The steel grating processing factory has centralized processing and programmed construction. The brief construction process is as follows:
Construction preparation, construction lofting; making molds, steel bar cutting, processing, steel grating welding, inspection and acceptance.
Process measures and work points:
1. Construction preparation
(1) Do a good job in the operation and debugging of construction electricity and mechanical equipment (such as electric welding machine, bending machine, cutting machine, hoist, etc.).
(2) Do a good job in the material consumption plan, the entry plan and so on.
(3) Do a good job of laying the steel platform for steel grating processing.
2. Construction lofting
According to the design drawing of the steel grating and the requirements of the operator, the surveyor will stake out the steel platform, and draw a 1:1 large sample drawing of the steel grating, including the normal direction of each connection point.
3. Making molds
The operator should first review the steel grating section design mold, the mold material steel plate and steel bar (Φ25) can be used, the mold can be directly welded on the steel platform according to the large sample line, and the welding must be firm and vertical.
4. Rebar cutting
(1) The operator first reviews the size of the steel bar on the blanking list and the specifications and models of the materials used, and bends a few less materials on site to check whether it meets the design requirements.
(2) The operator shall blank according to the blanking list after review. After blanking, various specifications and sizes are classified and marked separately to avoid misuse. Rational use of some small materials.
(3) The operator can bend the steel bar manually or mechanically, but the bending must meet the following requirements:
a: The starting point of the bend must be marked
b: The diameter of the mandrel of the bending machine should be 2.5 times the diameter of the steel bar.
c: The bending shape of the steel bar is correct, and there is no warping or unevenness on the plane.
5. Steel grating welding
(1) First, place the position and quantity of the bent stirrup section in the middle of the mold, and check the quantity.
(2) Pass the four main ribs one by one through the clamping groove of the mold, and adjust the spacing of the stirrups to meet the design requirements.
(3) After the adjustment of the main reinforcement and stirrups is completed, spot welding is performed to weld the stirrups and the main reinforcement flat. But it is not allowed to weld too deep and burn the main reinforcement.
(4) After the stirrup welding is completed, the length and height of the welding seam must be guaranteed when welding additional ribs and reinforcing ribs.
(5) Finally, weld the connecting plate (angle steel L100×100×10), and drill holes according to the design size of the angle steel before welding. The welding of the connecting plate must ensure that the distance between the hole position and the main rib, and the mold distance between the two plate holes must be consistent.
This process is one of the key points of steel grating operation. The construction in this process must meet the following requirements:
A: The pre-bending and installation of steel bars should ensure that the axes of the two steel bars are on the same straight line.
B: The tack weld should be more than 20mm away from the lapped end.
C: During welding, the main weld and the tack weld, especially at the beginning and end of the tack weld, should be well connected.
D: The length of the weld is not less than the lap length, the height of the weld is H ≥ 0.3d, and not less than 4mm, and the height of the weld is not less than 10mm when welding with the connecting plate.
E: The surface of the welding seam is flat, there should be no large depressions, and there should be no cracks at the joints of the welding seam. Welding slag must be knocked off after welding.
F: Unit welding must be standardized and standard parts.
6. Inspection and acceptance
(1) The welding seam inspection of steel grating should be inspected one by one.
(2) Make the test piece according to the requirements of the specification and check it experimentally.
(3) After the completion of the first piece, a trial spelling must be carried out to check the clearance size.
(4) Randomly check the clearance size and the position of the connecting plate in batch production.
Steel grating steel frame installation sequence
The finished steel grating is transported from the processing plant to the site; unit selection; lifting; in place; review; positioning; connection; inspection.
Process measures and work points:
1. Unit selection: Select the required unit according to the construction method (excavation method) and transport it to the wellhead.
2. Hoisting: The selected unit is hoisted from the soil storage yard to the tunnel by electric hoist, and then sent to the working face by motor. During this process, attention should be paid to protecting the steel grating to avoid bending and twisting.
3. Preliminary placement: Manually place the steel grating on the working face according to the position of the line. Connect each unit with bolts. Do not tighten for adjustment.
4. Review: After the steel grating is initially in place, review it immediately. Mainly review the center line and elevation, and adjust it in time to correctly meet the design requirements.
5. After the positioning review is qualified, tighten the connecting bolts and weld them firmly with the positioning ribs.
6. Connection: After the steel grating is positioned, weld the longitudinal connecting ribs and the arch channel steel in time, and weld them firmly with the previous one.
The installation process is reviewed, and the connection is the key point of the operation, so the following requirements must be met:
A: The clearance of the steel grating must meet the design requirements and must not be intruded.
B: The elevation of the steel grating must meet the design requirements.
C: The bolts must be tightened.
D: Welding of connecting ribs and channel steel must comply with construction specifications and regulations.
E: Accurately review the mileage to avoid longitudinal dislocation in the installation of steel gratings.
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