1.Bridge repair and reinforcement projects are often restricted by the space of the original structure and components. The construction site space is small, and it is difficult for large prefabricated components to enter the site and play a role;

2. In order to carry out construction without interrupting traffic or with less traffic interruption, bridge repair and reinforcement projects require simple and fast construction techniques, short construction periods, and are often carried out in stages;

3. In the process of bridge repair and reinforcement construction, there is a large amount of removal work, the process is cumbersome, and there will be many unsafe factors;

4. During the construction of bridge repair and reinforcement, it is often unfavorable to the original and adjacent structures and components, so the original structure should not be damaged as much as possible during the implementation of the project;

5. The balance of strength, stiffness and service life of new and old structures and the coordination of new and old structures should be fully considered in the reinforcement and enhancement of bridges;

6. When the structure is damaged due to freeze-thaw, corrosion, uneven settlement of the foundation, etc., it is necessary to consider effective measures to reduce, resist or all unfavorable factors to avoid continuous damage to the reinforced structure. When the upper and lower structures of the bridge have disease problems at the same time, it is necessary to treat the diseases of the lower structure before strengthening the upper structure;

7. For structures that may have unsafe factors such as cracking, tilting or collapse, temporary measures should be taken before reinforcement construction to prevent safety accidents;

8. Compared with newly built bridges, bridge reinforcement projects have higher economic benefits, and the cost only accounts for about 20-30% of the newly built bridges. How many years can the floor slab be used for ordinary reinforced concrete floor slabs, under normal stress conditions (the use does not exceed the normal design load), according to the current concrete strength life calculation, the general design life is 50 years, 70 years.