A double-stage buckling restrained brace with progressive failure pattern: Experimental verification and numerical calibration

Abstract

Buckling-restrained brace (BRB) is a widely used energy dissipator by the yielding of core steel plate. Single-core BRB (SBRB) only has one yielding point and a single failure pattern. Consequently, the SBRB has a risk of abrupt failure under extremely rare earthquakes, which may compromise the seismic safety and collapse mode of the building with SBRB. A new double-stage buckling-restrained brace (DSBRB) characterized by a progressive failure pattern is proposed. The progressive failure pattern of DSBRB is realized by setting up multiple core plates with different cross-sectional areas and lengths in the yielding part. A quasi-static test was conducted to investigate the difference in cyclic behavior and failure pattern between the SBRB and DSBRB. The test results showed that the yielding displacement and yielding force of the tested DSBRB were 8.74 % and 5.64 % smaller than those of SBRB respectively, resulting in a greater equivalent damping ratio for DSBRB under the small deformation. SBRB showed an abrupt failure pattern while the DSBRB was a progressive double-stage failure pattern at the cost of a reduced equivalent viscous damping ratio under the extreme deformation. The theory equations about the elastic stiffness, yielding force, and yielding displacement of DSBRB were derived and justified by the test results, i.e., differences between test results and theoretical derivation were all within ± 8.51 %. Two numerical models were established in ABAQUS and calibrated by the test results. The concept of double-stage BRB with a progressive failure pattern was verified.