Reinforced Concrete Buckling-Restrained Braced Frame with Structural Fuse Detailed for Seismic Loading

Buckling-restrained braces (BRBs) increase the strength of a system while dissipating a significant amount of hysteretic energy. This research presents a concept for a lateral force resisting system using a reinforced concrete buckling-restrained braced frame (RCBRB) as a structural fuse for the design of new buildings in seismic regions. Experimental and numerical analysis results are presented for a single-story subassembly. The experiment was performed on a reduced scale prototype reinforced concrete (RC) frame designed and constructed with modern seismic details and supplemented with a BRB as a structural fuse to examine the structural performance of the RCBRB frame under quasi-static cyclic loads. The BRB fractured in tension at approximately 3.5% drift ratio with minor repairable damage observed in the RC frame members. A numerical analysis model was developed in OpenSees with various material types and elements to model the nonlinear behavior of the proposed system compared with the numerical analysis model of the undamaged RC frame; the global and local experimental response of the RC frame and BRB was used to validate the numerical model. When compared to the numerical analysis results of the RC frame, the resulting RCBRB frame increased both the lateral load capacity and stiffness of the RC frame by approximately 250%. The resulting lateral force resisting system would be capable of resisting strong earthquake ground motions that can yield or even fracture the BRB without damaging the RC frame beyond a state of repair. The BRB was attached to the RC frame utilizing steel embed plates cast into the concrete that were designed using the uniform force method. A numerical model was developed and validated using the experimental results and showed that the RCBRB frame more than doubled the lateral strength and nearly tripled the total hysteretic energy dissipation when compared to the numerical analysis model results of an undamaged RC frame alone.