Sandwich type cold formed tubular braces: design, analysis and cyclic loading test

Abstract This study presents an experimental and numerical investigation on sandwich type cold formed tubular braces involving different designs with their load bearing members, inner buckling controllers, outer buckling controllers and end stiffeners. A total of 4 tubular brace specimens, using square HSS sections for the buckling controller and load bearing member, were tested under quasi-static cyclic loading conditions. In concert to previous research, a conventional tubular brace and tube in tube system were also used with all details relating to the specimens, including equations used for the designs, presented in full. The performance of the specimens were experimentally tested under quasi static cyclic loading, with all strain distribution patterns subsequently numerically evaluated. The effects, both individual and combined, on the outer buckling controller, inner buckling controller and end stiffeners on the load bearing member were all also carefully examined. The sandwich type tubular brace system showed symmetric and stable cyclic behavior up to a 3% drift ratio, with no global buckling during the cyclic loadings observed. Multiple instances of minor buckling were spread along the load bearing member. This study, to our knowledge, is the first to report such desired damage conditions for buckling controlled tubular braces. The energy dissipation capacity was found to increase almost 6 times the amount of the conventional tubular brace specimen. Contrary to results from previous studies, the usage of an outer buckling controller and end stiffeners provided the only control for global buckling. This type of design, therefore, was not effective in controlling local buckling or in providing significant energy dissipation when compared with conventional tubular braces.