1 Project Overview

The main body of a project has 18 floors above ground, and the height of the main body of the building is 63.45m. The height of the first floor is 5.1m, the second to fifth and tenth floors are 4.4m, and the other floors are 3.3m and 3.0m. The project adopts cast-in-place reinforced concrete frame shear wall structure, and the column size is 6.5×7.2m and 6.5×7.8m. The concrete strength grade is C40 below eight layers and C35 above. The seismic fortification intensity of the project is 8. , The design seismic acceleration is 0.20g, the seismic fortification category is Category C, the seismic group is the second group, the seismic grade frame is Class II, the shear wall is Class 1, and the site is Class II.

2 Questions raised

During the construction, a 2.5m cantilevered outer corridor was added, and the reinforcement of the four adjacent frame columns was not adjusted accordingly, which left hidden dangers to the quality and safety of the project. The main problems are as follows:

2.1

The minimum longitudinal steel reinforcement ratio after the 2~3 storey column is reinforced with outer concrete does not meet the requirement of 0.7, and further reinforcement is required.

2.2

The seismic performance of the first-layer outer concrete reinforcement method is not good, mainly because one side is not reinforced, and the reinforced stirrups are not closed and need to be further reinforced.

3 Reinforcement mechanism of carbon fiber reinforced frame columns

Since carbon fiber reinforcement is mostly used for reinforcement of flexural members, it is still necessary to understand its reinforcement mechanism when used for reinforcement of biased members.

When using carbon fiber to wrap and reinforce the frame column, the main function of carbon fiber cloth is to restrain the internal concrete. Because the tensile strength and elastic modulus of carbon fiber are high, this restraining effect is obvious. When the concrete is compressed and produces lateral deformation, the carbon fiber cloth can restrain the concrete deformation and increase the ultimate compressive strain of the concrete. As a result, the crushing of the concrete in the compression zone is postponed, the plastic deformation performance of the longitudinal reinforcement is fully exerted, the ductility of the reinforced concrete frame column is improved, and the bearing capacity and seismic performance of the frame column are improved.

4 Carbon fiber structural reinforced design

Under the premise of structural force analysis and calculation, combined with the comparison and selection of frame column reinforcement schemes, the selection of carbon fiber reinforcement method is more appropriate. The carbon fiber reinforcement design is shown in Figure 1-carbon fiber reinforcement construction drawing.

5 Carbon fiber structure reinforcement material

5.1 Carbon fiber cloth

The carbon fiber reinforcement material adopts woven carbon fiber cloth, and its specifications are shown in Table 1:

HM-30 Carbon Fiber Fabric TDS.pdf

5.2 Carbon fiber bonding material

The carbon fiber bonding material adopts HORSE carbon fiber adhesive.

HM CFRP Fabric Epoxy TDS - Horse.pdf

6 summary

For frame columns with poor seismic performance and insufficient structural reinforcement, carbon fiber structure is used for reinforcement. The carbon fiber reinforcement mechanism is clear and the design is reasonable. After reinforcement, it has been used for many years. The working performance of the components has not been abnormal. It shows that the carbon fiber reinforced frame columns can not only improve the bearing capacity, but also effectively improve the seismic performance of the components, which is worthy of promotion.