The earthquake resistant design of structures requires that structures should sustain, safely, any ground motions of an intensity that might occur during their construction or in their normal use. However ground motions are unique in the effects they have on structural responses. The most accurate analysis procedure for structures subjected to strong ground motions is the Push over analysis. Pushover analysis is based on the assumption that structures oscillate predominantly in the first mode or in the lower modes of vibration during a seismic event. This leads to a reduction of the multi-degree-of-freedom, MDOF system, to an equivalent single-degree-of- freedom, ESDOF system, with properties predicted by a nonlinear static analysis of the MDOF system. The ESDOF system is then subsequently subjected to a nonlinear time history analysis or to a response spectrum analysis with constant-ductility spectra, or damped spectra. The seismic demands calculated for the ESDOF system are transformed through modal relationships to the seismic demands of the MDOF system. In this study the seismic behaviour of a frame building has been analysed by using push over analysis. The seismic performance evaluation of the building has been carried out by changing the sizes of the columns and also by replacing the rectangular columns with the circular columns. Static type of pushover analysis is to be used in this research work where the loads consist of permanent gravity loads and incremental horizontal forces at each storey level. Capacity curves (base shear versus story total drift) obtained from static pushover analysis using commercially available software called Etabs (Etabs 2015) are used for the calculation of some seismic demand parameters. The dimensions of the buildings have been kept constant and only the column sizes have been changed. Three different combinations of the rectangular column dimensions are taken and the non linear response of each is evaluated by using the pushover analysis. The rectangular columns are then replaced with the circular columns of suitable dimension. The buildings are designed for the gravity and seismic loadings as per IS 456: 2000 and IS 1893: 2002.