The Finite Element Analysis And Experimental Research On Axial Forcing Of Round Steel-tubes Strengthened With CFRP Sheets

As an important branch of the construction industry, reinforcement industry is being paid more and more attention from engineering. Carbon fiber reinforced polymer (its abbreviation is CFRP) reinforcement technology is a newer reinforcement method, it has been researched and applied maturely in reinforcement areas of reinforced concrete structure and masonry structure, related codes and specifications also have been issued in recent years. However, the theoretical research and engineering application on this new technology are very little in steel structure reinforcement field. At present, traditional reinforcement methods are still being used in steel structure or components in most instances, they mainly include bolts connection, welding, sticky steel, etc. These traditional reinforcement methods own mature theories and simple operation, but we also cannot ignore the problems of welding residual stress, sections weaken, stress concentration and so on. Carbon fiber reinforced polymer reinforcement technique can perfectly offset the shortcomings of traditional steel structure reinforcement methods because of its excellent material properties and advantages in reinforcement construction technology, Based on sufficient understanding on raditional steel structure reinforcement methods and consulting related research literatures, this paper makes round steel-tubes as research objects. Combining finite element analysis and experimental research to explore the influence and laws of carbon fiber reinforced polymer on axial forcing properties of steel-tubes.The study work and results of this paper are as follows:(1) Axial tensile round steel-tubes strengthened longitudinally with CFRP sheets was calculated by ANSYS, having contrasted and analyzed the influence of longitudinal reinforcement length ratio, thickness, elastic modulus and the ways of reinforcing of CFRP sheets on axial tensile ultimate bearing capacity and ductility of steel-tubes. Research results show that the axial tensile ultimate bearing capacity of reinforced steel-tubes is significantly improved and the highest extent can reach up to about 20%, but their ductility is reduced at the same time. With the increase in longitudinal reinforcement length ratio of CFRP sheets, axial tensile ultimate bearing capacity is enhancing continually. The axial tensile ultimate bearing capacity almost won't be impacted by thickness and elastic modulus of CFRP sheets, but the increase in both will decrease ductility of rods. In addition, the reinforcement effect of full-circumference is obviously superior to the non-full-circumference;(2) Axial compression round steel-tubes strengthened circumferentially with CFRP sheets were analyzed on buckling by ANSYS, and having obtained the influence of longitudinal covering length ratio, thickness, elastic modulus of CFRP sheets on buckling bearing capacity and bending stiffness of steel-tubes. Research results show that eigenvalue buckling and nonlinear buckling bearing capacity of rods are enhanced effectively, and the two values can mostly reach up to 167.5% and 19.7%, so the reinforcement effect is considerable. Meanwhile, the bending stiffness of these rods is improved. The thickness and elastic modulus of CFRP sheets can significantly influence eigenvalue buckling bearing capacity of rods, and it enhances with the increase in these two factors. The CFRP sheets of high modulus and small thickness are good for the improvement in nonlinear buckling bearing capacity of rods, and the bending stiffness is increased. The eigenvalue buckling bearing capacity of rods is improved with the increase in longitudinal covering length ratio of CFRP sheets, and the increasing extent becomes more remarkable and more remarkable with the increase in thickness and elastic modulus of CFRP sheets. In the case of whole-length reinforcement, the improving extent of nonlinear buckling bearing capacity and bending stiffness are the biggest.(3) Axial tensile experiments on round steel-tubes strengthened with CFRP sheets was done. Having compared the test results and the finite element calculation results and proved the feasibility of numerical simulation method. Meanwhile, having found out reasons for the difference between experimental results and the finite element calculation results so as to give reference and guidance to the follow-up work.