DYNAMIC RESPONSE OF IRREGULAR MULTISTOREY BUILDINGS

Abstract

The objective of present work is to study dynamic response of irregular multistorey buildings. Two G+7 Buildings (approx floor area of 1000 m2) having plan irregularity have been designed as per Indian Standards. Twenty five different load combinations have been considered while designing the buildings. Sixteen models were prepared by varying earthquake loads with and without accidental torsion, strong column weak beam concept and location of shear wall. Response spectra analyses have been carried out for seismic analysis of buildings. All these buildings were considered in seismic zone IV. Pushover analyses have been carried out to study the demand capacity of buildings and thirty four cases were investigated on five 3-D buildings and eight 2-D frames. Performance point of building having shear wall at outer periphery is higher than those having shear wall at interior. Failure load and roof deflection in buildings designed by strong column weak beam concept is more than normally designed buildings. Buildings fail at lower loads and undergo less deflection when the eccentricity in lateral load increases. Buildings with shear wall at outer periphery are more efficient in resisting the accidental torsion in earthquake loading. The maximum storey drift in building having shear wall at outer periphery is lesser in magnitude (0.05% of storey height) compared to those storey drifts in buildings having no shear wall and shear wall at interior (0.08% of storey height). The strong column weak beam concept requires more percentage of longitudinal steel in vertical members (average 1.31%) as compared to normally designed column (average 1.81%). The difference of percentage of longitudinal steel required by strong column weak beam concept and normally designed columns is lesser in magnitude with buildings having shear wall at outer periphery, medium in building having no shear wall and higher in building having shear wall at interior. ETABS v9.2.0 is a sophisticated special purpose analysis and design program developed specifically for building systems. Various options in ETABS are understand and validated such as live load distribution on slab, wind loads as per IS 875 (part III) : 1987, etc. At present, ETABS does not conform to IS 13920: 1993.