1. Insufficient load-bearing capacity of beams defined by standards, severe rust on the main steel bars of vertical beams, or severe transverse cracks in the load-bearing beams of beam trusses can be addressed by bonding steel plates to the concrete structure's bending edges or thin sections using adhesive and bolts. This creates an overall bond with the structure, replacing the added reinforcing steel bars with steel plates.

2. Advantages:

(1) Technical L leads, with excellent features (2) Compact space requirement (3) Shortened reinforcement and renovation cycle time (4) Low raw material consumption (5) Simple processing technology

3. Application Areas: (1) Suitable for beams and beam components subjected to bending. (2) Integrated into girder bridges with ambient working temperatures not exceeding 60°C, relative humidity not exceeding 70%, and non-corrosive environments. (3) Utilizes advanced structural adhesives and approaches new adhesive types with caution. (4) Experimental evidence indicates that the bonding tensile and compressive strengths exceed those of concrete, with failure occurring in the concrete rather than the adhesive. The bonding strength between steel plate and concrete primarily depends on the concrete's own strength. The compressive strength of the component concrete should not be too low, otherwise, the full effectiveness of the steel plate and adhesive cannot be fully realized.

4. Raw Material Specifications: (1) Adhesive elastomer molds have high elasticity, low thermal expansion coefficient, excellent ductility, and good durability.

(2) Steel plates for structural reinforcement are generally suited for Grade 3 steel or 16 alloy steel. The design values for the strength of steel plate, bolted connections, and welding should be selected in accordance with the current standards for steel structural architectural design.

5、Steel ReinforcementLiang's Destruction Characteristics and Stress Analysis(1) The damage characteristics are within the range of the appropriate reinforcement. As the load increases, the steel reinforcement in the original beam yields, and the steel plate also accommodates the deformation. Subsequently, the concrete is damaged and fails. For reinforced concrete beams with steel plate bonding, the failure mechanism mostly involves partial detachment between the steel plate and concrete, with longer tensile cracks along the interface. The concrete is torn apart, leading to structural failure. In the case of shear-reinforced components with steel plate bonding, the failure is similar to that of general reinforced concrete shear components, starting with diagonal cracks, followed by rapid development of gaps, a significant increase in the stress on the steel plate, and ultimately causing the component to fail. However, in the latter stages of the loading process, it is noticeable that the anchorage ends of the steel reinforcement are damaged, and even detached. Some tests also indicate that the steel plates bonded to the foundation beam did not reach the tensile strength, but rather, the detachment between the steel plate and concrete caused the failure of the reinforced bonding beam.

(2) Stress analysis reveals that the reinforced steel beams exhibit a stress lag phenomenon, but during failure, the steel plates generally reach their tensile strength. Therefore, their cross-sectional bearing capacity can be measured according to that of typical bending components. Due to the delayed pressure of the bonded steel plates, when the steel plates reach a compromise, the deflection values and gaps of the structure reinforcement beams are slightly larger.

For reinforced concrete bending members strengthened with steel plate, there exists not only radial shear principal stress between the steel plate and concrete but also axial principal stress due to the bending effect of the member. As both the radial shear principal stress and the axial principal stress act together Chlorinated rubber sealant at the junction between the weather-resistant joint and the component has caused diagonal and horizontal cracks on the concrete surface. These cracks originate at the end of the structural reinforcement steel plate and expand along the length of the beam, eventually leading to the steel plate detaching from the concrete. Ductile failure should be prevented in such situations.

The key reasons for such damage are as follows:Rebar lap lengths are insufficient: The bending zone must not be less than 200t (where t represents the thickness of the steel plate) or less than 600mm. In the load-bearing area, it must not be less than 160t or less than 480mm. Quality issues with adhesive products: The weather-resistant adhesive used on-site must be regularly tested; its strength should not be less than that of concrete. However, there is no unified standard for testing weather-resistant adhesive, and only experience-based methods can be referred to. Impact on engineering quality: The effectiveness of steel plate reinforcement is closely related to the quality of construction work. The bonding, fixing, and pressure-filling should be continuously inspected to ensure the density of bonding. Otherwise, it is easy for the adhesive steel plate to be torn off. To ensure the quality of construction work, steel plate reinforcement must be carried out by systematic construction personnel.

6. Steel Reinforcement Calculation

7. Bonded SteelReinforcement EngineeringConstruction(1) The structural specification requires that the concrete mortar strength grade for the bottom layer reinforced with steel plate not be less than C20. The thickness of the steel plate for reinforcement should be between 2~6mm, with 4mm being commonly used. The length of the steel bars overlap must comply with certain structural regulations: for the bending zone, it should not be less than 200t (where t is the thickness of the steel plate) or less than 600mm; for the load-bearing zone, it should not be less than 160t or less than 480mm; for large-span steel structures or those likely to bear repeated loads, additional reinforcement measures such as U-shaped steel hoops or anchor bolts should be installed in the anchoring zone. To slow down the aging of the adhesive and prevent rust on the steel plate, as well as the adjacent concrete surface, a sealing, waterproof, and anticorrosive treatment should be applied. A simple and effective method is to use M15 cement mortar for coating, with a minimum thickness of 20mm for beams and 15mm for slabs.

Steel ReinforcementConstruction Techniques and Standards:

8. Process Quality Control and Engineering Reinforcement Product Quality Inspection Methods (1) Basic Principles ① The materials, specifications, and quality of steel plate structures used for reinforcement must comply with the design requirements; ② The construction process must follow the prescribed procedures, with pressure and curing times in accordance with the design requirements; ③ The total number, specifications, and anchoring length of the bolts must not be below the allowable values; ④ Rust prevention treatment must be conducted according to the design requirements.

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