Review of the torsional coupling of asymmetrical wall-frame buildings

Abstract

Significant dynamic torsional amplifications are known to occur in asymmetrical buildings when subject to earthquake excitations. The torsional effects are commonly taken into account in design by applying an eccentric triangularly distributed horizontal force in the static analysis of the building. To determine suitable effective eccentricities of such a quasi-static load, extensive studies have been carried out on the torsional response characteristics of singlestorey building models. For uniform multi-storey buildings which have the centre of mass (CM) and centre of stiffnesses (CS) vertically aligned, the quasi-static procedure is generally considered to be very reliable in estimating the dynamic torsional effects. However, extrapolating this static procedure to multi-storey buildings does not account for complex dynamic response and therefore needs clarification. This paper demonstrates, using examples, the fundamental problem of using static procedures based on a single-storey model to estimate dynamic torsional effects in multi-storey wall-frame buildings.