Behavior of channel-shaped reinforced concrete columns under combined biaxial bending and compression

The inelastic behavior of irregular shaped reinforced concrete columns has been a constant concern for a structural engineer, to design a safe and economic structure in modern buildings and bridge piers. The shape of the elements in a reinforced concrete structure may be used to optimize its structural strength, to make better use of the available space, to improve the aesthetic appearance of the structure, or to facilitate construction. Due to the locations of the columns, the shapes of the buildings and the nature of the applied loads, many columns are subject to combined biaxial bending and axial load. Seven 1/4 scale direct models of the short, tied columns with channel-shaped cross sections were constructed for the present investigation. All the specimens were tested and studied for their complete strength and deformation behavior under combined biaxial bending moments and axial compression, and were used to examine some of the variables involved such as relative eccentricities and loading variations. The end conditions are assumed to be pinned-ended. The experimental load-strain and biaxial moment-curvature curves have been compared with the analytical results of the strength and deformation for biaxially loaded channel-shaped column members, and a satisfactory agreement was obtained from zero up to the ultimate load condition. The above inelastic behavior of channel-shaped reinforced concrete columns has formed the basis of the redistribution of the moments and forces in a statically indeterminate structure, and these characteristics can also be found useful for the limit analysis and design of reinforced concrete structures