Amirkabir University of Technology Amirkabir Journal of Civil Engineering 2588-297X 57 3 2025 05 22 Evaluation of the Effect of Two-Part and Three-Part Braces on the Seismic Behavior of Strongback Braced Frames Evaluation of the Effect of Two-Part and Three-Part Braces on the Seismic Behavior of Strongback Braced Frames 445 468 5714 10.22060/ceej.2025.23688.8197 FA Aryan Fatahzadeh Department of Civil Engineering, Golestan University Ali Biglari Department of Civil Engineering, Faculty of Engineering, Golestan University, Gorgan, Iran 0000-0002-9616-1823 Journal Article 2024 11 20 <span style="letter-spacing: .05pt;">Steel bracing frames are efficient systems for resisting seismic loads. However, multi-story steel bracing frames tend to concentrate seismic demands in one or more stories in response to severe ground vibrations. Therefore, in recent years, mechanisms have been presented to distribute inelastic demands over the height of the structure. Strongback braced frame is one of the efforts made in this field. This system, using an elastic truss at the height of the structure, redistributes demands to other floors. In most studies conducted on conventional steel braces, they have been used as energy dissipation elements, while due to the buckling of the braces, adequate energy dissipation is not seen in these structures. In this study, the possibility of improving the behavior of a buckling-restrained braced frame with a crescent-shaped brace was evaluated. Initially, to provide more flexibility in design, a three-part brace or trapezoid brace was introduced, and finally, the possibility of improving the behavior of a strongback braced frame by adding a crescent-shaped or trapezoid brace was evaluated with Nonlinear static analysis. The results showed that the use of a crescent-shaped or trapezoid brace, while improving the energy dissipation of the structure by up to 440.9% and increasing the shear capacity of the structure by up to 57%, did not significantly increase the stiffness of the structure (maximum 14%) and the forces generated in the elastic truss elements formed a uniform distribution over the height of the structure.</span> <span style="letter-spacing: .05pt;">Steel bracing frames are efficient systems for resisting seismic loads. However, multi-story steel bracing frames tend to concentrate seismic demands in one or more stories in response to severe ground vibrations. Therefore, in recent years, mechanisms have been presented to distribute inelastic demands over the height of the structure. Strongback braced frame is one of the efforts made in this field. This system, using an elastic truss at the height of the structure, redistributes demands to other floors. In most studies conducted on conventional steel braces, they have been used as energy dissipation elements, while due to the buckling of the braces, adequate energy dissipation is not seen in these structures. In this study, the possibility of improving the behavior of a buckling-restrained braced frame with a crescent-shaped brace was evaluated. Initially, to provide more flexibility in design, a three-part brace or trapezoid brace was introduced, and finally, the possibility of improving the behavior of a strongback braced frame by adding a crescent-shaped or trapezoid brace was evaluated with Nonlinear static analysis. The results showed that the use of a crescent-shaped or trapezoid brace, while improving the energy dissipation of the structure by up to 440.9% and increasing the shear capacity of the structure by up to 57%, did not significantly increase the stiffness of the structure (maximum 14%) and the forces generated in the elastic truss elements formed a uniform distribution over the height of the structure.</span> https://ceej.aut.ac.ir/article_5714_0fe6a94848e5c68a54010b61b3e94b0e.pdf