Dynamic Soil-structure Interaction In Layered Half-space For Seismic Excitation

Dynamic soil-structure interaction (DSSI) is one of the key problems inseismic-design study of civil engineering, and compared with DSSI in homogeneoussite, DSSI in layered site is of more importance. However, most of the referencesavailable now are limited within the analysis in homogeneous site, and there is noinsightful knowledge about the characteristics of DSSI in layered site. This paper usesGreen’s functions in layered half-space and indirect boundary element method toanalyze the influences of dynamic characteristics of site on DSSI systematically.This paper adopts single layer on bedrock as site model, and the classical modelof rigid foundation-shear wall and rigid foundation-SDOF as structure model, to studytwo-dimensional DSSI and three-dimensional DSSI in elastic layered site under theexcitation of out-of-plane SH waves and in-plane P waves or SV waves; andtwo-dimensional DSSI in saturated layered site under the excitation of in-plane Pwaves or SV waves. Although the model adopted in this paper is simple, the essentialinfluences of dynamic characteristics of site on DSSI can be revealed, providingguidance to engineering.The analysis indicates that for both two-dimensional DSSI and three-dimensionalDSSI, in both elastic site and saturated site, an evident peak appears in layered site invicinity of the first natural frequency of the site, and this peak value is greater thanthat in homogeneous site. For other frequencies, the dynamic response in layered siteis also greater than that in homogeneous site in general. The dynamic characteristicsof the site (such as the stiffness ratio of bedrock to soil layer, and the thickness of thesoil layer) and the dynamic characteristics of the structure (such as its mass andstiffness) can work together to lead the change of resonant frequency and the resonantpeak of the system. Meanwhile, there are evident differences between the spectrum oftwo-dimensional DSSI and three-dimensional DSSI, and between the spectrum oflayered site and saturated site with different drained condition.