Effects of the intensity of design live load on the seismic design modification factors of reinforced concrete frames

Abstract

Seismic design modification factors that include the response modification factor (R), the overstrength factor (Ω), and the displacement amplification factor (Cd) play a significant role in the seismic design of structures. The recommended values for these factors in seismic design codes are empirical and do not account for the differences in the intensity of the design live load in structures. This study investigates the change in the value of these factors as a result of the change in the intensity of the design live load. For this purpose, eighteen reinforced concrete frames with the different number of stories and ductility classes were designed and analyzed. Nonlinear static analysis was used to calculate the capacity curve of frames and their seismic response modification factors. Results indicated that the values of Ω and Cd for both low and high-ductile reinforced concrete frames decreased slightly as the intensity of design live load increased. An increase in the intensity of the design live load increased the R-factor in the high-ductile RC frames.