SSI效应对层间隔震结构地震响应影响研究

Seismic response research of SSI effect on inter-story isolated structure

层间隔震结构是在基础隔震基础上发展而来的一种结构,以往的层间隔震研究多基于刚性地基假定,忽略了土与结构的相互作用(SSI),为此,基于离散弹簧模型,建立了考虑SSI效应的层间隔震结构简化5自由度体系的动力方程,利用MATLAB,采用Newmark法对层间隔震结构在远断层和近断层两种地震波作用下进行了考虑SSI效应与不考虑SSI效应的地震响应分析对比,研究SSI效应对不同隔震层阻尼比和不同隔震周期结构的地震响应的影响规律。结果表明:远场地震作用下SSI效应对结构的影响比近场地震作用下大;SSI效应基本不影响隔震层阻尼比和隔震层周期对层间隔震结构的地震响应变化趋势;远断层地震作用下,随着土体剪切波速的增加,层间隔震结构的地震响应减小,SSI效应对隔震层位移影响较小;近断层地震作用下,随土体剪切波速增加,层间隔震结构下部结构加速度增加,上部结构加速度及基底剪力减小,SSI效应对隔震层位移影响较小。

The inter-story isolated structure is a kind of structure developed on the basis of base isolated structure.Previous studies on inter-story isolated structures are mostly based on the assumption of rigid foundation,ignoring the interaction of soil and structure(SSI).Therefore,dynamic equation of simplified structure system with 5-degree of freedom using inter-story isolation considering SSI effect was built.Meanwhile based on SSI effect simulated by discrete spring model,using Newmark methods,the simplified analytic model of inter-story isolated structure was constructed to compare the situations of inter-story isolated structure with and without SSI effect according to far-fault and near-fault waves.The influence rules on different damping ratios and different seismic isolated layer periods were discussed.The results indicate that in the effect of far-fault seismic action,the influence of SSI effect is bigger than the case under the near-fault seismic action.It is found that SSI effect has little influence on the changing tendency of damping ratio and isolated layer period.As for the far-fault seismic action,SSI effect has little influence on the deformation of isolations.With the increase of velocity of soil shear wave,the seismic response of the structure is decreased.As for the near-fault seismic action,with the increase of velocity of soil shear wave,the acceleration of the substructure of the structure is increased,the acceleration and the base shear force of the superstructure are reduced,and the SSI effect has little influence on the displacement of the isolation layer.