Construction plays a crucial role in architecture, turning floor plans into physical structures that serve various functions and meet everyday needs. Different buildings require distinct construction approaches. Let’s explore some essential points in the construction of prefabricated buildings.
1. General Regulations for Structural Construction
Prior to commencing construction of prefabricated structures, a construction organization design and detailed plan must be developed. The construction organization design should comply with the national standard “Code for Construction Organization Design of Building Engineering”. The construction plan should include details on component installation, node construction methods, quality control, and safety measures.
Post-poured concrete sections of prefabricated structures require concealed engineering inspection before pouring. The inspection should verify the following:
- The grade, specifications, quantity, placement, and spacing of steel reinforcement;
- Connection methods, joint locations, number of joints, joint area ratios, and lap lengths of longitudinally stressed steel bars;
- Anchorage methods and lengths for longitudinally stressed steel bars;
- Specifications, quantity, position, and spacing of stirrups and transverse steel bars, including bending angles and hook lengths for hoop hooks;
- Specifications, quantity, and placement of embedded parts;
- Quality of concrete’s rough surface, specifications, quantity, and placement of key slots;
- Specifications, quantity, location, and securing methods for reserved pipelines, wiring boxes, and related fixtures.
All prefabricated components, installation materials, and accessories must meet design requirements and comply with relevant national standards.
Hoisting equipment used for lifting prefabricated components should be designed, verified, or tested according to national standards for prefabricated residential buildings. Equipment selection must consider the shape, size, weight, and other parameters of the components. The horizontal sling angle should be no less than 60°, and never below 45°. For large or complex components, lifting devices with distributed beams or trusses are recommended.
Before grouting steel sleeves, the grouting method for component connection joints should be trialed on-site. Each specific steel type must have at least three grouted sleeve connections tested for quality and tensile strength. Only after passing inspection is grouting allowed.
Throughout construction, protective measures must be implemented to prevent damage or contamination of prefabricated components, building accessories, embedded parts, and hanging fixtures.
Cutting or drilling prefabricated components without design approval is strictly prohibited.
Safety precautions during construction must comply with relevant regulations, including the 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”.
2. Installation Preparation
Transportation routes for components and temporary storage areas should be planned efficiently, with protective measures to safeguard finished products during stacking.
Before installation, verify the concrete strength, surface quality, and dimensional accuracy of completed structures to ensure compliance with “Construction Specification for Concrete Structures” and related regulations. Prefabricated components and fittings must be checked for conformity with design specifications, including type, size, and quantity.
Conduct precise measurements and establish installation positioning marks before assembly begins.
Review the assembly locations, node connection structures, and temporary support plans prior to installation.
Inspect lifting equipment and hoisting tools to confirm they are in safe working condition.
Ensure the onsite environment, weather conditions, and access roads meet requirements for safe lifting and construction.
Trial installations of representative prefabricated units should be conducted to test procedures. Construction plans should be adjusted promptly based on trial results.
3. Installation and Connection
Once prefabricated components are lifted into place, they must be promptly aligned and temporarily secured.
Before positioning components connected by steel sleeve grouting or steel slurry anchor overlaps, verify the following:
- Specifications, locations, quantities, and depths of sleeves and reserved holes;
- Specifications, quantities, locations, and lengths of connected steel bars.
Clean any impurities inside sleeves or reserved holes thoroughly. If connecting steel bars are bent, straighten them. The deviation from the centerline of the sleeve or hole should not exceed 5 mm.
Wall and column component installation must meet these criteria:
- Clean joint surfaces before installation;
- Install adjustable joint thickness and bottom elevation cushions at component bases;
- Seal the surrounding area of steel sleeve and steel slurry anchor joints before grouting;
- For multi-layer prefabricated shear walls, grout thickness at the base should not exceed 20 mm.
Grouting of steel sleeve and steel slurry anchor joints must follow the node connection construction plan and adhere to these requirements:
- Ambient temperature should be above 5°C during grouting. If the curing temperature falls below 10°C, heating and insulation must be applied;
- Dedicated inspectors should supervise the grouting process and maintain quality records;
- Grout materials and water volumes must be measured as per product guidelines and mixed thoroughly. Flowability tests should confirm compliance with specifications;
- Grout should be injected from the lower outlet, and the upper outlet sealed promptly once grout emerges;
- Prepared grout must be used within 30 minutes.
Welding or bolted connections must comply with national standards such as the “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 welding, precautions should prevent concrete cracking caused by continuous welding heat.
Mechanical connections of steel bars must follow the “Technical Specification for Mechanical Connection of Steel Bars” industry standard.
Post-poured concrete construction should meet the following:
- Remove and clean loose concrete from joint surfaces thoroughly;
- Use formwork that ensures accurate shape, size, and position of post-poured concrete, preventing grout leakage;
- Moisten joint surfaces before pouring, and compact concrete using vibration;
- For concrete with the same mix ratio, prepare standard curing specimens for each work shift, with building areas not exceeding 1,000 m². At least three sets of specimens should be made per floor.
Temporary supports may only be removed once poured concrete and grout have reached the required design strength.
Assembly of bent composite components requires:
- Installation of temporary supports as per design or construction plans;
- Even distribution of construction loads, ensuring they do not exceed design limits;
- Verification of joint surface roughness and exposed steel bars before concrete pouring;
- Removal of temporary supports only after post-poured concrete reaches the required strength.
When installing bent prefabricated components, the end length must comply with design requirements. A grout or support pad should be placed between the end and supporting component, with a maximum thickness of 20 mm.
Connection nodes and joints of exterior wall panels must meet design specifications. After installation, temporary support brackets and force transfer pads in wall panel joints should be promptly removed.
Waterproofing of exterior wall panel joints must adhere to the following:
- Thoroughly clean the inner cavity of the wall panel side joints before waterproofing;
- Fill backing materials as specified in the design;
- Apply sealing material fully, densely, uniformly, and smoothly, ensuring thickness meets design requirements.
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