Effect of Irregularities on Seismic Performance of Building

Abstract

During an earthquake, failure of structure starts at points of weakness. This weakness arises due to discontinuity in mass, stiffness and geometry of structure. The structures having this discontinuity are termed as Irregular structures. Irregular structures contribute a large portion of urban infrastructure. The irregularity in the building structures may be due to irregular distributions in their mass, strength and stiffness along the height of building. Irregularities such as mass, stiffness, plan, and torsion are one of the major reasons of failures of structures during earthquakes. So, the effect of these four irregularities in the seismic performance of structures becomes really important. Height-wise changes in stiffness and mass render the dynamic characteristics of these buildings different from the regular building. When such buildings are constructed in high seismic zones, the analysis and design become more complicated. There are two types of irregularities vertical and plan irregularity as per IS 1893(part 1):2016. The behavior of the multi-storey building of regular and irregular design under earthquake is problematical, and the variations of wind loads are implicit to act consecutively with earthquake loads. In the proposed project, a multi-storey (G + 4) RCC buildings with four irregularities (stiffness, mass, plan, torsion) are studied for earthquake and wind loads using response spectrum method (dynamic analysis) and STADD PRO. These analyses are carried out by considering seismic zone IV, and the behavior assessed by taking the Medium Soil. In this study effects of different irregularities are analysed based on storey displacement, storey drift, and storey shear.