Nonlinear Static-Oriented Pushover Analysis of Reinforced Concrete Columns Using Variable Oblique Finite-Element Discretization

Abstract

A fast converging and fairly accurate nonlinear simulation method to assess the behavior of reinforced concrete columns subjected to static-oriented pushover force and axial loading (sections under biaxial-bending moment and axial loading) is proposed. In the proposed method, the sections of column are discretized into “Variable Oblique Finite Elements” (VOFE). By applying the proposed oblique discretization method, the time of calculation is significantly decreased, and since VOFE are always parallel to neutral axis, a uniform stress distribution along each oblique element is established. Consequently, the variations of stress distribution across an element are quite small which increases the accuracy of the calculations. In the discretization of section, the number of VOFE is significantly smaller than the number of “Fixed Rectangular Finite Elements” (FRFE). The advantages of using VOFE compared to FRFE are faster convergence and more accurate results. The nonlinear local degradation of materials and the pseudo-plastic hinge produced in the critical sections of the column are also considered in the proposed simulation method. A computer program is developed to calculate the local and global behavior of reinforced concrete columns under static-oriented pushover and cyclic loading. The proposed simulation method is validated by the results of tests carried out on the full-scale reinforced concrete columns. The application of the “Components Effects Combination Method” is compared with the proposed “Simultaneous Direct Method” (SDM). The obtained results show the necessity of applying SDM for nonlinear calculations. Especially, during the post-elastic phase, which occurs frequently during earthquake loading.