Seismic Analysis of Torsional Irregularity in Multi-Storey Symmetric and Asymmetric Buildings

Abstract

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