Delamination of FRP-reinforced concrete by means of an extended finite element formulation

The present analysis focusses on the finite element modeling of delamination tests in FRP-reinforced concrete blocks using a continuous–discontinuous XFEM approach, which takes into direct consideration the mechanical properties of concrete, adhesive and FRP. Both FRP and adhesive layers are considered as linear elastic materials, while the constitutive behavior of the concrete is governed by an elasto-damaging constitutive law. As soon as a critical damage threshold is reached in the concrete, additional degrees of freedom, representative of the displacement discontinuity corresponding to the delamination process, are added. The proposed approach only requires the use of material parameters of direct mechanical meaning, which can be obtained by standard testing procedures. Hence the use of one-dimensional bond–stress–slip laws, whose parameters must be identified through a cumbersome procedure, appears to be unnecessary. Validation of the proposed approach is carried out by comparison of the computed results with two sets of experimental results. In both cases, after adoption of a simple damage criterion, structural behavior, slip, strain and stress profiles along the reinforcement are satisfactorily reproduced. Moreover, bond–stress–slip laws, which agree with those assumed in previous works based on the use of interface elements, were obtained retrospectively.