Effect of Vertical-Stepped Geometric Irregularity on the Seismic Performance of Buildings

Nowadays, irregular-stepped buildings are increasing in our modern construction due to serviceability and aesthetic reasons, and these type of structures show high vulnerability during an earthquake event because of their vertically geometric irregular configuration. The Indian IS code 1893:2016 (Part-1) suggests that the irregular buildings that are in Seismic Zones III, IV, and V analysis should be done by following the dynamic procedure. This study deals with the influence of offset distance on seismic factors such as storey drift, base shear and deflection. The aim of this study is to reflect the effect of setback ratios due to various vertical geometric irregularities (i.e. different offsets) on seismic factors of a 15 storied (G + 14) R.C building. Nine frames with different setback ratios, i.e. 0.25, 0.3125, 0.375, 0.4375, 0.5, 0.5625, 0.625, 0.6875 and 0.75 are modelled using STAAD Pro. Software. To study the behaviour of the irregular structures, both equivalent static method and dynamic analysis is carried out as per IS code 1893:2016 (Part-1) and used to evaluate the structures. This study shows the behaviour of vertical irregular structure under lateral load, especially seismic load. It is concluded that geometrically irregular buildings are more vulnerable to earthquakes and proper care should be taken in design of these buildings.