SSI效应对隔震结构的地震响应及损伤影响分析

基于弹性地基梁理论和波动理论计算群桩-土地基对上部结构的动力阻抗,进而研究桩土-结构动力相互作用对高层隔震结构地震响应及非线性损伤的影响。首先计算桩周地基水平刚度系数,采用改良的Penzien模型将群桩等效为单桩,考虑一定桩长范围计算桩头的水平刚度,同时根据结构振动频率与地基基本频率的大小关系,考虑地基材料阻尼和辐射阻尼的影响。以某高层隔震工程为例,根据实际桩布置及土层分布情况计算地基阻抗,利用等效线性化模型对结构进行反应谱分析,计算结构隔震前后SSI效应对其动力响应的影响,再利用三维非线性损伤模型分析SSI效应对结构主要构件损伤的影响。计算结果表明,随着结构层数的增加,SSI效应的影响减小,考虑SSI效应会使隔震层位移和隔震支座面压利用率提高,而对隔震层上部结构的层间位移基本没有影响;考虑SSI效应后结构连梁的损伤减小,而框架柱和剪力墙这些竖向构件损伤增加;长周期地震动作用下结构的SSI效应更显著。

Effects of soil-structure interaction on seismic response and damage of isolated structures

Based on the Winkler foundation theory and wave theory,the dynamic impedance of group soil-pile to the upper structure is calculated,and the effects of soil-structure interaction(SSI) on structural responses and non-linear damage of isolated high-rise structures is studied.The horizontal stiffness coefficient of foundation around pile is calculated first,then by equivalence of group piles to single pile using an improved Penzien model,the horizontal stiffness coefficient of top pile is calculated with consideration of certain length of pile.According to the magnitude of structural vibration frequency and basic frequency,the influence of the material damping and radiated damping is considered.In case of an isolated building,the dynamic impedance is calculated according to the actual arrangement of group piles and conditions of soil layer,and the seismic responses of the building is calculated by using the equivalent linear model of the structure and the response spectrum method.The effects of SSI on an isolated structure are discussed,and the effects of SSI on the damage of structural main members are calculated using non-linear seismic response analysis.Analysis results indicate that effect of SSI decreases with the increase of the story number.The displacement of isolation layer and pressure of bearing are increased by considering the effect of SSI,and there is no effect on story drifts of super structure.The damage of coupling beam is decreased,while the damage of column and shear wall is more serious by considering the effect of SSI.The effect of SSI is increased when the structure is subjected to long period earthquake motion.