Under the combined effect of the long-term natural environment and use environment, the reliability of reinforced concrete structures is bound to show a downward trend. Coupled with uncertain factors in the process of design, construction, and use, the function of the concrete structure is gradually weakened, and ultimately it cannot meet the reliability requirements of structural safety, applicability and durability. Therefore, in practice, strengthening projects for reinforced concrete structures are not uncommon, and they are increasing day by day and are becoming more and more intense. There are many strengthening methods for reinforced concrete structural members, among which the enlarged section method, the method of pasting steel plate and the method of pasting carbon fiber are more used. This paper takes the insufficient flexural bearing capacity of the reinforced concrete simply supported beam as an example, and uses the steel plate strengthening method and the carbon fiber composite material strengthening method for strengthening design calculations. From the perspectives of method, technology, economy, etc., it is comparatively investigated to provide a reference for selecting the best solution in practice.

Externally bonded carbon fiber structural strengthening method

Carbon fiber strengthening is to stick carbon fiber cloth on the surface of concrete components with high-performance epoxy structural adhesive, and use the good tensile strength of carbon fiber materials to achieve the purpose of enhancing the bearing capacity of the components. It is suitable for the strengthening of beams, slabs and shear walls of new and old concrete structures and some special components. Use special epoxy resin to paste carbon fiber cloth with extremely high tensile strength on the surface of concrete structure and form a whole with it to work together.

External bonding steel strengthening method

The bonding steel strengthening method is to use high bonding strength bonding material to adhere the steel plate to the surface of the reinforced concrete member with insufficient bearing capacity. The bonding force between the steel plate and the concrete surface is used to transfer the shear force, so that the steel plate and the original reinforced concrete form an integral body, forming a secondary combined force component, so that the overall work is under common force. The essence of this method is a kind of external strengthening, which is the same as the relationship between steel bars and concrete in reinforced concrete structures. As a part of the tension strengthening, the externally bonded steel plate plays the role of tension strengthening. By increasing the amount of strengthening of the original component, the rigidity, tension, compression, bending, and shear performance of the component are correspondingly improved.

Economical and technical comparison of bonded steel method and carbon fiber strengthening concrete beam

• Cost budget

According to the calculation data, under the premise that the flexural bearing capacity of the component section has the same increase, the total construction cost of the steel-bonded strengthening method is 4170.69 yuan, and the total construction cost of the carbon-bonded cloth strengthening method is 3217.58 yuan, which is quite different. The results show that the economical efficiency of steel-bonded strengthening is less than that of carbon-bonded cloth strengthening, but the same strengthening effect can be obtained.

• Comparison of technical performance of the two methods

The two strengthening methods have their own advantages and disadvantages in the comparison of the above projects. The technical performance of the two is equivalent, but the economic performance is significantly different. The author suggests that in the case of static strengthening, if economy is not considered, both methods can be selected. When the seismic performance requirements of the components are relatively high, the bonding steel strengthening method should be used instead of the carbon fiber bonding method.