火灾下柱失效对多层钢框架连续倒塌的影响

针对钢结构抗连续性倒塌分析中多数采用直接拆柱法，不能真实反映由于火灾引起钢结构发生连续性倒塌时的实际情况，用ANSYS有限元软件建立无楼板的多层钢框架模型，选取已有文献中角部区域不同失效柱个数的工况。采用热固耦合法，考虑火灾使柱失效和材料非线性、几何非线性进行分析。研究了火灾下钢框架结构抗连续倒塌性能及角部区域允许失效柱个数，并将分析结果与已有文献采用直接拆除法结果进行对比。结果表明:采用ANSYS中热 结构耦合功能，结合生死单元法能够较好模拟钢框架由于火灾导致结构发生连续性倒塌的过程；通过分析3种角部区域不同失效柱个数的工况结果，得出失效柱允许个数为3根；与现有文献采用直接拆除法的有限元分析结果进行对比，发现采用直接拆除法分析结果过于保守，考虑火灾导致柱失效更加贴近实际倒塌情况。

Influence of Column Failure on Progressive Collapse of Multi-story Steel Frames Under Fire

In the analysis of continuous collapse of steel structure, the direct demolition method was mostly used, but because of the continuous collapse of steel structure was caused by fire, the actual situation could not be truly reflected. Therefore, it was very important to analyze the resistance of steel structure to continuous collapse under fire. A multi layer steel frame model without floor was established by using ANSYS finite element software. The thermal and solid coupling method was used to consider the failure of fire, and the material nonlinearity and geometric nonlinearity were taken into account comprehensively. The continuous collapse resistance of steel frame structures under fire and the number of allowable failure columns in the corner region were studied, and the results were compared with the results of direct dismantling method used in the existing literature. The results show that the continuous collapse process of steel frame can be simulated by the method of thermal structural coupling in ANSYS, combined with the method of life and death unit. By analyzing the working conditions of different number of failure columns in 3 kinds of corner regions, the number of allowable numbers of the failure columns is 3. The results of the finite element analysis of dismantling method and the results of finite element analysis are compared. It is found that the result of direct dismantling is too conservative. Considering the fire is more close to the actual collapse situation.