Experimental Study On The Impact Of Thickness Of The Adhesive Layer Of Prestressed Carbon Fiber Sheet Reinforced Concrete Beam

With the development of bridge construction process, at the same time, the factors such as the rising traffic, the natural environment, and the aging structure of itself lead to the bridge in service bearing the capacity which is difficult to meet the practical requirements, so reinforcing the bridges in service has become an important research topic. Using new materials and new technology to reinforce the structures are the research mainstream, using the prestressed FRP to reinforce the existing structures, which not only makes full use of the properties of FRP material such as the light weight, the high strength, and the corrosion resistance, but also better enhances the bearing capacity of reinforced structure, improving the reinforced structure performance, and having less weight on the reinforced structure, etc. And in view of the prestressed CFRP sheet reinforced concrete beam in the condition of different initial stress conditions of adhesive bond thickness of the reinforced structure section stress, CFRP sheet after the tension of interface strain distribution and CFRP effect of stress distribution in the plate studies less. A total of 9 pieces of prestressed CFRP plates, which consider the initial stress equal to the ultimate bearing capacity of 10%,20% and 30%, the adhesive thickness of 2 mm,4 mm and 6 mm respectively, were carried out, and the following conclusions are reached:1. The thickness of bonded layer has little effect on cross section stress of prestressed CFRP reinforced concrete beam concrete, so it can calculate the stress distribution of the tension of concrete beam section by using the calculation method of concrete beam under eccentric compression.2. Using the method of pre-tensioning to the prestressed CFRP sheet prestressing, the strain of CFRP strips increase gradually from the end to mid-span after completing the release of tension, and the strain of CFRP strips close to the initial strain when reaches a certain bond length of CFRP. Putting forward the definition of zero bound initial stress, the initial stress reaches a certain value when affect the length of strain of the board interface increased dramatically, the set value is zero bound initial stress; Different adhesive bonding thickness lead to different zero initial stress.3. The end anchoring beam of circular CFRP formed in the interface resistance makes anchoring CFRP sheet interface stress is smaller than the nearby anchor at the interface stress; There exists hysteresis of interface stress of CFRP sheet interface near the anchoring by the annular end anchor.4. There is same numerical relationship between the CFRP sheet interfacial bond stress, releasing tension under the same thickness of adhesive bond, and obtaining the formula of the CFRP sheet interfacial bond stress and releasing tension under the different thickness of adhesive bond. The calculation formula is divided into nonlinear rise and down lines, different thickness of adhesive bonding with different interfacial bond stress maximum of CFRP sheets. The tests show that the adhesive thickness of bond line which 4mm is the most appropriate, and it has a certain referential value for reinforcing concrete structures with externally pasted CFRP sheet material.