Seismic performance assessment of a novel spring based piston bracing

Concentric Braced Frames (CBFs) are commonly used all over the world to resist seismic forces in buildings. Buckling, however, is a major concern for CBFs where they lose their strength and stiffness when subjected to load reversals during earthquakes. To tackle this problem, a novel easy-to-fabricate low-cost Spring Based Piston Bracing (SBPB) system is developed with single and double friction spring configurations. In this system, a brace member can carry a large magnitude of tension and compression forces where a special spring is employed in the piston cylinder. Stable and self-centering hysteresis behavior is achieved when the system is subjected to qualifying quasi-static loading. Strain rate effect is assessed, and comparable results are achieved without any performance degradation. Numerical simulation shows excellent matching with the test results. Two four-story braced steel buildings are designed: a) utilizing Buckling Restrained Braces (BRBs) and b) SBPB and their performances are compared in terms of interstory drift and residual drift. The proposed system experiences zero residual deformations but relatively larger drift values compared to BRBs.