Nonlinear finite-element analysis of RC shear panels and walls

In the assessment of existing reinforced concrete structures, finite-element analysis plays an important role, particularly in regard to the evaluation of critical regions, regions with special detailing, or regions of stress concentration. A popular class of concrete model uses an orthotropic constitutive relation in which the directions of orthotropy are the principal directions of total strain. Since these directions change during the load-displacement response, such an approach is known as a rotating crack model. The models proposed to date differ in the description of the biaxial failure envelope, the uniaxial equivalent stress-strain relation, Poisson ratio, and the tension-compression behavior. This paper describes the implementation of an orthotropic concrete constitutive model in the finite-element analysis of reinforced concrete members. The emphasis of the paper is on the evaluation of the effect of orthotropic model parameters on the monotonic lead-displacement relation of shear panels and walls under different stress states. The ability of the orthotropic concrete material model to assess failure mode, ultimate strength, and load-deformation behavior of this type of structural element is evaluated by correlation studies with available experimental data.