Construction is a very important part of architecture, transforming floor plans into physical buildings to achieve various functions and meet normal usage. Different buildings have different requirements and methods during construction. Let’s learn some key points in the construction of prefabricated buildings together.
1、 General regulations for structural construction
Before the construction of prefabricated structures, a construction organization design and construction plan should be formulated; The content of construction organization design should comply with the current national standard “Code for Construction Organization Design of Building Engineering”; The content of the construction plan should include component installation and node construction plan, quality management and safety measures for component installation, etc.
2. The post poured concrete parts of prefabricated structures should undergo concealed engineering acceptance before pouring. The acceptance items should include the following:
1) The grade, specification, quantity, position, spacing, etc. of the steel bars;
2) The connection method, joint position, number of joints, joint area percentage, lap length, etc. of longitudinally stressed steel bars;
3) The anchoring method and length of longitudinally stressed steel bars;
4) The grade, specification, quantity, position, and spacing of stirrups and transverse steel bars, as well as the bending angle and length of the straight section of the hoop hook;
5) Specification, quantity, and location of embedded parts;
6) Quality of rough surface of concrete, specifications, quantity, and position of key slots;
7) The specifications, quantity, location, and fixing measures of reserved pipelines, wire boxes, etc.
3. Prefabricated components, installation materials, and accessories should comply with design requirements and relevant national standards.
4. The lifting equipment used for hoisting should be designed, verified or tested in accordance with the relevant national standards. The lifting equipment should be configured according to the shape, size, weight and other parameters of the prefabricated components. The horizontal angle of the lifting equipment should not be less than 60 ° and should not be less than 45 º; For prefabricated components with large dimensions or complex shapes, it is advisable to use lifting devices with distributed beams or trusses.
Before grouting the steel sleeve, the grouting method of the component connection joints should be simulated on site. Each specification of steel should have no less than three sleeve grouting connection joints, and the grouting quality and tensile strength of the joints should be inspected; Only after passing the inspection can grouting operations be carried out.
6. During the entire construction process of prefabricated structures, protective measures should be taken to prevent damage or contamination to prefabricated components and building accessories, embedded parts, and suspended parts on prefabricated components.
7. Cutting or drilling of prefabricated components is not allowed without design permission.
8. Safety measures should be taken during the construction process of prefabricated structures, and relevant regulations such as the current industry standards “Technical Specification for Safety of High Altitude Operations in Construction”, “Technical Regulations for Safety of Construction Machinery Use”, and “Technical Specification for Safety of Temporary Electricity Use on Construction Sites” should be complied with.
2、 Installation preparation
1. Reasonable planning of component transportation channels and temporary storage areas should be carried out, and protective measures for finished product stacking should be taken.
2. Before installation and construction, the concrete strength, appearance quality, dimensional deviation, etc. of the completed structure should be checked to ensure compliance with the relevant provisions of the current national standard “Construction Specification for Concrete Structures” and this regulation. The concrete strength of prefabricated components and the model, specification, quantity, etc. of prefabricated components and fittings should also be checked to ensure compliance with the design and requirements
Before installation and construction, measurement and setting out should be carried out, and component installation positioning marks should be set up.
Before installation and construction, the assembly position of components, node connection structure, and temporary support scheme should be reviewed.
Before installation and construction, it is necessary to check and verify that the lifting equipment and hoisting tools are in a safe operating state.
Before installation and construction, it is necessary to verify that the on-site environment, weather, road conditions, etc. meet the requirements for lifting and construction.
Before the construction of prefabricated structures, representative units should be selected for trial installation of prefabricated components, and the construction plan and process should be adjusted and improved in a timely manner based on the results of the trial installation.
3、 Installation and Connection
After the prefabricated components are lifted into place, they should be calibrated in a timely manner and temporary fixing measures should be taken.
Before placing prefabricated components connected by steel sleeve grouting and steel slurry anchor overlap, the following contents should be checked:
1) Specification, location, quantity, and depth of sleeves and reserved holes;
1) The specifications, quantity, location, and length of the connected steel bars.
When there are impurities in the sleeve or reserved hole, they should be cleaned thoroughly; When the connecting steel bars are inclined, straightening should be carried out. The deviation of the connecting steel bars from the centerline of the sleeve or hole should not exceed 5mm.
3. The installation of wall and column components should meet the following requirements:
1) Before installing the components, the joint surface should be cleaned;
2) Adjustable joint thickness and bottom elevation cushion blocks should be installed at the bottom of the component;
3) Before grouting the steel sleeve grouting connection joint and the steel slurry anchor overlap connection joint, the surrounding area of the joint should be sealed;
4) When using precast assembly type grout material for the bottom of multi-layer prefabricated shear walls, its thickness should not exceed 20mm.
4. The grouting of the steel sleeve grouting connection joint and the steel slurry anchor overlap connection joint shall comply with the requirements of the node connection construction plan and shall meet the following requirements:
1) During grouting construction, the ambient temperature should not be lower than 5 ℃; When the maintenance temperature of the connection part is below 10 ℃, heating and insulation measures should be taken.
2) There should be dedicated inspectors responsible for on-site supervision and timely formation of construction quality inspection records throughout the grouting operation process.
3) The amount of grouting material and water should be measured according to the requirements of the product manual and mixed evenly; The flowability of the grout mixture mixed each time should be tested, and its flowability should meet the requirements of this regulation.
4) The grouting operation should use the grouting method to inject from the lower mouth, and when the grout flows out from the upper mouth, it should be promptly sealed.
5) The grout mixture should be used up within 30 minutes after preparation.
5. The construction of welding or bolted connections shall comply with the relevant requirements of the current national standards “Code for Welding and Acceptance of Reinforcing Steel”, “Code for Welding of Steel Structures”, “Code for Construction of Steel Structures” and “Code for Acceptance of Construction Quality of Steel Structures”.
When using welding connections, measures should be taken to prevent concrete cracking at the connection site caused by continuous welding.
6. The construction of mechanical connection of steel bars should comply with the relevant requirements of the current industry standard “Technical Specification for Mechanical Connection of Steel Bars”.
7. The construction of post poured concrete should meet the following requirements:
1) The concrete in the loose part of the joint surface of prefabricated components should be removed and cleaned thoroughly;
2) The formwork should ensure the accuracy of the shape, size, and position of the post poured concrete, and should prevent leakage of grout;
3) Before pouring concrete, the joint surface should be moistened with water, and the concrete should be compacted by vibration;
4) For concrete with the same mix ratio, a set of standard curing specimens should be made for each work shift and the building area should not exceed 1000m2. At least 3 sets of standard curing specimens should be made for the same floor.
8. The temporary fixing measures can only be removed after the strength of the poured concrete and grouting material at the connection part of the component meets the design requirements.
9. The assembly and construction of bent composite components shall meet the following requirements:
1) Temporary supports should be set up according to design requirements or construction plans;
2) The construction load should be evenly distributed and should not exceed the design requirements;
3) Before pouring concrete, the roughness of the joint surface and the exposed steel bars of the prefabricated components should be checked according to the design requirements;
4) The temporary support of the composite component can only be removed after the strength of the post poured concrete meets the design requirements.
10. When installing prefabricated bending components, the length of the end should meet the design requirements. A grout or support pad should be placed between the end and the supporting component, and the thickness of the grout or support pad should not exceed 20mm.
11. The connection nodes and joint structures of external wall panels should meet the design requirements; After the installation of the wall panel is completed, temporary support brackets and force transfer pads in the wall panel joints should be removed in a timely manner.
12. The waterproofing construction of exterior wall panel joints should meet the following requirements:
1) Before waterproofing construction, the inner cavity of the side joint of the wall panel should be cleaned thoroughly;
2) The backing material should be filled according to the design requirements;
3) The sealing material filling should be full, dense, uniform, straight, and have a smooth surface, and its thickness should meet the design requirements.
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