Ductile Hybrid Fiber Reinforced Plastic Reinforcing Bar for Concrete Structures: Design Methodology

Abstract

This paper addresses the need for a ductile or pseudo-ductile fiber reinforced plastic (FRP) reinforcement for concrete structures. The criteria to be met by the FRP, which are based on the properties of the steel reinforcing bar it is to replace, are threefold: high initial modulus, a definite yield point, and a high level of ultimate strain. It is shown that the use of a fiber architecture-based design methodology facilitates the optimization of the performance of FRP through material and geometric hybrid. Consequently, the advantages of FRP, such as high strength, low weight, and chemical inertness or noncorrosiveness, can be fully exploited. Using the material hybrid and geometric hybrid, it is demonstrated that the pseudoductility characteristic can be generated in FRP reinforcing bar. Critical material and geometric parameters such as elastic modulus, fiber volume fraction, twisting, crimp, and helical effect in the specimen components were investigated and parametric studies are reported. Ductile hybrid FRP bars were successfully fabricated at 3-mm and 5-mm nominal diameters using an in-line braiding and pultrusion process. Tensile specimens from these bars were tested and found to have consistent pseudoductile behavior and good agreement with the analytical predictions.