NON-LINEAR SEISMIC ANALYSIS OF RC MULTI-STOREY BUILDINGS

Abstract

Present era of fast development requires accommodation of large population under one single roof. Therefore, the reliability of multi-storey buildings against the natural calamities like earthquakes is of serious concern. In order to ensure the safety of the buildings and its occupants, properly justified and reliable analysis method and design philosophy should be adopted. From the past earthquakes, it has been observed that the structures which were not properly analyzed, designed and constructed considering earthquake loads did not perform well. Therefore, approximate analyses methods for seismic loads do not seem to be sufficient for the safety of structures. Hence, non-linear beahviour (i.e., degradation in strength and stiffness) need to be incorporated in the analyses of the structures under earthquake loading. In the present study, the seismic performance of six storey (G+5) reinforced concrete (RC) frame buildings with and without consideration of URM infills, has been evaluated by non-linear static as well as dynamic analyses procedures at maximum considered earthquake (MCE) level of seismic hazard. The buildings have been modelled as bare frames (BF-1 and BF-2) as well as frames with infills modelled by compression only struts of different configurations i.e., eccentrically braced infilled frame (EBIF), concentrically braced infilled frame (CBIF) and both eccentrically and concentrically braced infilled frame (BECBIF), in order to obtain a suitable configuration for better infill-frame interaction. Infills have been modelled as multi-linear plastic tie links with the pre-defined force-displacement relationship and hysteresis models. Strong column and weak beam (SC-WB) design philosophy have been adopted for designing of RC frames in this study. It has been observed that, URM infills and its configuration effect the time period, and the seismic performance. The failure mechanism of all frames was noticed to be in accordance with failure mechanism expected for SC-WB design philosophy. At DBE, all frames have been found to be in elastic region while at MCE, though the infilled frames (viz. EBIF, CBIF and BECBIF) remained in elastic region while the bare frames (BF-1and BF-2) reached to ‘IO’ and ‘LS’. For EBIF, responses from non-linear static and dynamic analyses have been found in the least agreement while for BECBIF better agreement has been observed.