Running Safety Assessment Of Railway Vehicles Under The Eartqhuake Excitations

With the rapid development of railway industry in China, the high-speed rail network has been preliminarily established in recent years. Since China is an earthquake-prone region, some of those high speed railway lines directly cross the earthquake region, which may impose dramatic threat to the running safety of railway vehicles during an earthquake. In addition, a vast number of railway viaducts have been employed in the high-speed railway lines to reduce the usage of the ground space, which may increase the risk of derailment during an earthquake due to the earthquake-induced railway bridge oscillations. Therefore, the running safety of high-speed train under the earthquake condition has become the focus of the railway industry. Since the methods of preventing or predicting the derailment have not yet been proposed, the countermeasures of reducing the loss of the derailment has become crucial for the running safety of railway vehicles. Based on such background, this thesis focused on the derailment mechanism of railway vehicles under the earthquake conditions, the post-derailment dynamic behaviors of railway vehicles and the safety protection technologies of railway vehicles after the derailment. The main researches are as follows:(1) Acoupled vehicle/track dynamic model is established to investigate the derailment mechanism of vehicle system during an earthquake. The feasibility of the coupled dynamic model is demonstrated through comparing the commercial software and the filed tests. A seismic response model of railway bridges considering bridge pier-pile-soil interaction is formulated to calculate the response of bridge under the earthquake excitations. In addition, the post-derailment dynamic models of a railway vehicle and train are developed using the OBBTrees(tight-fitting oriented bounding box trees) collision detection theory, and validated by the half-car and full car derailment experiments.(2) The derailment mechanisms of railway vehicles under the earthquake excitations are studied by using the coupled vehicle/track dynamic model. The effects of earthquake properties on the running safety are evaluated in terms of the wheel unload ratio and the derailment coefficient. A rocking derailment criterion is proposed to evaluate the risk of rocking derailment during an earthquake considering the lateral acceleration of earthquake wave and the amplitude-frequency characteristics of earthquake excitations. The effects of the deformed track on the running safety due to the earthquake excitations are subsequently analyzed using the coupled vehicle track dynamic model.(3) The post-derailment dynamic performance of a single vehicle and a train set are widely investigated, in terms of the derailment postures and contact situations, by using the post-derailment dynamic model validated by derailment experiments. The effects of marshalling type of the high-speed train on the post-derailment behaviors are further studied using the post-derailment dynamic model of high speed train, and the optimal marshalling strategy of high-speed train is identified to reduce the losses of derailment. Subsequently, the post-derailment dynamic model is employed to investigate the safety protection technologies of railway vehicles including the L-shaped axle box protection device, the vertical bump stop at the position of traction rod and the anti-derailment guild rail. The validity of the L-shaped axle box protection device is also demonstrated through the derailment experiments. A safety protection slab track structure considering is, then, proposed to reduce the loss of the derailment considering the post-derailment dynamic behaviors of the railway vehicle.