Effect of in-plan eccentricity in vertically mass irregular RC framed buildings under seismic loads

Abstract

Multi-storey buildings with complicated geometry and structural systems are common due to various possibilities offered by advanced construction methods. When these irregular buildings are subjected to lateral loads such as wind or earthquake, torsional effects become significant. The present study aims to evaluate the seismic response of vertically irregular multi-storey RC buildings of varying aspect ratios with different location of masses along the height and also with a stipulated amount of in-plan eccentricity. For this, building frames up to 15 storeys height incorporating an integration of vertical and in-plan eccentric masses are subjected to earthquake loads. Transient analysis is carried out by subjecting the three dimensional finite element models of building frames to El-Centro ground motion and the torsional behavior is evaluated in terms of variation in base shear, fundamental natural period, roof deflection and floor rotation. The results show that the in-plan eccentricity of the mass irregularities has least influence on the seismic response when irregularities are present in the lower half of the frames. The study proposes a parameter to quantify mass irregularity with respect to its location and in-plan eccentricity in the vertically irregular building.