F-rail show a significant decreasing trend with an increase of equivalent under-rail stiffness. The deformation of the track-bridge structure gradually tends toward the overall deformation as the equivalent under-rail stiffness increases. These findings can provide a reference for the seismic design of maglev lines.