Design of buckling-restrained steel braces and frame members in structures

In this thesis study, the structural behavior of Buckling-Restrained Braces (BRBs) under lateral loads has been investigated, and the performance improvements they provide when used for seismic retrofitting have been evaluated. Conventional steel braces tend to buckle under cyclic loading, which limits their ductility and energy dissipation capacity. In contrast, BRB systems eliminate these deficiencies by exhibiting stable behavior under both tensile and compressive forces, thanks to the Buckling-Restraining Mechanism (BRM). The study presents a detailed examination of the primary components of a BRB element—namely, the core element (CE), the BRM, and the unbonded interface and includes comparative analyses with conventional bracing systems. These analyses were conducted in accordance with the AISC 360-10 Standard, based on current criteria applicable in steel structure design. Experimental and analytical evaluations indicate that reinforced concrete frames retrofitted with BRBs demonstrate significant improvements in their load-bearing capacities under vertical loads. The findings show enhancements of up to 50% in shear strength and up to 35% in moment capacity. In conclusion, BRB systems not only prevent buckling but also enhance the ductility and energy dissipation capacity of structures under cyclic loading, thereby significantly improving structural safety. With these characteristics, BRBs are recommended as a reliable solution for the seismic strengthening of both new and existing structures.