Abstract

Thermoset fibre-reinforced polymer composite (FRP) rebars and laminates are widely used in reinforcing and strengthening concrete structures due to their advantages such as: corrosion free material, high strength to weight ratio, and electromagnetic resistance. However, thermoset composites have some limitations due to the fact that they cannot be bent once the resin solidifies when used as internal reinforcement (FRP rebars). On the other hand, externally bonded FRP sheets used in strengthening concrete structures is subject to non-ductile failure due to debonding. This emphasizes the need of exploring new methods for reinforcing and strengthening concrete structures. This thesis evaluates the performance of a new thermoplastic CFRP rebar that can be bent after the resin set and also examines the behaviour of using unbonded mechanically anchored dry carbon fibre (CF) sheets in shear strengthening of concrete T-beams to avoid debonding mode of failure. Three sets of tests were conducted on the developed CFRP rebars in order to evaluate their mechanical characteristics, minimum development length of the straight rebars, and the tail length of bent rebars. Based on the test results and the modes of failure of the tested specimens, recommendations were proposed to improve the behaviour of the new thermoplastic CFRP rebars. The properties of the newly developed CFRP rebars were compared to similar thermoset and thermoplastic FRP rebars available in the literature and market. Three reinforced concrete (RC) T-beams were tested up to failure in four point bending test. One was reserved as control beam, while two beams were strengthened in shear using mechanically anchored dry CF sheets. The tested beams were instrumented with the conventional measuring devices that were connected to a data acquisition system. Moreover, the beam was monitored using acoustic sensors which monitored the acoustic energy activity of the tested beams