Research On Mechanical Property Of FRP Bars And Flexural Property Of Concrete Beams With FRP Bars

The erosion of steel bars, which can result in the failure of bearing capacity of the RC structures, has also been considered to be a chief factor to affect the life span and the durability as well. Therefore, high-performance fibers including carbon and glass, with light weight, high strength, resistance to erosion, fatigue or electro-magnetic radiation, which can be made into FRP bars with special technique, can replace steel bars in concrete structures. However, as a type of elastic material, its sudden rupture without any yielding point or plastic property in the ultimate stage of tension will cause the unexpected failure of flexural members. It is of great importance to study mechanical property of FRP bars as well as the flexural property and failure mechanism of FRP-reinforced concrete beams.In this paper, the manufacturing and anchorage of the FRP bars are studied, and a new type of FRP bar is reserched and developed. Experiments are conducted to study the mechanical property of FRP bars and the flexural property of FRP-reinforced concrete beams. We also make FEM analysis of the whole process of the deformation of the beams. It is indicated that:1. In contrast to steel bars, FRP bars have higher tensile strength(the tensile strength of CFRP is 1779Mpa and GFRP is 993Mpa) along with lower elastic modulus and lower extension rate. The failure of single FRP bar is a kind of rupture failure with a basic linear stress-strain relationship, lacking evident plastic stage. The experimental method, stress-strain model and parameters for design have been proposed.2. For hybrid FRP(HFRP) bars, with two groups of fibers of different tensile strength, extension rate and ultimate strain, as long as the low elongation fibers doesn't exceed the boundary content, the stress-strain relationship of the HFRP bars will have a yielding stage similar to steel bars. The formula has been offered to design the boundary content, tensile strength and elastic modulus of HFRP bar.3. The deformation characteristics and failure mechanism have been studied. Strain along the cross section is proportional to the height, which we call a"plane section". With wide original cracks and fast development, the cracks have an even distribution. The deflection varies greatly, while the load-deflection curve looks like double lines. Tensile rigidity(elastic modulus multiple area of cross section) of FRP and height of the beams seem to affect the deflection in a greater extent than concrete strength and type of loads.4. Based on the"plane section"theory, the flexural bearing capacity formulas for the two types of failure modes have been produced. The deflection formula on the basis of double-line model of M-ï¿ curve is applied to obtain desirable agreement between calculated results and experimental data. The proposed design method can serve as a reference for those designers who are going to deal with FRP-reinforced concrete beams.