Testing of a Novel Induction Heat Treated Steel Brace with Enhanced Buckling Behaviour

Steel braces are widely used to stabilize steel structures forming horizontal or vertical truss structures; however, their relatively poor buckling behaviour is often lead to overdesigned structures. Induction Heat (IH) treatment technology is a novel contactless material transformation process to effectively strengthen local areas of steel sections. Utilizing IH to increase the strength of the middle length of steel brace sections, buckling behaviour can be improved. The present study experimentally investigates the compression behaviour of the novel braces fabricated by IH‐treated circular hollow steel sections. A Digital Image Correlation (DIC) system is used to measure the experimental deformation quantities, such as axial displacements, out‐of‐plane deformations, and strain distributions along the brace length. Four specimens were tested with two set of different slenderness ratios (λ). Each set includes one conventional steel brace (CSB) and one IH‐treated steel brace (IHSB) with a stronger section at its mid‐length. The specimens were subjected to a monotonic displacement‐controlled loading history until reaching an axial compressive strain of 2.5%. It was found that buckling load can increase up to 20% in IHSBs. IH treatment was also beneficial in improving the post‐buckling behaviour of the brace. The compression strength was found to be more than double in IHSBs than in CSBs at a ductility level of 5 (ductility is defined as the ratio of the target axial displacement to the yielding axial displacement). Moreover, out‐of‐plane displacements were reduced by 28% for the IHSBs at an axial strain of 1% showing a more evenly distribution of strain demands along the brace length.