Analysis of the stress characteristics of CFRP reinforcement

• Carbon fiber(CFRP) includes unidirectional carbon fiber cloth, unidirectional carbon fiber fabric, bi-directional carbon fiber interwoven fabric and unidirectional carbon fiber laminating material. The carbon fiber cloth can be selected according to the different parts and stress characteristics and direction of the reinforced structure.

   

• The carbon fiber cloth with excellent tensile properties is bonded to the bottom of the beam body or on the inner wall of the box beam, so that it can bear the tension together with the steel bar arranged in the original structure, in order to improve the bearing capacity of the old bridge. Compared with other reinforcement methods, CFRP ensures the joint stress in the design load range and the original structure, and changes the stress distribution of the original structure to a minimum. 
• In the direction of the main tensile stress of the bridge, the anchorage ends are set on the two ends, which can restrain the cracks on the concrete surface, prevent the crack expansion, improve the flexural rigidity of the component, reduce the deflection of the component and improve the stress state of the beam body. 
• The reinforced concrete beam bridge should be strengthened with CFRP according to the actual situation, because the CFRP can improve the flexural bearing capacity and affect the damage form of the flexural member. When the amount of carbon fiber cloth is too much, the failure mode of the component changes from the failure caused by the breaking of the carbon fiber to the sudden crushing of the concrete. Because carbon fiber is a completely elastic material, it will weaken the plastic property of reinforcing bar and work together with steel bar. The amount of carbon fiber cloth will be excessive and the ductility of component will be reduced. 
• After the reinforcement of CFRP, the final failure mode of the bridge structure changes into a sudden (brittle failure), and the ultimate bearing capacity of the bridge should be calculated according to the 2/3 of the tensile strength of carbon fiber, which can not be considered according to the ordinary reinforced concrete. 
• Carbon fiber cloth can improve the shear capacity of concrete beams, the mechanism of which is similar to the stirrup, and it can also improve the deformation properties of the components and enhance the deformation capacity of the components.