连续倒塌工况下钢管混凝土柱-钢梁外伸端板连接节点受力性能研究

Study on the Behavior of CFST Column-Steel Beam Joint with Extended Endplate in the Scenario of Progressive Collapse

设计了3个采用穿心螺栓的钢管混凝土柱-钢梁外伸端板连接节点,详细分析了连续倒塌工况下的节点的承载机制和破坏模式,进行了节点抗倒塌转动能力评价和等效动力分析,主要结论如下:在连续倒塌工况下,采用穿心螺栓的钢管混凝土柱-钢梁外伸端板节点具有较好的受力性能.对于外伸式端板连接,端板厚度和螺栓直径的匹配程度会影响节点中悬索机制的形成与发展,当端板相对于螺栓较弱时,有利于增大连接处的变形和悬索机制的发展,同时应保证外伸端板连接节点的抗弯承载力不能明显低于钢梁的抗弯承载力.提出了适用于外伸端板连接节点的考虑螺栓组高度、端板厚度和螺栓直径影响的抗倒塌转动能力需求计算公式.DoD规范的动力放大系数计算公式仅考虑了节点抗弯机制的影响,当悬索机制参与承载后,节点的实际响应会逐渐大于公式结果.

Three CFST column-steel beam joints with long bolts and extended endplate were tested in the scenario of progressive collapse.The load-carrying mechanism and failure mode of the joints are investigated in detail.The assessment for the rotation capacity in anti-collapse design and the equivalent dynamic analysis for the specimens are conducted.The analysis results show that the CFST column-steel beam joints with long bolts and extended endplates behave well in the scenario of anti-collapse.For extended endplate connection,the matching degree between endplate thickness and bolt diameter has effects on the formation and development of catenary mechanism in the connection.Relatively weaker endplate compared to bolt would increase the deformation capacity of the connection and contribute to the development of catenary action.It should be guaranteed that the strength of the joint is not significantly lower than that of the beam.A formula which considers the effects of bolt-group height,endplate thickness and bolt diameter for the rotation limitation of extended endplate joint in the design of anti-collapse is proposed.The method for calculating dynamic increase factor in DoD standard only considers the influence of the bending mechanism of joint.Once the catenary mechanism of joint gets involved in load-carrying,the actual response of joint would gradually become larger than that predicted by the method in DoD standard.