Finite elements with an embedded reinforcement for the simulation of reinforced concrete structures strengthened with FRP

The embedding of anchoring systems in the retrofitting of Reinforced Concrete (RC) structures by means of Fiber Reinforced Polymers (FRP) often implies local failure modes associated to high stress concentrations. In order to account for such mechanical behaviours in standard finite element computations, an explicit representation of interfaces is required. This strategy presents, however , several limitations in terms of computational cost and mesh-related issues. On the other hand, implicit models may not be sufficiently accurate in order to reproduce the aforementioned localized phenomena. Specific finite elements for the simulation of pull-out mechanisms are here presented. The presence of interfaces is taken into account by enriching the displacement approximation by means of additional unknowns defined at the element level. Static-condensation, therefore, allows preserving the structure of the finite element procedure and limiting the computational effort.