Experimental study on shear behavior of steel fiber high strength concrete beams reinforced with GFRP bars

Corrosion of steel reinforcement is the main cause of durability of reinforced concrete structures, and the use of fiber reinforced polymer (FRP) bars to replace steel bars is an effective way to solve the durability problems. Although FRP material has the advantages of high tensile strength and corrosion resistance, its lower elastic modulus leads to wider cracks and larger deformation in the service state. By adding steel fibers to the concrete matrix, the development of cracks in concrete members can be effectively inhibited and the shear capacity can be improved, and thus part or all the stirrups can be replaced to reduce the cost of manual tying. Therefore, experimental studies on the shear performance of 10 steel fiber high strength concrete beams reinforced with GFRP bars are carried out, and the effects of steel fiber content, stirrups spacing, and concrete strength on the failure mode, deformation, and shear capacity are analyzed. The results showed that under the same stirrups reinforcement ratio and concrete strength, adding steel fibers with a volume fraction of 0.75 % increased the shear capacity by 154.8 %. which indicates that the addition of steel fibers can significantly improve the shear capacity of the beam. Steel fibers can replace part or all the stirrups. Adding steel fibers with a volume fraction of 0.16 % can increase the spacing of stirrups from 150 mm to 200 mm, indicating that steels fibers can replace part of the stirrups. Steel fibers with a volume fraction of 0.65 % can completely replace the GFRP stirrups with a stirrup reinforcement ratio of 0.45 %. In addition, the equations for the shear cracking load and shear capacity of GFRP reinforced steel-fiber high-strength concrete beams are proposed, and the calculated results are in good agreement with the test values.