采用等效斜撑模型的砌体结构地震易损性分析

Seismic fragility analysis of masonry structures based on equivalent diagonal brace model

摘要:

为解决目前砌体结构中弹塑性模型在精确性方面的不足和对地震易损性分析的需要,将等效斜撑模型引入砌体结构有限元模型,根据实体墙、开窗墙和开门洞的侧向刚度特性,提出相应的等效斜撑宽度计算公式.基于等效斜撑模型分别建立上述三类砌体墙的弹塑性有限元模型并进行低周往复加载分析,结合试验结果验证其准确性和实用性.在此基础上建立一典型的三层砌体结构有限元模型,基于增量动力分析方法,分别将最大层间位移角和弹塑性耗能差率作为损伤参数进行地震易损性分析,并对比分析仅考虑横墙砌体结构模型与同时考虑纵横墙结构的易损性曲线的区别.结果表明:传统的层间位移角不能充分体现纵墙的抗震性能,基于能量的损伤参数能够更准确地反映结构损伤演变过程和纵墙性能；宜根据易损性评价需求和计算效率综合建立适宜精度的砌体结构有限元模型.

Abstract:

To solve the problem of precision of the current elastic-plastic models in masonry structures and the need for seismic fragility analysis, the equivalent diagonal brace model was introduced into the finite element model of masonry structures. According to the lateral stiffness characteristics of solid wall, window wall, and door wall, the corresponding equivalent diagonal brace width calculation formula was proposed. Based on the equivalent diagonal brace model, the elastic-plastic finite element models of the three types of masonry walls were established and analyzed under low-cycle reciprocating loading. The accuracy and practicability of the models were verified by the test results. On this basis, a typical three-story masonry structure finite element model was established. Following the incremental dynamic analysis method, seismic fragility analysis was carried out by taking the maximum inter-story displacement angle and elastic-plastic energy dissipation difference as damage parameters. The fragility curves of the masonry structure model of transverse wall and that of both longitudinal and transverse walls were compared and analyzed. Results show that the traditional inter-story displacement angle could not fully represent the seismic performance of the longitudinal wall, and the damage parameters based on energy could more accurately reflect the evolution process of structural damage and the performance of the longitudinal wall. The finite element model of masonry structures with appropriate precision should be established according to the needs of fragility evaluation and calculation efficiency.