Experimental Study On Flexural Behavior Of RC Beams Strengthened With BFRP

Bonding FRP technique is a new reinforcement to strengthen the reinforced concrete structure. But at present, research almost focuses on CFRP, little research has been done on BFRP. As a new kind of FRP, BFRP has high tensile strength, corrosion resistance, high temperatures resistant and it can not pollute the environment. It has an application prospect in strengthening of concrete structures extensively.3 RC beams strengthened with externally bonded BFRP and 6 comparative RC beams are tested to investigate the flexural behavior by the orthogonal experimental design method, and three factors are considered in the experiment, which are the number of FRP layer, the type of the FRP and steel reinforcement ratio, the effect of each factor on flexural behavior of beams and the difference among each factor levels are analyzed. The main experimental results are as follows:(1) BFRP reinforcement can increase the yield load and ultimate load. The bearing capacity of beams with BFRP is higher than that of unreinforced beams with amplitude of 10%-20% in this experiment, and the increase of bearing capacity of beams with BFRP is less than that of beams with CFRP with amplitude of 1/3-1/2. The ultimate bearing capacity of beam increases with the increase of FRP layer, but it is not a linear relationship, and it shows the increase in the number of layer can reduce the utilization of FRP. As to beams with less steel reinforcement ratio, the effect of FRP is more obvious. Steel reinforcement ratio and the types of FRP are the main influence on ultimate bearing capacity.(2) BFRP reinforcement can reduce the propagation of cracks obviously, it can reduce the width of cracks and crack spacing. But the effect of BFRP is less than the effect of CFRP. And BFRP has little effect on the beams with high steel reinforcement ratio.(3) BFRP reinforcement can increase the flexural rigidity of beams, but it will result in the decline of ductility, the ductility of beams with BFRP is less than that of unreinforced beams with amplitude of 24% in this experiment. And the type of FRP is the main influence on ductility.(4) Based on the experimental results, the calculation formulas for beams strengthened with BFRP are validated and derived. The calculation formulas include ultimate bearing capacity, crack spacing, width of cracks and stiffness. Compare the calculated value with experimental value, the result shows that good agreement is achieved.