Investigating the Effects of Geometric Parameters of Buckling Restrained Braces on the Cyclic Behavior of Buckling Restrained Braced Frames

Today, the buckling-restrained bracing frames (BRBFs) are widely used as a new system contributing to the absorption of a high amount of energy through yielding of the buckling-restrained brace (BRB) core when exposed to compression and tension. The relatively high cost of exploitation of this system has prompted researchers to seek for ways to reduce the costs while providing seismic performance. The present study was carried out to investigate the effect of the ratio of the yielding segment cross-sectional area to the elastic segment cross-sectional area as well as the length of the yielding segment to the total length of the BRB core on energy absorption demand of these braces in different stories of the BRB frames. For this purpose, two 5-and-10-story BRB frames have been modeled in Open Sees software, then the nonlinear time history analysis was performed on these frames under seven earthquake records. Using the results of the analysis, the energy absorption demand of braces on different stories with different ratios of the yielding segment cross-sectional area to the elastic segment cross-sectional area as well as the length of the yielding segment to the total length of the BRB core has been calculated. The results indicated that the variation of these ratios in the BRB can be effective in the amount of energy absorption demand of, in addition, the nature of this effect depended on the braced story in the BRB frame. However, the effect of stiffness modification factor on the uniformity of the energy absorption demand of braces in different stories is insignificant compared to the changes in the cross-sectional area of braces in different stories.