Prefabricated Floor Slab Hanging Formwork Construction

The construction of hanging formwork for prefabricated floor slabs in buildings should be systematically carried out from three aspects: construction preparation, lifting construction process, and hanging formwork fixing methods. The specific key points are as follows:

I. Construction Preparation Stage

1. Technical Preparation
Organize a technical team to conduct a drawing review, clarify key parameters for floor slab lifting (such as load and installation position), and draw a hierarchical lifting layout plan. At the same time, prepare special technical disclosure documents and train the lifting team to ensure that operators are familiar with the process flow and safety regulations.

2. On-site Preparation

• Site Planning: After leveling the site, divide it into component stacking areas, lifting operation areas, and material processing areas, and set up protective railings for isolation. The site hardening uses 200mm thick C20 concrete, and drainage slopes and drainage ditches are set up to prevent water accumulation from affecting construction.
• Support System Erection: Use a full-house scaffold as temporary support, with post spacing ≤ 1.2m, sweeping rods 200mm from the ground, horizontal rod step spacing ≤ 1.8m, and wooden planks at the bottom of the posts. Adjustable U-shaped brackets are installed at the top of the support, with the protruding length of the bracket screw ≤ 200mm. The support system must pass a load test (bearing capacity ≥ 2.5kN/m²) before it can be put into use.
• Surveying and Setting Out: Use a total station to set out the axis control lines and floor slab installation side lines, and snap the elevation control lines on the support system (error ≤ ±3mm). Set up 4 elevation control points in each room and mark them with red paint.

3. Material and Equipment Preparation

• Prefabricated Slab Acceptance: Check the factory certificate, structural performance test report, and concrete strength report (≥ C30). The appearance should be free of cracks (excessive width), warping, or dimensional deviations. Unqualified components should be immediately returned.
• Lifting Equipment Configuration: Select a truck crane according to the weight of the floor slab, equipped with steel wire ropes, universal lifting fixtures, and shackles. Before use, check the wear amount of the steel wire ropes, the safety device of the lifting hook, and the welding strength of the lifting rings.
• Auxiliary Materials: Prepare C40 bedding mortar, hard rubber strips, iron wires, wooden wedges, and special grouting materials, etc.

II. Lifting Construction Process

1. Component Transportation and Stacking
The transportation vehicle should check the road smoothness, with a speed ≤ 5km/h, and a dedicated person should be assigned to direct at turns. Components should be transported flat, with special brackets set up on the vehicle, and the stacking height ≤ 4 layers. On-site stacking should be carried out according to the lifting sequence, with the wooden pads 300mm from the end of the slab, the upper and lower layers aligned, and the bottom of the slab elevated 200mm for moisture prevention.

2. Lifting Operation

• Lifting Preparation: Clean up debris at the bottom of the floor slab, install special lifting rings 300mm from the end of the slab, adopt a four-point lifting method, with the angle between the lifting rope and the horizontal plane ≥ 60°. Conduct a trial lifting before lifting, and stop and check when the slab is lifted 50cm above the ground.
• Positioning and Installation: When the floor slab is lifted to 60cm above the working surface, workers should hold it to control the direction and slowly lower it to 2cm above the support surface, aligning it with the ground elevation control line to complete the preliminary positioning.

III. Hanging Formwork Fixing Methods

Hanging formwork refers to suspended formwork without lower support. Common fixing methods include:

• Water-stop Tie Rod Support: Fix the formwork on both sides of the structure through tie rods, suitable for parts with waterproof requirements.
• Support-free Bolt Rod Hanging Formwork Device: Use bolt rods to connect with the formwork and provide support force through the upper structure or embedded parts.
• Prefabricated Beam Wet Joint Hanging Formwork Structure: Set up formwork at the joints of prefabricated beams, and form an overall support after pouring wet joint concrete.