Retrofitting of reinforced concrete bridge

Bridge retrofitting reasons:

1, With the development of economy, the traffic volume increases and the load grade changes.

2. The guiding ideology of early design focuses on material saving and low safety.

3, Poor bridge durability and aging, such as brick arch bridge.

4. Because of improper design or poor construction quality, the bridge built is also reinforced.

Difficulty in retrofitting :

1, The opened  bridge has realistic traffic needs, because it needs to be reinforced without interruption of traffic, so there is traffic interference during reinforcement.

2, The restriction of structural form, the principle of reinforcement must generally be carried out by using the original structure, so it is limited.

3, The combination of new and old structures is a difficult problem, including changes and transitions in the old and new structural systems, including the joint of new and old bridges.

4, The risk is large, most of the bridges to be reinforced are dangerous bridges, the structure is in a bad state, some of the old bridges lack the original design data and construction records, the internal structure is unknown, the existing stress situation is different, it is difficult to determine the limit of its force, which brings the risk to the old bridge reinforcement.

According to the location of bridge reinforcement, the bridge can be divided into upper structure reinforcement and substructure reinforcement.

There are commonly used methods to reinforce the superstructure of bridges, such as enlarging section method, externally bonded carbon fiber reinfroced  fabric sticking steel reinforcement method, strengthening method of external prestressing force, adding auxiliary component method and system conversion method, etc.

The reinforcement methods of bridge substructure include expanding foundation reinforcement method, high pressure jet grouting reinforcement method, reinforced concrete hoop and outer steel plate.

It is necessary to explain that the application of these methods is not single. It is necessary to choose the reinforcement method or combine with each other according to the actual conditions. And before the use of these methods, it is necessary to strengthen the cracks and the hemp defects after the treatment of the bridge.