Assessment of Seismic Response Reduction Factor According to Redundancy of RC Buildings

Abstract

The major task for the present study is to assess the seismic response reduction factor (R factor) of RC frames. Seismic codes combine the nonlinear response of a structure by the regulation of a factor which is called (Response reduction factor) “R”. We know that the actual earthquake force or earthquake intensity is incredibly higher than what we design the structures for. The structures cannot be designed for the actual value of earthquake intensity as the cost of the structures will be much high. The actual intensity of earthquake is reduced by a factor called response reduction factor R. Basically the R value is depending on ductility factor, strength factor, structural redundancy and damping. The strength factor depends upon the over strength of material used in construction, where Damping on normal RCC damping. IS Code subsumes ductility in a hazy aspect, for OMRF (not ductile detailed) R factor is 3, for SMRF (Ductile detailed) it is 5.But code is speechless on redundancy of structure. A parametric study is performed to assess the effect of redundancy in ductile reinforced concrete (RC) buildings and the studied variables were the number of bays. Nonlinear static analysis or also called pushover analysis is conducted on the analytical models using SAP 2000 software which is basically a finite element analysis software. The Response reduction factor components are calculated from the results gained from the nonlinear static pushover analysis (pushover curve) and lastly the response reduction factor is computed for all the models. The results obtained from the entire calculations show that for buildings with low redundancy, Seismic response reduction factor 5, given in IS1893-2016 is overblown. As a result it minimizes the earthquake forces on such buildings