基于IDA方法的地铁车站结构抗震性能评价

Seismic Performance Evaluation of Station Structures Based on IDA Method

针对目前大型地下结构抗震性能评价尚不完善,提出了一种基于非线性增量动力分析(incremental dynamic analysis,IDA)的多层多跨地下结构横断面地震易损性分析的方法.选用典型三层三跨地铁车站建立土-结构二维整体分析有限元模型,采取等效线性化模型模拟土体在地震作用下的剪切模量退化和阻尼增加特性,纤维梁单元模拟多层地下结构在地震作用下的滞回特性.基于PEER强震记录数据库的21条地表地震动峰值加速度中位值,将其统一调幅到不同强度水平,作为非线性IDA的输入地震动.根据IDA结果的统计分析,对于浅埋多层地下结构而言,地表峰值加速度和峰值速度是有效且合适的地震动强度指标,可以用来构建地下结构的易损性曲线.通过与现有的矩形地下结构经验地震易损性曲线和数值地震易损性曲线比较,验证了数值模拟得到的地震易损性曲线的有效性,可以作为快速评价地下结构抗震性能的有效工具.

A new method for seismic vulnerability analysis of multi-story and multi-span underground structures based on nonlinear incremental dynamic analysis(IDA)was presented.A two-dimensional finite element model was established for a typical three-storey and three-span subway station by considering nonlinear soil-structure interaction.The equivalent linear model was adopted in the analysis to simulate the shear modulus degradation and damping characteristics of the soil under seismic excitations.The hysteretic behavior of the multistory underground structures under ground shaking was simulated by using fiber beam-column elements.A set of 21 ground motion records selected from the PEER strong earthquake record database were uniformly scaled based on the median peak ground acceleration to different intensity levels as the input ground motions at the bedrock of nonlinear IDA.It is found that the peak acceleration and peak velocity at the ground surface are efficient and appropriate intensity measures of the ground motions for the prediction of seismic response of the shallowly buried multistory underground structures and can be used to construct the seismic fragility curves of underground structures.Besides,the seismic fragility curves obtained from this numerical study were validated against the existing empirical and numerical seismic fragility functions of buried rectangular underground structures.The validated fragility curves can be used as an effective tool to quickly assess the seismic performance of the underground structures.