Seismic analysis and design of high-hazard nuclear facilities requires evaluation of soil-structure interaction (SSI) effects on structure and soil response due to earthquake ground motion and other loading conditions, such as applied loads to the structure. System for Analysis of Soil-Structure Interaction (SASSI) is a finite element model (FEM) computer code that is widely used in the nuclear industry and in the Department of Energy (DOE). SASSI was first developed in 1981 at the University of California (UC) at Berkeley. The SSI analysts are using several modified proprietary versions of SASSI.