Evaluation of the Response Modification Factor in Steel Braced Frames Incorporating Buckling-Restrained Braces

Buckling-restrained braces (BRBs) are widely adopted for their superior energy dissipation and ductility. While it is generally recognized that the response modification factor (R-factor) decreases with building height, the specific quantification of this reduction for BRB frames (BRBFs) and the influence of frame geometry remain less explored. This study evaluates the R-factor of BRBFs, quantifying the effects of the number of stories, span width, and story height. Six BRB-braced steel frames, comprising ۵-, ۱۰-, and ۱۵-story configurations with different span widths, were modeled in OpenSees. Using pushover analysis and bilinear idealization, their ductility, overstrength, and overall R-factors were determined. The results provide a quantification of the R-factor's steep decline with height, revealing a reduction of approximately ۳۵% over the studied range. Furthermore, the analysis demonstrates that expanding the span width can partially mitigate this decline, enhancing nonlinear performance and ductility, particularly in mid- and high-rise frames, thereby improving the overall seismic performance of BRB-equipped steel structures.

کلیدواژه ها:

Buckling-restrained brace ، Cyclic response ، Numerical analysis ، Overstrength ، Response modification factor