Influence of Cross-Sectional Size on Seismic Performance of Reinforced Concrete Columns

Current ACI code provisions (ACI 318-14) for the design of reinforced concrete (RC) columns are based on previous experiments on column specimens that featured smaller cross-sectional dimensions compared to those currently used in mid- or high-rise buildings. A study on a database of RC columns, including those recently tested at the MAST Laboratory of the University of Minnesota and the ACI 369 Rectangular Column Database, suggests that flexural moment capacity, drift ratio capacity, and displacement ductility of columns are not generally affected by column dimension (that is, cross-sectional depth). However, longitudinal bar buckling can start earlier in larger columns. Additionally, observations from the MAST tests reveal a bar buckling mode that is seldom observed in tests on smaller columns, in which the bars buckle parallel to the face of the column. A simple study suggests that larger columns are more prone to this in-plane mode of bar buckling.