Effect Of The Site Dynamic Characteristics On Dynamic Soil-Structure Interaction

Dynamic soil-structure interaction is one of the basic issues in Earthquake Engineering for many years.The near-surface soil is layered.However,most of the studies available of dynamic soil-structure interaction don't consider the site dynamic characteristics systematically.So the study of effect of the site dynamic characteristics on soil-structure interaction is more valuable in theory and engineering.The soil is always fluid-saturated in the coastal areas,which influences the dynamic response of the structure.Using a 3D model of multi-particles on rigid foundation in fluid-saturated poroelastic layered half-space,it studies the effect of the site dynamic characteristics on the response of the structure subjected to plane SV,SH,P1 waves by the indirect boundary element method(IBEM)in this dissertation.It's shown that the dynamic characteristics of the site have significant influence on the SSI system response.The peak value and resonant frequency decrease with increasing of soil layer thickness or decreasing of bedrock stiffness.And the pore fluid influences the peak value and the corresponding resonant frequency of the dynamic structural displacement,which are up to 20% and 7% for the example in this study.The amplitude of pore pressure is evident at the surface of foundation,and the frequency of the first peak is very close to that of the foundation horizontal displacement.When the separation distances between buildings are small,the adjacent buildings influence each other through the underlying soil called dynamic structure-soil-structure interaction.Using the two-dimensional out-plane and in-plane models of twin buildings placed on rigid foundations embedded in layered half-space,it studies the influence of the dynamic characteristics of the site and the distances between twin buildings subjected to SH wave and SV wave by indirect boundary element method(IBEM)in this dissertation.It's shown that,although the dominant features in the response of flexible structures are those related to the structural resonances,the structure-soil-structure interaction effects are not negligible.It may increase the structural response at a particular frequency up to 40% compared to the stand-alone structure,and results in apparent frequency shifts.Further,due to the site dynamic characteristics,the structure-soil-structure interaction effects are enhanced by the soil layering,and are more pronounced for shallower layer and stiffer bedrock.The influence of the separation distance between buildings on the dynamic response amplitude is not linear,but in a way of oscillation,which is dependent on the dynamic characteristics of the site and the building.In addition,the horizontal,rotational and vertical motion of the foundation are coupled together when subjected to SV waves,so that the structure-soil-structure interaction effect is more complicated than that of SH wave incidence.