Hysteretic behavior of tubular T-joints after exposure to elevated temperature

Experimental tests on circular hollow section (CHS) tubular T-joints under axial loading after exposure to elevated temperature are conducted to investigate their hysteretic behavior. Two full-scale specimens with different brace-to-chord diameter ratios are heated firstly in an electrical furnace to 500 °C and then they are cooled down to ambient temperature. After exposure to elevated temperature, the two specimens are tested together with two corresponding identical T-joints without exposure to elevated temperature in order to compare the different hysteretic performance. In the tests, all the specimens experience cyclic axial loading at the brace end while the ends of the chord are pinned. From experimental observation, both the heated and the unheated specimens are found to experience local yielding in compression and cracking in tension around the brace/chord intersection before final failure. To investigate the influence of elevated temperature on the hysteretic behavior, hysteretic curves, skeleton curves, ductility, accumulative energy dissipation, strength and rigidity degradation are all analyzed based on experimentally measured results. The detailed analyses indicate heating and cooling process in fire condition has minor effect on the hysteretic behavior of CHS T-joints subjected to service loading.