覆板加强的方钢管T形节点轴向滞回性能试验研究

Axial hysteretic behavior test of doubler plate reinforced square tubular T-joints

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 effect of doubler plate on the axial hysteretic behavior of reinforced square tubular joints, two groups of unreinforced and doubler plate reinforced （DPR） square tubular joints were tested under axial cyclic loading, where the ratios of brace to chord width are 0. 4 and 0.8 respectively. The design scheme, experiment process as well as failure modes of the specimens were presented. Hysteretic performance of the specimens such as hysteretic loops, skeleton curves, energy dissipation and ductility were analyzed. Experimental results show that although the crack position of each specimen is different, the specimens mainly experience five stages under axial cyclic loading, namely the chord yielding, initial cracking, crack closure, crack expansion and crack penetration. The doubler plate can prevent the development of cracks into the chord wall, which can effectively avoid the tearing failure of the chord flange. Therefore, the compression capacity of the DPR joints can continue to rise after cracking, and the tensile capacity of the DPR joints is higher than un-reinforced ones. The energy dissipation and ductility of the joints are increased with the decrease of the ratio of brace to chord width. The energy dissipation capacity of DPR joints is lower than the corresponding un-reinforced ones, and this kind of degeneration is more significant when the ratio of brace to chord width is lower. The tensile cracks reduce the ductility of the specimens, and the ductility of the specimens under axial tensile cycle is lower than the corresponding compression cycle. The ductility of the joint is improved by doubler plate when the ratio of brace to chord width is 0.8, while degenerated when the ratio of brace to chord width is 0. 4. The unbalanced of the tension and compression capacity of the DRP joints under axial cyclic loading should be paid more attention to.