PARAMETRIC STUDY OF BEAMS WITH EXTERNALLY BONDED FRP REINFORCEMENT

FRP reinforcement may be externally bonded to the soffit of existing f lexural members in order to increase their strength and rigidity. A pa rametric analysis is conducted to investigate the effects of FRP reinf orcement on serviceability, strength, and failure mechanisms of repair ed RC beams. FRP reinforcement parameters considered in the analysis a re: stiffness, bonded length, thickness, and the adhesive stiffness. T he choice of the repair material parameters is important in the design phase in order to obtain the desired results of strengthening or stif fening without other unforeseen effects. in this paper; three typical RC beam cross sections are considered with height-to-width ratios of 0 .5, 1, and 4. Two characteristic compressive strength levels (20 and 3 0 MPa), and two shear span-to-reinforcement depth ratios (4.5 and 7) a re considered. All other parameters related to material and geometry o f the beams are maintained constant. The results of the analysis are s hown in terms of repaired-ro-un-repaired strength and deflection ratio s. They indicate that brittle failure mechanisms can develop at loads much lower than expected when considering only flexural performance co ntrolled by concrete crushing and FRP tensile rupture. The analytical model used for the parametrization accounts for brittle failure mechan isms induced by debonding of the FRP reinforcement or shear-tension fa ilure in concrete in the plane of the main longitudinal steel reinforc ing bars. Even when considering the limitation of the RC member due to its un-modifiable shear resistance, it is shown that the application of FRP reinforcement can considerably increase load resistance capacit y and limit deflection at service.