During the past years, various systems for repairing reinforced concrete structures using fiber reinforced polymers (FRPs) have been developed. These systems can be used, essentially by bonding FRP plates, sheets, or strips to the exterior surfaces of reinforced concrete members with a structural adhesive such as an epoxy polymer resin, to strengthen concrete beams and slabs in both flexure and shear, to increase the strength of structural connections. There is a little readily available information on FRP performance at elevated temperature, as would be experienced in hot service environments (70°C to 200°C) or during well-developed building fires (exceed 1000°C), or after exposure to elevated temperatures resulting from various causes.
The most common strengthening technique is based on the application of the FRP on the surface of the elements to be strengthened and is designated as externally bonded reinforcement (EBR) technique. Recent research has revealed that this technique cannot mobilize the full tensile strength of FRP materials due to premature de-bonding; several attempts have been made to overcome the defects of EBR. Strengthening with near-surface mounted (NSM) FRP which is based on the concept of bonding glass or carbon FRP rods or laminates into pre-cut grooves opened in the concrete cover of the elements to be strengthened.
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