| The buckling restrained brace (BRB) or UB (unbonded brace) is a late-model member for severe seismic applications. A BRBs commonly found is composed of a load-carrying element, a lateral-support element and unbonding material. When the braces are subjected to compressions, the lateral support element will provide lateral support to the core element and the steel core member will resist the axial forces with a full tension or compression yield capacity without the local or global flexural buckling failure. Past studies have shown that the BRB is able to prevent early buckling and cracking that occur in conventional braces and develop to the full capacity of the strength, ductility and energy-dissipation capacity of the steel used.Through elastic response spectrum analysis as well as the elastic and plastic time-history analysis by inputting two strong ground motion records, the study compared the story drift and displacement between a frame using BRBs, a frame using conventional braces and a non-braces frame. The comparisons show that the story drift and displacement of the frame using BRBs are smaller that those of the other two frames. And drew the conclusions that the use of BRBs can enhance the structure's ductility, dissipate the energy effectively, and reduce the nonlinear demand of the columns and girders. The paper also carried out non-linear push-over analysis using the displacement coefficient method and gave the failure modes of the three structures respectively.At present, there are no applications, or relevant design codes and specifications at home. These papers, referring to foreign codes, carried out thorough seismic studies on frames using BRBs using the infinite computing program ETABS, and probed into the design method as well as the evaluation on its seismic performance.
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