Experimental Study On Concrete Beams Strengthened With Prestressed Carbon Fiber Sheet Under Freeze-thaw Cycles

With the increase of the time of the concrete structure, the phenomenon of aging, carbonation, fatigue, cracking and so on, it is imperative to strengthen the concrete structure. The existing research shows that the technology of prestressed carbon fiber sheet strengthening technology not only improves the bearing capacity of the structure, but also improves the working performance of the structure. Under this background, this paper mainly considers the basic mechanical properties of carbon fiber cloth, the size of the continuous stress and the number of freeze-thaw cycles.The main work is as follows:(1) The effect of freeze thaw cycles on mechanical properties of carbo n fiber cloth were studied by tensile test of 20 carbon fiber sheets;Through the double shear test of 12 specimens, the failure mode of the interface was observed, and the influence of different freeze-thaw cycles on the bond strength of carbon fiber reinforced concrete interface was studied.(2) The influence of freeze-thaw cycles on the mechanical properties of concrete beams strengthened with 36 concrete beams with different pre stress levels and freeze-thaw cycles was studied.(3) Through the ANSYS software to simulate the concrete beam strengthened with prestressed CFRP sheets, the influence of freeze-thaw cycles on the mechanical properties of concrete beams strengthened with CFRP sheets is analyzed.The main research results are as follows:(1) The tensile strength and elastic modulus of carbon fiber sheets are decreased with the increase of freezing and thawing cycles. With the increase of freezing thawing cycles, the elongation of carbon fiber sheets is decreased, and the 50 times and 75 times of freezing and thawing are 3.1%, 6.8%, and 100 times of freeze-thaw cycles are reduced by 11.8%. Carbon fiber cloth- concrete interface bond strength test showed that with the increase in the number of freezing and thawing, failure mode by concrete internal da mage to the concrete adhesive interface failure and adhesive layer- carbon fiber interfaces damage development and failure mode change.(2) The experimental results show that the cracking load and ultimate load of the specimens are decreased with the freeze-thaw cycles. The higher the initial prestress level is, the faster the cracking load and the ultimate load decrease.(3) ANSYS software is used to simula te the concrete beams strengthened with prestressed CFRP sheets. The results show that the mechanical improvement of concrete beams strengthened with the simulation results are in good agreement with the experimental results.