Research On Ductility Of High Strength Concrete Square Columns Retrofitted With CFRP Jacketing And Hybridized Methods

Along with the continuous growth of demand and the development of construction technology, high strength concrete has been increasingly applied in the long-span and high-rise structures in recent years. Nevertheless, when the high strength concrete structure damage occurs, it always presents the defect of poor ductility. Therefore, we should pay more attention to the high strength concrete structures rehabilitation. Because of the advantages of superior strength-to-weight ratio, high corrosion resistance and easy construction, it must be an effective approach to use fiber reinforce ploymer (FRP) to improve the ductility of high strength concrete structures. Under the above-mentioned background and in support of the research programs of National Natural Science Foundation of China, the ductility of high strength concrete columns retrofitted with CFRP sheets were discussed in the thesis just based on the work done by team members before. The main contents and conclusions are listed as follows:(1) The ductility performances of pre-damaged high strength concrete columns repaired with the wrapped CFRP jacketing and the L-shaped CFRP jacketing combined with wrapped CFRP jacketing separately were studied. Four high strength concrete square columns were tested under low reversed cyclic loading. Based on the test data, the load-displacement curves, ductility performance, energy dissipation, bearing capacity, stiffness degradation, and CFRP sheets strain development for different columns are compared systematically. The results show that the repaired columns develop significantly improved ductility behavior. Compared with the wrapped CFRP jacketing method, the method of the L-shaped CFRP jacketing combined with wrapped CFRP jacketing is more effective in repairing the damaged column.(2) Base on the wrapped CFRP jacketing with clamping plates hybrid method which was proposed by the team, five high strength concrete square columns which lack in shear capacity were tested to investigate the effect of the wrapped CFRP jacketing with clamping plates hybrid method on shear behavior. Test results show that the retrofitting methods mentioned above are effective to improve the shear behavior and the deformation of specimens, and especially, the wrapped CFRP jacketing with narrow clamping plates hybrid method is better.(3) A comparative study of the effectiveness of three different CFRP jacketing hybridized methods to retrofit high strength concrete columns for improving the ductility behavior is carried out. These retrofitting methods include the wrapped jacketing plus clamp plates, the L-shaped jacketing combined with wrapped jacketing and the L-shaped jacketing. wrapped jacketing plus clamp plates. The study found that the specimens retrofitted with the above three CFRP jacketing hybridized methods exhibit high levels of ductility superior to the other specimens. Among the three CFRP jacketing hybridized methods, the method of the L-shaped jacketing, wrapped jacketing plus clamp plates performs best, the method of the wrapped jacketing plus clamp plates has better performance compared to the method of the L-shaped jacketing combined with wrapped jacketing.