Experimental investigation of a novel reinforced concrete buckling-restrained brace

This paper describes an experimental investigation of a novel reinforced concrete buckling-restrained brace for precast concrete lateral load-resisting frame structures in seismic regions. The proposed brace uses ductile reinforcing bars with unbonded lengths across end gaps and bonded lengths at the middle region for lateral stiffness, strength, energy dissipation, and ductility. The experimental program included four isolated diagonal brace subassemblies subjected to reversed-cyclic pseudostatic lateral loading. Local buckling of the energy-dissipation bars across the end gaps is the most critical failure mode that can limit the ductility of the brace in compression. Up to this failure, the bonded and unbonded regions of the braces performed as designed. The results demonstrated the different deformation and stiffness behaviors of the braces in tension and compression. Subsequent loading to large tension displacements provided evidence of the large energy dissipation that can be expected if premature failure of the brace can be prevented. Simplified numerical models provided good predictions of the measured brace behavior until failure. This research featured the first set of tests for this brace, and the results highlighted adjustments needed to design and modeling to achieve the desired behavior of the brace. Recommendations for future research include improved shear dowel and confinement designs to prevent local buckling of the energy-dissipation bars and improved longitudinal reinforcement designs to prevent yielding of the energy-dissipation bars in the middle bonded region of the braces.