Do you all know? High-performance carbon fiber with only one-tenth the thickness of a human hair has a tensile strength of 7 to 9 times that of steel, and its specific gravity is only one-fourth of that of steel. The seemingly humble carbon fiber is a "dark horse" in the world of new materials. Under the high temperature of several thousand degrees, other fibers have been reduced to ashes, but it has not changed.

With the rapid increase in the number of infrastructure in my country, the focus of the construction industry has gradually tilted towards the reinforcement and transformation of existing structures. Structural reinforcement In recent years, pasting carbon fiber sheet to reinforce the structure has gradually become the mainstream method.

Carbon fiber sheet reinforcement is used in the bending and shear reinforcement of concrete beams, the bending reinforcement of slabs, and the seismic reinforcement of columns. It is widely used in the reinforcement of roads and bridges, water conservancy, energy, factories, buildings, school buildings, hospitals and other industrial, civil, and municipal buildings. It can enhance the reliability and bearing capacity of buildings, and ensure the safety, durability and applicability of concrete structures.

Reinforcing with carbon fiber sheet has many advantages, but what is the critical value of carbon fiber sheet reinforcement to the building structure?

In fact, as the number of layers of carbon sheet reinforcement increases, the flexural capacity will increase accordingly. However, the increase of carbon sheet reinforcement should not exceed 40% of the flexural bearing capacity of the front section of the member. This severely limits the strength and high performance of carbon fiber sheet. This is undoubtedly a waste of carbon fiber sheet, but why?

First of all, there is a phenomenon of force lag in the reinforcement of carbon fiber sheet, which can only play a role when the original structure continues to be deformed by force. If the increase is not controlled, it may cause brittle failure of the concrete in the tension zone prior to the carbon fiber sheet. At the same time, the excessive increase will easily cause the concrete in the compression zone to bear excessive load and be crushed, which should be avoided during reinforcement.

Secondly, the increased load of flexural members like beams may cause flexural failure and shear failure. Among them, the shear failure has a high degree of suddenness. The failure has no warning and the consequences are serious. Therefore, it is necessary to control the increase in the bending bearing capacity during reinforcement, and pay attention to "strong shear and weak bending" to prevent shear failure.

In summary, when using carbon fiber sheet for reinforcement, it is necessary to integrate the component conditions and formulate a reasonable reinforcement plan instead of blindly strengthening.