Bend-strength of novel filament wound shear reinforcement

The winding of Fibre Reinforced Polymer (FRP) tows around longitudinal reinforcing bars provides a novel method for the fabrication of reinforcement cages. Complex geometries of internal reinforcement can be fabricated using this technique, a particular advantage for the construction of optimised concrete beams. A key limitation on the contribution of FRP to the shear capacity of a concrete member is found at corners, where the presence of stress concentrations in different directions can lead to premature failure. A new test methodology was developed to allow for rapid testing of the samples as well as sample realignment during load application, reducing the effects of eccentricities and imperfections created during their fabrication. An experimental program, comprising 30 test samples, was undertaken to assess the bend capacity of filament wound FRP (W-FRP) shear links manufactured using a carbon tow impregnated with epoxy resin. A fixed bend radius of 5 mm and six non-circular fibre cross sectional areas having different width-thickness ratios were considered. Additionally, 18 samples were tested to measure the tensile properties of the straight reinforcement. The test results indicate that W-FRP shear links exhibit improved bend strength as compared to conventional stirrups with circular sections (up to +53%), as a larger width-thickness ratio of the reinforcement provided more strength for a given cross sectional area. A good correlation between the test results and predictions of the W-FRP bend strength was observed when the specimens were modelled as a collection of transformed individual circular sections