火灾下门式钢刚架倒塌预警可靠度研究

Research on reliability of early-warning methods for collapse prediction of steel portal frames under fire

为了解决实际火灾救援中火灾场景、荷载水平等不确定因素对倒塌预警准确性的影响,基于可靠度理论提出了预测受火建筑倒塌剩余时间的方法。采用经试验验证的三维有限元模型对火灾下门式钢刚架结构倒塌进行仿真模拟,基于火灾下门式钢刚架结构四种倒塌模式和三级倒塌预警指标,研究升温工况、柱脚刚性、荷载比等因素对倒塌剩余时间预测的不定性影响,通过蒙特卡罗抽样,研究考虑各种影响的火灾下门式钢刚架倒塌预警指标概率统计参数。结果表明:倒塌剩余时间比仅与可靠度和倒塌模式有关,不受火灾现场的各种不确定性因素影响,可以在火灾发生前通过理论分析提前计算得到;火灾中采用可靠度60%~80%对应的倒塌剩余时间比可以快速合理地预测受火刚架的剩余倒塌时间。

To consider the effects of uncertainties such as fire scenarios, load levels on the accuracy of early-warning methods for collapse in real fire, a method based on reliability theory was proposed herein to predict the remaining time of burning frame. A three-dimensional finite element model verified by experiments was used to simulate the collapse process of steel portal frames under fire. Based on the four collapse modes of steel portal frames under fire and the three-level early-warning methods, the influence of the heating condition of steel member, foot stiff, load ratio et al, on the prediction of remaining time before collapse was analyzed. Through Monte Carlo sampling, the statistical parameters with a certain probability guarantee rate were explored to ensure the reliability of the early warning index of steel portal frames under fire. The results show that the ratio of remaining time to collapse time, which can be determined before fire, is only related to the reliability level and collapse modes regardless of the values of uncertainties. The predetermined remaining time ratios with a reliability level of 60%-80% are advised to be adopted for fire rescue to predict the actual remaining time of the burning frame.