Post-derailment dynamic behaviour of a high-speed train under earthquake excitations

• A post-derailment dynamic model of a high-speed train consisting of four vehicles is developed.
• Post-derailment dynamic behaviours of a high-speed train are investigated under earthquake excitations
• Effects of the marshalling type of a high-speed train on the post-derailment dynamics are investigated.
• Buckling pattern of a high-speed train after derailment is studied.

A post-derailment dynamic model of a high-speed train is developed to investigate the post-derailment dynamic behaviours of a high-speed train travelling on a railway bridge during an earthquake. The train model is comprised of two trailer cars and two motor cars. The adjacent two cars are coupled with a coupler model considering the nonlinear characteristic and limit rotation angle of the coupler. A bridge seismic response model is formulated by using the finite element method to evaluate the dynamic responses of the railway bridge under earthquake excitations, and then the responses are used as the input of the post-derailment dynamic model to analyze the post-derailment dynamic behaviours of a high-speed train. Before derailment the high-speed train runs over the rails, the nonlinear Hertzain contact model and the FASTSIM algorithm are employed to estimate the wheel/rail normal forces and tangent forces respectively. After derailment the high-speed train runs on the slab track, the OBBtrees theory is adopted to detect the contact situations between the vehicle components and the track, while the normal forces and tangent forces at the contact points are evaluated by the nonlinear Hertzain contact theory and the Coulomb friction law respectively. Using the post-derailment dynamic model of a high-speed train, the derailment postures of the high-speed train under earthquake excitations are investigated, and the effects of marshalling type of train on the post-derailment dynamic behaviours are further discussed in this study. The results indicate that the trailer car has a better self-protection capacity compared to those of a motor car during a derailment. The marshalling type (TC1 + MC2 + MC3 + TC4) of a high-speed train can easily form the buckling pattern after a derailment, which may contribute considerably to the outcomes of a derailment. Therefore, it is necessary to take some countermeasures to eliminate the buckling pattern of train during a derailment.