Font Size: 

FRP materials are currently used to repair and strengthen existing civil engineering constructions by bonding suitably disposed FRP laminae to the external surface of the structural elements to be reinforced. The success of such interventions, however, is threatened by delamination and decohesion phenomena. In particular, for concrete structures, delamination and decohesion phenomena can occur at different levels, involving the FRP laminae, the adhesive or the superficial layers of the concrete itself.
In this paper we analyse the problem of a beam strengthened by an FRP strip bonded to its intrados and subjected to applied bending couples at its end sections. In the proposed mechanical model the beam and reinforcement strip are modelled according to classical beam theory, while the adhesive and its neighbouring layers are modelled as an interface having a tri-linear constitutive law (elastic-softening-rupture). The model is described by a set of differential equations, endowed with appropriate boundary conditions. An analytical solution to the problem is determined, including explicit expressions for the main quantities of interest (internal forces, displacements, etc.). Based on the developed model, the reinforced beam exhibits an overall nonlinear mechanical response, ranging over several stages: from linear elastic behaviour to damage, until the complete debonding of the FRP reinforcement.