Verification of irregularities in a reinforced concrete tall structure

Building plans with simple, regular and compact arrangements are preferred to perform well during the occurrence of earthquakes. In practice, planning a regular layout may not be possible in all occasions due to irregular shape of building sites in the plan as well as in elevation due to uneven ground conditions. It is a challenge both for the architect and structural designer to plan and design such buildings. Further, the planning is to be made in compliance with the rules and regulations of the local approving authorities, which sometimes may lead to irregular shapes both in plan and elevation. Most of the times, the owner’s and / or builder’s requirement is to be fulfilled such that the project is viable to them. This is a challenge for the practising professionals designing the structures that are built in earthquake zones of III, IV and V. The earthquake resistant design code i.e., IS 1893 (Part 1) was revised in the year 2016 and adopting the provisions of building irregularities with more restrictions on their allowable limits. This paper addresses the identification or verification of the existence of building irregularities in a 17 storey multipurpose tall structure with two parking, two commercial and 13 residential floors. From the results, it is opined that there is a need for a review of the procedure and some of the limits set on irregular building configurations particularly Stiffness, Excessive openings, Out-of-plane offsets, Strength, In-plane discontinuity and Irregular modes of oscillation.