Civil engineering construction can be roughly divided into three stages: the new stage, the stage of demolition and reinforcement, and the stage of structural strengthening.

Many developed countries have stepped into the stage of strengthening mainly. At present, our country is in the stage of construction and maintenance plus coexistence. The characteristics of this stage are that the reasons for the lack of design consideration or data collection, construction error and environmental conditions are often unable to meet the requirements of structural safety, applicability and durability.

Limited to the current conditions of our country, the demolition and reconstruction of these buildings is not only a waste of material, pollution, delay time, but also a huge cost, which is not allowed for the national conditions and financial resources of the same.

Therefore, in order to ensure the safe use of these buildings, it is necessary to carry out reasonable maintenance and reinforcement.

According to different engineering structures, the reinforcement methods proposed by people are different. How to choose a reasonable reinforcement method is a problem that must be considered in reinforcement design. Additional methods such as increasing cross section reinforcement, in vitro pre reinforcement, sticking steel reinforcement, and sticking carbon fiber fabric (CFRP) reinforcement, but more or less have some shortcomings or deficiencies.

In recent years, many new reinforcement methods have been put forward to meet different needs. In this paper, the new reinforcement methods are analyzed and discussed from the strengthening nature, so that the designers can choose more reasonable reinforcement schemes according to different reinforcement purposes.

According to the different additive properties. The addition of the structural strengthening includes three aspects: bearing capacity (strength) reinforcement, service function (rigidity) reinforcement and durability reinforcement.

1) reinforcement of bearing capacity

Strengthening of bearing capacity is the basis for ensuring structural safety. Due to the long or unreasonable design and construction error, the existing or newly built structures need to be strengthened and strengthened to meet the requirements.

2) use function reinforcement

The use of functional reinforcement is necessary to ensure the normal work of the structure. Due to material aging, load aggravation and function change, the engineering structure has too large deformation and insufficient bearing capacity. It is necessary to reinforce and reinforce it, increase the rigidity of the section, and ensure the normal work of the structure.

3) durability reinforcement

Durability reinforcement refers to the repair and reinforcement of structural damage parts, improving the reliability of structures, improving the use function of structures, and prolonging the service life of structures. The structural damage parts should be repaired, reinforced and reinforced for the cracks and corrosion of the steel bars in order to prevent the deterioration of the structural damage part and eliminate the hidden damage and prolong the service life of the structure.

Structural strengthening is an important measure to improve the safety, applicability, durability and normal use of the structure. Whether the selection of reinforcement methods is reasonable related to the strength, stiffness and durability of the material in the original structure. Therefore, how to choose a suitable reinforcement plan is one of the keys to decide whether the reinforcement design is successful.