楼层侧向刚度比对砌体结构地震易损性的影响分析

砌体结构的震害现象表明楼层侧向刚度不均匀分布是造成其破坏的重要原因之一。本文开展楼层侧向刚度变化对结构易损性的影响分析。以3层和6层砌体结构为例，采用等效多自由度层间剪切模型，基于非线性动力时程分析，定量研究了竖向刚度不规则性对砌体结构易损性的影响。以结构最大层间位移角为地震反应参数，借助增量动力分析及回归拟合方法，建立了基于峰值加速度的结构易损性曲线。通过改变楼层的侧向刚度值来模拟薄弱层，研究了楼层刚度变化对结构不同破坏状态超越概率的影响。通过改变底层与二层的侧向刚度比，分析了底部刚度突变对结构不同破坏状态超越概率分布的影响。研究表明:与规则结构相比，当刚度突变位于结构底层时，在地震作用下结构易损性相对较高；随着底层与二层的侧向刚度比从0.5增大至1.2，结构易损性逐渐降低。当刚度比为1.5时，结构薄弱层由底层转移至二层，结构整体易损性增加；当底层与二层侧向刚度比小于1时，结构倒塌易损性要显著高于规则结构。

Analysis of Influence of Floor Lateral Stiffness Ratio on Seismic Vulnerability of Masonry Structures

Earthquake damage investigations have shown that the irregular vertical stiffness is one of the important causes of the serious destruction of masonry structures. In this paper, based on multi-degree-of-freedom shear type models, we take the vertical stiffness irregular masonry structure of three-story and six-story as example to evaluate structural behavior through change the position of irregulars tiffness from story drift ratios obtained through nonlinear time history analysis. Then, the structural response was obtained through incremental dynamic analysis, and the vulnerability curve of masonry structure based on the peak ground acceleration was established. At last, the influence of the stiffness change on the probability of the structure beyond the different damage states is analyzed. Meanwhile, the different lateral stiffness ratio of two adjacent structures is analyzed. The results show that under a given ground motion, in contrast to regular tifness, it could be found that the greater the change of the structure bottom stiffness, the more severe the structural damage in the earthquake. When the lateral stiffness ratio of the bottom two layers increase from 0.5 to 1.2, the earthquake resistance capacity of the structure increase, but when the lateral stiffness ratio increase to 1.5,structural weak-layer has been transferred, and its seismic capacity decreased. This study can be used to estimate the probability of vertical stiffness irregular masonry structures exceeding different damage states in future earthquakes.