Serviceability Limit State of MF-FRP Beams

Reinforced concrete (RC) structural members are usually strengthened with epoxy bonded pre-cured FRP strips. An innovative strengthening technique application is based on the use of FRP strips, with enhanced bearing strength, attached to concrete substrate by using mechanical fasteners (MF-FRP) in place of epoxy adhesive. The MF-FRP method is a viable technique for strengthening concrete members, particularly where speed of installation and immediacy of use are imperative. Laboratory testing and a number of field applications have shown the effectiveness of such method. An analytical model is discussed for RC beams strengthening using MF-FRP strips. The model accounts for equilibrium, compatibility and constitutive relationships of materials, in particular, it accounts explicitly for the slip between the concrete substrate and the FRP strip due to the behavior of fasteners. The proposed flexural model, coupled with an appropriate computation algorithm, is able to predict the fundamentals of flexural behavior of RC members strengthened with MF-FRP strips in terms of serviceability limit state, such as load vs. deflection curves, strain profiles and curvatures. A comparison between the analytical predictions and the experimental results has been performed to validate the proposed model. The comparison shows a good agreement between the analytical predictions and the experimental results.