Analytical Modelling Strategies for Performing Seismic Evaluation of Open Ground Storey RC Buildings Located in Medium Seismic Zone of India

Abstract

AbstractIn this paper, authors have made an attempt to bring out the possible limitations in the analysis, design and seismic evaluation of Open Ground Storey (OGS) buildings in urban India and have suggested a suitable modelling strategy to be adopted in nonlinear analysis for satisfactory performance at demand earthquake. Nonlinear Time History (NTH) and Nonlinear Pushover analyses (NSP) are performed on 10-storeyed OMRF RC building located in medium seismic zone designed as per IS codes for DBE. NTH analysis was carried out to get useful insights on the results predicted by NSP analysis on the performance evaluation of OGS building model studied. Peak responses in terms of base shear, roof displacements and hinge status were studied for the model for each scenario. It was concluded that NSP analysis, which is the currently preferred method for performance evaluation, overestimates the base shear by 20% and underestimates the roof displacements by 20–40%. This clearly implies that NSP analysis tends to overestimate the building strength by 20% compared to NTH analysis in the present study. The hinge status showed that NSP analysis predicts severe damage like CP and LS in some of the frame elements, while it shows conservative estimate of performance levels in other elements compared to the results obtained from NTH analysis. It is therefore important to remember that results of NSP are conservative when that method is used for performance analysis. It is also observed that prediction of performance levels in NSP and NTH analyses depends on nonlinear properties of frame elements in the structure, quantified by strength and deformation capacities, which depend on modelling assumptions depicted in each scenario.KeywordsPushover analysisPerformance-based designSeismic evaluation