Project overview
The building size of the plant is 42m × 34.5m,
The column spacing of the plant is 6m,
The elevation of column top is 20.4m,
The top elevation of roof truss is 35.508m,
The elevation of skylight top is 39.341m.
The roof truss is triangular,
There are vertical supports between roof trusses and skylights.
All steel structure materials are q235af,
When manual welding is adopted, E43 ~ E50 series electrode is adopted.
The weld length meets the minimum requirement.
The permanent bolt is Ф 22,
The opening diameter is 23.5mm,
The mounting bolt is Ф 16,
The opening diameter is 17.5mm.
F06-1 phenolic primer is used as the paint, and the color is light gray.
The roof panel adopts yx35-125-750 color steel plate.
The fabrication and installation capacity of steel roof truss in this project is about 79t,
The fabrication and installation capacity of roof truss support is about 24t,
The manufacturing and installation capacity of steel skylight is about 11T,
The fabrication and installation capacity of steel purlin is about 12t.
The construction difficulties of this project lie in the large span of roof truss and the difficulty of hoisting; the installation quantity of horizontal support and vertical support is large, and there are many unsafe factors in high-altitude operation and cross operation; in addition, the construction site is narrow, and the on-site production and assembly site are not easy to meet.
Main construction methods
1、 Roof system fabrication
Roof system manufacturing → component transportation → roof truss installation → purlin installation → upper chord horizontal support installation → vertical support installation → lower chord horizontal support installation → roof panel installation.
Roof system includes roof truss, support, purlin, etc. its manufacturing method is represented by roof truss production, and roof truss includes support and other components. Therefore, this paper only describes the fabrication method of roof truss, and references the fabrication of other components.Due to the narrow site, the roof truss is planned to be fabricated outside the site. Each roof truss is fabricated in two sections. Before installation, the roof truss is assembled on site. The assembly method is ridge node assembly. After the assembly is completed, the hoisting and installation work can be carried out after passing the inspection.
Figure 1 manufacturing process flow chart of triangular steel roof truss
The manufacturing process of roof truss is shown in Figure 1
2、 Production of operation platform
In order to ensure the manufacturing quality of steel structure components, two large platforms are set up at the construction site.Among them, platform I is the platform between (1) and 7 (7), platform II is used as operating platform on 25 m × 15 m floor, and roof truss is assembled on platform I.
The lofting shall be strictly reviewed according to the requirements of construction drawings and the standards adopted.The site construction lofting shall be carried out according to the reviewed construction drawings. The setting out shall be carried out according to the 1:1 ratio of physical lofting. The sample plate and sample rod shall be made as the basis for blanking and processing.The sample and sample rod shall be marked with job number, drawing number, part number, quantity, etc. the sample and sample rod shall be properly kept until the end of the project.When setting out and marking, the assembly mark, screw hole mark, position and direction of reinforcing plate, inclination mark, center line, datum line and inspection line shall be clearly marked. If necessary, sample plate shall be made.Attention should be paid to the reservation of welding shrinkage allowance during fabrication and installation (considered as 2mm); allowance for cutting, edge planing and milling; and the requirements for reserved dimensions for installation.Before marking, the bending and deformation of materials shall be corrected.The allowable deviation of setting out and template is shown in Table 1.
Project allowable deviation table 1
| Parallel line distance and segment size | ±0.5mm | Diagonal difference | 1.0mm |
| Width, length | ±0.5mm | Processing template angle | ±20′ |
| Distance between holes | ±0.5mm | ||
| Quality inspection method: check with steel ruler |
3、 Blanking
According to the template and the list of ingredients for nesting, as far as possible to save materials, while easy to cut.Gas cutting is used for steel cutting and cutting is used for profile to ensure the quality of cutting section.Before cutting, rust and dirt on the surface of steel cutting area shall be removed, and slag and spatter shall be removed after cutting.
The allowable deviation of blanking is shown in Table 2
Item allowable deviation (mm) table 2
| Dimensions | ±1.0 | Distance between holes | ±0.5 |
Welding shrinkage allowance, cutting allowance, end face and edge processing allowance shall be reserved during blanking. The empirical data are shown in Table 3.
Cutting and machining allowance (mm Table 3
| Machining allowance | Sawing | shear | Manual cutting | Semi automatic cutting | Precision cutting |
| Cutting seam | 1 | 4～5 | 3～4 | 2～3 | |
| Edge planing | 2～3 | 2～3 | 3～4 | 1 | 1 |
| Milling | 3～4 | 2～3 | 4～5 | 2～3 | 2～3 |
When welding X-shaped V-shaped joint in edge processing, flame processing is adopted, and grinding wheel is used to grind the surface roughness
Check according to precision cutting.The error of groove plus dimension shall meet the requirements of national standards and regulations. The end face of component shall be processed after the finished product is corrected, and the processing surface shall be perpendicular to the center line.
4、 Assembly
Before assembly, all parts shall be inspected to be qualified. The connecting contact surface and welding edge shall be cleaned every 30-50 (mm) range. Plates shall be assembled after splicing of profiles and before assembly. The assembly of articles shall be carried out after welding and correction of each component. The allowable deviation of intersection point of truss structure axis shall not be greater than 3 mm.
5、 Welding
Be familiar with the construction drawing before welding, and the welder must have welder’s operation certificate.Before welding, the quality of the welded joint and the treatment of the welder shall be checked repeatedly. During welding, the welder shall comply with the welding process, and shall not conduct welding by himself or strike arc on the secondary base metal on the weld bead.Each pass shall be welded continuously. The welding slag shall be removed in time after each layer of welding is completed, and the welding quality shall be inspected.
6、 Bolted connection
Roof truss and skylight, skylight support and skylight are connected by bolts and field welding.If the construction is sure, some installation bolts can be cancelled and directly welded on site.The design of the position deviation of the installation bolt hole is not clearly given, so it should be carried out according to the specification, and the deviation should be carried out according to the requirements of Table 4 and table 5.
Bolt hole deviation (mm) table 4
| diameter | ＋1.0 | Roundness | 2.0 | verticality | 0.03t and no more than 2.0 |
Bolt hole distance deviation (mm) table 5
| project | ≤500 | 501～1200 | 1200～3000 | ＞3000 |
| Distance between any holes in the same group | ±1.0 | ±1.5 | ———— | ———— |
| Distance between two adjacent groups of end holes | ±1.5 | ±2.0 | ±2.5 | ±3.0 |
7、 Material splicing material splicing includes the transverse joints (along the length direction) of cross shaped and I-shaped beams and the length butt joint of roof truss and other steel materials. All butt welds of factory materials are grade I welds.
1) For the section steel or steel plate of beam and column, the allowable joint number shall meet the requirements of table 6, and the shortest splicing length shall not be less than 500mm.Allowable number of seam strips table 6
| Section length of beam and column L (mm) | L≤6000 | 6000<L
≤10000 |
L>10000 |
| Number of stitches | 1 | 2 | 3 |
2) The seams of adjacent parts in the assembly must be staggered, and the staggered distance between the center lines shall not be less than 200 mm.3) Automatic submerged arc welding is used for splicing groove, and semi-automatic cutting or edge planing machine is used for groove preparation. The groove type of 10-24mm plate thickness is shown in Fig. 2.
| δ(mm) | ≥10～16 | >16～24 |
| b(mm) | 2+ 1 | 3+ 1 |
| P(mm) | 3+ 1 | 4+ 1 |
Fig. 2 Schematic diagram of 10-24mm plate thickness splicing groove type
4) Before splicing welding, the welding area shall be free of slag, floating rust, oil dirt and other impurities affecting the welding quality; the surface of welding wire shall be free of oil and rust; the flux must be dried according to the requirements of the instructions; the instruments on the welding equipment shall be intact and work normally; arc striking and extinguishing plates shall be installed at both ends of the seam.
Steel structure installation works
Hoisting of structural members includes hoisting of steel roof truss and support.For the installation of steel structure in this project, firstly, the axis of concrete column, the elevation of column top surface and the plane position and elevation of embedded M30 bolt shall be rechecked, and the intermediate handover work shall be completed with civil engineering specialty; secondly, the fabrication of steel members shall be assessed as qualified with complete data.
1 Steel roof truss hoisting
The weight of the single roof truss is about 7.2t, and the weight of the skylight is about 2.3t. According to the hoisting capacity of the crane and the safety of construction, the skylight truss and the roof truss are separately hoisted, and the skylight frame is hoisted after the roof truss and purlin are installed.
The hoisting sequence of steel roof truss is as follows: assembly → lifting → positioning → temporary fixation → correction → final fixation.
The steel roof truss shall be assembled before hoisting. The assembly shall be carried out according to different models. After the assembly of the same roof truss, the whole surface shall be on the same plane, and the center of the lower chord shall be on the same line. The welding between the assembly connecting plate and the bottom chord section steel shall be correct and reliable.
After the steel roof truss is assembled, a φ 48 steel pipe iron pole shall be tied horizontally at the middle line of the triangular steel roof truss to ensure that the components will not deform and fracture during lifting, which will cause accidents.Because the span of the roof truss is more than 18m, it is difficult to lift at two points, so it is considered to use an iron pole to lift the roof truss.The position of roof truss lifting point is within the range of 300 mm around the top chord node.
Qy80 truck crane is selected as crane, and the parameters of crane truck are shown in Table 7.The traveling path of the crane is located at the center line of the roof truss, which is 8m away from the center line of the roof truss.After the crane selects the lifting point, find the binding point of the steel wire rope on the component, and the crane starts to turn over and lift.In the process of lifting, it should be slow, stable and slowly rise to ensure that the components can rise and fall and rotate smoothly in the air.The cable wind rope is tied at both ends of the component to control the rotation of the component.When the component is lifted to a height of about 100 mm higher than the installation position, it shall be lowered slowly. At the same time, the plane position and perpendicularity of the component shall be preliminarily corrected by visual inspection or plumb hammer. After confirmation, it can be temporarily fixed and the hook can be removed.Temporary fixing shall ensure the safety of components and facilitate correction, including plane position, elevation, perpendicularity, etc.When the calibration is accurate and meets the requirements, the final fixation can be carried out according to the connection method required by the construction drawing.When the second truss is fixed, it can be connected with the first one by purlins.
Qy80 truck crane parameter table 7
| Model and specification qy80 | |
| Basic arm length (m) | 12～44 |
| Maximum lifting capacity of basic arm (T) | 80 |
| Maximum lifting height of basic boom (m) | 43.3 |
| Jib length (m) | 9.5～15 |
| Maximum lifting capacity of jib (T) | 4.0～6.0 |
| Maximum lifting height of jib (m) | 53.4～59 |
| Single rope speed (M / min) | 0～100 |
| Rotation speed (R / min) | 0～1.45 |
| External dimension (length × width × height) (m) | 14.765×2.78×3.985 |
| Maximum driving speed (km / h) | 60 |
2 Support system and purlin installation
After the roof truss and skylight are finally fixed, the purlin is installed first, the roof truss is fixed, and the roof truss and column are finally connected.After the purlin is fixed, the upper chord horizontal support and the rigid and flexible pull rod are installed, then the vertical support is installed, and finally the lower chord horizontal support is installed.The fabrication of support is carried out according to the unit. The support with small weight is lifted in place by artificial cable and the heavy one is hoisted in place by crane or chain block.In the process of installation, attention should be paid to whether there is cross-section between various supports and purlins. In case of such situation, the designer shall be contacted in time, and shall not be handled at will.
3 Roof and wall works
The roof of the workshop is yx35-125-750 color steel plate, which is profiled steel plate with a thickness of 0.3mm.During installation, attention should be paid to the reliable connection between the tile and the roof truss purlin. The installation should be carried out from bottom to top. The length of the tile under the upper cover should not be less than 300 mm. The joint between the tiles should follow the dominant wind direction and lap a wave width.
The wallboard is yx35-125-750 color steel plate with a thickness of 0.3mm.The installation shall be carried out from one end according to the purlin position. The plates must be clamped tightly and fixed with screws. Waterproof treatment shall be done at the joints of wall panels.During the installation of profiled steel sheet, its position should be adjusted while laying and fixed at the same time.See Table 8 for allowable manufacturing deviation of metal profiled plate.
Allowable deviation table 8 for manufacturing metal profiled plate
| project | Allowable deviation (mm) | Inspection method | ||
| Covering width of metal profiled plate | Molding
steel plate |
h≤70mm | -2.0～+8.0 | Check with steel ruler |
| h>70mm | -2.0～+5.0 | |||
| Molding
Aluminum plate |
h≤70mm | -2.0～+10.0 | ||
| h>70mm | -2.0～+7.0 | |||
| Plate length | ±7.0 | |||
| Transverse shear deviation | 5.0 | |||
| Flashover and corner plate
size |
Plate length | ±5.0 | ||
| Width of bending surface | ±2.0 | |||
| Included angle of bending surface | 2Degree | Check with angle square | ||
(where h is the height of the metal profiled plate)
4 Steel surface after rust removal in decoration and painting works
The next process can only be carried out after cleaning with brush and other tools. If rust has returned to the steel surface after rust removal, it is necessary to remove rust again.
After the rust removal of the steel is qualified, the first primer shall be applied on the surface. Generally, after rust removal, the steel shall be stored in the workshop, and the primer can be applied within 24 hours.If it is stored outside the workshop, the primer shall be finished on duty.The paint shall be used in accordance with the design requirements. After the first primer is dried, the intermediate paint and top coat shall be applied to ensure that the coating thickness meets the design requirements.The paint shall be uniform and free from falling.
Figure 3 painting process flow chart
Process quality assurance measures
Section 1 fabrication of steel structure
(1) The selected steel must have the factory certificate and original data. After entering the site, the steel must be sampled and retested, and can be used only after passing the test.
(2) Select the processing equipment with good performance and complete functions.
(3) The welding rod shall be provided with factory certificate or material report. The welding rod shall be dried in a drying oven before use. The welding wire and flux selected for submerged arc welding must be matched with the base metal used.
(4) After the steel members are fabricated, rust removal shall be carried out, and primer shall be applied within 24 hours after rust removal to ensure that the paint film thickness meets the design requirements.
(5) All operators must strictly follow the contents of technical, quality and safety disclosure, and welding personnel must work with certificates.
(6) In order to ensure the manufacturing accuracy, the shrinkage of steel members should be pre placed when blanking, and the pre setting amount depends on the size of the workpiece, according to the similar engineering experience of the enterprise and the requirements of the specification.
(7) When several kinds of welds are to be welded, the transverse seam with large shrinkage deformation should be welded first, then the longitudinal weld, or the butt weld and then the fillet weld.
(8) The main weld of welded section steel shall be welded before assembling stiffener parts.The welding sequence of the main weld should be staggered according to the need of welding deformation after welding.
Section 2 installation of steel structure
(1) The hoisting process of steel structure shall be in strict accordance with code for construction and acceptance of steel structure (GB 502052001).
(2) Before hoisting, the vertical and horizontal axis and horizontal elevation of the foundation, the overall dimension of steel members and welding quality must be rechecked before construction.
(3) Technical disclosure must be carried out before construction.
(4) During the construction, the personnel of special type of work must have the post certificate issued by the labor bureau.
(5) The measuring instrument can only be used after passing the metrological verification.
(6) During the construction, adhere to the three inspection (self inspection, mutual inspection, professional inspection) system, and strictly inspect the process quality.
Section 3 installation of profiled steel sheet
(1) Under the condition of transportation and hoisting permission, long size plates should be used to reduce joints, improve thermal insulation performance and waterproof effect.
(2) The profiled steel plate is fixed. There is one wave overlap between two plates in transverse wave. The lap surface is sealed with sealant strip, then sealed with waterproof sealing paste, and fixed with self tapping screw and purlin.
(3) The end of each plate shall not be less than 3 screws, and the middle support shall be connected with at least one self tapping screw when the distance between purlins is greater than 3m.
(4) The plate is lapped on the purlin to ensure the lap length requirement. The lap part is connected with rivet and applied with waterproof sealing paste. The exposed nail head is coated with sealing paste.
(5) The lap joint of the steel plate with edge wrapping should be away from the wind direction as far as possible. The lap length should be more than 20-50 mm, and the rivet spacing should be less than 500 mm.
(6) The self tapping rivet is set on the wave crest and is waterproof.
(7) Once the color coating is scratched or rusted, the corresponding series of coatings shall be used for patching.
Safety construction measures
(1) A full-time safety officer shall be set up at the construction site to implement and supervise the implementation of safety measures on site, and conduct unified management on site construction personnel, on-site mechanical equipment and on-site power consumption.It is required that the operators of special types of work participating in the construction must be trained and work with certificates.Before construction, safety technical disclosure shall be carried out for all construction personnel.Personnel entering the construction site must wear safety helmet and anti-skid shoes, electricians and welders should wear insulating shoes, and high-altitude operation must wear safety belt.
(2) Before operation, the tools, machines and equipment used shall be inspected, and the safety devices shall be complete and effective.
(3) The operation surface shall be provided with reliable platform and body protection, and the operation shall be carried out after the inspection.The binding method of components shall be correct, anti-skid measures shall be taken at the lifting point, and the tools and materials used for high-altitude operation shall be placed in a safe place, and it is forbidden to place them casually.
(4) When lifting steel members, the lifting or lowering should be stable to avoid emergency braking or impact.The signal is clear, loud and clear, and illegal operation is strictly prohibited.After installation, the quality of the components must be checked, and the shackles can only be broken out if they are safe and reliable.The work must reach the safe position every day before work can be finished.
(5) The mechanical and electrical equipment, gate box and electric welding machine on the construction site shall be provided with reliable rain proof measures.Electrical operation must be carried out by professional personnel, and non professional personnel are strictly prohibited.The electric welding machine shall be used in strict safety operation procedures, and the primary line shall not exceed 2m, and the secondary line shall not be exposed.
(6) The safety facilities shall be set uniformly by special personnel according to the regulations, and other people shall not dismantle them at will.When it is necessary to dismantle due to work needs, it shall be allowed by relevant personnel, and it shall be restored in time after the event, and the safety officer shall carefully inspect it.
(7) Do a good job in the safe use of electricity. Professional electricians are responsible for the removal of all electrical equipment and on-site lighting. The electric tools used must be installed with leakage protector.
(8) Pay attention to the high-altitude operation. Drinking and fighting are strictly prohibited during the working period. The hand-held tools should be tied with safety ropes to avoid straight-line vertical cross operation.
(9) Do a good job in fire prevention, and all operations should be used correctly according to the regulations.
(10) When the roof is installed, the safety net shall be arranged and the fence shall be set.
(11) Adhere to the pre shift safety meeting system, and disclose the work arrangement and safety precautions of the day.
(12) Carry out safety inspection regularly to prevent and control the unsafe factors of accidents.
(13) Lifting command should be decisive and instructions should be concise and clear.
(14) Strengthen the site security, pay attention to anti-theft.
(15) Safety warning line shall be set within the hoisting operation range, and non operators are not allowed to enter.
(16) All safety activity records and documents shall be complete.
Post time: Jul-04-2020