Structural Behaviour of Multi-Storey Buildings with Circular and Rectangular Columns under Earthquake Loads

Abstract

Moment-resisting frames (MRF) of reinforced concrete (RC) are the most popular structural system for multi-storey construction in seismically active zones and the size and shape of the columns have significant impact on the seismic performance of the MRF structure. The paper presents a comparative nonlinear static (pushover) analysis of a ten-storey (G+9) RC moment-resisting frame with six different types of cross-sectional area of the columns, three rectangular cross sections (450×600 mm, 500×600 mm and 550×600 mm), and three circular cross sections (250 mm, 300 mm and 350 mm). All the other geometric and material parameters were kept constant and shape and size of the columns were the only variables. The nonlinear static pushover analysis was performed based on the Indian seismic design provisions in ETABS, and seismic demand parameters were estimated by equivalent linearisation method developed by FEMA-440. The results of the Storey shear, Storey drift and Storey displacement indicate that the circular column configurations always have lower base shears than the rectangular column configurations of similar size, and storey drift and storey displacement are marginal, while equivalentlinearization performance points are more favourable. The six base-shear and storey-shear profiles in the above comparison confirm this tendency at all three size pairings, and show that circular columns have a slight seismic performance benefit over the rectangular columns in multi-storey RC frames