Strengthening of RC by external steel plate

Project overview

The program is buildings seismic reinforcement project, the total construction area is 16892 M², the structure type is brick concrete. The main contents of reinforcement are internal and external walls, floors, gird and structural columns, repair of cracks in windows, openings and walls. After the reinforcement of the project, its subsequent service life is no less than thirty or forty years. Structure safety grade two; seismic fortification class B; seismic fortification intensity 7 degrees, first group 0.10g, seismic measures 8 degrees, component aseismic grade three, standard freezing depth 0.73 m, basic wind pressure 0.50 kN/m 2, basic snow pressure 0.35 kN/m 2, masonry construction quality control grade B grade.

Construction characteristics of bonded steel palte reinforcement

Compared with other reinforcement methods, the method of structural bonded steel has many unique advantages and advanced nature. Its bonding strength is high, its strength after curing is much more than the strength of the original component. It has good water resistance and medium resistance, and also has good physical and mechanical properties. The stress on the joint of the riveted and welded components is uniform, and the stress concentration phenomenon is not produced, and the fatigue resistance, crack resistance and integrity are good. The utility model has the advantages of simple technology, convenient operation, fast construction speed, high efficiency, short construction period, low cost and good effect.

Application scope

The bonded steel reinforcement method is applicable to members bearing static loads, such as bending, tension, shear and other components. The specific application scope is as follows:

1) the welding point breakage of reinforcing steel bar and reinforcement of leakage reinforcement during construction.

2) the strength level of the structure or component is not up to that, and the structural strength is strengthened.

3) comprehensive reinforcement of old buildings and seismic reinforcement with adding layers;

4) bridge crane girder and suspension crane beam to improve load reinforcement;

5) the fracture of the root of the balcony and the fracture of the thin abdominal beam are strengthened.

6) improve the bearing capacity of columns to solve the problem of column axial compression ratio exceeding standard reinforcement.

7) the consolidation of the floor load;

8) Liang Zhu was strengthened by chemical corrosion.

9) the corrosion of the lower string of the frame beam is seriously exposed to reinforcement

Basic principle

Uses the strong adhesive bonding to concrete, work together. It makes full use of the bearing capacity of the original component, improves the bearing capacity of the structure through the joint action of the post stick steel plate and the original component, and strengthens the shear, earthquake resistance and stability, and improves the stress state.

Construction technology

1.Steel plate prepare

According to the design drawings, according to the actual size of concrete components, the steel plate is blanking, forming and drilling.

2.Surface treatment of concrete and steel plate

2.1 Concrete surface treatment

According to the design requirements of the drawings, lay the thread and drill holes on the concrete surface first, then bury the bolts. For the adhesive surface of the original concrete component, it is dipped in acetone with a hard brush, washed away from the surface oil and dirt, then flushed with cold water, and then grinding the adhesive surface to remove 2 mm ~ 3 mm thick surface until the new surface is completely exposed, and the powder is blown away with the oil free compressed air, and the surface can be wiped with the defatted cotton dipped in acetone after completely drying.

2.2 Surface treatment of steel plate

The bonding surface of the steel plate must be derudied and rough treated. If the steel plate is not rusted or lightly corroded, sandblasting, abrasive cloth or flat grinding wheel can be used until the metallic luster appears. The bigger the roughness is, the better the grinding texture should be perpendicular to the stress direction of the steel plate. Then, use the skimmed cotton dipped in acetone to wipe clean. If the corrosion of the steel plate is serious, we must first soak 20 min with moderate hydrochloric acid, make the rust layer fall off, rinse with lime water, neutralize the acid ion, and finally use the flat grinding wheel to grind out the grain

3.Unloading of reinforced components

The reinforcement members should be unloaded before sticking steel plates. If the jack lifting is adopted, a multi point (at least 2 point) top lift should be adopted for the beam bearing the uniform load. For the main beam with the action of the second beam, 1 Jack shall be set under each beam, and the top tonnage does not appear on the top surface.

4.Applying steel plate adhesive

When the adhesive is prepared, the adhesive is applied to the treated concrete surface and the steel plate surface. In order to make the adhesive fully infiltrate, permeate, diffuse and adhere to the surface, it should be wiped back and forth with a small amount of glue first, to the design thickness of 1 mm to 3 mm, the middle thick edge is thin, and then the steel plate is attached to the reservation. Position. After sticking the steel plate, gently hammer the steel plate along the paste surface with the hammer. If there is no voids, it means that it has been pasted tightly. Otherwise, the steel plate should be stripped and pasted again.

5.Fixed, pressurized

After the steel plate is properly adhered, the expansion bolts should be tightened and pressurized immediately so that the glue liquid is just extruded from the side seam of the steel plate.

6.Curing 

Curing at room temperature, holding at 20 degrees centigrade, 24 h can dismantle clamp or support, 3 D can be used force, if the temperature is below 15 C, should take artificial heating, the general use of infrared light or electric blanket heating insulation, curing period must not have any disturbance to the steel plate.

7.Test

When the sticky steel reaches the design strength, the relevant personnel will be checked and accepted.

8.Protect

After acceptance, the surface of the steel plate is bonded with a layer of lead wire mesh and 20 M15 cement mortar protection layer is applied.