A new self-centering brace with zero secondary stiffness using elastic buckling

Abstract

It has been shown that having a low post-elastic (secondary) stiffness for conventional structures can be beneficial in terms of putting a limit on base shear of the structure although it could result in having a residual and permanent drift. A well-recognized example can be Buckling-Restrained Braced Frames (BRBFs) offering stable, repeatable and reliable damping while suffering from residual displacements owing to low secondary stiffness. This paper introduces a new type of self-centring brace with a flag-shape behaviour possessing a zero post-elastic (secondary) stiffness, Self-Centring Zero-Stiffness Brace (SC-ZSB), bringing the benefit of systems with minimal secondary stiffness without their deficiency. Basically, the elastic damage-free buckling of the brace is combined with the friction damping to form the intended flag-shape behaviour with zero post-elastic stiffness. The introduced bracing system will recover and re-centre at the end of buckling without any inelastic deformation, strength and stiffness degradation meanwhile providing passive damping. The proposed SC-ZSB is experimentally validated using a scaled self-centring brace. Besides, a comparative study is performed using OpenSeeS software to illustrate the seismic performance of the SC-ZSB in comparison with a BRB Frame. The results demonstrate that SC-ZSB system efficiently limits the base shear of the structure with an almost similar inter-story drift of the BRB frame, while it can eliminate any residual drifts as well.