The Application Of Multiple Transmission Formula MTF In Finite Element

Multi-Transmitting Formula is a local artificial boundary condition(MTF for short).For multiple transmission boundaries,The current research is mostly focuses on its stability but less on its accuracy.Therefore,this paper adopts the method of combining implicit finite element with multiple transmission boundary,aiming at uniform half space and layered half space,analyzes the influence of different space step and time step on the accuracy of numerical simulation of transmission boundary;at the same time,it compares the accuracy of combining implicit finite element with first-order and second-order multiple transmission formula in the depression terrain.The main achievements are as follows.The main results are as follows:(1)When the seismic wave is perpendicularly incident,the meshing of the finite element analysis usually adopts the case of taking 10 units per wavelength.However,by increasing the number of grids in a unit wavelength,that is,reducing the space step of the model grid division,the accuracy of numerical simulation can be improved.(2)In the case of oblique incidence of seismic wave,by changing the time step with a certain space step can improve the accuracy of numerical simulation;With the increase of incident wave angle,the accuracy of numerical simulation of transmission boundary will decrease.In this case,in addition to the space step and time step,the accuracy of numerical simulation can be improved by using higher-order transmission formula;(3)For complex terrain,it is recommended to adopt the grid number of 20 in unit wavelength and the second-order transmission boundary for both vertical and oblique incidence of seismic wave,so that the numerical simulation accuracy of field-ground response under seismic action is high.