Study On Dynamic Behavior Of Vehicle/Track Systems Based On Longitudinal Elastic Sleepers

The track system with longitudinal sleepers is a new type of track structure, which is developed on the basis of ladder sleeper track. Compared with ladder sleeper, the longitudinal sleeper retains the features with light weight and good vibration damping performance and its crossbeams, fixation and construction methods are improved. This thesis will systematically study the dynamical behavior of vehicle/track system based on longitudinal sleepers and analyze the influence of structure parameters on the dynamical performance.According to the vehicle-track vertical coupling dynamic theory, the vertical coupling dynamic model of vehicle-longitudinal sleeper track system is established. The new explicit integration method is used to solve the differential equations and the responses of each part of system are obtained. The results show that the ride performance and running safety of vehicle system can be guaranteed within the speed range of this study. However, the dynamic responses of system are affected by the design parameters of vehicle and track, especially by the speed and load bearing of vehicle. Therefore, it is necessary to consider the vehicle and track parameters synthetically in the design of longitudinal sleeper track.Based on the finite element theory, the finite element model of longitudinal sleeper track on the viaduct bridge is built. First, the model is verified and the vibration characteristic of longitudinal sleeper track is obtained through modal analysis and harmonic response analysis. Then, the dynamic response of the track structure and its transfer characteristic is obtained by loading the wheel/rail forces on the finite element model. These forces are calculated by the vehicle-track coupling model. The results show that, with a damping material stiffness of20MN/m, the acceleration level of bridge deck is lower than that of sleepers by40dB for the frequencies above31.5Hz and the Z direction vibration level is lower by36.1dB. Therefore, the damping materials are very effective for the vibration reduction of longitudinal sleeper track system. In the general design (within a small change of structure parameters), the influence of the structural parameters of longitudinal sleeper track on its dynamical performance is mainly around the structure natural frequencies. This research can provide theoretical support for the optimization design of track structures.