Debonding failure analysis of FRP-plated RC beams via an inter-element cohesive fracture approach

Abstract

Debonding mechanisms in the externally reinforced structural elements have been widely studied by the scientific community since they lead to premature failure in concrete structures. Different numerical models, based on simplified strength approaches, have been proposed in the literature to simulate such debonding phenomena, but often are unable to accurately predict the development of diffuse crack patterns which are typical for reinforced concrete (RC) structures. In this context, the present work aims to propose a cohesive modeling technique, based on a diffuse interface fracture approach, to in-depth investigate the plate-end and mid-span debonding failures in FRP-strengthened RC structural elements. This model, already presented by some of the authors, is used in combination with bond-slip elements, to simulate the stress transfer between the rebars and the surrounding concrete, and with additional cohesive elements along the adhesive/concrete (AC) and adhesive/plate (AP) material interfaces. Numerical simulations have been performed by using the present fracture approach for predicting the load-carrying capacity and the related failure modes of real-scale retrofitted RC elements. The reliability and the effectiveness of the proposed fracture approach have been demonstrated through suitable comparisons with available experimental results. In particular, this model results to be an innovative and versatile numerical tool able to analyze the debonding mechanisms in FRP-strengthened RC elements as well as to provide more accurate crack patterns, including multiple crack branching and coalescence, than commonly used existing models.