A method for calculating the reinforcement of RC annular columns by hand

Purpose To calculate the bearing capacity of annular reinforced concrete (RC) columns, if the second-order effects of members under bending and axial forces are further considered, both the nominal curvature method and the nominal stiffness method in EC2 require iterative calculations. To obtain a non-iterative calculation method. Design/methodology/approach The constitutive relationship of RC in EC2 is adopted, the known cross-sectional strain is used to determine the bearing capacity of the section, and the model column method is adopted to calculate the component’s second-order effect. The curvature distribution law of the equilibrium point of sectional resistance and external action is analysed, and the simplified formula for calculating the equilibrium curvature is proposed. Findings Based on the above work, a nomogram is drawn to determine the bearing capacity of columns. Finally, the nomogram and numerical calculation results are compared through specific examples. The results show that the nomogram is very close to the numerical calculation and always leans towards safety. It can serve as a supplement to the code and provide a method for the design and verification of annular columns. Originality/value A method for calculating the reinforcement of RC annular columns by hand.