Investigation of Axial Load Capacity of (+)-Shaped Section BRBs with Friction and Frictionless

This study presents designing the conventional braces with (+) shaped cross-sections as buckling restrained braces (BRB) with friction and frictionless surfaces without a gap. In this context, cyclic axial loading tests were carried out on seven braces members (one was a reference brace and the others had an outer casing and mortar). In addition, numerical models of the specimens were created and analysed with ANSYS. The core brace members were confined by two different types of steel profiles (SHS and CHS series) for the design. Each series consisted of three specimens separately. The specimen of reference and core of BRBs was a (+)-shaped section brace. In the experimental study, while a natural friction surface was preserved between the brace-steel outer casing in the first specimen of the series, a frictionless surface was created in the second. In the third specimen of the series, the gap between the core-steel outer casing was filled with mortar. The performance of the specimens was evaluated depending on the axial load capacity, hysteric behaviour and ductility. Compared to the reference in the unfilled specimens, the tensile strength increased by 3.4–6.0%, while this increase was 22.4–32.0% in the mortar-filled specimens. When the axial load capacities were considered, the increases were 268.3 and 249.8% in the mortar-filled specimens. On the other hand, mortar-filled specimens reached the highest axial load capacity. While there is an increase in energy ductility, it might be said that there is a decrease in general ductility in all specimens because of early failures. It had been observed that the lateral-torsional buckling effect of the (+) section has a direct effect on the failure mechanism.