Source: Building Industrialization Innovation Alliance
Chapter 3: Lifting Operations of Prefabricated Concrete Components
Content Summary
The lifting operation of prefabricated concrete components is crucial for the lifting, positioning, and adjustment of these components throughout the construction process of prefabricated buildings. It completes the temporary positioning of prefabricated concrete parts. This chapter provides a detailed overview of the lifting operations involved, including the types and characteristics of commonly used lifting machinery, the selection of lifting equipment, and specific lifting procedures for various prefabricated concrete elements such as wall panels, floor slabs, beams, stairs, and others.
Initially, the chapter explains guidelines for selecting and matching equipment and tools before lifting prefabricated concrete components. It then offers a comprehensive explanation of the lifting process, operational methods, temporary fixing facilities, and important considerations for different types of prefabricated concrete components.
3.5 Hoisting Operation of Precast Concrete Beams
3.5.1 Construction Process of Precast Concrete Beam Hoisting (Figure 3-27)
Figure 3-27 Construction Process of Prefabricated Concrete Beam
3.5.2 Preparation Work Before Construction
- Verify that the support frame is properly installed and that the top elevation is accurate.
- Inspect the position, orientation, and numbering of the main beam reinforcement as well as the small beam joint keyways in prefabricated residential buildings.
- If the elevation error of the column head exceeds allowable limits, apply a soft gasket to the column head before installation to adjust height differences.
- Lift from the designated lifting points according to original design specifications and prepare all necessary tools.
- If upper main reinforcement bars are incorrectly crossed, correct them prior to lifting.
- Confirm the lifting sequence diagram of prefabricated beams as per detailed component drawings.
- During hoisting of primary and secondary beams of different sizes, install safety nets to protect workers.
3.5.3 Prefabricated Concrete Beam Hoisting Process
1) Confirm Direction, Numbering, and Upper Main Reinforcement of Beams
- Inspect beams before entry for serious defects or missing corners, check straightness between outer protective layers of hoop reinforcement and beam hoop, and verify beam perforations.
- Before hoisting, verify the main beam reinforcement, direction, and numbering.
Figure 3-28 Sequence Number for Hoisting Precast Concrete Beams
2) Marking Reference Lines for Secondary Beam Positioning
Before hoisting the main beam, mark the installation reference lines for the secondary beams. These lines serve as the basis for positioning the secondary beams during hoisting.
3) Main Beam Lifting and Installation
If the elevation error of the column head exceeds allowable values, adjustments are required:
- If the column head elevation is too low, place an iron plate on the column head to compensate for the height difference before hoisting the main beam.
- If the column head elevation is too high, correct the column head to the design elevation before hoisting the main beam.
Figure 3-29 Prefabricated Concrete Beam Hoisting
4) Adjusting Column Head Position and Mid-Beam Elevation
After hoisting, a team should adjust the top elevation of the support frame to ensure the column head position and beam elevation are consistent and perfectly horizontal.
5) Lifting the Secondary Beam After Installing the Two-Way Main Beams
The secondary beam can only be lifted after the two main beams have been installed. Confirm the lifting sequence of the main beams to ensure correct alignment of the upper and lower steel bars before installing the secondary beam.
Figure 3-30 The Lifting of Primary and Secondary Beams Completed
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 the scaffolding. Control their height according to construction elevations, proceeding in the order of installing stair beams first, then stair slabs. Apply mortar inside the L-shaped supports of the stairs using a soft seating method before placing the stairs and stair beams.
Figure 3-31 Prefabricated Concrete Staircase Support System
When reinforcement bars are embedded at both ends of the prefabricated staircase, use a chain block for lifting. This allows adjustment of the relative elevations of the upper and lower ends of the staircase, facilitating easier installation.
Figure 3-32 Prefabricated Concrete Staircase Hoisting
When connecting prefabricated stairs to cast-in-place beams or slabs using pre-embedded welding connections, construct the cast-in-place beams or slabs first. Then place the prefabricated stairs for welding connections.
Note: The copyright of the above materials belongs to Shanghai Jianfeng College and Shanghai Construction Second Construction Group.
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