基于节点刚度的钢框架梁柱子结构抗倒塌性能试验研究

EXPERIMENTAL STUDY ON ANTI-COLLAPSE PERFORMANCE FOR BEAM-TO-COLUMN ASSEMBLIES OF STEEL FRAME BASED ON JOINT STIFFNESS

以钢框架中3种不同连接节点形式(栓焊连接、顶底角钢腹板双角钢连接和腹板双角钢连接)的两跨三柱型梁柱子结构为研究对象,通过对中柱施加静力荷载的大变形试验考察梁柱子结构在中柱失效连续倒塌条件下的破坏模式、力学形态和抗倒塌机理。结果表明:栓焊连接试件因梁柱节点处梁端受拉翼缘发生断裂而失效;顶底角钢腹板双角钢连接试件为梁柱相连的受拉角钢在螺栓孔处发生断裂,且因梁端腹板螺栓孔发生承压破坏而失效;腹板双角钢连接试件因腹板两侧角钢在螺栓孔处断裂而破坏。梁柱节点刚度对结构的抗倒塌性能影响较大,腹板双角钢连接试件主要通过悬链线机制提供抗力;而其他两类试件在加载前期主要通过梁机制提供抗力,进而转变由悬链线机制来抵抗外部荷载。其中,顶底角钢腹板双角钢连接试件在后期更能充分发展梁端节点转角和梁截面轴力,表现出更为富余的抗倒塌能力储备。

Three specimens with different stiffness connections（welded flange-bolted web connection, top-seat angle with double web angle connection, and double web angle connection）, which comprised three columns and two beams, were statically tested. The failure mode, the mechanical behavior, and the resistance mechanism of the specimens under the condition of progressive collapse were studied. The results indicated that： the specimen with welded flange-bolted web connection was failed because the tension flanges of the beam fractured near the joint; the specimen with top-seat angle with double web angle connection was failed because of the fracture of the tension angle connecting the column and the beam at the bolt holes, and the section with bolt hole of the beam web was failed with severe bearing damage; the specimen with double web angle was failed owing to the damage of double web angles at the bolt hole. Beam-to-column connections had a great influence on anti-collapse performance of assembly. The resistance of the specimen with double web angle connection was mainly provided by the catenary mechanism; for others, the flexural mechanism contributed the mainly resistance in the early stage of loading, and then the dominant force transfer mechanism was converted to the catenary mechanism to resistexternal loads. Thereinto, the joint rotation and the axial force of the beam of the specimen with both a top-seat angle and a double web angle connection could be fully developed in the later stage, which showed a greater anti-collapse bearing capacity for reserve.