Experimental Study On Bond Behavior Between FRP And Concrete Based On Fiber Layers And U-shape Anchorage

Fiber-reinforced plastic (FRP), due to high-strength,lightweight and good corrosion resistance, has been widely used in the reinforcement of concrete and other structures. Bonding of a FRP plate to the tension face of a beam or plate is one of the most popular method for flexural strengthening. However, debonding of FRP is a typical failure mode when EB FRP is used to strengthen concrete structures. A large number of studies have indicated that the end anchorage system can be used to reduce or prevent the occurrence of debonding failure and improve the utilization ratio and the effect of FRP sheet. However, research on the mechanism of anchors and anchor design is also less. Therefore, in this paper, two groups of single shear specimens are designed to study the effect of two common anchor fiber-fiber layering and U-shaped hoop on FRP-concrete interfacial bond properties,and to further explore force transfer mechanism of the fiber anchorage and single shear strip. On this basis, the design method of anchorage will be put forward. This paper includes three parts as follow:(1)The interface bonding performance of fiber concrete based on layering anchorage FRP-concrete. A total of 10 externally bonded FRP flexural reinforcement concrete slab were tested with single shear test to study the influences of a number of factors, incluidng the bond length, strip width, bonding angle,and the number of layers, on the bond behavior between FRP and concrete and further explore force transfer mechanism of the fiber layering and single shear strip. The test results show that, fiber layering has obvious effect on bond behaviour between FRP and concrete. Fiber layering which incline to 45 degrees or 30 degrees can effectively limit FRP single shear strip debonding failure and obviously improved ultimate bearing capacity and ductility of concrete slab. At the same time, the maximum strain of FRP single shear strip has been improved too.(2)The study on bond behavior of FRP-concrete interface based on U hoop anchorage. A total of 13 externally bonded FRP flexural reinforcement concrete beam were tested with single shear test to study the influences of a number of factors, incluidng the bond length, strip width, bonding angle,and beam corner radius, on the bond behavior between FRP and concrete and further explore force transfer mechanism of the U hoop anchorage and single shear strip.The test results show that the bonding length and paste angle of U-shaped hoop has great influence on the anchorage efficiency and the influence law consistent with fiber layering. Compared with the most widely used vertical U type hoop, FRP single shear strip can more effectively transfer the force to U-shaped hoop when inclined to 45 degrees and 30 degrees, thus its failure would be limited by inclining U-shaped hoop, and improved ultimate bearing capacity and ductility more obviously. At the same time, setting chamfer in the beam corner can effectively avoid the stress concentration which causes U-shaped hoop tensile failure.(3)The design of fiber anchorage bases on the test results. Through the analysis of the different transfer coefficient, approximate rules of transfer coefficient are obtained. The preliminary design of anchorage size with the value of fiber anchorage design parameters. In the end, the paper elaborate the design method of fiber layering and U type hoop with a numerical example.