火灾下高层建筑钢框架结构连续性倒塌的模式与设计方法研究

Steel structures have many advantages such as light weight, high strength, ease of erection, and recyclable use of materials. These advantages make them particularly suitable for application in high-rise buildings. However, steel structures are not inherently fire resistant that much of the resistance of steel components would be lost when their temperature reaches 600oC during a fire. The high probability of high-rise buildings being subjected to fire may lead to a high risk of losing local load bearing capacity and subsequently induce global progressive collapse. Currently, researches on the performance of high-rise steel framed structures against fire-induced progressive collapse are rare. To this end, this project will establish simplified mechanical model of steel sub-structures in fire through studies on the post-buckling performance of restrained steel columns and catenary effects of restrained steel beams. Embedding the proposed local failure model due to fire in terms of a equivalent spring model into the global model of the whole structure, the collapse modes and influencing factors of the progressive collapse of structures are then investigated. The failure criterion of structures and components are to be proposed to estimate the probability of the progressive collapse and determine the collapse modes of structures. Finally, a practical design method of fire-induced progressive collapse of high-rise steel framed structures will be proposed.

钢结构因其轻质、高强、施工方便和材料可循环等优点，在我国高层建筑中得到了广泛应用。但钢材不耐火，在火灾600oC下，钢材将丧失大部分强度，由于高层建筑火灾隐患多，会造成结构局部构件的破坏，并引发整个建筑物连续性倒塌。目前，国内外对火灾下高层建筑钢框架结构抗连续性倒塌性能研究甚少。本项目拟通过对火灾下约束钢柱屈曲后性能和约束钢梁悬链线效应的研究，建立受火开间钢框架子结构局部破坏简化模型，通过在结构整体分析模型中引入该局部破坏模型，研究局部破坏后高层建筑钢框架结构连续性倒塌的模式及其影响因素，进而提出针对不同倒塌模式的判定方法，建立防止高层建筑钢框架结构火灾下连续性倒塌的实用计算和设计方法。

钢结构日益成为我国高层建筑的主要结构，而火灾在高层建筑中极可能发生，导致钢材强度降低和断裂，最终引发高层建筑钢结构连续性倒塌。本项目首先建立了火灾条件下结构局部破坏的简化力学模型，研究受约束构件在火灾荷载下承载力和刚度的退化，通过对钢框架结构进行理论和试验分析，研究钢框架结构连续性破坏与倒塌的特征，确定了影响连续性倒塌模式的关键因素，提出了高层钢结构抵抗火灾连续性倒塌的鲁棒性综合指标与临界条件，从而提出了火灾下高层建筑钢框架结构抗连续性倒塌的实用计算和设计方法。