RETROFIT OF SHEAR STRENGTH DEFICIENT RC BEAMS WITH SPRAYED GFRP

Worldwide, a great deal of research is currently being conducted concerning the use of fibre reinforced plastic wraps or laminates in the repair and strengthening of reinforced concrete members. Such techniques can be both effective and economical when compared to the existing practice of retrofitting with steel plates. A novel technique which further simplifies the application procedure is to apply the fibre using a spraying process. By spraying the fibres onto the member surface concurrently with a suitable matrix resin a two dimensional random distribution of discontinuous fibres is obtained, resulting in an FRP plate that exhibits isotropic in-plane behaviour. This work reports the application of a sprayed glass fibre reinforced plastic (GFRP) retrofit system on reinforced concrete beams. Using E-glass fibres embedded in a polyester matrix, a sprayed FRP system was used to strengthen beams intentionally designed to be deficient in shear capacity. This approach was shown to be capable of significantly increasing both the strength and stiffness of such concrete beams, while at the same time dramatically improving their energy absorption characteristics. When compared with fabric wrapped specimens, and with published literature on similar specimens retrofitted with either fabric or laminates, the sprayed GFRP material proved to be capable of producing results equivalent or better than any of the other techniques. The sprayed FRP approach also tended to improve the bond between the FRP and concrete surface, thus providing resistance to the primary mode of failure exhibited in FRP retrofit systems; failure at the bond line.