The use of a hybrid FRP-steel reinforcement to optimise the structural performances of flexural concrete members

The use of a hybrid Fiber Reinforced Polymers (FRP)-steel reinforcement for flexural concrete members is analysed in the paper. The analysis refers to concrete beams reinforced with FRP rods placed in the tensile zone near the external surfaces and steel rods placed within the member and protected from aggressive agents by high concrete cover thickness. Structural performances of members are evaluated supposing that the tensile strength is carried out entirely from FRP rebars while steel rebars; furnish a good contribution in terms of ductility and rigidity. Moment-curvature laws, used in the structural analysis, are evaluated by means of a theoretical investigation, founded on the traditional cross-sectional approach. Results of an experimental investigation that refers to concrete beams, reinforced with hybrid AFRP-steel rebars, tested up to failure, are described and compared with theoretical predictions. Obtained results evidence the effectiveness of the adopted technological solution to optimise the performances of reinforced concrete members in terms of strength, deflection, cracking and ductility.