Refined modeling and coupled vibration analysis of the sleeper lifting device in long span bridges under temperature and train dynamics

The safety and smoothness of high-speed train operations, particularly through bridge zones, are crucial for ensuring operational stability and comfort. Regions such as large-span continuous and simply supported girder bridges, specifically the beam joint regions and beam ends, pose significant challenges due to the dynamic interaction between trains, tracks, and bridges. This study develops a refined coupled model of the train-track-sleeper lifting device-bridge (TTSB) system to simulate the dynamic responses of trains passing through large-displacement sleeper-lifting device (LSD) zones. The model incorporates the effect of axial displacement changes caused by temperature variations at the bridge girder ends, which influence the spacing of fasteners. The refined modeling approach improves both the accuracy and computational efficiency of dynamic simulations. The methodology employs a numerical model to simulate train dynamics at various speeds (250-425 km/h) and fastener spacing ranges (0.35-0.85 m). The study examines key parameters, including vertical and lateral displacements, accelerations, wheel load reduction rates, and derailment coefficients. The results show that increased fastener spacing leads to significant changes in vertical and lateral displacement and acceleration (up to 45.8% for Fastener A and 43.4% for Fastener B). Additionally, the wheel load reduction rate and derailment coefficient exhibit fluctuations with varying fastener spacing, highlighting safety implications. These findings validate the model's effectiveness and offer insights for optimizing track structure design in high-speed railways, improving safety and operational stability.