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为研究采用覆板加强的冷弯方钢管T形节点的轴向滞回性能,对2组支管与主管的截面宽度比β分别为0.4和0.8的方钢管直接焊接节点和采用覆板加强的方钢管T形节点进行了轴向往复加载试验。详细介绍了试验节点的设计、试验过程及破坏形态,并对节点试件的滞回曲线、骨架曲线、耗能和延性等性能进行了分析。试验中,试验节点经历了主管屈服、初始开裂、裂纹闭合、裂缝扩展、裂缝贯通五个主要阶段,但各试件的开裂位置并不相同。加强覆板阻止了裂缝向主管管壁发展,有效避免了主管管壁的撕裂破坏,使开裂后支管的受压荷载继续上升,因而节点开裂后受拉能力较未加强节点的好。支管与主管截面宽度比越小,试件的耗能能力和延性越好。但覆板加强处理降低了试件的耗能能力,且支管与主管宽度比越小其耗能能力的降低越明显。受拉裂缝会降低试件的延性,故轴拉循环的延性较对应的轴压循环的差。在β=0.8时,覆板加强对试件的抗震延性有所改善,但β=0.4时加强节点试件的位移延性系数低于未加强节点。覆板加强节点在支管轴向往复荷载作用下的拉压不均衡问题应引起重视。
In order to study the axial hysteretic behavior of T-shaped joints of cold-formed square steel tube strengthened by superstructure, the square welded joints of square steel tube with cross-section width ratio β of two groups of branch pipes and main tube of 0.4 and 0.8, respectively, Steel T-joints were axially reciprocating loading test. The design, test process and failure mode of the test node are introduced in detail. The hysteresis curve, skeleton curve, energy dissipation and ductility of the joint are analyzed. During the experiment, the test nodes experienced five main stages of yielding, initial cracking, crack closure, crack propagation and fracture penetration, but the cracking locations of the specimens were not the same. Reinforcing the superstrate prevents the crack from developing to the main pipe wall and effectively avoids the tear damage of the main pipe wall, so that the compressive load of the branch pipe after the cracking continues to rise. Therefore, the tensile strength of the node after cracking is better than that of the non-strengthened node. The smaller the ratio of the width of the branch pipe to the length of the supervisor, the better the energy dissipation capacity and ductility of the test piece. However, the strengthening of the covering plate reduces the energy dissipation capacity of the test piece, and the smaller the width of the branch pipe to the main pipe is, the more obvious the reduction of the power consumption capacity is. Tensile cracks will reduce the ductility of the specimen, so the ductility of the axial compression cycle is less than the corresponding axial compression cycle. At β = 0.8, the anti-seismic ductility of the test piece is improved with the reinforcement of the panel, but the displacement ductility coefficient of the test piece of the strengthened joint is lower than that of the unstressed point when β = 0.4. The problem of unbalanced tension and compression under the action of axial load on the branch pipe to strengthen the joint should be paid more attention.