The low-to-medium-speed maglev train is stably suspended near the rated suspension gap. The suspension force acts directly on the track and is transmitted to the bridge. The maglev track structure is novel, and the influence mechanism of the track structure on the coupled vibration of the maglev train-bridge system is unknown. Therefore, in this study, we propose vertical dynamic interaction models of the low-to-medium-speed maglev train-bridge system and the low-to-medium-speed maglev train-track-bridge system to analyse the influence mechanism of the maglev track structure on the vertical dynamic interaction of the low-to-medium-speed maglev train-bridge system. The vibration characteristics of the F-rail and the influence mechanism of the track structure on the dynamic responses of the bridge are discussed in detail. The study verifies that the local deformation of the F-rail is self-evident and cannot be ignored. In addition, the influence of the F-rail on the dynamic interaction of the maglev train-bridge system is mainly reflected in two aspects: first, the vibration of the bridge in the high-frequency band increases due to the high frequency and intensive local vibration of the F-rail itself. Second, the vibrations of the bridge and the F-rail in the low-frequency band increase due to the periodic irregularities caused by the local deformation of the F-rail. In this study, we consider the vertical dynamic interaction model of the low-to-medium-speed maglev train-track-bridge system.
The structure of low-to-medium–speed maglev trains significantly differs from that of traditional wheel/rail trains, leading to significant differences between the coupling vibration mechanism of the train and bridge systems. To determine the vertical dynamic interaction of the low-to-medium–speed maglev train–bridge system, a dynamic interaction model was established and studied, based on a proportional–integral–derivative active suspension control system and modal superposition method. The simulation model was validated through bridge dynamic field tests on the Changsha low-to-medium–speed maglev commercial line. The vertical dynamic characteristics of the system were analyzed for bridges with different girder heights. Subsequently, the mechanism of the vertical resonance of the bridge induced by the maglev train was analyzed carefully. The results show that reducing the bridge rigidity increases the electromagnetic levitation force, thereby increasing the dynamic response. The low-speed resonance in the bridge is caused by the circulation loading frequency of the adjacent electromagnetic force, whereas the normal-speed resonance is induced by the self-frequency of the electromagnetic levitation force.
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