INTERACTION DIAGRAMS FOR RECTANGULAR COLUMNS WITH HIGH STRENGTH CONCRETE

High strength concrete (grades higher than M55) results in smaller sizes of columns leading to the availability of higher floor spaces. Compared to concrete grades of M55 and less, high strength concrete undergoes lesser strains for the same stress. Hence, use of high strength concrete in members will result in reduction in deflections and sway. The use of high strength concrete is increasing in the construction of high-rise buildings, industrial buildings and long span bridges. Design aids in the form of interaction curves are an inevitable requirement for the design of columns subjected to axial load and bending moment. Availability of interaction diagrams for columns made of concrete grades beyond M55 is scarce. Considering this requirement, an attempt is made in this paper to suggest a systematic step by step procedure to formulate interaction curves for concrete grades above M55. In this paper, mathematical expressions have been derived for rectangular columns with reinforcement equally distributed on two sides. As the procedure suggested involves iterative computations using a systematic approach, it is well-suited to be developed as a computer program.The typical output of such a program has been validated and presented for M70 concrete, Fe-500 grade of steel and, dʹ/D = 0.05, in the form of interaction curves. © 2022, Associated Cement Companies Ltd.. All rights reserved.