Semi-Analytic Analysis And Experimental Study Of Ground Vibration Induced By Trains Moving Over High-Speed Railway Bridges

With the continuous development of the railway network and the increase of the train speed, people's livelihood and going out have acquired a lot of convenience. However, the environmental vibration problems draw more and more concern. With the train speed increasing, dynamic interaction of the vehicle and track structure can be aggravated, which may influence the train's running safety. At the same time, the running train induced vibrations are propagated into the soil in vicinity of the railway line. Then the living and working environments of human beings, the normal performance of building structures, precise instruments and high-tech facilities are affected more and more seriously, which has promoted the researchers at home and abroad.In this dissertation, the vibration problems of Tianjin-Qinhuangdao high-speed railway (JQHSR) are researched by combining theoretical analysis and field tests. The major contents and results are as follows:(1) Based on the investigation of the relevant literatures at home and abroad, the research status of elevated railway transit induced environmental vibration problems are summarized and reviewed. Then the research contents and priorities are pointed out.(2) A 1/8 vehicle-slab ballastless track-bridge vertical coupled vibration model is established to simulate the situation that the train running over high-speed railway bridges laid by the typical CRTS ? slab ballastless track. The formulas of admittances and the dynamic wheel-rail force are deduced in detail, and then the dynamic bearing force is solved. When multiple wheels act on the track at the same time, some problems arise, such as the interaction between wheels induced by the suspension system and the pitch motion of the vehicle, and the time delay problem of the excitation at multiple wheel-rail contact points. Then the 1/2 vehicle-4 layered beam coupled model is established. On this basis, the influences of the parameters of the vehicle and track model on the dynamic wheel-rail force and dynamic bridge bearing force are explored. The parameters whose influences are small are omitted. Then a simplified train-track-bridge vertical coupled model is obtained, namely, the wheel-2 layered beam coupled model.(3) On the basis of thin-layer element method (TLEM), shape function is introduced to express the response of arbitrary location inside a thin-layer clement. Combining Galerkin method of weighted residual, stiffness matrixes of all thin-layer elements are acquired. Introducing the viscous boundary conditions, the total stiffness matrix is lumped by all element stiffness matrixes. The eigenvalues and eigenvectors can be obtained with the spectral decomposition of the total stiffness matrix. The displacement response of the layered soil in frequency-wave number domain can then be deduced with mode superposition method. Based on the displacement relationship of the layered soil in frequency-wave number domain and frequency-space domain, the displacement response of the layered soil in frequency-space domain can be finally acquired. A computer program based on these strategies is developed on FORTRAN(?) platform, which is verified by case studies. Then the frequency dispersion characteristics of the soil are analysed.(4) Based on the displacement solution of TLEM, a coupled dynamic analysis model incorporating the pile foundation and the three-dimensional layered ground is established by using the flexible volume method. A computer program is developed on FORTRAN(?) platform to solve the dynamic impedance function of the pile foundation and dynamic response of the ground. After that, the influences of the foundation types, the shear wave speed, density and damping ratio of the soil on the dynamic response of the ground are explored.(5) A field test is carried out in vicinity of a simply supported box-girder with a span of 32 m on JQHSR. The test datas are analyzed in time and frequency domains. Then propagation rules of the vibration wave in the soil for different train speeds are summarized, guiding and validating the theoretical research in the dissertation.(6) Based on the proposed train-track-bridge vertical coupled vibration model and the three-dimensional pile foundation-layered ground coupled vibration model in this dissertation, the prediction model solving the ground vibration induced by trains moving through high-speed railway bridge is established. The bridge dynamic bearing forces acting on the top of the pier are calculated by the train-track-bridge vertical coupled vibration model. Then the force can be applied to the three-dimensional pile foundation-layered ground coupled vibration model to solve the vibration response of arbitrary location on the free field. The proposed prediction model is validated by comparing the theoretical analysis results to the field test results. After that, the influences of the train speed, rail fastener's stiffness and bridge bearing's stiffness on the dynamic response of the train, bridge and ground in the prediction model are investigated.