Nonlinear finite element modeling of reinforced concrete columns

Abstract

Analytical modeling of the lateral load response of reinforced concrete columns under reversed cyclic loading conditions is investigated in this study, using a relatively simple finite element model formulation developed originally for reinforced concrete walls. The objective of this analytical study is successful simulation of the lateral load response of RC columns, irrespective of whether the response and failure mode is flexure-controlled, shear-controlled or a combination of flexural and shear responses. The behavior of the constitutive panel elements in the finite element model formulation is based on a fixed-crack-angle modeling approach. Shear aggregate interlock stresses along cracks and dowel action on the reinforcing bars are considered in the model formulation. The model also incorporates rotational springs at the column-pedestal interface, in order to represent strain penetration effects on the reinforcing bars an chored within the pedestal. Regularization of the post-peak stress-strain behavior of concrete in compression was also conducted, using a simple methodology, to minimize strain localization effects in the analysis results. For calibration and experimental val idation of the model, column specimens tested as part of four experimental programs, with both flexure-controlled and shear-controlled responses, are used. Model predic tions are compared with test results for selected twelve column specimens with a variety of geometric properties, reinforcement configurations, loading conditions, and response characteristics. The model is shown to provide reasonably accurate response predic tions for the specimens investigated, in terms of lateral load capacity, drift capacity, stiffness, strength degradation behavior, and pinching characteristics. Based on com parison of model results with the test observations, model capabilities and limitations are identified.