A Critical Review of Displacement-Based Criteria for Torsional Irregularity of Buildings

Reckless construction of tall buildings and the ever-increasing demand of clients for an iconic/special shape for their building has only complicated the scenario of increasing seismicity worldwide. Apart from the inherent challenges taken up by engineers for ensuring a safe design, building codes are bracing for this situation with detailed guidelines on classifying buildings as irregular. This short communication paper reports the findings obtained as part of a larger study on torsional irregularity guidelines of Indian standard code, IS 1893(Part 1). The code in its revision from 2002 to 2016 introduced changes in criteria to check the torsional irregularity of buildings from its original drift-based criteria in the former to the displacement and mode of oscillation-based criteria in the latter. Analysis of 35 buildings (with a combination of circular and rectangular shapes) with stories ranging from 1 to 5 was performed using ETABS, and it was found that the guidelines of 2016 related to torsional irregularity have inherent deficiencies. The results of the study are presented with suggestions on the possible ways of correcting the guidelines.