The effect of vehicle on the seismic responses of highway bridge has usually been neglected under the assumption that the possibility of vehicles crossing highway bridge or viaduct with a concurrent earthquake is extremely low. Furthermore, there is no in phase movement of vehicle and bridge was observed in past earthquake events. However, in the heavily trafficked urban area this is probably not the case. The mechanism of vehicle–bridge dynamic interaction still remains unclear. Therefore, an analytical vehicle–bridge model with contact elements is built to study the dynamic interaction and the seismic responses of vehicle–bridge system when subjected to near-fault ground motions. In this vehicle–bridge model, vehicle and highway bridge are coupled through Coulomb friction forces in the horizontal directions and through Hertz impact force in the vertical direction, respectively. The horizontal Coulomb friction forces varying with the variation of vertical Hertz impact force under earthquake excitations. Analysis results reveal that vehicle sometimes has a significant influence on the vertical seismic displacement response of bridge and mass ratio of vehicle to bridge is one of the primary factors governing the effect of vehicle on the seismic responses of bridge. Influence of vehicle frequency and damping ratio on the seismic responses of bridge are both related to mass ratio and become significant with the increasing of mass ratio. However, for the responses of the vehicle itself, influence of vehicle frequency and damping ratio is significant only when the mass ratio is small. Due to the weak coupling of vehicle and bridge in the horizontal directions, horizontal displacements of the vehicle can reach several meters, hence possibly endanger the traveling safety of vehicle on highway bridge.

中文翻译：

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近断层地震动下车桥动力相互作用机理研究

车辆对公路桥梁地震响应的影响通常被忽略，假设车辆通过公路桥梁或高架桥同时发生地震的可能性极低。此外，在过去的地震事件中没有观察到车辆和桥梁的同相运动。然而，在交通繁忙的城市地区，情况可能并非如此。车桥动态相互作用的机制仍不清楚。因此，建立了具有接触单元的分析车桥模型来研究车桥系统在受到近断层地震动时的动力相互作用和地震响应。在这个车桥模型中，车辆和公路桥梁分别通过水平方向的库仑摩擦力和垂直方向的赫兹冲击力耦合。地震激发下水平库仑摩擦力随垂直赫兹冲击力的变化而变化。分析结果表明，车辆有时会对桥梁的竖向地震位移响应产生显着影响，车桥质量比是影响车辆对桥梁地震响应影响的主要因素之一。车辆频率和阻尼比对桥梁地震响应的影响都与质量比有关，并且随着质量比的增加而显着。但是，对于车辆本身的反应，仅当质量比较小时，车辆频率和阻尼比的影响才显着。由于车辆与桥梁在水平方向上的耦合较弱，车辆的水平位移可达数米，可能危及车辆在公路桥梁上的行驶安全。