Fiber Reinforced Polymer Reinforcement for Concrete Structures

An experimental program conducted at the University of Manitoba, Canada, to examine the structural performance of fiber reinforced polymer (FRP) stirrups as shear reinforcement for concrete structures is summarized. A total of ten large-scale reinforced concrete beams were tested to investigate the modes of failure and the contribution of the FRP stirrups in the beam mechanism. The ten beams included four beams reinforced with carbon FRP stirrups, four beams reinforced with glass FRP, one beam reinforced with steel stirrups and one control beam without shear reinforcement. The variables are the material type of the stirrups, the material type of the flexural reinforcement, and the stirrup spacing. Due to the unidirectional characteristics of FRP, significant reduction in the strength of the stirrup relative to the tensile strength parallel to the fibers is introduced by bending FRP bars into stirrup configuration and by the kinking action due to inclination of the diagonal shear crack with respect to the direction of the stirrups. A total of 40 specially designed panel specimens were tested to investigate the bend effect on the stirrup capacity, along with two control specimens reinforced with steel stirrups. The variables considered in the bend specimens are the material type of stirrups, the bar diameter, then bend radius, the configuration of the stirrup anchorage, and the tail length beyond the bend portion. A total of 12 specially designed panel specimens were also tested to investigate the effect of the angle of cracks on the stirrup capacity. The two variables considered in this case are material type of the stirrups and the crack angle. Description of the experimental program, test results and design recommendations are presented.