IMPROVING SAFETY MARGIN OF BUCKLING-RESTRAINED BRACES AGAINST MULTIPLE EARTHQUAKES

摘要

This paper presents an experimental study about the low-cycle fatigue performance and the safety margin of the buckling-restrained brace (BRB) to develop the high-performance BRB (HPBRB) used in bridge engineering. The HPBRB is expected to withstand three strong earthquakes without severe damage and thus, it does not need to be replaced during the lifecycle of a steel bridge. Ten all-steel specimens tested with a constant strain amplitude are used to evaluate the influence of the welding and the stopper on the performance of the BRB. The weld is employed to connect the rib to the core member's ends and improve the non-yield portion's out-of-plane stiffness. The stopper is used to prevent the restraining system from slipping off the core member. According to test results, all the specimens have a good fatigue performance. The cracks started at the weld toes of the ribs and induced the failure of the as-welded specimen under the relatively small amplitude. After polishing the weld toes, the performance of the toefinished specimens is clearly improved and the corresponding failure mode is changed. Besides, the specimens with the stoppers possess the greater performance and the relatively larger safety margin than the specimens without stoppers. The cumulative inelastic deformation performance of the specimens without stoppers is 40% lower than the specimens with the stoppers.