Study On The Flexural Behavior Of RC Beams Strengthened With Prestressed CFRP Under Secondary Load

Carbon fiber material has high strength, light weight, good durability, etc. Compared with the traditional strengthening method of pasting unprestressed CFRP,using reliable carbon fiber anchorage for tension and then pasting prestressed carbon fiber, can give full play to the carbon fiber high strength characteristics, a substantial increase in stiffness and bearing capacity of reinforced components and improve the mechanical properties of components. And in practical reinforcement project can be divided into a force reinforcement and the secondary stress of the reinforcement. Compared with a force reinforcement, the component has a load history in the secondary stress of the reinforcement, which will be affected by different degree of damage, and after the reinforcement reinforcement materials may have different degree of strain hysteresis, so the stress distribution is more complicated.Considering that the secondary stress of the reinforcement is more common in the actual reinforcement project, three reinforced concrete beams have been tested to explore the flexural behavior of RC beams strengthened with prestressed CFRP under secondary load. When the longitudinal steels are close to yield after loading, two experimental beams are tensioned by CFRP for ten times with improved clamp plate anchorage for carbon fiber plate, obtaining some significant results. The increase effect of bearing capacity is compared between the strengthened beams and the unstrengthened one. Related curves from resuming load to structural failure are analyzed for the strengthened beams. The experiment results show that after tensioning CFRP, the flexural behavior of the loaded beams is effectively improved.The calculation formulas of maximum crack width and deflection for the beams under loaded tensioning stage are preliminarily deduced, and the comparison between the calculated results and the experimental values has been made.On the basis of three main kinds of bending failure pattern of RC beams strengthened with prestressed CFRP, calculation formula of each bearing stage is deduced, and the calculation formula of load bearing capacity under different failure patterns is concluded. Furthermore, the existed testing data and the experimental data of the author are used to validate these formulas.By finite element analysis software ANSYS, a nonlinear simulation for three experimental beams has been carried out. And by changing the parameters of an experimental beam, the different carbon fiber tension、the initial load and reinforcement ratio effect on the properties of component force are explored.