Nonlinear finite element analysis of reinforced concrete columns: Evaluation of different modeling approaches for considering stirrup confinement effects.

The present study aimed to introduce an accurate modeling strategy for the three‐dimensional (3D) nonlinear finite element analysis of reinforced concrete (RC) columns considering the effects of the stirrup confinement. For this purpose, concrete columns with different geometric characteristics and various reinforcement details whose experimental test data are available, were analyzed using the finite element method. The concrete damaged plasticity (CDP) was used to model the nonlinear behavior of the concrete material in the compression and the tension. The ideal elastic–plastic constitutive law was utilized for modeling the behavior of longitudinal and transverse rebars. Through comparing the experimental data and numerical results, the effect of various parameters, such as the type of stress–strain relationships used for modeling the behavior of confined concrete and the type of element used to model the stirrups, were evaluated. Additionally, the sensitivity of numerical results against the CDP model parameters (i.e., the viscosity parameter, the flow potential eccentricity, the dilation angle, the ratio of biaxial compressive strength to its uniaxial compressive strength, and the ratio of the second stress invariant on the tensile meridian) were investigated. The results show that the presence and modeling of stirrups in the RC columns alone are not enough for capturing the effects of concrete confinement. The use of beam elements instead of truss elements for modeling the stirrups as well as the use of Vallenas stress–strain relations for modeling the uniaxial behavior confined concrete, leads to numerical results that are more close to the experimental data. [ABSTRACT FROM AUTHOR]