According to the engineering quantity of this project, steel columns and trusses are processed and produced in large quantities, with high technical standards and quality requirements. In order to ensure the high-quality goal of this project, a 50m×6m=300mm operation platform needs to be set on the construction site. Engineering practice: After the site is leveled, the original soil will be tamped and compacted, then C20 concrete with a thickness of 15cm will be poured, leveled and compacted, and finally the surface will be covered with 10mm steel plate.
2. Material requirements
(1) All steel products, spare parts, finished products and standard parts entering the site shall be accompanied by product certificates, quality specifications, use certificates, etc. After acceptance, the inspection lot shall conduct on-site sampling inspection according to the current construction quality acceptance specifications. It can be used only after it meets the design requirements and relevant national standards.
(2) Mechanical equipment: steel bar cutting machine, steel plate cutting machine, edge planer, planer, drilling machine, grinder, submerged arc welding machine, AC and DC welding machine, crane, etc. After maintenance and trial use, the processing machines and tools are in good condition before operation.
(3) In order to prevent the deformation and corrosion of steel and spare parts, they must be classified and stacked in the shed, with boards under them and signs. When stored in winter, the site should be free of ice, snow and water in rainy season.
(4) Before fabrication, the structural lofting shall be carried out according to the standards stipulated in the design documents and construction quality acceptance specifications, and it can be implemented only after self-inspection, pre-inspection and re-inspection confirm that the design and specification requirements are correct.
(5) Steel rulers, instruments and measuring tools required for production, installation, inspection and acceptance have the same accuracy, and can only be used after being tested and appraised by qualified testing units.
(6) Steel columns and steel trusses shall be equipped with steel, covered electrode and flux, with qualified quality and complete specifications, and shall be neatly stacked according to models and specifications for standby.
3. Construction operation technology
1. Operation process
Raw material correction → lofting → marking → blanking (shearing and gas cutting) → parts → flat slag removal → edge drilling → semi-finished products classified stacking → groove oil stain removal → steel plate receiving → welding → ultrasonic flaw detection → leveling → component assembly → actual welding → weld inspection → flange correction → assembly → grinding → welding → weld inspection → correction → finished product drilling →
2. Set out on the lofting platform, draw the shape and size of the components under the lofting platform with the ratio of 1: 1, and then make templates or sample rods according to the actual size as the basis for cutting, bending, milling, drilling and other processing, and verify the joint plates and actual lofting of each component.
Step 3 make disappear
Build a cutting table with the size of 3m× 10m. The cutting table is composed of I-beam and angle steel. Select a length plate and draw a plate arrangement diagram and a material receiving diagram on the cutting table. When cutting and blanking according to the drawing, the reserved welding shrinkage and secondary machining allowance should be considered.
4. Vertical milling
For the drawing end face that needs to be planed and jacked, the H-beam cutting machine is used to cut the I-beam, and after cutting, the local unevenness is polished by an angular grinder. Check the clearance at the top with a feeler gauge. After being qualified, tack welding shall be carried out.
drill
Bolt holes, especially group holes and row holes, require accurate hole spacing. Drilling tools can be used to drill holes and parts holes, and steel plates can be stacked to drill holes. When drilling a hole in a steel column, you can use a hand-lift rod to drill a hole, and the burr should be removed after drilling.
put together
It must be carried out on the operating platform to ensure the accurate section size.
weld
For heavy I-beam columns, automatic submerged arc welding is adopted. When welding the boat-shaped turnover fixture made by this construction method, two fillet welds can be welded on one side of two flange plates at a time, and then the other two welds can be welded. This can make the fillet weld in the best position of automatic submerged arc welding, ensure the penetration depth and height, and it is easy to turn over and cross, weld symmetrically and control the deformation.
8. Leveling
After welding the I-beam, the flange will be deformed due to welding shrinkage and must be leveled. Using flange leveler or heating correction method, finishing, cutting to length and using three-way precision cutting machine can effectively replace cold leveler and end face milling machine.
9. Support production
The bracket is composed of angle steel, and connecting plates are welded at the middle and both ends of the right-angle steel bracket. The production procedure is material correction → sample bar making → marking and blanking → assembly and welding → deformation correction → inspection → derusting → painting. Cross braces must be made by lofting, the dimensions of connecting plates and sample strips are made by actual lofting, and the braces must be assembled according to lofting. For cross support, it is convenient for field installation. The connecting plate at one end of the cross brace can also be welded, which is convenient for adjustment during assembly, or temporarily connected by bolts.
4, steel structure installation
1. Material requirements for semi-finished products
(1) components, models, geometric dimensions and production quality must meet the design requirements and construction quality acceptance specifications;
(2) Connecting materials, covered electrode, bolts and other connecting materials have quality certificates, and connecting accessories meet the design requirements and relevant national standards;
(3) The varieties, brands, colors, matching primers and putty of paints and coatings shall meet the design requirements and technical standards of related products, and shall have product quality certificates.
2. Main machines and equipment
There are mainly tire cranes, trucks, electric welding and gas welding equipment.
3. Fuck oak parts
(1) Calculate the number of hoisting components, the weight of a single piece, the installation height, and the number of installation ironware such as connecting plate bolts;
(2) Formulate the installation measures, type selection, installation procedures, methods and component settings of mechanical equipment, and ensure the quality and safety precautions;
(3) Check that the quality deviation of components beyond the design or specification should be corrected;
(4) on the steel member, according to the needs of positioning and correction, play the axis, installation position line and installation center line;
(5) According to the inspection results of member length, bracket distance and flatness of steel plate bottom plate, leveling shall be carried out, and the inspection position of embedded anchor bolts and elevation roughening shall be inspected;
(6) The steel truss of No.29 belt gallery is assembled and hoisted as a whole;
(7) Hoisting the steel column and truss of No.30 belt corridor. First, after the steel column is installed in place, preliminarily correct the elevation of the support surface of the vertical axis, install it in place, and temporarily reinforce it; After the truss is installed and corrected, the bottom of the steel column is grouted and covered with wet straw bags or straw bags for maintenance; Integral assembly and hoisting of truss.
5, quality standards
(1) The variety, model, specification and quality of steel must meet the design requirements and current construction specifications;
(2) The cutting section of steel must be free of cracks. Sandwich and no more than 1.0mm missing edge;
(3) covered electrode, flux, welding wire and shielding gas used for welding steel members must meet the design requirements and the special provisions for steel structure welding. Welders must pass the examination and obtain corresponding welding condition certificates;
(4) Welds that bear tension and pressure and require the same strength as the parent metal must be inspected by ultrasonic X-ray flaw detection. Make inspection records, and the inspection results must meet the design requirements, current construction specifications and special provisions for steel structure welding;
(5) Cracks, slag inclusion, flash, burn-through, arc pits, needles, blowholes, molten splashes and other defects and blowholes are strictly prohibited on the welding surface of steel columns. Bite even must comply with the provisions of the construction quality acceptance specification;
(6) The allowable deviation shall meet the requirements specified in the table of Code for Acceptance of Construction Quality of Steel Structure Engineering (GB50205-200 1).
6, finished product protection
(1) The component stacking area should be flat and solid without water, and the steel components should be stored in different areas according to the installation order of types and models, and the bottom skids should have sufficient bearing surface. When the steel members of the same model are stacked, the supporting points of each layer of steel members should be on the same vertical line to prevent the steel members from being deformed or inclined;
(2) The lifting point and binding method of component installation shall ensure that the steel component does not deform and damage the coating;
(3) It is not allowed to open holes and cut off any steel bars or cut off the installed permanent bolts on the installed components at will, and it is not allowed to weld iron pieces or anchor rings beyond the design on the components.
7. Safety measures
(1) After the steel structure column beam support and other components are installed in place, they should be corrected and fixed immediately. The steel components installed that day should form a stable spatial system to prevent deformation or toppling;
(2) When the hoisting machinery and equipment installed and used are connected with the main structure, whether the connecting device is safe and reliable must be calculated;
(3) When working high above the ground, the tools used should be prevented from falling, the temporary operation console should be tied firmly, the scaffolding should be paved and tied firmly, and hanging plates are strictly prohibited.
8, construction matters needing attention
(1) tack welding of steel members shall be operated by qualified welders. The welding materials, models and materials used for spot welding shall be the same as the weldment. The covered electrode diameter of spot welding shall not exceed 4.0mm, the weld height shall not exceed 2/3 of the design weld height, the length shall not exceed 6 ~ 7 times of the height, and the spacing shall be 300 ~ 400mm. The spot welding quality shall meet the design requirements.
(2) Except for fixed-point welding, it is forbidden to weld other useless solder joints on the assembled components or strike an arc or strike a light on the parent metal other than the weld;
(3) The installation of high-strength bolts shall be undertaken by specially trained teams to ensure the quality of installation and connection;
(4) The installation and positioning axis of steel members should be controlled from the ground, and the axis should be directly led out, not from the axis of the lower member. For components with the same installation height in the same flow section, the positioning axis of the last column can be led out from the ground to eliminate installation errors and avoid error accumulation.
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