A Study on Mass Irregularity Limits of RC Structures for Various Seismic Zones of India

Abstract

The performance of any structure under lateral loads depends on its structural configuration. Most of the codes worldwide mentioned the provisions for the lateral load analysis for regular structures. Structures may be irregular in practice due to uneven distributions in mass, stiffness and strength. In India, most common type of multi-storied apartments constructed varies from 5 to 15 storeys and many apartments are constructed with penthouse which creates mass irregularity in the structures. The present study investigates the performance of mass irregular structures which are created by providing penthouse and also modeled as a stepped setback structure. Total four structures, 5, 7, 11 and 16 storied with an aspect ratio (height to width of the structure) of 0.64, 0.88, 1.36 and 1.96 are considered. For each structure response spectrum analysis is carried and the response parameters like storey displacements, storey drift and base shear variation in 4 seismic zones of India is studied. The main focus of the investigation is to understand the acceptance of mass irregularity with respect to the aspect ratio of the structure. The acceptance limit of the mass irregularity is also investigated as per 4 seismic zones of India. The results are compared with Indian standard code limits and concluded the acceptance limit as per seismic zones of India.