With the continuous increase of the total number of bridges, most of the bridges are facing the problems of low technical standards and poor capacity, so that they cannot meet today's growing traffic demand, and have even threatened the bridge's driving safety.

In order to ensure the safety and normal operation of the bridge and extend the service life of the bridge, it is essential for bridge inspection, maintenance, and maintenance. However, with the continuous increase of the service life of the bridge, the problems of reduced bearing capacity and excessive capacity are prone to occur. At this time, it is necessary to take necessary maintenance and reinforcement measures for the bridge to meet new requirements for use.

Basic conditions for bridge reinforcement

Due to the special features of bridge use functions, not all bridges are suitable for reinforcement.

First of all, the reinforced bridge must meet the requirements in terms of bearing capacity and durability. Reinforcement of the bridge does not mean that the bearing capacity of the bridge can be increased without limit. The integrity and joint work of the new reinforcement system and the old concrete structure need to be considered. Avoid the situation where the reinforcement system is delayed and the concrete structure is preferentially damaged.

Secondly, the reinforced bridge should have obvious economic and social benefits. When the bridge is severely diseased, it may be considered to abolish and rebuild it, but this method not only needs to consider the cost and time consuming of the new bridge, but also the cost of dismantling the old bridge. Generally, the reinforcement and reconstruction of the old bridge is less than about 50% of the investment in newly-built bridges of the same size. Therefore, the method of reinforcement and reconstruction is more advantageous when the safety conditions are met.

Application of carbon fiber in bridge reinforcement

In bridge reinforcement, it is necessary to reduce disturbance, damage to the original structure and increase of self-weight after reinforcement as much as possible, while taking into account the feasibility of construction operations. Carbon fiber cloth is lightweight, high-strength, and convenient for construction, which can be fully used in bridge reinforcement. Therefore, carbon fiber cloth can be used in bridges and can be used in load-bearing members such as main beams and piers, and can also be used in non-load-bearing members.

In the reinforcement of the bridge's main beam, carbon fiber cloth can be equivalent to steel bars. Carbon fiber cloth is pasted along the main tensile stress direction of the bridge, and anchoring sections are set at both ends, which can effectively prevent the generation of cracks and improve the bending stiffness of the main beam. It can also be affixed to the side of the beam to play a similar mechanism to the stirrup to improve the shear bearing capacity of the main beam. Carbon fiber cloth can also be used in the reinforcement of axially compressed pier columns. The hoop beam method can be used to wind the pier columns with carbon fiber cloth to restrain the lateral deformation of the column, thereby improving the compressive strength of the pier column.

It should be noted that carbon fiber reinforcement not only needs to pay attention to anchoring, but also needs to pay attention to the issue of dosage. First of all, the carbon fiber cloth has high strength, and excessive use will cause waste of materials. Secondly, the arbitrary use of carbon fiber cloth will reduce the ductility of concrete and affect the failure form of flexural members. The tensile failure of the carbon fiber cloth is transformed into sudden collapse of the concrete in the upper compression zone of the bending member. The compression failure is sudden and dangerous.