PERFORMANCE EVALUATION OF R.C. BUILDINGS USING NONLINEAR SEISMIC ANALYSIS

Abstract

Performance evaluation of a multistoreyed building located in high seismic zones provides a conviction regarding its behavior under a seismic activity. Nonlinear analysis, both static (Pushover) and dynamic (Time history), are used in the present study for evaluating the performance of a newly designed, 10 storey, reinforced concrete frame. ETABS 2013 software has been used for the elastic analysis, design and response evaluation of the frame using Pushover and Time history analysis. Performance evaluation of the frame was carried out by computing the demands imposed on the frame under the site specific earthquake response spectra as well as El Centro and Kobe accelerogram in terms of rotational and displacement ductility and the performance levels ascertained by comparing the same with the acceptance criteria of the different damage levels defined. The nonlinear static analysis was found to give very conservative results compared to the nonlinear dynamic analysis as far as the demand was concerned. This was attributed to the highly idealized mathematical model adopted for pushover analysis. The significance of applying ductile detailing based on IS 456 and IS 13920 codes to meet the demand ductility of a frame in seismic zone V and II was evaluated against an ordinarily designed frame confirming to IS 456 specifications by quantity estimation. It is observed that carrying out ductile design and detailing in R.C. buildings in Zone V is economical as ordinary designed frame accounted for 65% higher reinforcing steel as compared to ductile design and detailing. Same procedure carried out on Zone II established that ductile designed frame accounted for 6% higher reinforcing steel as compared to ordinary design and detailing, rendering the former uneconomical. The results were substantiated with nonlinear analysis by quantifying the demands imposed, hence checking the applicability of the economical design.