STRENGTHENING OF REINFORCED CONCRETE BEAMS WITH AN EXTERNALLY BONDED COMPOSITE MATERIAL COMPOSED OF FRP FABRIC AND STEEL PLATE

Bonding steel plates or FRP laminates to the tension faces of reinforced concrete beams are among the common strengthening methods. Among these two strengthening materials, FRP generally is not capable of fulfilling the ductility demand while fulfilling the high strength demand. Mild steel, on the other hand, is capable of fulfilling both the strength and the ductility demands. However, the use of thick plates, whose application is impractical, might be needed in the case of high strength demand. In the present study, the effects of the composite use of the two materials to overcome the shortcomings of the individual use of each material on the behavior of reinforced concrete beams was investigated. For this purpose, a total of 11 reinforced concrete beams, including a plain beam, two reference beams strengthened with only FRP laminates and 8 beams strengthened with both steel plates and FRP laminates, were tested under transverse loading. The number of CFRP and steel layers, the bonding sequence of these layers and the plate thickness were adopted as the parameters of the present study. The composite use of CFRP and steel proved to have significant contributions to the behavior and strength of reinforced concrete beams and the bonding sequence of the layers was found to be the most important parameter influencing the beam behavior.