Fiber reinforced polymer(FRP) strengthening and steel plate reinforcement are all similar of bonding form and strengthening mechanism. Essentially, they are equivalent to increase the reinforcement of members, and they can replace each other in shear and flexural strengthening.

If the design value of tensile strength of CFRP is 2000Mpa, the tensile strength design value of steel (Q235) is 200Mpa, which can be replaced by the principle of 0.1mm thick carbon fiber cloth equivalent to 1mm thick steel plate.

However, we should pay attention to the following points:

1. The modulus of elasticity of carbon fiber and steel is basically the same, but the tensile strength of carbon fiber is about 10 times that of steel. Therefore, we should give full play to the strength of reinforcing materials, and carbon fiber needs reinforced components to produce greater deformation. That is to say, under the condition of small deformation, the stress hysteresis of CFRP reinforcement is significant, so when the bearing capacity of components is quite different, the bonding steel reinforcement shall be preferred.

2. The elastic modulus of carbon fiber and steel is basically the same, reaching the same force value, and the steel cross section is much larger. Therefore, the magnitude of stiffness of steel members strengthened by bonded steel is more than that of carbon fiber reinforcement. That is to say, if the same bending resistance is supplemented, the flexure and crack width of the member bonded steel are less than that of the bonded carbon fiber reinforcement.

3. The steel plate can be welded with anchor bars and can also be bored by drilling and anchoring, so the anchorage method is more flexible than the carbon fiber.

4. The carbon fiber is light and thin, the construction is simple, the same amount of engineering, the construction period is about 40% of the sticky steel.

5. Carbon fiber, compared with steel, is an inert material, not corroded, and is not easily corroded by harmful medium. It has good durability in bad environment.