钢管混凝土柱-钢梁穿心螺栓外伸端板式节点抗连续倒塌性能研究

针对钢管混凝土柱-钢梁穿心螺栓外伸端板式节点进行抗连续倒塌单调加载试验，考察节点在连续倒塌工况下的整体变形、破坏形态、节点抗力以及关键截面应变发展等，并建立穿心螺栓外伸端板式节点有限元模型，进行节点失效模式、节点核心区应力及抗力机制分析。结果表明，钢管混凝土柱-钢梁穿心螺栓外伸端板式节点在连续倒塌工况下主要经历4个阶段，即梁机制阶段、混合机制阶段、悬链线机制阶段及破坏阶段；节点抗倒塌承载力由节点抗弯能力和抗拉能力提供，其中抗拉能力对节点抗连续倒塌能力贡献远超于抗弯能力；节点的倒塌破坏一般发生在钢梁与外伸端板连接处，裂缝贯穿下翼缘后迅速延伸至钢梁腹板；形心轴下方穿心螺栓群拉应力持续增大，形心轴上方穿心螺栓群在加载初期拉应力较小，随着竖向位移的增大其拉应力逐渐增大；外伸端板应力主要集中在螺栓孔周围，随着竖向位移增大形心轴上方应力集中区面积减小，形心轴下方应力增大。

Research on performance of CFST column to steel beam joint with through bolts-extended endplate against progressive collapse

In order to investigate the performance of the concrete filled steel tubular (CFST) column to steel beam joint with through bolts-extended endplate against progressive collapse, a monotonic loading test was conducted. The deformation process, failure modes, column resistance, and key section strains were observed and analyzed. The finite element model of these joints was established to study the fracture behavior, stress development and resistance mechanism of the joint. The results show that the CFST column-steel beam joint with through bolts-extended endplate undergoes four stages to reach progressive collapse, i.e., beam mechanism stage, mixing mechanism stage, catenary mechanism stage and failure stage. The resistance of the joint against progressive collapse is provided by the bending capacity and the tensile capacity. The tensile capacity contributes more resistance to the joint against progressive collapse than the bending capacity. The collapse fracture of the joint generally occurs at the connection-section of the extended endplate and the steel beam. After the crack penetrates the lower flange, it quickly extends to the web of the beam. The tensile stress of the through bolts below the centroidal axis continues to increase. The tensile stress of the through bolts above the centroidal axis is small at the initial stage of loading, and gradually increases with the increase of vertical displacement. For extended endplate, the stress mainly concentrates around the bolt hole. With the increasing of the vertical displacement, the stress concentration area above the centroidal axis decreases, and the stress below the centroidal axis increases.