Research On Derailment Load Of High-speed Train Based On Vehicle-bridge Coupling Vibration

With the rapid development of high-speed railway,its operating environment has become more complex and diverse.Meanwhile,bridge structures are widely adopted in high-speed railway.The reasons for derailments on high-speed railway bridges are complex.Once an accident occurs,it will cause huge losses of people’s life and property.In addition,derailment loads may also cause structural damage and lateral overturning to the bridge,further affecting the safety of the bridge and vehicles.Therefore,it is essential to research the impact of trains on bridges after derailments.In this dissertation,the finite element method is used to simulate the derailed wheel colliding on the simply-supported beam and obtain the vertical derailment loads.Based on the train-bridge coupling vibration theory,the dynamic response of the bridge and the running safety of the train under derailment impacts are analyzed.The main research contents are as follows:(1)The problem of train-bridge coupling vibration is introduced,and the current research status of the train post-derailment behaviors and train derailments on bridges are reviewed.The analysis methods of train-bridge coupling vibration theory are summarized.Based on the formulas of train derailment loads in design codes and related research results at home and abroad,the characteristics of derailment loads are elaborated.(2)The derailed wheel colliding on a simply-supported bridge is simulated by using the finite element software Ansys/LS-DYNA,and calculation results are validated by comparing the references.Based on this model,the influences of derailment types,train axle weight,bridge span and bridge width on the derailment loads are studied.(3)The analysis model of train-bridge coupling system subjected to vertical derailment loads is established,where the train and bridge models are established with Lagrange method and model superposition method respectively.The whole process wheel-rail relationship is obtained,where the vertical and lateral wheel-rail forces before derailment are defined by the wheel-rail close contact assumption and the Kalker’s Creep Theory.When derailing,the wheel-rail relationship is released,and the vertical wheel-rail close contact assumption is used after derailing.The derailment load-train-bridge interaction vibration equation is derived with the direct coupling method,and the derailment loads are simulated as nodal dynamic loads in the coupling model.A calculation program formatted by MATLAB for solving the dynamic responseof the derailment load-train-bridge system is developed.(4)Two derailment triggering types,including track defects and lateral seismic waves,are introduced.The offload factor,derailment factor and lateral wheel-rail force are used to evaluate derailment,and the train-bridge coupling MATLAB model considering derailment is improved.The dynamic response of 6×32m single-track and double-track high-speed railway simply-supported bridges under vertical derailment loads are calculated.Furthermore,the influence of a derailment in one track on the running safety of trains on the other track of the bridge is analyzed.(5)The equivalent static forces of typical derailment loads are obtained with the general average method,which are further converted into uniformly distributed loads and compared with the derailment loads in codes.Moreover,the overturning safety and the damage of bridges under derailment loads are analyzed.