EFFICIENT ANALYSIS SCHEME FOR SEISMIC SOIL-STRUCTURE INTERACTION WITH DEEP SOIL LAYER

The direct finite element method is a widely used time history method for seismic soil-structure interaction (SSI) analysis. In this method, the viscous-spring boundary condition is used to model the radiation damping of infinite domain, and the seismic site response is transformed into the equivalent loading. When the soil layer is extraordinary thick, the computational efficiency of seismic SSI analysis especially for three-dimensional problem is very low due to the finite element model of the whole deep soil layer. In this paper, an efficient analysis scheme is developed. In which, the one-dimensional site response analysis is still performed for the whole deep soil layer, and subsequently the bottom artificial boundary of SSI model is moved up from the actual soil layer bottom (bedrock surface) to the location sufficiently near the structure. The theoretical analyses and numerical examples are presented to indicate the accuracy and efficiency of the proposed efficient analysis scheme. The different boundary treatments and seismic inputs at different locations of the moved bottom boundary are compared with the finite element model of the whole deep soil layer. The proposed scheme meets the precision requirements, and some suggestions on artificial boundary treatment and location are given.