There are many factors that affect the effect of bonded steel reinforcement, mainly from the selection of materials, construction technology and other aspects to optimize. This time we summarized the following 5 points:

First. Surface treatment

Second, steel plate selection

Third, the quality of glued steel glue

Four, U-shaped hoop and bead setting

Five, anchor bolt installation

Surface treatment

The bonding surface treatment of the reinforcing member and the steel plate bonding surface treatment are particularly important. If the base surface treatment is not in place, the bonding effect will be poor, and bonding peeling may occur in severe cases.

1. The local damage of the reinforcing member needs to be chipped first, and then repaired with fine-stone concrete not lower than the original concrete strength level, and then reinforced.

2. Treatment of the old concrete base surface (with grease stains): Use a stiff brush dipped in high-efficiency detergent to remove the grease stains on the surface, clean with water, and then polish the bonding surface to remove the 2~3mm thick surface layer and dry it deal with.

3. The concrete with high humidity needs to be dried until it is completely dried.

Second, steel plate selection

1. The thickness of the steel plate that is directly glued should not be greater than 5mm; the thickness of the steel plate is greater than 5mm, and it should be bonded by low-pressure glue injection.

2. When strengthening the normal section of reinforced concrete bending members, the steel plate should be pasted with strips, and the width to thickness ratio of the steel plate should not be less than 30.

Third, the quality of glued steel glue

The quality of glued steel glue often determines the reinforcement effect. Therefore, we need to pay attention to the following points when choosing high-quality glued steel glue:

1. Choose high-quality steel glue. According to GB 50728-2011 "Technical Specification for Safety Appraisal of Engineering Structure Reinforcement Materials" 3.0.1, it clearly requires that all engineering structure reinforcement materials and products that involve engineering safety must pass the safety appraisal according to the requirements of this code.

2. Choose suitable adhesives. In case of some special construction environments, you must choose customized products. For example, for steel bonding reinforcement in a high temperature environment, it is necessary to select a special high temperature resistant structural adhesive for construction. Conventional adhesives cannot still be used, otherwise it will cause bonding failure and affect the quality of the project.

Four, U-shaped hoop and bead setting

The following content is compiled from JTG/T J22-2008 "Code for Design of Highway Bridge Reinforcement".

When the pasted steel plate extends to the edge of the support and still does not meet the extension length requirements of Article 6.2.5, the following anchoring measures shall be taken:

1. On the beam

U-shaped hoop should be uniformly arranged within the extension length, and a reinforcing hoop should be arranged at the end. The U-shaped hoop should extend to the bottom surface of the beam flange plate. The width of the U-shaped hoop should not be less than 200mm for the end hoop; for the middle hoop, it should not be less than 1/2 of the width of the steel plate under bending and should not be less than 100mm. The thickness of the U-shaped hoop shall not be less than 1/2 of the thickness of the steel plate under bending. The upper end of the U-shaped hoop should be provided with longitudinal steel bead; the gap under the bead should be filled with glued steel spacers.

2. On the slab

A bead perpendicular to the direction of the stressed steel plate should usually be set within the extension length. The bead shall be evenly arranged within the extension length, and one line shall be provided at the end of the extension length. The width of the steel bead shall not be less than 3/5 of the width of the reinforced steel plate under bending, and the thickness of the steel bead shall not be less than 1/2 of the thickness of the reinforced steel plate under bending.

Five, anchor bolt installation

GB 50550-2010 "Code for Acceptance of Construction Quality of Building Structure Reinforcement Engineering" clearly stipulates that chemical anchor bolts shall be used for anchor bolts reinforced by bonded steel, and expansion bolts shall not be used.

Anchor bolts should be used to directly apply glue to the steel plate, and the anchoring depth should not be less than 6.5 times the diameter of the anchor bolt. The spacing between anchor bolts should meet the following requirements:

1. The maximum distance between anchor bolt centers is 24 times the thickness of the steel plate; the minimum distance is 3 times the anchor bolt hole diameter.

2. The maximum distance between the anchor bolt center and the edge of the steel plate is 8 times the thickness of the steel plate or 120mm, whichever is less. The minimum distance is 2 times the hole diameter of the anchor bolt.

3. If the anchor bolt is only used for steel plate positioning or pasting and pressing, it is not subject to the above restrictions.