Analysis Of Environment Vibration Under Moving Loads By Finite Element Method

With the national economic increasing, railway, subway and lightway have gained great development. But the effects on the environment caused by moving loads have reached such an extent that great attention has to be paid. But current domestic evaluation of along railway's environment vibration and forecast method still focuses on the site experiments and empirical formulas, lacking of systematic study and quantitative analysis; therefore we cannot conduct design and execution effectively before construction. In order to properly evaluate vibration of the environment along railway, it is quite necessary to penetrate into the research of dynamic response of ground.1. Assuming prismatic cross-section in the direction of the track, when the difference of the characteristic of soil along track is slight, and then processing expansion in wavenumbers along this direction. The solution of three-dimension still can be obtained, though it was just discreted in two-dimension comparing to three freedoms at each node, so this two-dimension model was called 2.5 D model. Based on this assumption, the 2.5 D finite element basic formulas had been established and compiled the FEM program by FORTRAN.2. Based on the FEM program and predigestion of train load, the dynamic response of ground soil by railway and subway had been simulated, and the propagation characteristic of vibration in soil was obtained. So this program can predict the environmental vibration induced by railway and subway and can provide foundation for feasibility study and construction design of railway and subway.3. As to the vibration analysis of ground under lightway train load, it is different to railway and subway since its structural form generally is viaduct, whose load is time depending and located in some stationary position. When to simulate this problem, the finite element software ANSYS was adopted, because of its complete solution about the problem. So the solution is obtained by ANSYS. At those places with excessive vibration along the lightway, two field measures (Wave Impending Block and Isolation Trench) were adopted to reduce vibration. Then the effects of the two vibration mitigation measureswere compared, and the result is satisfying. So this vibration analysis of lightway can provide foundation for the feasibility study and construction design of lightway engineering. Simultaneously it also can offer guidance to take reduced vibration measure along the constructed lightway which have produced excessive influence on the surrounding environment.