| In recent years, with the improvement of steel production and the progress of production technology in China, the steel structure will be used in more and more structural engineering. At the same time, with its unique advantages such as light weight, high strength and strong spanning ability, the steel structure has been favored by more and more bridge engineers. In 2015, China published the "Code for design of highway steel structure bridge JTG D64 2015", which further indicates that the steel structure has become one of the main structural forms of the bridge. However, the operating environment and load of the bridge is complex, it makes stability, fatigue, and corrosion of steel structure become more serious. The traditional steel structure reinforcement technology often has the defects, and carbon fiber reinforced polymer(CFRP) reinforcement technology can make up for the shortcomings of traditional methods.Steel tubes are usually used as a compression member in bridge engineering, and at present, there is a limited research on the carbon fiber reinforced axial compression steel tube. Therefore, this paper will do further research on the carbon fiber reinforced axial compression steel tube. Based on the experimental results of the carbon fiber reinforced axial compression steel tube, the numerical simulation is carried out, and the stress state and strengthening mechanism of fiber materials are discussed. The major work and conclusions of this paper are as follows:(1) A finite element analysis method of carbon fiber reinforced steel tubular column is presented. The rationality of the finite element method is verified by comparing the numerical results with test results of short column strengthened with CFRP. On this basis, the reinforcement mechanism and parameters of steel tube strengthened by CFRP are analyzed. Result shows that the efficiency of CFRP is increased linearly with the increase of the number of layers, increased with the initial geometric imperfection and the ratio of diameter to thickness increased, and decreased with the increase of the slenderness ratio. It is suggested that the fiber should be s laid along the longitudinal direction when the slenderness ratio of steel tube is more than 15. The strengthening efficiency of the carbon fiber cloth to the circular section steel tube is larger than that of the rectangular section.(2)The finite element method is used to analyze the steel tube long column reinforced with CFRP, and according to the test and numerical calculation results, the reinforcement mechanism and the mechanical properties of CFRP are analyzed. Result shows that the improvement of the bearing capacity of reinforced member is mainly due to CFRP provides a certain compressive stiffness, and the compressive elastic modulus increases with the number of reinforcement layers. The load bearing capacity of carbon fiber reinforced steel tube column can be calculated according to the Perry formula or Code for Design of Steel Structure in China.(3) The numerical analysis of steel tube long columns strengthened with CFRP sheet is made by the fiber model method, using MATLAB to compile the calculation program, and considering the fracture and the stress transfer of CFRP sheet. The results show that the fiber model method can more fully consider the stress state of CFRP sheet in the loading process. The numerical method is used to analyze the steel tube columns strengthened with CFRP plate, and the results were compared with the test. Based on this the failure process of the carbon fiber board was analyzed. The results show that the interface relationship between CFRP plate and steel can be analyzed by the bilinear bond slip model, the compressive stiffness and tensile stiffness of CFRP plate in reinforcing member are approximately equal. |
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