Effect Of Fiber Dosage And Bond Length On Pullout Mechanical Property Study

Fiber reinforced concrete has developed a new composite building material at present rapidly, among which steel fiber reinforced concrete and carbon fiber reinforced concrete with the functions of crack-resistance, reinforcing and roughing develops fastest and have been applied in various engineering fields. The bond between steel bar and concrete is the basis of the two materials working together. In this paper, the bond slip characteristic of steel bar pulled out from fiber reinforced concrete matrix considering interface with the experimental test and simulation analysis methods combing with the acoustic emission technique was researched. Meso- inhomogeneous damage model was built on the basis of Weibull random distribution using RFPA2 D and RFPA3 D, in which the interface between the steel bar and fiber reinforced concrete matrix as an individual phase for analyzing the damage failure process. The effect on the bond slip characteristic of bond length, dosages of steel fiber and carbon fiber were focused on. The main contents included:(1) Basic mechanical properties the steel fiber reinforced concrete and the carbon fiber reinforced concrete with different dosages were studied. Six various fiber reinforced concrete specimens with the dosage of steel fiber was 1.0%, 1.2% and 1.5% and the carbon fiber0.15%, 0.20% and 0.25%, compared with common concrete specimen. Then the uniaxialcompression numerical model of fiber reinforced concrete was built up with RFPA2 D. The numerical analysis results including the acoustic emission figures and stress-strain curve were compared with the experimental test, in order to verify the rationality of the physical parameters in the numerical model.(2) The effect of different bond lengths on the bond slip characteristic considering interface. Firstly pullout force- pullout displacement curves were obtained through center pullout test. Then the acoustic emission technique was set to monitor the whole progress of pullout test by which the acoustic emission figures of steel bar with different bond lengths were obtained and that was compared with pullout force-pullout displacement curves. And then with RFPA2 D, the center pullout numerical model through which the whole failure process of steel bars being pulled out from the concrete matrix was built up including the cement, the aggregate, the interface between the steel bar and the concrete and the steel bar.The information of interface unit was analyzed to calculate the shear stress. Finally the 3D numerical model was set up to analyze the characteristic of steel bars being pulled out from the concrete in 3D models.(3) The bond slip characteristic of the steel bars being pulled out from the steel fiber reinforced concrete and carbon fiber reinforced concrete with different dosages. The bond length is 5d(d is the diameter of the bar). The experimental test and the numeral analysis combining the acoustic emission technique were carried out to do the research on the pullout process with different dosages of steel fiber and carbon fiber.