Effect of in-plan eccentricity on vertically stiffness irregular buildings under earthquake loading

Abstract

A regular building happens to be an idealized concept since real buildings have numerous discrepancies or ir-regularities along the height or along the planar directions. These buildings under the effect of wind, earthquake, or other dynamic loads, exhibit torsional behavior attributed to the significance of the higher modes of vibration. The present study evaluates the seismic responses of buildings with an integration of vertical stiffness irregu-larities as well as in-plan eccentricity in stiffness distribution. Transient analysis was carried out on three dimensional building frames with stiffness irregularities in plan as well as along the height by subjecting them to seismic loading and the torsional response of the irregular configurations were assessed in terms of the variations in natural period, base shear, roof deflection, roof rotation and storey drifts. Soft storey at the base of the building is the most critical case which when combined with the in-plan stiffness eccentricity has the most adverse effect on the seismic behavior of the buildings. A new coefficient to quantify the irregularity in a vertically stiffness irregular building based on its geometrical dimensions, in-plan stiffness eccentricity and location of stiffness irregularity along the height has also been proposed.