Kinematics and Preliminary FEMA P-695 Evaluation of the NewZ-BREAKSS Steel Boundary Frame with Buckling Restrained Brace Structural Fuses

Abstract

Buckling Restrained Braced Frames (BRBFs) have become a popular seismic force resisting system (SFRS) due to their high ductility and energy dissipation. However, BRBFs are also susceptible to large residual drifts, which can make repair difficult. Efforts to reduce the residual drift of BRBFs typically involve special self-centering braces, or by using a dual system in tandem with the BRBF. This study proposes an alternative approach, in which a self-centering steel rocking frame is used as the boundary frame for the BRBF. The proposed system, called the NewZ-BREAKSS Buckling Restrained Braced Frame (NZ-BRBF) utilizes the recently proposed NewZ-BREAKSS (NZ) boundary frame to increase the post-yield stiffness of the system while concentrating all damage to the BRBs. The NZ-BRBF system is expected to behave similarly to conventional BRBF, but with smaller residual drifts and a boundary frame that remains essentially elastic, simplifying repair. This study presents a numerical investigation of the proposed low-damage SFRS, using the FEMA P-695 methodology as a guiding framework. The results suggest that the NZ-BRBF can exhibit better performance than conventional BRBFs and can be designed with the same response modification factor (R factor) as conventional BRBFs.