Document Type : Research Article
Authors
1 department of civil engineering west tehran branch islamic azad university tehran iran
2 Department of Civil Engineering, Engineering Faculty,University of Eyvanekey, Semnan, Iran
3 Department of Civil Engineering, Engineering Faculty, Eyvanakey University, Semnan, Iran
Abstract
Application of dual SMRF-BRBF system can be considered as an appropriate choice for resisting seismic loads in high seismicity regions. Taking advantage of having buckling resistant braces which can resist high axial compressive forces without local and global buckling, buckling restrained bracing frame (BRBF) system can be used as an efficient alternative for conventional bracing system. Response modification factor (R factor) is required for seismic design of structures. Therefore, in this research, performance-based R factor is evaluated for dual SMRF-BRBF structures. Considering the fact that in addition to structural properties the seismic load characteristics effect on the load-carrying capacity and R factor, R factor is evaluated specifically for near fault ground motions. To consider the effect of performance level, the R factor is calculated distinctly for Life Safety (LS) and Collapse Prevention (CP) limit states. Nonlinear time history and pushover analysis results are employed for determination of ductility, over-strength and R factor of the sample structures. According to the obtained results, the average of R factor coincident to LS and CP performance levels is 6.1 and 7.9, respectively. The comparison of results obtained for near fault records with those obtained for far fault motions reveals that the R factor is averagely 25% lower for near fault ground motions.
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