Effect of Shape Irregularity on Flat Slab Building under Lateral Loading

A flat slab is a reinforced concrete slab supported directly by concrete columns without the use of beams. Reinforced concrete flat slabs are one of the most popular floor systems used in residential buildings, car parks and many other structures. They represent elegant and easy-to-construct floor systems. Flat slabs are favored by both architects and clients because of their aesthetic appeal and economic advantage. Now taking into consideration the Earthquake is one of the natural disasters which the world is facing time to time. Based on previous earthquakes data, loss of human lives and properties which ultimately affects the national economy. The structure should possess namely simple and regular configuration, adequate lateral strength, stiffness and ductility to accomplish well under Earthquake. Structures with simple regular geometry and uniformly distributed mass and stiffness in plan as well as in elevation are considered to suffer much lesser damage than structures with irregular forms. But nowadays, irregular buildings are preferred due to their functional and aesthetic considerations are evident from examples of realistic existing irregular buildings. As per IS 1893(part1):2002 enlists the irregularity in buildings. These irregularities are categorised as follows 1) Vertical irregularities referring to sudden change of strength, stiffness, geometry and mass results in irregular distribution of forces or distribution over the height of the building. 2) Plan irregularities which refer to asymmetrical plan shapes (L-,T-,U-,F-) or discontinuities in the horizontal resting elements (diaphragms) such as cut-outs, large openings, re-entrant corners and other abrupt changes resulting in torsion, diaphragm deformations and stress concentration. Present work is carried out to investigate the performance of irregular flat slab with column drops subjected to lateral loads i.e, earthquake and wind loads in seismic zone V soil type III using ETABS 2015 Software. The study is restricted to diaphragm discontinuity and vertical discontinuity. The flat slab building is analyzed for models with a regular plan without any discontinuity, model with Re-entrant corners, model with Re-entrant corners L-shape, model with vertical irregularity on one side, model with vertical irregularity on two side, model with rectangular shape as diaphragm discontinuity, model with inverse T as diaphragm irregularity. Linear static and dynamic analysis is performed for seismic forces and the building is also analyzed for wind loading. The effect of irregularity on the flat slab building is examined for various parameters.. The main parameters considered in the study are Base shear, Time Period, Lateral displacement and Storey drift. Present study provides a good source of information on all the parameters considered. Conclusions are woven based on the obtained results.