After the epoxy resin is combined with the structure, it has high tensile strength in the fiber direction, and its characteristics are high in strength and good in corrosion resistance, without fatigue and aging. The main role of carbon fiber in the reinforcement of reinforced concrete members is to resist tensile force. Generally, it is suitable for the shear-resistant parts of beams and columns (piers), the reinforcement of columns or piers, and the parts where the anchoring (wrapped) length of steel bars is insufficient.

Key Technical Issues In Carbon Fiber Strengthening

1 Durability issues

The reinforcement effect and durability of the reinforced concrete members after carbon fiber reinforcement are issues that the engineering community is more concerned about. Because carbon fiber reinforcement technology is an emerging reinforcement technology, and the factors that affect the durability of carbon fiber include environmental factors, temperature, ultraviolet radiation, freeze-thaw cycles, and so on. Through indoor salt spray test, alkali resistance test, fatigue test of specimens and other accelerated aging tests and investigation of reinforced bridges, the conclusion is that carbon fiber has sufficient durability to ensure that carbon fiber is used in structural repair and reinforcement.

2 Structure dynamic performance

Carbon fiber material is a kind of linear elastic brittle material. The brittle failure of carbon fiber reinforced concrete structure under impact load or dynamic load should be paid more attention. Through the impact load test of the reinforced bridge, it is proved that the impact resistance of the carbon fiber reinforced beam under the impact load is good. If appropriate anchoring measures are adopted at the end of the carbon fiber, the impact resistance of the carbon fiber reinforced beam can be improved.

3 Anti-fatigue problem

The fatigue resistance evaluation of carbon fiber reinforced concrete structures generally should be conducted for two failure modes: bending fatigue failure and shear fatigue failure. The research shows that the carbon fiber reinforced concrete has undergone a certain number of fatigue cyclic loading, and the static load test and deflection test have not reduced its strength and ductility compared with the specimens that have not undergone fatigue cyclic loading. This shows the excellent performance of the carbon fiber material itself in anti-fatigue.

4 Bonding performance and ductility

The overall composite effect of carbon fiber-reinforced concrete structures is mainly achieved through good bonding between carbon fiber and concrete. The failure of the bonding zone may lead to brittle failure of the structure, and the peeling failure of the bonding interface can be summarized into three types.

(1) The peeling failure caused by the stress concentration at the end of the carbon fiber that spreads toward the middle of the beam.

(2) At the point where the bending moment is the largest, the peeling failure caused by the bending crack to expand to both ends.

(3) The peeling failure caused by the shear cracks.