A 3D Model Combining Cohesive Zone Approach and Friction to Model the Steel-Concrete Interface
Résumé
It is essential to model the behavior of the interfaces between steel reinforcement and concrete in order to understand the stress transfer between these two components in reinforced concrete structures. The interface models commonly used include several parameters whose identification is based on pull-out tests, for which sensitivity to a number of parameters is not fully explained. In this contribution, the steel-concrete interface is studied at the mesoscopic scale through the simulation of pull-out tests. The three dimensional numerical reinforced concrete samples are first generated by applying a procedure, in which each sample is made up of concrete surrounding a ribbed or smooth bar embedded in the center of a cubic sample. The detailed geometry of the ribs of the steel bar is modelled with different possible shapes. Then, the finite element code Cast3M is used to perform the pull-out numerical simulations on the generated samples, using Mazar’s damage approach with regularization to describe cracking in concrete. The steel-concrete interface is modelled by combining a modified cohesive zone model (CZM) based on Tvergaard’s approach and a frictional model accounting for the frictional behavior in the damaged part of the interface. This is done by modifying an initial approach, by replacing the Crisfield’s damage model by the more adapted Tvergaard’s model and modifying the corresponding stresses to account for its exponential behavior. The interface is divided into an undamaged part where the CZM model applies and a damaged part where the frictional model dominates. The total stress is then the addition of the two corresponding stresses, and is equivalent to the CZM stress when the interface is initially undamaged, and fully equivalent to frictional model’s stress when the joint element is finally fully damaged. The overall response is studied in terms of the damage near the steel bar, the applied force versus displacement curves, and free end displacements. The results of mean bond stress versus the free end displacement are compared to available experimental data.