Issue 22

S. Bennati et alii, Frattura ed Integrità Strutturale, 22 (2012) 39-55 ; DOI: 10.3221/IGF-ESIS.22.06 41 ( )  s the transverse displacement and rotation (positive if clockwise) of the cross section of the beam, respectively, and by ( ) w s the axial displacement of the cross section of the reinforcement. Figure 1 : FRP-strengthened beam in bending. Figure 2 : Mechanical model of the strengthened beam. Figure 3 : Constitutive law of the interface. In the proposed mechanical model, the beam is flexible, but inextensible, while the reinforcement strip is extensible only. We denote E and J as the Young’s modulus and moment of inertia of the cross section of the beam, respectively, and f E and f A as the Young’s modulus and area of the cross section of the FRP strip, respectively. With f B the width of the reinforcement strip, and f t its thickness, we have  f f f A B t . The beam and reinforcement are connected to each other by an interface of negligible thickness. Since the reinforcement is subject to axial stresses alone, the interface transmits only tangential stresses, ( )  s , which we assume are functions of the relative displacement between beam and reinforcement in correspondence to the interface,