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The Project of Pasting Steel Transformation

The Project of Pasting Steel Transformation

A, project summary
This project has been completed the main structure pouring, not done the decoration engineering construction. because the construction institution modifies the building plane and function of this project, parts of the structure should be reinforced. According to the construction drawing of reinforcement that an architectural design institute provides, combined with the relevant state reinforcement technique specification and requirements, to ensure the construction quality, making the construction plan.

Second, the construction technology of sticking the steel and reinforcement
1.1, the material requirements
the material design of sticking steel plate adopts Q345 steel. the thickness of the steel plate is 3 mm. the adhesive of sticking steel structure
(1)adopts the domestic class A adhesive. its safety performance must meet the regulations of  GB50728-2011 "the application safety appraisal standard of the engineering structure reinforcement material".
(2)the adhesive for sticking the steel structure is strictly forbidden to use ethylenediamine modified epoxy resin curing agent;It is forbidden to add volatile harmful solvents and non-reactive diluents.
U-type hoop uses chemical anchor bolt M12; if there is not design description at the bottom of plate, the bottom of the beam, the steel plate of the beam surface, we can use M8 bolt to fix and  pressure the anchoring.
1.2, the construction requirements
Before the installation of steel plate, removing the oil and rust of the bonding surface, and polishing it until it has the metallic luster and texture with the grinding wheel and grinding slice.
After the bonding and full curing, brushing the preservative on the surface of steel plate or smearing the protective layer of  25 thickness and 1:3 cement mortar on the structural steel surface.
2, construction preparation
2.1 site cleaning: cleaning the barrie of  bonded steel operation, the component fabrication and material configuration operation scene, and setting up the operation platform. cleaning the floor of the area of making up the adhesive.
2.2 setting up the scaffold or platform: according to the kind of bonded steel component, location, elevation and the actual conditions of the scene, setting up the appropriate and safe scaffold or platform. Scaffold and platform are stable and solid. installing the insulation bar, skirting board and other safety protection equipment.
2.3 insulation power wires and power supply can lead in the operation area and connect with the brake box of the electricity by erecting and connecting. the linear distance of the electricity brake box and operation platform workers should satisfy the safe distance of the electrical equipment. The scene lighting should meet the visual brightness and lighting requirements of the normal operation.
2.4 steel plate production: after purchasing the steel plate according to the design requirements of the Q345 steel plate material, calculating the pasting length of each steel plate in accordance with the thickness and width that the design drawings require and also combining with the actual size of the scene. cutting and blanking (hydraulic shearing machine)the bottom of the plate, the bottom of the beam, steel plate of the beam surface and u-shaped hoop. the diameter of the fixed pressure bolt’s hole is 12 mm, arranging the beam bottom, steel plate of the beam surface according to the distance of 200mm, double row and between the bottom of the beam, beam surface steel plate 200 mm, by double row and plum shape, setting the bottom plate according to the distance of 200mm in the midline of the width of steel plate 200 mm and by single row. the diameter of the U-shaped hoop anchorage chemical bolt’s hole is 16 mm.
3, construction technology and procedure:
Pasting surface processing→pressure fixing and unloading systems preparation→making up the bonded steel structural adhesive →painting the adhesive and pasting the steel→solidifying, discharging pressure fixing system,→inspection →maintenance
4, the construction method
4.1. Pasting surface processing
4.4.1. cutting out the plaster layer,oil and dirt of the concrete pasting surface, and then using Angle grinding machine to remove the 2-3mm thick surface of the concrete surface, after polishing, using the compressed air to blow off the dust, and finally using the cotton cloth with acetone to wipe the surface, repairing the larger cavity with concrete repair adhesive.
4.1.2. The pasting surface of the steel plate should be done the rough handling with the angle grinder until it has the metallic luster, and then using cotton cloth with acetone to wipe clean the surface, reserving it after it is completely dry.
4.1.3. The main equipment of the process: the impact hammer and flat spade, hammer, angle grinder, diamond grinding slice, grinding wheel slice, strong blower, degreasing cotton cloth, acetone, goggles, rustproof masks.
4.2 pressure fixing and unloading system preparation
4.2.1.the live load like the personnel and office machines that the components bear should be temporarily removed, and trying to reduce the  temporary load of the construction.
4.2.2. using the bolt for the pressure fixing, drilling hole on the steel plate, anchoring the screw, it will produce the composite anchorage force for the steel plate. the effect is good, and it is suitable for pasting steel plate.This project adopts the
4.2.3 this project uses the bolt hole. the space distance is  200 ㎜. the bolt specification is M8 * 70.
4.3. making up the bonded steel structural adhesive.
4.3.1.the bonded steel structural adhesive is divided into A and B two parts. the specific mixture ratio should be in accordance with the requirements of the product specifications.Taking out the clean containers (plastic or metal basin, do not have oil, water or impurities) mixing it with the weighing scales according to the mixture ratio, and using blender to mix them about 5 minutes until A and B parts are even. when mixing, it is recommended to mix it along the same direction, and avoiding mixing with air to form the bubble.
4.3.2. it is not appropriate to make up too much adhesive every time. once finishing making up, using it.
4.3.3. The main equipment used for the process: blender, container, weighing apparatus, putty knife and gloves.
4.4. painting the adhesive and pasting
4.4.1. after making up the bonded steel adhesive, using the putty knife to smear it on the surface of steel plate(or the concrete surface) that has been managed, the cross section of adhesive should be triangle. the thickness of the middle part is about 3 mm, and the edge is about 1mm. and then pasting the steel plate on the concrete surface, fixing it with the prepared fixing pressure system (bolt), pressuring it appropriately. it is the most appropriate that the adhesive just squeezes out the steel plate seam.
4.4.2. the order of pasting the steel: pasting the steel at the bottom of the plate(pasting short span transverse tensile steel plate firstly, and then pasting the layerings on the both ends); Sticking the steel at the bottom of the beam (pasting the steel plate of the beam bottom, and then pasting the “U-shaped” hoop plate, finally pasting the layering. If the height of this project’s beam is equal to or higher than 600 mm, setting up two thick steel plate layering of 100mm wide and 3mm thick at the top of beam plate bottom) and the middle of the beam height,the length is commonly set, using M8 bolts to fix and pressure).
4.4.3. The main instruments used for this process: bolt, hammers,   putty knife and gloves.
4.5.Solidified,maintained bonded steel structural adhesive can solidify well both at normal or low temperature. if the curing temperature is about 25℃, we can remove the pressure fixing system after 24 hours. it can be used normally after 72 hours. if the curing temperature is about 5℃, we can remove the pressure fixing system after 48 hours. it can be used normally after 120 hours.
4.6.Checking that the operating performance of the bonded steel structural adhesive is excellent. normal operation can reach 100% plumpness. using small hammer to tap the bonded steel gently when checking. judging the effect of pasting from the stereo. ultrasonic instrument can also be adopted to test. if the effective pasting area of anchorage zone is less than 90% and the effective passing area of none-anchoring zone is less than 70%, removing the steel plate and pasting it again
4.7. after maintenance and reinforcement, steel plate can adopt 25mm and 1:3 cement mortar plaster to be protected in order to prevent the rust. it can also be coated antirust paint to be protected.
4.8. notes:  whether the pasting surface is managed according to the requirements. whether the adhesive ratio is accurate. whether it is mixed evenly. whether the adhesive layer is even and dense determines the effect of pasting.
Repair methods
Quality inspection and acceptance
During the construction, construction team needs to do the self-inspection at any time; after the construction, quality inspector will check firstly, and then party A and supervision party check according to the CECS25:90 requirements of “ the technical specification for concrete structure strengthening”.
After dismantling the temporary fixing facilities, using small hammer to knock gently the pasting steel plate, judging the pasting quality from the sound or using ultrasonic to detect the pasting compactness. for the anchorage zone that the pasting area is less than 90% and the none-anchoring zone that the pasting area is less than 70%, the pasting is invalid and it needs to be constructed again.
For the major projects, we should do the loading test for the real effect of checking and reinforcement.
Common problems that affect the quality of construction and remedies
2.1.  Because of smearing the structural adhesive unevenly,causing the empty drum. the consistency of structural adhesive is different by the kind  and brand of adhesive and construction environment. if the consistency is too low, the structural adhesive is easy to flow down so that it will cause the empty drum inside the upper steel plate. therefor, when constructing, firstly controlling the consistency according to the construction environment, at the same time pasting the steel plate as soon as possible to make the structural adhesive and steel plate paste completely and evenly.
The empty drum that the remedial area is smaller: using electric drill of small aperture to drill,and using the method of needle injection for the  glue pouring to fill the empty drum. the empty drum that the area is bigger: if it still can’t meet the requirements of the specified acceptance after the needle injection, we must dismantle the steel plate and paste it again.

Four, safety measures

1, partyA and party B that make up the bonded steel adhesive should be sealed storage, away from the fire, preventing from the direct irradiation of the sun.
2, the operator should wear work clothes and respirator mask.
3, the construction site should be equipped with all necessary fire extinguisher in case of emergency.
4, acetone for wiping should be controlled strictly. using the container of small aperture as far as possible, it is strictly prohibited to throw disorderly the cotton yarn and brush that are for wiping. they must be handled uniformly.
5, the use of acetone should be away from the fire.