Effect of Seismic Zone and Story Height on Response Reduction Factor for SMRF Designed According to IS 1893(Part-1):2002

Abstract

Indian seismic code design procedure, which permit the estimation of inelastic deformation capacity of lateral force resisting systems, has been questioned since no coherence exists for determining the values of response reduction factor tabulated in code. Indian code at present does not give any deterministic values of ductility reduction factor and overstrength factor to be used in the design, because of the inadequacy of research results currently available. Hence, this study focuses on the variation of overstrength and ductility factors in steel moment resisting frame with different seismic zones and number of story. A total of 12 steel moment resisting frames were analyzed and designed. Response reduction factor has been determined by performing the non-linear static pushover analysis. The result shows that overstrength and ductility factors varies with number of story and seismic zones. It is also observed that for different seismic zones and story, ductility reduction factor is found to be different from overall structural ductility. It is observed that three buildings of different heights had an average overstrength of 63% higher in Zone-II as compared to Zone-V. These observations are extremely significant for building seismic provision codes, that at present not taking into consideration the variation of response reduction factor.