A Parametric Study on Torsionally Coupled Base-Isolated Structures

Abstract

Extensive studies on the behaviour of base-isolated symmetrical structures have been carried out everywhere throughout the world. However, limited work has been reported on behaviour of base-isolated asymmetric structures. Because of torsion of stories in asymmetric structures, destructive effects on structures arise, during the earthquake. Consequently, on the grounds that asymmetric structures are progressively helpless against seismic burdens, researchers have given more consideration to the behaviour of such structures. In structures, mass asymmetry is typically present at various floor levels. This mass asymmetry might be because of water tank given at top of the structure, any overwhelming weight machine set at any floor level, etc. Because of this mass asymmetry in structure, the centre of mass does not correspond with the centre of stiffness causing unusualness. As the eccentricity increases, displacement and the torsion in the building will also increase (Colunga 2002). In this paper, torsionally coupled base-isolated buildings of different heights have been analysed for different spectrum compatible time histories of different code standards. A parametric study is presented and is very helpful to define base-isolated structures having torsional irregularity. The empirical equations obtained for structures are useful in estimating the displacement of the asymmetric structure, and further, it is useful for the adjustment required in the stiffness of base-isolated buildings so as to neutralize the effect of torsion.