Seismic Evaluation of RC Building with Vertical Setbacks as per IS1893 (Part 1):2016

Abstract

Earthquake forces are the least predictable and most devastating form of forces. These forces are not only responsible for loss of economy, property and material but possess a huge threat to lives of people as well. In past several years, severe damages to buildings and causalities have been witnessed due to these disastrous forces there by challenging the designing and construction authorities. Many buildings are designed with vertical setbacks due to architectural, functional or economic reasons wherein fewer stories in a building are wider than rest of the building. Such setbacks in buildings cause sudden jump in seismic forces at the level of discontinuity due to change in stiffness, mass and strength distribution along height. This might lead to torsion in the building under seismic forces. Structures incorporating vertical irregularities need to be studied for their behavioural aspects, identifying the weak links which might trigger the collapse. In the present study, effect of vertical geometric irregularities in a building is studied with respect to a regular building using equivalent static method and response spectrum method as per IS1893 (Part 1): 2016. The results obtained are compared in terms of displacements, storey drift, base shear, forces, modal time period, modal mass participation factor and % increase in structural members along with concrete quantity.