Seismic analysis of torsional irregularity in multi-storey symmetric and asymmetric buildings

The torsion-induced failures are catastrophic for multi-storey buildings because torsional response of structure not only changes the uniform translational seismic floor displacement but also cause stress concentration and therefore it demands higher strength and ductility for structural members. A structure demonstrates weakness primarily due to discontinuous geometry, mass and/or stiffness and becomes prime source of failure during earthquake. The objective of present work is aimed at comprehensive understanding of the torsional behavior of building structural systems for symmetric and asymmetric buildings with plan irregularity. In symmetric structures center of mass and rigidity usually coincide with each other, hence torsion effect for such structures is due to accidental eccentricity; whereas asymmetric structures have irregular distribution of mass and stiffness that results in torsion and becomes most critical factor influencing the seismic damage of the structure. In present study, the performance of such structures is evaluated as per procedures described in prevailing codes of practice for significant parameters such as storey drift, base shear, maximum lateral displacement, natural time-period, frequency and modal mass participating ratio to have a comprehensive review on structural response for involved torsional irregularities.