Influence And Analysis Of Environmental Vibration Induced By Elevated High-Speed Railway

The cause and characteristics of environmental vibration, which is induced by elevated high-speed railway, are briefly introduced in this paper. Based on summation of former research work, the developing status, research methods and current achievements for this research subject are introduced.The environmental vibration induced by high-speed trains running on the elevated bridges is analyzed by numerical simulation method. The finite element model of the system consists of two parts:the train-bridge-pier sub-model and the foundation-soil sub-model, which are connected by the reactions of piers at bottom. The reactions can be acquired by the train-bridge-pier model. Then they are applied on the foundation-soil model as external forces. The characteristics of surrounding soil can be calculated by the software of FEM.In the train-bridge-pier model, the train is simulated as moving load series, the main girder and the piers are simulated by the Beam4 elements. Except vertical degrees-of-freedoms, all other degrees-of-freedoms of coincide nodes of main girder and piers are coupled. In vertical direction, the main girder and the piers are connected though supports. The supports are simulated by the Combin14 elements. Using this model, the reaction curves of piers at bottom and the displacement curves of bridge at mid-span are obtained.In the foundation-soil model, the piles and the surrounding soil are simulated by the Solid45 elements. All degrees-of-freedoms of coincide nodes on the piles and soil are coupled. Fixed boundary is adopted in the bottom of soil, and three-dimensional viscoelastic artificial boundaries are employed for the rest of the soil profile. The reactions on the bottom of pier are applied to the foundation-soil model as external forces. When the solution is done, the displacement, velocity and acceleration responses of nodes on ground surface can be drawn.The analysis results show that the basic frequencies of nodes on the ground are mainly in the low frequency region. The ground responses decrease with increase of distance to piers, as well as with increase of train speed, while decrease with increase of damping ratio. The characteristics of soil layers have big influence on transmission of soil vibration along ground surface and as well as in depth direction.