N.F. Grace (USA), W.F. Ragheb (Egypt), and G. Abdel-Sayed (Canada)
Flexural strengthening, Shear Strengthening, Ductility, Hybrid Composites.
The mechanical properties of currently available commercial fiber reinforced polymer (FRP) materials are not always ideal for strengthening reinforced concrete beams. These FRP materials are very brittle and hence invariably raise concerns about ductility. In addition, their strengths are not always fully exploited when they are used for beam strengthening, either for flexure or shear; so their use is not economical. Therefore, new FRP strengthening systems have been developed that offer the required strengthening level without loss of ductility and to be fully exploited. In this paper, the development of a new FRP fabric is discussed. The fabric is pseudo-ductile and hybrids of carbon and glass fibers. The fabric has triaxially braided bundles of fibers braided in three directions (+45o , 0o , -45o ). The 0o fibers act mainly for flexural strengthening, while the (+45o , -45o ) fibers act mainly for shear strengthening. The ideal characteristics of the developed strengthening fabric investigated. A parametric study was conducted. Based on these investigations, the fabric geometry was selected. A special micromechanical analytical modeling technique developed by NASA was used to analyze and design the fabric. The fabric was manufactured and its tensile mechanical properties were evaluated by testing samples according to ASTM D 3039 specifications. The fabrics exhibited yield plateaus similar to that exhibited by steel.
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