方钢管混凝土柱-组合梁框架抗连续倒塌性能试验研究

为了研究组合梁对方钢管混凝土柱-组合梁框架抗连续倒塌性能的影响,设计了带有混凝土现浇楼板方钢管混凝土柱-组合梁框架(CFSTCBF)及不带楼板的方钢管混凝土柱-钢梁框架(CFSTSBF)，采用拆除构件法对两个试件的抗连续倒塌性能进行竖向加载试验研究，对其在中柱失效工况下的破坏模式、受力机理以及主要的抗力机制进行分析，同时对现浇混凝土楼板和节点在连续倒塌过程中的性能进行探讨。研究表明：两个试件的破坏均是由正弯矩区钢梁破坏引起，结构的倒塌阶段可分为弹塑性阶段、塑性阶段、过渡阶段和悬链线阶段，压拱机制和悬链线机制均能改善结构的抗倒塌性能；混凝土楼板可以有效增强结构的承载能力，提高结构的初始转动刚度，但在改善结构变形能力方面的作用较弱。

Experimental investigation on progressive collapse behavior of concrete-filled square steel tubes-composite beam frame

In this research, the square concrete-filled steel tubular column-composite beam frame (CFSTCBF) with concrete cast-in-place floor slab and the square concrete-filled steel tubular column-steel beam frame (CFSTSBF) without concrete cast-in-place floor slab were designed，and vertical loading test was carried out on them by alternate path method to investigate their behaviors against progressive collapse. The failure mode, bearing mechanism and main resistance mechanism of the specimens were also discussed under middle column failure scenario, and the performances of cast-in-place concrete slabs and joints were examined. The results indicate that the damage of the two specimens is caused by the failure of the steel beam in the positive bending moment zone, and their collapse processes include four stages: the elastic-plastic stage, the plastic stage, the transition stage and the catenary stage. Both arching and catenary mechanism improve the structural performance against progressive collapse. The concrete slab effectively enhances the bearing capacity and improves the initial rotational stiffness of the structure, but its impact on the structural deformability is small.