Analysis of the deformability of concrete beams strengthened with FRP sheets

The deformability of concrete beams strengthened with externally bonded Fiber Reinforced Polymers (FRP) sheets is analyzed in the paper. A theoretical non-linear model, derived from a cracking analysis founded on slip and bond stresses is adopted in order to take into account both the tension stiffening effects of the concrete and the force transfer between the concrete and the FRP sheet at the interface. A local bond-slip law, defined by experimental tests made on concrete elements strengthened with Carbon FRP sheets, is adopted in the model. Theoretical predictions of the model are compared with available experimental results. A parametric study, focusing on the influence of some geometrical and mechanical parameters (FRP reinforcement ratio, mechanical properties of FRP sheet and adhesive layer) on the deformability of strengthened beams is carried out; obtained results, in terms of cracking and deflections of beams under service conditions, are presented and discussed.