An exact analysis is carried out utilizing the stress-strain curve for concrete confined by circular hoops and a typical idealized stress-strain curve for steel to develop the moment-curvature relationship for reinforced concrete (RC) circular column sections. Based on that, the flexural rigidity EI of the section is determined at the yield curvature. A computer program is written in Fortran 77 to handle the required computations. The influence of material properties, the effect of steel ratios and the impact of axial loads on the EI estimation were investigated. This study leads to the development of a new equation to estimate the flexural rigidity EI of RC circular columns in which these factors were considered. It is shown that the new equation stems from the actual behaviour of the column. Therefore, it is recommended for general use in the design of slender columns.
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