Approximate calculation of circular reinforced concrete columns with nomograms

Abstract

Calculating the reinforcement of circular reinforced concrete (RC) columns involves not only the dual nonlinearity of the geometry and material but also the nonlinearity of the section width. Accurate solutions require iterative calculations. To develop the calculation method manually, the model column method was proposed to compute the second-order effect of the columns, and the strain method was used to calculate the ultimate strength of the sections analytically. The nomograms required to calculate the reinforcing steel content of the columns without iterations were obtained. The nomogram for calculating the section bearing capacity and reinforcing steel has three parameters (axial force, bending moment, and mechanical ratio of the reinforcing steel). Further, the nomogram for calculating the column bearing capacity and reinforcing steel has five parameters (axial force, bending moment, curvature, slenderness ratio, and mechanical ratio of the reinforcing steel), and the relationship between the five parameters can be expressed in a plan, which makes the application convenient. Finally, the calculation results of the nomograph were compared with those of the existing approximate calculation formulas and exact numerical methods, and the accuracy of the nomograms was verified.