# Seismic Response Analysis of Multi-Story Steel Frames Using BRB and SCB Hybrid Bracing System  
[PERSON]  
1 School of Civil Engineering and Architecture, Northeast Electric Power University, Jilin 132012, China; [EMAIL_ADDRESS]  
[PERSON]  
2 Key Laboratory of Urban Security and Disaster Engineering of Ministry of Education, Beijing University of Technology, Beijing 100124, China [EMAIL_ADDRESS] (R.C. ); qiucanxing@bjut. mitigate buckling-induced weak story behavior. Being different from normal steel braces, BRBs avoid buckling-induced instability and thus show stable cyclic behavior under both tension and compression loads. Owing to their outstanding damping capacity and economical production, BRB frames (BRBFs) have become popular seismic resistant structural systems and are being widely used over many countries [10]. According to prior work [6; 10], BRBs exhibited plumb hysteresis, which enables BRBFs to successfully absorb seismic energy. [PERSON] et al. [6] numerically quantified the seismic demands of BRBFs. [PERSON] and [PERSON] [11] evaluated the effect of reserve strength on the seismic performance of BRBFs. Many numerical studies can be found elsewhere [12]. However, it is noted that the plumb cyclic behavior of BRBs leads to excessive residual deformation in the global system. As reported, under earthquakes, BRBFs usually exhibited satisfactory seismic performance but were prone to producing noticeable residual deformation, even after moderate earthquakes [6; 13]. Through the numerical analysis reported by [PERSON] et al. [6], the average residual story drift ratio of multi-story BRBFs was over 0.5% when subjected to design basis earthquake (DBE) ground motion records. Excessive residual deformations may hinder the post-event recovery of building function and repairing work and, thus, have gained increasing attention among the community of earthquake engineering [14; 15; 16]. Post-event investigations found that a lot of building structures were finally demolished and rebuilt due to unrecoverable deformation, although they performed satisfactorily during earthquakes. Recognizing the problems associated with excessive residual deformations, the community quantitatively defined several thresholds of residual deformation that correspond to several damage levels. When the residual story drift ratio was over 0.5%, it would be more suggestible to rebuild a new structure rather than repairing the damaged one [17]. Besides, with the separability, the out-of-plumb limits were also determined by the magnitudes of residual story drift ratios, which were determined to be 0.2% and 0.1% for the 3- and 6-story frames, respectively, based on relevant analytical results [18]. Many strategies were recently proposed and found effective in reducing the residual deformation demands of BRBFs [19; 20; 21; 22; 23; 24; 25; 26]. For example, adopting moment-resisting frame (MRF) as the backup system for BRBFs was a methodology recommended by [PERSON] [27] from the aspect of system level. By paralleling MRF to share 25% of the total design base shear, the residual story drift ratios of BRBF was reduced remarkably although not completely eliminated [27]. [PERSON] and [PERSON] [11] also found that the participation of MRF reduced the residual story drift ratios. In their work, the residual deformations were decreased by approximately 50%. Combining MRF brings noticeable efficacy on reducing residual story drifts; however, it deserves further improvement because the residual story drifts were still over 0.5% upon a few earthquake records that correspond to the DBE level. As a consequence, the BRBF-MRF system still violated the separability limit defined by a post-earthquake renaissance report [17]. As have been pointed out by prior studies [22; 26; 28; 29; 30; 31; 32; 33; 34; 35; 36; 37; 38], self-centering braces (SCBs) are an alternative to conventional braces because they can recover large deformation and can absorb input seismic energy.