A fracture-ALE formulation to predict dynamic debonding in FRP strengthened concrete beams

A dynamic modeling technique able to reproduce interfacial debonding phenomena in FRP reinforced concrete beams is proposed to investigate the unstable behavior of concrete beams produced by interlaminar debonding mechanisms. The structural formulation adopts plane stress modeling and beam theory to predict the behavior of the RC beam and the FRP external reinforcement, respectively. The proposed methodology is consistent with a numerical methodology, which couples the ALE (Arbitrary Lagrangian-Eulerian) formulation with the Fracture Mechanics approach. The moving mesh strategy is used to reproduce the crack tip growth at the interfacial scale level by means of a geometry variation of the computational mesh points. Moreover, fracture variables, evaluated by means of the J-integral decomposition technique, define the crack growth motion during the debonding phenomena on the basis of an explicit crack tip speed criterion. Comparisons between static and dynamic behaviors are proposed to quantify, numerically, the dynamic amplification effects on the debonding variables produced by external and inertial loads. Moreover, a parametric study in terms of the structural characteristics of the beam constituents is developed to investigate the effects produced by the dynamic nature of the debonding phenomena on the crack evolution.