Chapter 3: Lifting Operations of Prefabricated Concrete Components
Content Summary
The lifting of prefabricated concrete components is essential for their positioning and adjustment during the construction of prefabricated buildings. This process completes the temporary placement of these components. This chapter provides a comprehensive overview of lifting operations for prefabricated concrete components, detailing the types and characteristics of commonly used lifting machinery, the selection of lifting equipment, and specific procedures for lifting various components such as concrete wall panels, floor slabs, beams, and stairs.
Initially, the chapter covers the selection and matching of equipment and tools required for lifting operations, establishing relevant regulations. It then thoroughly explains the lifting procedures, methods, temporary fixing facilities, and critical considerations for different prefabricated concrete components.
3.5 Hoisting Operation of Precast Concrete Beams
3.5.1 Construction Process of Precast Concrete Beam Hoisting
3.5.2 Preparation Before Construction
(1) Verify that the support frame is properly installed and that the top elevation is accurate.
(2) Check the position, orientation, and numbering of the joint keyway between the main beam reinforcement and the secondary beam.
(3) If the elevation error of the column head exceeds allowable limits, apply a soft gasket to the column head before installation to adjust the height difference.
(4) Ensure the lifting points conform to original design specifications and prepare all necessary tools.
(5) Correct any known errors in the upper main reinforcement before lifting.
(6) Confirm the lifting sequence diagram for prefabricated beams as detailed in the component drawings.
(7) When hoisting primary and secondary beams of varying sizes, install safety nets to protect workers during construction.
3.5.3 Prefabricated Concrete Beam Hoisting Process
1) Verification of Direction, Numbering, and Upper Main Reinforcement of Beams
(1) Inspect beams upon delivery for serious defects or missing corners. Confirm the straightness between the outer protective layer of hoop reinforcement and the beam hoop, and check for any perforations.
(2) Before lifting, verify the main beam reinforcement, orientation, and numbering.
2) Marking Reference Lines for Secondary Beam Positioning
Before hoisting the main beam, mark the installation reference lines for the secondary beams. This will serve as the basis for positioning during the secondary beam hoisting.
3) Main Beam Lifting and Installation
If the elevation error of the column head exceeds allowable limits, adjust accordingly: place an iron plate on the column head if it is too low, or correct the column head to the design elevation if it is too high before lifting the main beam.
4) Adjustment of Column Head Position and Beam Elevation
After lifting, dispatch a team to adjust the top elevation of the support frame, ensuring that the column head position and beam elevation are aligned and level.
5) Lifting Secondary Beams After Main Beam Installation
The secondary beams can only be lifted after the two-way main beams are fully installed. Before lifting, verify the lifting sequence for the main beams and confirm the position of integrated steel reinforcing bars on the upper and lower parts of the main beams. Then proceed with the installation of secondary beams.
3.6 Hoisting Operation of Prefabricated Concrete Stairs
3.6.1 Hoisting Process of Precast Concrete Stairs
Before installation, set up stair beams (platform slabs) to support scaffolding, controlling their height according to the construction elevation. Proceed with installing the stair beams first, followed by the stair slabs. Prior to placing the stairs and stair beams, apply mortar inside the L-shaped stair supports using a soft seating method.
When reinforcement bars are present at both ends of the prefabricated staircase, use a chain block for lifting. This allows adjustment of the relative elevation between the upper and lower ends of the stairs, facilitating installation.
For prefabricated stairs connected to cast-in-place beams or slabs via pre-embedded welding, ensure the cast-in-place beams or slabs are constructed first. Then place the prefabricated stairs for welding connection.
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