This paper describes the implementation of an orthotropic concrete constitutive model into the nonlinear finite element analysis of reinforced concrete structures such as panels, deep beams, and shear walls subjected to in-plane shear and normal stresses.
Based on the concept of equivalent uniaxial strain, constitutive relations of concrete are presented in the axes of orthotropy which coincide with the principal axes of total strain and rotate according to the loading history. The proposed model includes the description of biaxial failure criteria which show compressive strength enhancement and tensile resistance reduction effects for the stress state of biaxial compression and tension-compression, respectively. After tensile cracking, concrete compressive strength degradation is implemented and tensile capacity of concrete maintained by reinforcing steel so-called tension-stiffening effect is considered. Using the concept of average stresses and strains, a criterion is proposed to simulate the tension-stiffening effect based on the force equilibriums, compatibility conditions, and bond stress-slip relationship between reinforcement and surrounding concrete.
The finite element model predictions are validated by comparison with available experimental data. In this paper correlation studies between analytical results and test values from idealized shear panel tests are conducted and then load-displacement relations of shear panel beam and walls under different stress conditions are evaluated to verify the soundness of proposed model.