Spatial Coupling Vibration Of Vehicle-Track-Bridge System And Its Ambient Vibration

With rapid developing of urban construction, urban elevated rail transit has been constructed frequently. The problem of structural vibration induced by the urban elevated rail transit and its ambient vibration becomes more serious and has been paid more attention in the research and engineering field. In this dissertation, the occurrence mechanism of structural vibration induced by the urban elevated rail transit and the propagation characteristics in soil and its ambient vibration effect for surrounding buildings are systematically studied, which will have important theoretical significance and engineering value for protecting the safe operation of the urban elevated rail transmit and deducing the ambient vibration influence. The main research work and innovation achievements are presented as following.(1) Study on vertical coupled vibration of vehicle-track-bridge system. A model for vertical coupled vibration of vehicle-sludgeless track-bridge system is established. In the model, a vehicle model with 10 degrees of freedom is used. The steel rail is considered as an infinite Euler beam, and a damped vibration model with single mass (i.e. supporting block) and two-layer springs (i.e. steel rail-supporting block-structure) is built by taking the supporting shoes under rail as the fundamental element. The bridge is modeled as a two-dimensional beam element. The vertical interaction between wheel and rail is calculated by nonlinear Hertz contact theory. Through coupling of interaction forces between vehicle, track and bridge, equations of motion of the vertical coupled vibration of the vehicle-track-bridge system are deduced. The vertical random vibration responses of vehicle, track and bridge are obtained by employing the Newmark-βnumerical integration algorithm.(2) Study on spatial coupled vibration of vehicle-track-bridge system. A model for spatial coupled vibration of vehicle-sludgeless track-bridge system is established. In the model, a vehicle model with 35 degrees of freedom is used. The left and right rails are considered as two Euler beams, the supporting blocks under left and right rails are modeled separately, and the elastic fastener, rail pad, block pad and rubber coat and pad are all modeled by spring-damping elements. The bridge is modeled as spatial beam elements. The wheel-rail contact geometry model, wheel-rail normal contact force model and wheel-rail creep force model are all considered. Through coupling of interaction forces between vehicle, track and bridge, equations of motion of the spatial coupled vibration of the vehicle-track-bridge system are deduced. The spatial random vibration responses of vehicle, track and bridge are obtained by employing the novel explicit integration algorithm. The advantages and disadvantages of the vertical random vibration model and the spatial random vibration model are analyzed by comparing the vertical vibration responses of the two models under excitation with same level of track irregularity. The influence of excitation with different level of track irregularity on the spatial coupled vibration of the vehicle-track-bridge system is also investigated.(3) Study on ambient vibration induced by the spatial coupled vibration of the vehicle-track-bridge system. A three-dimension finite element model of soil-building is established. The soil is modeled as spatial isoparametric element with eight nodes, in which Mohr-Coulomb's yielding principle is taken as the elastic-plastic constitutive relationship and a viscoelastic boundary is considered. The building is modeled by spatial beam elements. Taking the reaction at bottom of bridge pier generated by the spatial coupled vibration of the vehicle-track-bridge system as the excitation of the three-dimensional model of soil-building, the propagation pattern of the ambient vibration in soil and its vibration effect on the surrounding building are numerically analyzed. The isolation effect of vibration isolation trench installed between bridge pier and building is also investigated.