Studying the Effect of Torsional Irregularity on Seismic Response Modification Factor in RC Dual System

Abstract

In this research, the effect of torsion due to the irregularity of the reinforced concrete dual system on seismic response factors and building behavior was investigated. As the demands of modern architecture increase, the effects of twisting are amplified, altering the actual earthquake response of a structure. A fifteen-storey 3D building has been modeled using Incremental Dynamic Analysis )IDA (under 20 seismic records that are selected to match the seismological specifications of Syria country. Eleven different scales were used for each seismic record, and a force-displacement curve was derived to determine the necessary parameters and calculate the seismic response modification factor. These values were then compared with the values of the Syrian and American codes, and differences in decreases by 35% were observed relating to the eccentricity ratio 42%. These differences vary according to the eccentricity ratio and torsional effects in these systems. Therefore, it is recommended to use a dimensionless factor that considers the effect of the torsion ratio on the response modification factor instead of using a fixed value for the R factor as stated in the codes.