Construction Plan for Purlins of Prefabricated Houses

The construction plan for purlins of prefabricated houses should be systematically implemented from four aspects: pre-construction preparation, construction techniques, quality control, and safety measures, as detailed below:

I. Pre-construction Preparation

1. Technical Preparation: Organize management personnel and operational teams to review the drawings, clarify the specifications, spacing, connection methods, and node details of the purlins, and verify the avoidance designs for roof openings, fan foundations, and other areas. Develop adjustment plans for any deviations in the span of steel beams and conduct safety and technical briefings for all personnel, retaining signed records.
2. Surveying and Setting Out: Based on the completion acceptance records of the steel beams, use a laser level or theodolite to set out the installation positioning lines for the purlins, mark the spacing, and verify the deviations between adjacent steel beams (adjustments are required if exceeding 5mm). For double-pitched roofs, additional horizontal control lines should be set up to prevent the purlins from shifting along the slope.
3. Material Preparation:
   • Purlins: Use cold-formed thin-walled C-section or Z-section steel. Check the factory quality certificates (material reports, galvanized layer inspection records, etc.), inspect each piece for appearance (no cracks, rust, or bending deflection ≤ 10mm), and conduct dimensional and galvanized layer thickness inspections on 3 out of every 100 pieces. Double the inspection or reject non-compliant batches. When stacking, the height of the wooden pads should be ≥ 100mm, the stacking height should be ≤ 1.5m, and they should be classified and labeled to avoid misuse.
   • Connection Materials: Bolts (hot-dip galvanized high-strength or ordinary galvanized) should be checked for torque coefficient reports, and high-strength bolts should be used up on the day they are unpacked; tie rods (round steel hot-dip galvanized) should be checked for diameter and galvanized layer quality.

II. Construction Techniques

1. Positioning and Setting Out: Use a laser level to accurately set out the lines according to the design drawings, with purlin spacing ranging from 1.2 to 1.5 meters to avoid roof sagging or material waste.
2. Scaffold Board Laying: Lay scaffold boards on the purlins, secure them with steel bars, and wrap them with cloth strips to prevent scratching the coating.
3. Installation and Leveling: Proceed from the eaves to the ridge, connect the purlins to the main structure with扣板 (buckle plates) and secure them with screws, following the principle of "positioning first, then fastening," and tighten the screws after leveling. Bent purlins should be replaced to prevent stress concentration.
4. Tie Rod System: Start tensioning the tie rods from the eaves, using special tools to control the deflection deviation ≤ 1/200 of the span. For multi-span continuous purlins, the recommended cantilever length is 0.146 times the distance between supports to optimize stress distribution.

III. Construction Quality Control

1. Material Quality: Strictly inspect the specifications and performance of purlins and connection materials to ensure they meet design requirements.
2. Process Control: Follow the construction techniques, combining self-inspection, mutual inspection, and special inspection, with a focus on checking purlin spacing, leveling accuracy, and tie rod tension.
3. Acceptance Criteria: Conduct a completion acceptance after construction to ensure the purlins are securely installed, evenly spaced, and free of deformation, and the tie rod system is stable.

IV. Construction Safety Measures

1. Personnel Protection: Construction personnel should work with certificates, wearing safety helmets, non-slip shoes, and safety belts, and safety nets should be set up for high-altitude operations.
2. Equipment Management: Regularly inspect construction equipment, clear flammable materials before welding or cutting, and equip with fire extinguishers.
3. Site Management: Set up warning signs and stack materials neatly (C-section steel stacking height ≤ 1.5m) to prevent slipping.
4. Operational Specifications: Strictly adhere to regulations for high-altitude operations and electrical safety, and杜绝 (eliminate)违规 (non-compliant) operations.