Title: An evaluation of the seismic response modification factor R for RC special moment-resisting frame system

Authors: Rania Al-Ahmar; Mohammad Al-Samara

Addresses: General Company for Engineering and Consulting, Damascus, Syria ' Faculty of Civil Engineering, Damascus University, Syria

Abstract: Many countries still adopt the seismic design approach in UBC97 for RC special moment-resisting frame buildings (SMRFs), which suggests a fixed value of the seismic response modification factor R of 8.5 for all types of SMRFs. This paper investigates, using two case studies comprising 25 numerical analyses, the R factor for SMRFs by performing pushover analysis and focusing on the effect of the number and span of bays and the number of stories. The analysis results show that the R factor is significantly dependent on the number of stories in which it decreases with the increase in the number of stories. Conversely, the number and length of bays had insignificant effect on R in comparison to the number of stories. The calculated R values range from 5 to 12. Thus, the results suggest that the use of a fixed value for R could result in unsafe or uneconomic building designs.

Keywords: seismic response modification; overstrength factor; ductility reduction factor; special moment-resisting frames; SMRFs; seismic design; earthquakes; R factor; structural design; seismic forces; multistory frames; reinforced concrete frames; building design.

DOI: 10.1504/IJSTRUCTE.2015.072479

International Journal of Structural Engineering, 2015 Vol.6 No.4, pp.368 - 387

Available online: 14 Oct 2015 *

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