When we use CFRP in a reinforced concrete structures?

According to the mechanical characteristics of bonded fiber composite, the carbon fiber reinforcement method is only applicable to the reinforcement of reinforced concrete members under bending, tension, axial compression and large eccentric compression. It is not recommended to be used for strengthening small eccentric compression members. Because fiber reinforced composites are only suitable for bearing tensile stress, and the longitudinal tensile reinforcement of small eccentric compression members cannot reach the yield strength, the use of bonded fiber reinforced composites will cause a great waste of materials. Therefore, for small eccentric compression members, other appropriate methods should be recommended.

In practical projects, it is often encountered that the concrete strength of the original structure is lower than the minimum strength grade specified in the current design code. If the strength of the original structural concrete is too low, the bond strength between it and the fiber composite will also be very low, which is prone to brittle peeling failure. At this time, the fiber composite cannot fully play its role.

The fiber composite cannot bear the pressure, and only its tensile effect can be considered, so the fiber stress mode is required to be designed to bear only the tensile stress.

When strengthening with fiber reinforced composite materials, measures should be taken to unload the load as much as possible, which is to reduce the impact of secondary stress, that is, reduce the hysteresis strain of fiber reinforced composite materials, so that the strengthened structure can make full use of the strength of fiber materials

Why use carbon fiber to reinforce concrete structures?

First of all, the high strength of the carbon fiber cloth and the construction fit of the reinforced concrete building structure are important factors. The test proves that the strength of the carbon fiber cloth is seven times that of ordinary steel, and the tensile strength is not comparable to ordinary steel. The use of carbon fiber cloth to strengthen reinforced concrete structures is fundamentally determined by its characteristics.

Secondly, the carbon fiber cloth is very light, soft and flexible, much better than ordinary steel. On the premise of shape fixation, the carbon fiber cloth is attached to the surface of the reinforced concrete structure for reinforcement. The shape of the carbon fiber cloth can be changed at will, and will not increase the weight of the reinforced concrete structure, nor increase the burden of the reinforced concrete structure, nor affect its load capacity.

In addition, the corrosion resistance of carbon fiber cloth is very strong, and the weathering wear caused by sunshine, wind and rain is very low. When the carbon fiber cloth is used to strengthen the concrete structure, even if the carbon fiber cloth is exposed and attached to the concrete surface, the carbon fiber cloth receives little environmental wear during the use of concrete buildings, and can even play a role in protecting the concrete structure.