Finite Element Method for Uniaxially Loaded RC Columns

A method based on finite element technique is presented for the analysis of braced and unbraced columns. This method considers nonlinear behavior of reinforced concrete columns arising out of material nonlinearity and large displacements. The method consists of several special features. It uses a single beam‐column element with five degrees‐of‐freedom (i.e. two end rotations, two end deflections, and one deflection at mid‐length position). Analytical integration leading to closed form solution is used to evaluate the contribution of concrete area to the axial load and moment acting on the cross section. The iterative method which is used for solution of nonlinear equations is based on modified Newton‐Raphson technique. This method determines the loaddeflection response including the drooping branch. Convergence is ensured by resorting to Aitken's delta square extrapolation technique. This method is verified against available solutions and is found to be satisfactory. This method can deal with columns under all possible combinations of uniaxial (proportional)loading and end conditions (pin‐ended, braced, and unbraced).