Probabilistic collapse analysis of steel frame structures exposed to fire scenarios

Abstract

In this paper, we propose a probabilistic method for analysing the collapse time of steel frame structures in a fire. The method considers the uncertainty of influencing factors. Tornado diagrams are used for sensitivity analysis of random variables. Structural analysis samples are selected by Monte Carlo method, and the collapse times of different structural samples are calculated by fire time history analysis. A collapse time fragility curve is fitted according to the calculated collapse times of the samples. A reliability index of the collapse time is used as a quantitative standard to evaluate the collapse performance of a steel frame in a fire. Finally, this method is applied to analyse the collapse time fragility of an eight-storey 3D steel frame structure under different compartment fire scenarios and fire protection levels. According to the collapse time fragility curve, the effects of the different fire scenarios and protection levels on the collapse resistance of the structure under fire are evaluated.

概要

目的

1. 研究结构设计参数的不确定性对火灾场景下钢框架结构倒塌性能的影响;2. 研究室内火灾发生位置对钢框架结构抗倒塌性能的影响;3. 研究室内火灾下钢框架结构倒塌时间的可靠指标,并将其用于火灾下钢框架结构抗倒塌设计。

创新点

1. 通过蒙特卡罗法和易损性分析方法,提出了火灾下钢框架结构倒塌概率分析方法;2. 采用结构倒塌时间的可靠指标对火灾下钢框架结构的倒塌性能进行了定量分析。

方法

1. 通过绘制火灾下钢框架结构倒塌时间龙卷风图,分析结构设计参数的不确定性对钢框架结构火灾下倒塌时间的影响;2. 根据结构易损性分析方法,通过蒙特卡罗法抽取分析样本,并采用样本倒塌时间拟合钢框架结构倒塌时间易损性曲线;3. 通过结构倒塌时间易损性曲线得到结构倒塌时间的可靠指标,并根据倒塌时间的可靠指标定量分析室内火灾下钢框架结构的抗倒塌性能。

结论

1. 钢材屈服强度和钢柱防火保护对火灾下钢框架结构的倒塌时间影响最大;2. 角部房间以及短跨边房间发生火灾时,钢框架结构更容易发生倒塌;3. 通过计算火灾下钢框架结构倒塌时间的可靠指标,可以定量评估火灾下钢框架结构的抗倒塌性能。