考虑节点影响的钢框架结构连续倒塌分析

Progressive collapse analysis of steel frame structures considering influence of steel connection

针对目前钢框架结构抗连续倒塌分析中通常忽略节点轴力-弯矩耦合效应,并假设节点不发生破坏的问题,提出一种考虑节点轴力-弯矩耦合效应和楼板作用的钢框架连续倒塌分析模型,通过对已有试验的模拟验证了该模型的准确性;采用所提出的模型和基于能量的Pushdown方法对2个10层钢框架结构进行结构抗倒塌能力、破坏模式和抗倒塌机制分析。结果表明:不考虑节点轴力-弯矩耦合效应将高估钢框架结构的抗倒塌能力;钢框架结构典型破坏模式为钢柱屈曲引发的水平向倒塌及铰接节点断裂失效引发的竖向倒塌;当失效柱与梁刚性连接时,结构发生水平向倒塌破坏,破坏前竖向变形较小,主要的抗倒塌机制是梁端的轴力、弯矩及各层不均匀发展轴力产生的空腹桁架效应;而失效柱与梁铰接时,结构发生竖向倒塌破坏,破坏前结构发生较为明显的竖向变形,节点失效前后结构主要抗倒塌机制分别为悬链线机制和楼板薄膜力机制。

Most progressive collapse analyses of steel frame structures exclude the failure of connections and axial force-moment interactions of connections. A computational efficient steel frame model was proposed to study the progressive collapse behavior of steel frame structures. The model proposed was verified by experimental results. Based on the models above,energy-based Pushdown analysis method was utilized to study the ultimate progressive resistance capacity,failure mode and progressive collapse resisting mechanisms of two typical ten-story steel frames buildings.Research results show that connection models neglecting axial force-moment interaction effect may overestimate the ultimate progressive resistance of steel frame buildings. Typical collapse modes of steel frame structures are horizontal collapse mode induced by buckling of steel columns and vertical collapse mode induced by fracture of simple connections under cantenry actions. The steel frames suffer from horizontal collapse mode with minor vertical displacement when removal column is connected by rigid joints. The major progressive collapse resisting mechanisms is axial forces and moment at beam end and vierendeel action resulting from uneven distributed axial forces at different stories. The steel frames suffer from vertical collapse mode with large vertical displacement when removal column is connected by simple joints. Catenary action of steel beam and membrane action of steel-composite floor contribute significantly to the resisting mechanisms before and after the fracture of simple connections.