ANALYSIS OF SEISMIC BEHAVIOUR OF IRREGULAR STRUCTURES

Abstract

A structure can be categorised as irregular, if it contains uneven distributions of mass, stiffness and strength or due to irregular geometry. Most structures contain irregularity due to functional and aesthetic reasons. One of the significant reasons for a structure’s collapse from past earthquakes, is the irregular configuration of the building either in plan or elevation as the performance of a building during a seismic event primarily depends on its configuration. Thus, irregular structures situated in highly seismic zones are a matter of concern. Structures do not always contain single irregularity but may contain combination of structural irregularities. The choice of type, location and degree of irregularity is crucial in the design of structures. IS code 1893 (part1) 2016 recommends that all efforts should be made to remove irregularities by revising architectural planning and structural configurations. However, in structures the concept of “perfect regularity” is just an idealisation as real structures contain irregularity necessitated due to various needs and demands and also constitutes a large portion of modern urban infrastructure. Hence irregularities in a structure has become inevitable and the current study aims to incorporate irregularities in a structure without compromising the performance. A G+7 storey regular building RC frame is modified by incorporating single as well as combined irregularities involving mass, stiffness, and vertical geometric irregularities. All the models are subjected to earthquake loading and the responses are computed using CSI ETABS software. The objective will be accomplished by comparing the responses of the various models by two methods of seismic analysis namely Response Spectrum Analysis and Pushover Analysis.