Analytical Study of Reinforced Concrete Beams Strengthened with Web-Bonded Fiber Reinforced Plastic Plates or Fabrics

摘要

Bonding fiber reinforced plastic (FRP) plates or fabrics to the web of reinforced concrete beams can increase the shear and flexural capacity of the beam. This paper presents analytical models to calculate the stresses in the strengthened beam, and the shear force resisted by the composite plate before cracking and after formation of flexural cracks. The anisotropic (orthotropic) behavior of the composite plate or fabric has been considered in the analytical models. The companion paper extends this discussion into post cracking behavior at the ultimate load, where the diagonal shear cracks are formed. The method has been developed assuming perfect bond between FRP and concrete (i.e., no slip), and using compatibility of the strains in the FRP and the concrete beam. The validity of the assumptions used in this method has been verified by comparing the results to the finite element method. A parametric study has been performed to reveal the effect of important variable parameters, such as fiber orientation angle on the shear force resisted by the FRP plate. The method has been developed for both uncracked and cracked beams, and it can be used for stress analysis of these types of beams.