Bend-strength of wound carbon fibre reinforced polymer shear reinforcement

The filament winding of Fibre Reinforced Polymer (FRP) tows around longitudinal reinforcing bars provides a novel method for the fabrication of shear reinforcement cages. 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. Current methods to test FRP reinforcement at corners have limited use for filament wound reinforcement. A new test methodology was developed to allow for rapid testing of curved FRP reinforcement that allows for sample re-alignment during load application, reducing the effects of eccentricities. An experimental programme, comprising of 8 test samples, was undertaken to assess the bend capacity of wound Carbon FRP (CFRP) shear links, considering three variations in bend radius and two variations of cross sectional area. It was found that an increase in bend radius resulted in increase in failure load. It was also observed that an increase in cross sectional area led to a decrease in the ratio between the bend capacity and the ultimate tensile capacity. From comparison between the experimental results and values from theoretical bend strength estimations, it was established that further developments of bend strength predictions for wound shear reinforcement are required in order to accurately reflect their behaviour.