---------------------------------------------------------------------***--------------------------------------------------------------------Abstract The conventional slabs have proven to be heavy structures, with larger depths of beams covering most of the storey height. The flat slabs have been replacing the conventional slabs due to their functional and aesthetical advantages. The use of flat slabs in structures has lead to reduction in storey height, ease of construction and cost effective technology. However, the higher flexibility of flat slabs has resulted in their inability to sustain earthquake loads. The present study involves the evaluation of the nonlinear seismic behaviour of various flat slab structures when circular columns are provided. Specific investigation on the behaviour of seven storey building models is considered. All the buildings are assumed to be located in seismic zone III. The medium soil stratum is chosen for the study. The buildings are modelled as bare frame and brick infill frame models. The pushover analysis is performed considering parameters of FEMA 440, with user defined hinge properties. The analysis is performed using ETABS 2013 V13.2. The hinge status, ductility ratio, safety ratio and global stiffness are studied to assess performance of the models.