Flexural strength enhancement of confined reinforced concrete columns

As part of a continuing research study, this paper proposes a new design aid to calculate the actual moment capacity of confined reinforced concrete columns. Up to now the moment capacity of a reinforced concrete column is calculated based on the code's guidelines for an unconfined section. As most reinforced concrete columns contain transverse or confining reinforcement, which will enhance the column moment capacity, the actual moment capacity will be much higher than the unconfined moment capacity. This additional flexural strength will increase the shear force demand in the column, and if it is not accounted for in the design will jeopardise the column to fail in shear. In this study the actual moment capacity of a confined reinforced concrete column is obtained by multiplying the moment capacity calculated using the BS 8110 method with the proposed flexural strength enhancement factor. By using regression analysis, an equation for the flexural strength enhancement factor is derived as the function of all the parameters that have effects on the moment capacity. An example is presented to show the accuracy of the proposed method.