Parametric study of beams with externally bonded FRP reinforcement

FRP reinforcement may be externally bonded to the soffit of existing flexural members in order to increase their strength and rigidity. A parametric analysis is conducted to investigate the effects of FRP reinforcement on serviceability, strength, and failure mechanisms of repaired RC beams. FRP reinforcement parameters considered in the analysis are: stiffness, bonded length, thickness, and the adhesive stiffness. The choice of the repair material parameters is important in the design phase in order to obtain the desired results of strengthening or stiffening 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 30 MPa), and two shear span-to-reinforcement depth ratios (4.5 and 7) are considered. All other parameters related to material and geometry of the beams are maintained constant. The results of the analysis are shown in terms of repaired-ro-un-repaired strength and deflection ratios. They indicate that brittle failure mechanisms can develop at loads much lower than expected when considering only flexural performance controlled by concrete crushing and FRP tensile rupture. The analytical model used for the parametrization accounts for brittle failure mechanisms induced by debonding of the FRP reinforcement or shear-tension failure in concrete in the plane of the main longitudinal steel reinforcing 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 capacity and limit deflection at service.