The concrete column is mainly used to bear the vertical and horizontal loads, and it is easy to be damaged under the earthquake. There are four types of failure: shear failure, bending failure, longitudinal reinforcement overlapping failure and bending shear failure. In order to improve the seismic performance of concrete columns, it is a better choice to strengthen them with carbon fiber sheets, which can prevent the deformation of columns before they are damaged.

At present, the common reinforcement method on the market is to paste carbon fiber cloth in a circular way, which is a little like adding stirrups to constrain the transverse deformation of concrete, so as to improve the ductility of concrete columns to a certain extent. Of course, the longitudinal carbon fiber cloth can also be used to enhance the seismic performance of concrete columns.

1. Reinforcement method of pasting carbon fiber cloth along the column circumference

The seismic strengthening method of concrete columns is the same as the strengthening method of the normal section of columns.

The carbon fiber cloth mainly plays a similar role to the stirrup. The carbon fiber cloth forms an effective constraint on the core concrete, which can inhibit the concrete spalling and buckling of longitudinal bars, so that the column has a good inelastic bending deformation capacity. The constraint provided by the carbon fiber cloth can prevent the bond failure and sliding of the longitudinal bar lap joint, and the carbon fiber cloth can improve the shear resistance of the column.

Therefore, pasting CFRP along the circumference of the column can prevent the shear failure, bending plastic hinge failure and longitudinal reinforcement lap failure of the column, and improve its seismic performance.

2. Reinforcement method of pasting carbon fiber cloth along the column longitudinal direction

It is mainly to improve the bending resistance of the column. This pasting method requires that the end of the carbon fiber cloth is anchored reliably, and usually the carbon fiber cloth is also pasted along the column ring.

However, it should be noted that this strengthening method will also cause a large additional force to the adjacent members. Therefore, when the column is strengthened with CFRP sheets in the longitudinal direction, attention should also be paid to the improvement of the flexural capacity of the strengthened column. It is not advisable to increase the flexural capacity of the column too much.

Finally, it is necessary to comprehensively master the reinforcement methods of concrete columns, so that according to the different types, section forms, positions and stress conditions of columns, the corresponding reinforcement structure can be used to achieve the goal of safety and reliability.