Existing building structures Due to changes in the use of functions, errors in design or construction, aging of the structure itself, changes in code requirements and seismic effects, the structural bearing capacity and structure cannot meet the requirements. Therefore, it needs to be reinforced and repaired. For the reinforcement of columns, methods such as increasing the cross-section, enclosing steel plates, and applying prestressed braces have been used in the past. 

In recent years, with the development of fiber composite materials, composite strengthening have been widely used in the reinforcement of columns. On the one hand, the fiber composite material can improve the seismic performance of the column. On the other hand, the bearing capacity of the column can also be improved by its restraining effect on the core concrete.

Externally bonded FRP materials technology

Fiber reinforced concrete column is the most commonly used construction method of reinforced concrete column reinforced with fiber composite material. This method was first proposed by Fardis and Khalili in 1981, and Japan applied it to actual projects in the mid-1980s. 

According to the different methods of fiber cloth infiltration resin, this construction method can be divided into two construction procedures. One is to pass the fiber cloth through the special equipment at the construction site to make it fully infiltrated with resin, and then paste the fiber cloth infiltrated with resin on the outer surface of the reinforced concrete column; 

Another method is to first paint resin on the outer surface of the reinforced concrete to which the fiber cloth needs to be pasted. Then stick the fiber cloth, and then use the roller to fully immerse the fiber cloth in the resin. Then brush another layer of resin and paste a layer of fiber cloth, and so on.

The construction technology using fiber cloth is either one-layer or multi-layer full-wrapping method (a), spirally wrapped fiber cloth (b) or ring-shaped part-wrapped fiber cloth (c).

Advantage of externally bonded FRP materials technology

The method of wrapping fiber cloth is widely used, mainly because it is suitable for reinforced concrete columns of various cross-sectional shapes, does not require special construction equipment, and is convenient for on-site construction and flexible to use.