Development and experimental verification for the coaxially formed self-centering buckling-restrained brace

Abstract

The development for a new construction of self-centering buckling restrained braces (SCBRBs) was made by letting either an assembled steel BRB part or an integrally formed composite BRB part coaxially pass through an outer self-centering (SC) part with steel disc springs, and tests on the SCBRBs were conducted to validate the seismic performance and the configurations, mainly including the pattern of BRBs and that of pull rods in SC parts to keep the initial stiffness under two loading sides as close as possible. Tests show that, contrary to BRBs, the SCBRBs presenting flag-shape hysteretic curves have a significant reduction of residual drifts. Variation laws show that the residual drifts of the SCBRBs at horizontal drift levels of 2% are almost within 0.5% if self-centering ratios exceed 0.66. Besides, when the ratios under drift levels of 2% are close to 1.0, the residual drifts are approximately within the start displacements of the specimen with a SC part only. For the four SCBRBs adopting the same SC part within the drifts from 2% to 3.5%, approximately 56–73% axial strength and about 13–21% energy dissipation are from the SC part. Both types of BRB parts work stably. Except for tension fracture of plate braces, other members remain intact in SCBRBs, facilitating replacement of plate brace and reuse of intact SC part. Moreover, the interaction between two tubes in the SC part provides additional energy dissipation and horizontal resistance. Both tests and theoretical predictions reveal that the adjustment of pull rods in the SC part can adjust its initial stiffness in tension, and the pattern of employing two groups of six rods applying tension forces by two stages is preferred to decrease the difference between the initial stiffness in tension and that in compression.