双跨门式刚架钢结构火灾下倒塌模式

Collapse Modes of Double Span Steel portal frames under fire

摘要:

采用有限元模型对双跨门式刚架钢结构的火灾试验进行了模拟，表明有限元模型可以准确预测火灾下双跨门式刚架钢结构的倒塌行为与倒塌模式。采用经试验验证的有限元模型，对火灾下双跨门式刚架钢结构的倒塌过程进行了数值模拟，归纳出双跨门式刚架钢结构的6种典型倒塌模式，并与单跨门式刚架钢结构的倒塌模式进行了对比，说明了中柱的存在对双跨门式刚架钢结构倒塌机制的重要影响。最后，通过大量的参数分析，研究了升温工况、柱脚刚性、中柱柱顶连接形式、荷载比、防火保护、温度梯度、跨高比和柱距等因素对火灾下双跨门式刚架钢结构倒塌模式的影响。参数分析结果表明，升温工况对双跨门式刚架钢结构的倒塌模式有显著影响，柱脚刚性、中柱柱顶连接形式、荷载比、跨高比和柱距对边柱倒塌模式和整体倒塌模式有一定影响，防火保护对中柱倒塌模式有一定影响，截面温度梯度对倒塌模式影响较小。结果可为双跨门式刚架钢结构在火灾下的倒塌预警提供参考。

Abstract:

This paper adopts a finite element model to simulate a fire test of a double span steel portal frame and the result proves its accuracy in simulating the collapse behavior and collapse mode of double span steel portal frames. Then the finite element model verified by the fire test is used in the numerical simulation of the collapse process of double span steel portal frames. Six typical collapse modes are summarized and compared with the collapse modes of single span steel portal frames. The influence of the mid-column on the collapse mechanism of double span steel portal frames under fire is analyzed. The effects of heating conditions， stiffness of column base， connection form of mid column， load ratio， fire protection， cross-sectional temperature gradient， span-height ratio， and column spacing on the collapse mode of the frame are investigated. The results prove the accuracy of the finite element program in predicting the collapse process and collapse mode of double span steel portal frames. The parametric analysis indicates that heating conditions have a great impact on the collapse mode. Stiffness of column base， connection form of mid column， load ratio， span-height ratio， and column spacing only affect the side column collapse modes and overall collapse modes while fire protection only affects the mid-column collapse mode. The existence of cross-sectional temperature gradient rarely affects the collapse mode. This paper can provide an important basis for the early-warning of the fire-induced collapse of double span steel portal frames.