考虑全填充墙作用的钢筋混凝土框架抗连续倒塌性能分析

为探究钢筋混凝土(RC)全填充墙框架在边中柱失效情况下的抗连续倒塌性能及其承载力计算方法，基于已有试验和有限元程序OpenSees建立宏观有限元数值模型展开研究。数值模型中的梁柱采用基于力的纤维梁单元模拟，填充墙则转化为等效斜撑并用桁架单元进行表征。填充墙宏观模型涉及等效斜撑的宽度、数量和相应材料属性的确定，为此对比了不同等效斜撑模型的适用性，确定了一种连续倒塌工况下全填充墙的宏观模拟方案。进而利用验证的数值模型，揭示全填充墙框架防倒塌的荷载传递机制，并研究了层数和填充墙砌体抗压强度对抗倒塌性能的影响。结果表明：全填充墙框架荷载主要通过墙体对角传递且全填充墙会与周围框架形成一种桁架机制；随填充墙砌体抗压强度降低，结构抗力峰值呈下降趋势。最后，以填充墙和周边框架竖向承载刚度比为基本参数，建立了通过求得填充墙和框架刚度以及纯框架理论弯曲承载力，便可快速评估规则RC填充墙框架防倒塌能力的回归模型。

Analysis of progressive collapse performance of reinforced concrete frames with full-height infill walls

To investigate the progressive collapse performance and bearing capacity of reinforced concrete (RC) frames with full-height infill walls subjected to a middle column removal scenario, macro-based numerical models were built based on previous test results and finite element (FE) program OpenSees, and used to conduct systematic analyses. In the macro-FE models, beams and columns were modeled using force-based fiber beam elements, and the infill walls were converted into equivalent struts and modeled using truss elements. The macro-models of infill walls involved the width and the number of the equivalent struts, as well as the corresponding material properties. Through thorough comparisons of many strut models, eventually, the way to convert infill walls into struts suitable for progressive collapse analysis was suggested. After the validation, the numerical models were used to demonstrate the load transfer mechanisms of the RC and infilled frame and to investigate the effects of frame stories and compressive strength of infill wall on the progressive collapse performance. The results indicate that infill walls and surrounding frame members form a truss mechanism to transfer vertical load, in which the strut contributed by the infill is the most critical. The peak structural resistance decreases with the decreasing of the compressive strength of masonry units. Finally, taking the stiffness ratio of the infill wall to the surrounding frame as the main parameter, a model is proposed to quickly evaluate the progressive collapse capacity of regular RC frames with full-height infill walls.