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

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. [ABSTRACT FROM AUTHOR]