Comparative Seismic Performance Analysis of Rectangular and Circular Columns: Effects of Replacing Rectangular Columns with Circular Columns in RC Structures

Designing earthquake-resistant structures necessitates ensuring their safety throughout both the construction phase and their operational lifespan, regardless of the intensity or frequency of seismic events. Ground motion effects are particularly complex due to their dynamic and multifaceted impact on structural behaviour. Among the various analytical techniques available, pushover analysis is considered one of the most dependable for evaluating a structure's response to intense seismic forces. This approach is based on the assumption that during seismic events, buildings predominantly respond in their fundamental or lower vibration modes. Therefore, a multi-degree-of-freedom (MDOF) system can be effectively transformed into an equivalent single-degree-of-freedom (ESDOF) model. This ESDOF model is derived using nonlinear static analysis and subsequently subjected to nonlinear time history or response spectrum analysis utilizing constant-ductility or damped response spectra. The seismic demand parameters obtained from the ESDOF model are then mapped back to the MDOF system through modal transformation techniques. In this research, the seismic behaviour of a moment-resisting RC frame structure is analyzed using the pushover method. The study focuses on the effect of changing column shapes and sizes, specifically replacing rectangular columns with circular ones, to assess variations in seismic performance. The static pushover approach incorporates both constant gravity loads and incrementally applied lateral loads at each story level. Capacity curves, illustrating the relationship between base shear and total story drift, are generated using ETABS 2015 to extract critical seismic response parameters. Throughout the simulation, the overall plan dimensions of the building are maintained constant, while only the column dimensions are varied. Three sets of rectangular column sizes are examined for their nonlinear seismic response and subsequently compared with equivalent circular columns. All structural models are designed following the provisions of IS 456:2000 for concrete design and IS 1893:2002 for seismic loading conditions..