Evaluating the Response Modification Factors of RC Frames Designed with Different Geometric Configurations

The response modification factor (R-factor) of reinforced concrete (RC) moment resisting frames (MRFs) designed with adequate ductility in accordance with the Egyptian code is evaluated. Static pushover and earthquake time history analyses are employed to determine the actual R-factors of nine RC-MRFs with different geometric configurations. The geometric configuration parameters considered include the number of stories, the number of bays, the bay-width and the story height. The results obtained in this study indicate that the R-factor value decreases with the increase in the frame height and that the changes in the number and span of bays have a minor effect on the R-factor. The R-factors calculated by earthquake analysis are generally smaller than the corresponding values calculated by static pushover loading. The R-factors calculated for the frames considered in this study vary from 6.18 to 9.85 in case of static analysis and from 5.43 to 8.43 in case of earthquake analysis. The minimum limit of the calculated R-factors is smaller than the R-factor of seven specified by the Egyptian code for the design of RC-MRFs with adequate ductility.