(1. Engineering Institute Corps of Engineers，PLA University of Science and Technology，Nanjing，Jiangsu 210007，China； 2. Engineering Research and Design Institute in Guangzhou Military Area，Guangzhou，Guangdong 510515，China)
Abstract：Local artificial boundary of seismic analysis is widely used in time-domain finite element method for its good feasibility and high numerical stability. A new equation for three-dimensional viscoelastic artificial boundary based on the theories of expansion wave(P-wave) motion and shear wave(S-wave) motion in spherical coordinate system is presented by introducing the constitutive relation of linear elastic infinite media and mixing the planar waves and the far-field scattered waves. A new numerical simulation technology for seismic responses is developed by introducing the equivalent boundary element into the finite element method and translating the seismic acceleration into the equivalent nodal force of boundary element on the bottom of the model. Finally，as a numerical example of seismic analysis for civil defense structure，the influences of elastic，transmission，viscoelastic boundary on the results are conducted by LS-DYNA. It is indicated that the viscoelastic artificial boundary is simple and can be easily used. The problems of seismic input and simulation of ground response are solved，and the elastic resume capability and energy radiation effectiveness of half infinite media outside the artificial boundary can be simulated very well. The validity of the proposed method is verified by the numerical example.
