考虑SSI效应的基础隔震结构隔震性能参数分析

Parametric analysis of seismic performance of base-isolated buildings considering SSI effects

目前规范中关于隔震结构的分析及设计均采用刚性地基假定,忽略地基土刚度的影响。基于此,本文以软土场地上的LRB(Lead Rubber Bearing)基础隔震结构为研究对象,首先提出了同时考虑地基动力响应的频率相关性与隔震层非线性的土与基础隔震结构系统简化模型。其次,利用反应谱分析的方法,揭示了屈重比、结构-地基刚度比、高宽比以及上部结构周期等参数对于系统水平向减震系数的影响规律。研究表明:软土地基上隔震结构存在最优屈重比,其值随上部结构周期增加而减小;地基土越软,隔震层的有效隔震效率越低;在软土地基上,对于周期较短的建筑能够达到更高的隔震目标,周期较长的建筑难以达到较高的隔震目标;地基土刚度对高宽比较小的结构影响较大。

In the current seismic design building code,the isolation design is based upon a rigid-base assumption,ignoring soil stiffness.This paper studies the LRB(lead Rubber Bearing)base-isolated structures located on soft soil deposits.Firstly,a simplified model of soil-base isolation structure system is proposed,considering both frequency dependence of dynamic response of foundation and non-linearity of isolation layer.Secondly,the influence of yield to weight coefficient,structural-foundation stiffness ratio,aspect ratio and period of a superstructure on the horizontal seismic force reduction coefficient of the system is investigated by response-spectrum analysis.Results shows that there exists an optimal yield to weight coefficient for isolated structures on soft soil site,whose value decreases with the increase of the period of superstructure;the softer the site,the lower the effective isolation efficiency of the isolation layer;on soft soil site,shorter-period buildings can achieve higher isolation targets;the stiffness of site soil has greater influence on the structure with smaller aspect ratio.