1、 Key points of supervision and control in preparation of steel structure engineering

01

Qualification examination of construction unit

Due to the strong specialization of steel structure engineering, the requirements for professional equipment, processing site, workers’ quality and the construction technical standards, quality assurance system, quality control and inspection system of the enterprise are high. Generally, most of them are subcontract projects under the general contract. In this case, the qualification and management level of construction enterprises are very important.Therefore, the qualification examination is an important link, and the examination contents are as follows:

(1) Whether the business scope of construction qualification meets the engineering requirements. 

(2) Whether the construction technical standards, quality assurance system, quality control and inspection system meet the requirements of engineering design technical indicators. 

(3) Inspect whether the production capacity of construction enterprises meets the requirements of project schedule. 

02

Review of welder quality 

The welder must pass the examination and obtain the qualification certificate, and the welder with the certificate must weld around the qualified items and the approved scope.

(1) Inspection quantity: full inspection (on-site personnel). 

(2) Inspection method: check the welder certificate and its approval scope and validity. 

03

Drawing review and technical preparation 

   According to the drawing joint examination procedure in supervision planning, be familiar with the drawings before the commencement of the project, call and preside over the joint review of the drawings by the professional and technical personnel of the designer, the owner, the supervisor and the construction unit. According to the design documents and relevant data and specifications, the errors and omissions, unreasonable, non-compliance with the specifications and the provisions of the national construction documents shall be solved before the construction.

   Coordinate with the owner, design and construction units to determine specific treatment measures or design optimization for drawing problems.Supervise and urge the construction unit to sort out the minutes of joint review, and distribute them to all units after being signed and sealed by all parties.

04

Review of construction organization design (scheme) 

(1) Supervise and urge the construction unit to prepare special construction organization design (scheme) according to the construction contract.After being approved by the superior unit, it shall be reported to the supervisor.

(2) If it is necessary to change the construction scheme (method) in the construction of the reviewed construction organization design (scheme), the reason and content of the change must be reported to the supervision and construction unit for examination and approval before the change can be made.

05

Regular meeting 

Organize and participate in the regular site meeting held by the construction, construction and supervision units once a week to solve the problems in the construction in time.

06

Concrete control points of steel structure engineering preparation 

(1) According to the unified standard for construction quality acceptance of Building Engineering (GB 50300-2001) and code for acceptance of construction quality of steel structures (GB 50205-2001), as a part of the project, it is divided into steel structure welding, fastener connection, steel parts and steel parts processing, steel parts assembly, steel structure pre assembly, steel structure installation engineering, profiled metal plate, steel structure coating, etcAs the raw materials of steel structure (including steel, welding materials, coating materials, etc.) have great influence on the quality of steel structure, they are separately set up in the steel structure specification.

(2) Check the welder’s qualification certificate and its approval scope and validity period.

(3) The construction party shall carry out welding procedure qualification for the steel, welding material, welding method and welding heat treatment adopted for the first time, and determine the welding process according to the qualification report.The supervisor shall check all welding procedure qualification reports and inspect them according to the design requirements.

(4) Before the installation of steel members, the positioning axis (Bay size and span size) and elevation of the building, the specification and fastening of embedded parts shall meet the design requirements.

(5) When the embedded steel plate on the reinforced concrete corbel top of the engineering column is directly used as the bearing surface of the steel member, the allowable position deviation of the embedded steel plate on the bearing surface shall comply with the specification.

(6) Steel members shall meet the design requirements and the provisions of this specification.The deformation of steel members and coating shedding caused by transportation, stacking and hoisting should be corrected and modified.

(7) The maximum distance of embedded steel plate on the top surface shall not be less than 70% of the steel plate.

(8) Before coating, the rust on the steel surface shall meet the design requirements and the provisions of the current national standards. The steel surface after treatment shall be free of welding slag, welding scar, dust, oil, water and burr.

(9) The coating, coating times and coating thickness shall meet the design requirements, and the allowable deviation is – 25mm, and the allowable deviation of dry film thickness of each layer is – 5mm.

(10) The surface of the component shall not be wrongly coated or missed, and the coating shall not be peeled or rusted. The coating shall be uniform and free from obvious wrinkle, sagging, pinhole and bubble.

(11) According to the actual situation and structural form of the project, the inspection lot division of each sub project is confirmed as follows:

1）Steel structure welding sub project: for the project, each one can be used as an inspection lot; or it can be divided into several inspection batches according to different steel structure monomer or component type combined with steel structure fabrication and installation.

2）Fastener connection sub project: for the project, inspection lot can be divided according to different steel structure monomer and fastener of different specifications.

3）Steel parts and steel parts processing: steel parts and steel parts can be divided into several inspection batches according to different types

4）Steel component assembly: for large steel structure, the steel parts made in the factory shall be assembled into steel components as hoisting unit before hoisting.Due to the high requirements of component assembly, several components can be used as one inspection lot according to the actual situation on site.

5）Pre assembly of steel structure: for the steel structure with complex shape, in order to ensure the smooth assembly during high-altitude installation, the pre assembly and inspection batch between related components shall be conducted on the ground after the fabrication, and the inspection batch can be divided according to the assembly of similar components as an inspection lot.

6）Installation of steel structure: the installation of steel structure can be divided into single-layer steel structure installation or multi-layer and high-rise steel structure installation.The single story steel structure installation high-rise building can be divided into several inspection batches according to the project division.The installation of multi-storey and high-rise steel structures can be divided into one or several inspection lots according to the floor or construction section.

7）Profiled metal plate Engineering: the profiled metal sheet engineering includes the profiled metal plate used for roof, wall panel, floor, etc.In terms of material, it includes profiled steel plate and profiled aluminum plate with anti-corrosion coating on the surface.It can be divided into one or several inspection lots according to deformation joint, floor, construction section or roof, wall, floor, etc.

8）Steel structure coating engineering: steel structure coating engineering includes anticorrosive coating and fireproof coating.The inspection lot can be divided into one or several inspection lots according to the division principle of inspection lot for steel structure fabrication or steel structure installation engineering.

(12) The quality acceptance contents and corresponding qualification standards of divisional works shall meet the following requirements:

1）Steel structure welding, fastener connection, steel parts and steel parts processing, steel component assembly, steel component pre assembly, steel structure installation, profiled metal plate, steel structure coating and other sub projects shall meet the qualified quality standards;

2）Quality control data and documents shall be complete;

3）The inspection and witness test results related to safety and function shall meet the requirements of corresponding qualified quality standards in GB 50205-2001;

2、 Control points of supervision work in steel structure engineering

01

Control points of supervision work for acceptance of raw materials and finished products 

(1) Key points of engineering material quality:

1）Check the appearance quality and quality certification materials of steel, welding materials, bolts, studs and other materials used in the project.

2）Supervise and urge the construction unit to conduct witness sampling and inspection for section steel base metal, representative welding test pieces, bolts, etc. according to the regulations on witness sampling and inspection of housing construction engineering and municipal infrastructure engineering issued by the Ministry of construction, and the test unit shall issue qualified test report with witness sampling.

3）Supervise and urge the construction unit to reasonably organize the material supply to meet the needs of continuous construction, strengthen the material management system of on-site material transportation, storage, inspection and acceptance, and do a good job in the protection measures of moisture, dew and pollution.

① Steel: the steel grade, reference standard number, chemical composition and physical performance index shall be specified according to the design requirements.The raw material supplier shall provide complete quality assurance certificate and material test report.The variety, specification and performance of steel and steel castings shall meet the current national product standards and design requirements, and the quality of imported steel shall meet the requirements of design and contract standards.The supervisor shall require the steel structure contractor to submit the quality certificate, Chinese mark and inspection report to the supervisor for approval, and the supervision engineer shall inspect them all.

② Welding materials: the variety, specification and performance of welding materials shall meet the current national product standards and design requirements.The supervisor shall require the steel structure contractor to submit the quality certificate, Chinese mark and inspection report to the supervisor for approval, and the supervision engineer shall inspect them all.The welding materials used in important steel structures shall be sampled and rechecked.The supervision engineer shall check the re inspection report.

③ Standard fasteners for connection: the commonly used fasteners in steel structure engineering include high-strength bolts (divided into large hexagon type and torsion shear type), ordinary bolts, anchor bolts, anchor bolts, etc., and their varieties, specifications and performance shall meet the current national product standards and design requirements.The supervisor shall require the steel structure contractor to submit the product quality certificate, Chinese mark and inspection report to the supervisor for approval, and the supervision engineer shall inspect them all.

④ Welding ball: the supervisor shall require the contractor to provide the quality certificate of raw materials, Chinese mark and inspection report, and nondestructive test report of welding ball.The diameter, roundness and wall thickness reduction of welding ball are checked by caliper and metal thickness gauge.

⑤ Bolt ball: the supervisor shall require the contractor to provide quality certificate, Chinese mark and inspection of raw materials used for welding ball.Check the surface quality of bolt ball with 10 times magnifying glass.Spot check the size, diameter, roundness of the bolt ball thread and the angle between the center lines of two adjacent bolt holes.

⑥ Metal profiled plate: metal profiled plate, profiled metal flashing plate, corner plate, spare parts and their raw materials. Their varieties, specifications and performance shall meet the current national product standards and design requirements.The supervisor shall require the contractor to provide product quality certificate, Chinese mark and inspection report.The dimension deviation, surface and coating quality of profiled sheet metal can be spot checked (10 times magnifying glass can be used).

⑦ Coating materials: the supervisor shall require the contractor to provide product quality certificate, Chinese mark and inspection report.The variety and technical performance of materials and fire retardant coating used for steel structure anti-corrosion coating shall meet the design requirements. The fire-retardant coating shall be tested by qualified inspection organization and meet the provisions of current national standards, and confirmed by local fire management department.

⑧ The control of raw materials and finished products of steel structure engineering is the key to ensure the engineering quality certification, and it is also one of the key control points. The quality specifications and performance of all raw materials and finished products shall meet the national product standards and design requirements. The product positioning, quality qualification certificate and inspection report shall be fully inspected as the main control items.

⑨ The welding materials used in the project shall be provided with complete quality certificate and baked according to the requirements of the manual before use.The supervision engineer shall check the validity of quality certificate and welding material baking record.Check the welder qualification certificate, including whether the qualified items can cover the actual welding content and whether the certificate is within the validity period.Check whether the welding procedure qualification report items cover all joints of the project.Ultrasonic testing must be carried out for the first and second level welds.For the weld requiring preheating before welding or heat treatment after welding, the temperature between welding passes shall not be lower than the preheating temperature during the whole welding process, and the preheating width on both sides of the weld shall not be less than 1.5 times of the thickness of the weldment.And shall not be less than 100 mm.

⑩ The supervisor shall inspect the reinforcement, undercut, surface overlap and shrinkage cavity of butt weld; the fillet size and undercut surface quality of fillet weld shall not be less than 20%, and inspection records shall be made.For stud welding, the supervisor shall check the welding procedure qualification report and porcelain ring baking record.After stud welding, 10% of similar components (no less than 10 pieces) shall be selected by the supervisor together with the quality inspection personnel of the construction unit, and 1% of the number of studs shall be inspected for bending test.After bending 30 ° angle, observe with angle ruler and naked eye, and the surrounding of stud shall be bent and fused with weldment.

11.If the welding procedure qualification is valid, the welding material quality certificate documents are complete, the weld surface quality meets the specification requirements, the relevant welding dimensions meet the drawing requirements, the weld nondestructive testing is qualified, and there is an effective flaw detection report, the stud welding bending test is qualified and there is an inspection report, and the supervision sampling inspection is qualified, then the steel structure welding is qualified.

02

Control points of fastener connection project supervision 

(1) The supervisor shall witness the anti sliding coefficient test on the friction surface of high strength bolt connection, and the anti sliding coefficient shall meet the design requirements, and the supervisor shall inspect the production of steel structure.It should be noted that the sandblasting of the friction surface of the steel structure should meet the quality requirements of the test plate which has passed the anti sliding coefficient test of the connecting friction surface.(the anti sliding coefficient of the friction surface of high strength bolt connection is related to the type of steel, the type of sand used for surface treatment, wind pressure, sandblasting time and the corrosion degree of friction surface before test.Therefore, the steel structure manufacturing unit must carry out the representative anti sliding coefficient test.The treatment of the test plate should be consistent with the actual production. The specification requires that every 2000 tons of steel structure should be subject to a group of tests, and each group of tests should have six pairs of test plates. Among them, three pairs should be tested before the production of steel structure, and the other three pairs should be retested before the installation of high-strength bolts, so as to verify that the anti sliding coefficient of friction surface of high-strength bolt connection is still within the scope of specification or design requirements.In the production of steel structure, if the pretreatment site of high-strength bolt connection friction surface is changed or the treatment method is changed, the anti sliding coefficient test must be conducted again.)

(2) The installation quality of high-strength bolt connection friction surface and the tightening degree of high-strength bolt shall be inspected at least 10%.The torque wrench shall be calibrated. The torque wrench shall be rechecked before and after each shift, and the inspection record shall be made.After 1 hour and 48 hours after the final tightening, the supervisor shall check the final tightening torque together with the quality inspection of the construction unit.At the same time, check that the exposed bolt thread should be 2-3 threads (1 or 4 threads are allowed to be exposed for 10% of the bolt threads).(the construction unit shall prepare two torque spanners, one for construction, with the error less than 5%, and the other as the testing wrench, with the error less than 3%.The inspection wrench for construction wrench shall be tested before and after each shift.High strength bolts can not be used as positioning bolts. The initial tightening to final tightening of high-strength bolts should be completed within 24 hours.The final tightening torque of high-strength bolts shall be tested with a testing wrench.)

(3) If the anti sliding coefficient test of the friction surface of the high-strength bolt connection is qualified, the quality certificate of the high-strength bolt is qualified and valid, the final tightening torque inspection is qualified, and the supervision smoking is qualified, then the fastener connection item is qualified.

03

Control points of steel parts processing engineering supervision 

(1) Check the cutting and blanking quality of steel, including observing the quality of steel from the cutting surface, checking the quality of cutting edge with steel ruler and feeler gauge, etc., which shall meet the specification requirements.

(2) The steel and steel components shall be controlled for thermal correction, and the heating temperature shall not be greater than 9000c (the temperature shall be controlled by the color of the heating zone). Forced cooling (such as watering) of low alloy steel is strictly prohibited.Use vernier caliper or aperture gauge to spot check 10% of bolt hole diameter and hole wall quality, and spot check bolt hole spacing.

(3) If the self inspection of steel structure contractor is qualified and the supervision spot check is qualified, then the steel parts and steel parts processing engineering are qualified.

04

Control points for supervision of pre assembly and assembly of steel members 

(1) The support stool or steel platform used for pre assembly shall be checked to be stable and reliable, and its relative position shall be checked.Check that all zero time fixing and tensioning devices on steel members are removed.The hole tester is used to spot check the perforation rate of bolt hole on the supervision site, and it meets the requirements of code for acceptance of construction quality of steel structure engineering (GB 50205).

(2) The supervisor shall require the steel structure manufacturer to check the assembly size according to the pre assembly unit, and comply with the requirements of Appendix D table of code for acceptance of construction quality of steel structure engineering (GB 50205).

(3) For welded H-beam, spot check the weld arrangement according to the specification requirements, and the distance between flange plate splicing weld and web splicing weld shall be greater than 200 mm.The dimension deviation of welded H-beam shall meet the specification requirements.

(4) Check that the crane beam and truss should not be down warped by level gauge and steel ruler.

(5) For the size of steel structure assembly, the supervisor shall inspect the assembled jig frame, inspect each inspection lot, and carry out sampling inspection for no less than 10% of each inspection lot, and make monitoring records.Use 0.3mm feeler gauge to check the top tight surface, and the inserted area should be less than 25%.

(6) If the dimensional inspection report submitted by the steel structure manufacturer is qualified, and the sampling inspection of the supervisor is qualified, the steel component assembly project is qualified.

05

Control points of steel structure installation supervision 

(1) Control points of steel structure installation supervision

1）Be familiar with the design description of construction drawings, clarify the design requirements, and preside over the joint review of drawings and design disclosure.

2）Review the professional construction scheme such as steel structure processing, fabrication and hoisting.Focus on the review of the organization quality assurance system of the construction unit, the construction methods, welding points and technical quality control measures of main sub projects.

3）Steel structure installation unit, construction personnel and supervision and inspection personnel must have corresponding qualifications, and must comply with relevant national regulations.

4）The steel structure installation unit shall establish the steel structure installation quality assurance system at the construction site, and its main members shall be the corresponding qualified personnel, and the welding personnel shall hold the welder qualification certificate of the corresponding welding position and within the validity period; the construction machinery entering the site shall ensure the intact rate of the equipment, and shall have the corresponding safe operation performance (such as the voltage of the electric welding machine)Meters, ammeters, tower crane safety operation permit, etc.).

5）After entering the site, the steel structure components and accessories shall be inspected according to the arrival batch.

(2) Key points for quality control of steel structure fabrication:

1）Supervise and urge the construction unit to carry out on-site manufacturing and mechanical processing, prepare the processing drawing, check the enlarged sample of beam plate contact, and process after inspection and confirmation.

2）According to the actual situation of the project, supervise and urge the general contractor to be responsible for the production management and quality control of the subcontractor, such as making action scale, steel member lofting, cutting, correction, edge processing, hole making (bolt hole, reinforcement hole, concrete vibration hole and other mechanical drilling), assembly, engineering welding and welding inspection, derusting, numbering, etc., and the first piece manufacturing shall be emphasizedPoint monitoring.

3）Irregular sampling inspection is carried out in the manufacturing process of section steel (stiffened) members, focusing on the acceptance of base metal, retest, test of welding specimen, welding, ultrasonic flaw detection of weld and appearance inspection.

4）The problems occurred in the process of mass production should be coordinated and controlled with relevant units in time to ensure that the fabrication of components meets the needs of hoisting.

5）The allowable deviation of section steel member fabrication shall conform to the allowable deviation of steel member assembly in Appendix C of code for acceptance of construction quality of steel structures (GB 50205-2001).

(3) Quality control points for storage, transportation and acceptance of steel structure members:

1）Supervise and urge the processing party to stack the steel members according to the component number and installation sequence. When stacking the components, the wood pad should be added between the components.

2）Check that the processing party shall arrange the transportation according to the component mobilization plan, and bind it well when loading, so as to avoid the deformation of components and ensure the safety of transportation.

3）After the rigid steel members are manufactured and pass the self inspection, fill in the self inspection form and inspection application form and apply for inspection, and carry out the acceptance according to the steel structure manufacturing and acceptance basis, and check whether the documents are complete.

4）100% inspection of various steel members.

5）The acceptance of all steel members in the processing plant is only the preliminary inspection, and the final inspection is carried out at the hoisting site.

(4) Key points of quality control for installation of steel members:

1）The steel members must be inspected and accepted when they enter the construction site;

2）Urge the construction company to determine the stacking position of components according to the position and lifting capacity of tower crane (or truck crane). The storage site of steel members shall be flat, solid and free of ponding. The steel members shall be stacked in different areas according to the type, model and installation sequence. The bottom pad wood of steel members shall have sufficient supporting surface. When steel members of the same type are stacked, the fulcrum of each layer of steel members shall be on the same straight lineTo prevent the steel structure from deformation and crushing.

3）The lifting point and binding method of component installation shall ensure that the steel structure will not deform, and trial hoisting shall be conducted before formal hoisting

4）The operation process is monitored during the hoisting process. If the previous process does not meet the acceptance requirements, it is not allowed to enter the next process.

5）The precision of anchor bolt and steel plate pre embedding shall be strictly controlled. The reserved length and elevation of bolts shall be checked. The position must meet the requirements of drawings and specifications. The elevation of steel plate at the bottom of column shall be accurately controlled to ensure the firmness of embedding, and corresponding protection measures shall be taken.

6）Before the installation of the first layer of rigid steel column, check whether the strength of the test block of the foundation concrete under the same conditions meets the design requirements.The positioning axis and elevation of the steel column, the diameter of the anchor bolt and the extension length (steel plate size and height) shall be inspected and accepted, and the steel column number, overall dimension, bolt hole position and diameter shall be checked, and the steel structure hoisting can be started only after confirming that it meets the design drawings.

7）The steel column of the floor section shall be hoisted according to the number, the erection and fixation of the connecting plate at the joint of the steel column shall be checked according to the drawing requirements, and the elevation and perpendicularity of the column top shall be rechecked, and the steel column welding can be carried out after meeting the requirements.Supervise and inspect the common quality problems in the hoisting process of steel members, such as steel column displacement, steel column verticality deviation out of tolerance, installation hole position deviation, component installation holes not coincident, bolts can not penetrate, etc.

8）Before hoisting, the lifting lug and effective welding seam shall be checked to see whether the hoisting points of steel wire rope for hoisting meet the requirements (the lifting points of columns are on both sides).

9）Installation control: after the rigid steel framework is hoisted in place, the bottom fastening bolts are temporarily fixed, and then the axis is aligned. The deviation must be less than 3mm, and the perpendicularity deviation should be strictly controlled within 5mm.Welding can be carried out after the adjustment is qualified, and the temperature should be controlled before welding.

10）Check the welding sequence, welding method, welding protection, etc.Supervise and urge the construction unit to pay attention to the changes of weather conditions, such as the influence of wind, rain, humidity and sunlight when hoisting and welding, and require to formulate pre control measures.

11）Strictly check the quality certificate of the welding rod used, and the welding rod must be carried in the drying cylinder.After cooling for 24 hours after welding construction, ultrasonic flaw detection shall be carried out for welds under the witness of the supervisor according to the design and specification requirements.

12）Section steel column and beam connector shall be made of materials with good welding performance, and the welding reliability with steel beam shall be ensured.

13）Before pouring concrete, it is necessary to control the processing of arc striking plate and arc plate, cut off the redundant support for temporary deformation control, and strengthen the inspection for the compensation work of temporary hole enlargement (through beam reinforcement hole) to eliminate the quality hidden danger.

14）The allowable deviation of section steel member installation shall comply with the provisions on allowable deviation of steel structure installation in Appendix E of code for acceptance of construction quality of steel structures (GB 50205-2001): (table e.0.5 allowable deviation for installation in multi-storey and high-rise steel structures).

① Before the installation of steel structure, the supervisor uses theodolite, level gauge and total station to check the positioning axis and elevation of steel column.The inspection quantity shall not be less than 10%.

② The supervisor shall check the joints that are required to be tightened in the design, and the inspection content is that the contact surface shall not be less than 70%, and the edge clearance shall not be greater than 0.8mm.The number of check nodes is greater than 10%.

③ For the installed steel roof truss and column, the supervision engineer can use suspension wire, stay wire, theodolite steel ruler to check.The allowable deviation of the roof truss’s midspan perpendicularity is H / 250 and should not be greater than 15.0; the lateral bending height loss of the roof truss between the two vertical columns is less than 1 / 1000 and not more than 10.0.The allowable deviation of overall perpendicularity and overall plane bending of main structure shall meet the following requirements: the allowable deviation of overall perpendicularity is H / 1000 and not more than 25.0, and the overall plane bending is L / 1500 and not more than 25.0.

④ The overall perpendicularity (H / 2500 + 10.0) of main structure of multi-storey and high-rise steel structure shall be checked by laser theodolite and total station, and the allowable deviation of overall plane bending shall be L / 1500 and not more than 25.0.

⑤ The supervisor carries out on-site supervision during the installation of steel structure, mainly controlling the center line of components, elevation datum point and other marks, alignment quality of positioning axis during steel member installation, cleanliness of steel member surface, etc.

⑥ If the steel component factory certificate is complete; the high-strength bolt connection construction is completed and passed the supervision inspection, the project is qualified.

(5) Quality control elements of steel truss installation

1）The fabrication of steel truss shall be carried out in strict accordance with the requirements of design drawings and specifications (GB 50205-95).Anti deformation measures shall be taken during welding and manufacturing of H-beam, and welding shall be carried out in sections and in sequence. J507 welding rod shall be used as welding material.Semi automatic cutting is adopted in steel structure fabrication, and chamfering is carried out on the cutting surface with a grinder to ensure the adhesion of paint and fire retardant coating.The connecting bolt hole of steel structure is made by machine, and the drilling accuracy must meet the requirements of specification and installation.The friction surface of high strength bolt connection is treated by manual rust removal and sand blasting.The friction coefficient of friction surface and high strength bolt are tested according to the specification.

2）Before the installation of steel truss, the foundation elevation and steel structure installation geometric dimension shall be tested, and the clearance of each part shall meet the drawing requirements.According to the construction drawings and specifications, the next step of work can be carried out after the acceptance is qualified.

3）The fabricated steel structure shall be pre assembled at the installation site, and the installation work shall be started after the dimension is checked.

4）Due to the large span of steel truss, structural deformation should be prevented during lifting.The steel truss is installed with a 50 ton crane, and the construction method of symmetrical hoisting with multiple lifting points is adopted for hoisting.

5）The construction of high-strength bolt adopts torque method, and the initial and final tightening of high-strength bolt are conducted by electric torque wrench.The torque value must meet the design requirements and specifications.There shall be no over tightening and leakage.

6）Acceptance grade of welding quality: the butt weld of steel frame and main column, groove weld and butt weld of crane beam shall be inspected according to grade I weld in (GB 50205-95), and other welds shall be inspected according to grade II weld standard.

7）After the steel beam column is stressed, it is not allowed to weld the connector on it at will, and the welding connector must be completed before the member is stressed and the high-strength bolt is finally screwed

8）After the steel structure is completed, the profiled steel plate shall be installed. The purlin must be installed horizontally and vertically. The profiled steel plate shall be installed after the above work is completed.Profiled steel sheet and purlin must be installed in strict accordance with the drawings.

06

Control points of steel structure painting project supervision 

(1) Control points of steel structure painting project supervision

1）The Monitoring Engineer shall first inspect the quality of sand blasting and derusting on the surface of steel members, including whether the surface roughness meets the coating requirements, and the home inspection quantity shall not be less than 10%.The allowable deviation is – 25um.

2）The application of surface paint (fire retardant coating).The supervisor shall check that the intermediate paint has been completely cured, and the bonding strength shall be tested once every 100 tons or less of thin fire retardant coatings.The thickness detection quantity of fire retardant coating shall not be less than 10% of the component quantity.Each component is tested at 5 places, and the value of each part is the average value of dry paint film thickness of 3 measuring points with a distance of 50 mm.The thickness of fire retardant coating shall meet the design requirements of fire resistance.

3）If the coating quality assurance certificate submitted by the construction unit is valid, the specification requires that the drawing bond strength test report is complete, the coating thickness test report is complete and qualified, and the supervision sampling inspection is qualified, then this sub project is qualified.

07

Precautions 

(1) Review the design qualification of steel structure professional design unit. The steel structure drawing is an important document of steel structure engineering construction, and is the basic basis for the construction quality acceptance of steel structure engineering. The designed steel structure staff drawing must be signed and approved by the general design unit.

(2) Check and accept the qualification and quality management content of construction units engaged in steel structure engineering.The general inspection contents of steel structure engineering mainly include: quality management system and quality inspection system, construction technology enterprise standard, professional technical management and professional job certificate.Construction qualification and subcontracting qualification, construction organization design (construction scheme), testing equipment and measuring equipment, etc.

(3) Review the quality assurance data of raw materials and finished products, the certificate of quality of raw materials and components submitted by the construction unit for approval. The specification stipulates that there are six kinds of raw materials, and the supervisor shall participate in witness sampling when re inspection is required.The thickness of the steel plate, the specification and size of the section steel are the main factors affecting the bearing capacity. The thickness of the steel plate and the specification and size of the section steel should be mainly inspected during the site acceptance.

(4) The welding materials have great influence on the welding quality. The welding materials used should be selected according to the design requirements and meet the current national standards.The welding materials whose appearance does not meet the requirements shall not be used in engineering.

(5) in addition to the inspection data file, the acceptance check of the paint should be checked with a bucket. Besides checking the phenomenon of coating crust, caking and gel, it is also necessary to compare the type, name, color and validity of the coating with the quality certificate.

(6) In order to ensure the welding quality of the project, the welding procedure qualification must be carried out before the component manufacturing and structure installation welding, and the corresponding construction welding procedure specification should be formulated according to the result of the welding procedure qualification.

(7) For welding H-beam and flange plate, longitudinal joint shall not be set, only length splicing is allowed, while web plate length and width can be spliced, but flange plate or web joint shall be staggered by more than 200 mm.

(8) In order to check the integrity of its fabrication, the steel components should be assembled in the factory before leaving the factory, and the pre assembly should be carried out in the factory support stool.The supporting stool or platform shall be measured and leveled, and the hammer shall not be used for pre assembly. All temporary fixing and tensioning devices shall be removed during inspection.

(9) Before the installation of steel structure, the installation and hoisting construction scheme shall be reviewed.

(10) The inspection lot for steel structure installation shall be accepted on the basis of acceptance of the site, welding connection, fastener connection and other sub project and project acceptance.

(11) The detection of installation deviation should be carried out after the structure forms space stiffness unit and is connected and fixed.

(12) During installation, the construction load of roof and platform must be controlled.

(13) The quality of steel structure installation engineering should start from the quality of raw materials and components. Not only the quality of component manufacturing should be strictly controlled, but also the quality of component transportation, stacking and hoisting should be controlled.Practical and reliable measures shall be taken to prevent deformation or paint peeling of components in the above process.In case of deformation or paint peeling of components due to carelessness, it should be corrected or repaired before installation.

(14) On the basis of qualified self inspection by the construction unit, the acceptance records of construction quality of steel structure engineering shall be inspected.The steel structure in the project belongs to sub divisional works, which shall be inspected and accepted according to the inspection lot, sub project, sub item and sub divisional works.