Several existing fracture modeling strategies for the debonding mechanism simulation in strengthened structural elements rely on simplified cohesive approaches for concrete/FRP interfaces thus neglecting the prediction of the complex concrete nonlinear behavior. In this work, a cohesive/volumetric modeling technique, based on a diffuse interface fracture approach, is proposed to in-depth investigate the debonding mechanisms in FRP-plated RC beams and subsequently validated through experimental results. This model is used in combination with elastoplastic truss elements for the reinforcing bars, for which a bond-slip behavior with surrounding concrete is admitted, and with additional cohesive elements along the adhesive/concrete and adhesive/plate material interfaces. Moreover, a novel hybrid continuation strategy has been proposed to capture potential snapback behaviors in the equilibrium path usually observed during the brittle failure of existing retrofitted structures. Failure simulations have been performed to assess the capabilities of the adopted fracture approach to predict the load-carrying capacity and the related debonding phenomena in real-scale strengthened RC elements, also providing detailed interfacial stress analyses in the FRP system. The reliability and the effectiveness of the proposed fracture approach have been demonstrated by means of suitable comparisons with available experimental results.
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