Improving Low-Cycle Fatigue Performance of High-Performance Buckling-Restrained Braces by Toe-Finished Method

The purpose of this research is to improve the low-cycle fatigue life of the buckling-restrained brace (BRB) for the development of the high-performance buckling-restrained brace (HPBRB) used in bridge engineering. The HPBRB is expected to suffer three strong earthquakes without severe damage during the lifecycle of a bridge. This article employs a low-cycle fatigue experiment, including two series of BRB specimens, all of which had been tested to failure. In the second batch, the weld toes of the rib had been ground to improve the weld's low-cycle fatigue life. According to test results under constant and variable strain amplitudes, the specimens have a great low-cycle fatigue performance. The weld of the rib clearly affects the performance of the as-welded specimens tested with the relatively small strain amplitude. The toe-finished method effectively improves the BRB's low-cycle fatigue performance. Besides, the in-plane gap width of the BRB slightly affects the low-cycle fatigue life. Finally, the low-cycle fatigue curves are compared between the BRB and the materials and the low-cycle fatigue damage evaluation formulae of the as-welded and toe-finished BRBs are recommended for the strain-based evaluation of the low-cycle fatigue damage.