Carbon fiber composite reinforcement technology is a new structural reinforcement technology emerging in civil engineering in recent years. Due to the advantages of low density, high strength, corrosion resistance, and simple construction operation, the material has been widely used as soon as it appeared. The carbon fiber composite reinforcement method is to use epoxy resin glue to directly bond the carbon fiber cloth to the weakened part of the reinforced concrete structure, and form an integral part with the reinforced object, and work together to improve the cross-section bearing capacity.

 Analysis of the reinforcement effect of directly pasting carbon fiber composite materials

1. The reinforcement of reinforced concrete flexural members with carbon fiber composite materials has a limited effect on improving the bending and shear bearing capacity of beams. In principle, the direct bonding of carbon fiber material belongs to the category of passive reinforcement. The strain stress of carbon fiber material is relatively lagging, and the degree of stress (tensile strength) of carbon fiber depends on the deformation of the reinforced bending member.

2. Pasting carbon fiber material can restrict the development of cracks and indirectly improve the crack resistance of the structure.

Carbon fiber reinforcement requires the use of matching epoxy resin structural adhesive. The epoxy resin structural adhesive is painted on the surface of the reinforced concrete member to form an adhesive layer on the surface, so it can indirectly improve the corrosion resistance and carbonization ability of the concrete. Therefore, it also has a certain promoting effect on the durability reinforcement whose main purpose is to extend the service life of the structure.

Analysis on the reinforcement effect of winding and sticking carbon fiber material

Generally speaking, the method of winding and sticking carbon fiber material reinforcement (circular encircling beam method) is used, which is generally used in axial compression members. In principle, when the hoop method is used for reinforcement, the reinforced member has obvious restraining effect. Under the action of axial pressure, the concrete member is under three-dimensional compression, which can greatly increase the concrete compression. Carrying capacity and enhanced structural ductility can significantly improve the seismic performance of the structure.

It should be noted that when the ring beam method is used to strengthen the cross section of the member or to increase the ductility of the seismic reinforcement, the number of layers of carbon fiber material for different types of cross sections is also different. For the circular cross-section, there should be no less than 2 layers of carbon fiber material, and for the rectangular cross-section, there should be no less than 3 layers. And the overlap width between the upper and lower layers of the enclosure should not be less than 50mm, the extension length of the carbon fiber material to the truncation point should not be less than 200mm, and the overlap position of each strip should be staggered from each other.

In general, the appearance of carbon fiber composite materials has greatly promoted the progress of my country's structural reinforcement technology. But how to use it reasonably is a question worth considering. We can achieve the purpose of strengthening and reinforcing concrete members only by applying carbon fiber composite materials in a targeted manner while knowing the reinforcement mechanism.

Case: Tsinghua Affiliated Middle School Teaching Building Reinforcement Project with Carbon Fiber

The entire project is reinforced with carbon fiber cloth. The selected carbon fiber cloth and various structural adhesives use Horse carbon fiber reinforcement materials. Considering that the campus teaching building is a public place for long-term teaching by students and teachers, in order to ensure the safety of personnel, non-toxic and environmentally friendly Horse carbon fiber reinforced materials are specially used for construction, and good results and reputation have been achieved.