Currently, large formwork is widely utilized in engineering projects, primarily for wall pouring. This construction method offers a straightforward process, rapid construction speed, high-quality results, strong structural integrity, excellent seismic resistance, and a smooth concrete surface. Additionally, it reduces the need for wet plastering. Below are the essential points to consider when working with large formwork. Let’s explore them together.
Key Points for Large Formwork Inspection
1. Deformation Test
Apply a uniformly distributed or concentrated load to test the formwork. The maximum deflection must not exceed 1.5mm under a 10N/mm concentrated load. No local damage or bending should occur under a 15N/mm load, and residual deformation after unloading should be less than 0.2mm. After maintaining the load for 2 hours, all weld points must remain free of cracks.
2. Elasticity Test
(1) Insert a U-shaped clamp into the test plate and hold the load for 5 minutes after clamping the plate rib. Check for maximum residual deformation and ensure no transverse cracks appear around the clamp hole.
(2) Open the bayonet of the U-shaped clamp, hold the load for 5 minutes to measure its clamping force. After repeated operations, verify that the clamping force meets design requirements and confirm that no transverse cracks appear near the clamp hole.
3. Compression Test
(1) When the steel pillar is vertical, test its load-bearing capacity during plane support. Ensure the steel pillar remains vertical and meets load requirements.
(2) Using blade-shaped support, place a ruler in the middle of the steel pillar and conduct a deflection test by applying load. Measure the lateral deflection and observe the maximum lateral deflection at failure.
Key Points for Supporting Large Formwork
(1) For formwork installations over 3.0 meters high, scaffolding must be erected. No one except operators is permitted under scaffolding. High-altitude lifting should cease during wind speeds of level 5 or higher.
(2) When storing flat formwork, it must meet the regional self-stabilizing angle requirements. Two large formworks should be stored face-to-face. For long-term storage, formworks should be connected as a whole. They must be stored on construction floors with reliable anti-tip measures and positioned perpendicular to the outer wall rather than along its edge. Unsupported or insufficiently stabilized large formwork should be placed on dedicated racks or stacked flat, avoiding leaning against other formworks or objects to prevent slipping or tipping.
(3) Before lifting, inspect all ropes, fixtures, and lifting rings on each template to ensure they are intact and effective. Remove all temporary supports before proceeding with lifting.
(4) Cylindrical molds can be transported whole by trailer or disassembled into flat molds for horizontal stacking and transport. When stacking flat molds, wooden pads must be vertically aligned and securely tied.
(5) When installing external formwork for fully cast-in-place structures, fix and accurately adjust suspension arms before removing hooks. Immediately thread and tighten pin rods after installing external formwork. Operators working on outer floors must wear safety belts.
(6) During assembly or dismantling, commanding, dismantling, and hanging personnel must be positioned in safe, secure locations. Personnel are strictly prohibited from lifting while attached to large formwork.
(7) Before dismantling and lifting, verify that all through-wall dowels have been completely removed. Only lift when the formwork is fully detached from the wall. When removing external formwork, hang the hook first, tighten the rope, then remove dowels and supports. Hooks should be perpendicular to the formwork and must not be lifted diagonally to avoid collisions. Do not release the hook until it is lifted above head height. Only after surpassing the allowable clearance can the crane be moved or the arm rotated.
(8) Install large formwork from inside to outside. After placing single-sided formwork, fix it firmly with brackets. For double-sided horizontal plates, secure them with tension rods and bolts. Hooks should remain until the formwork is properly fixed. Protective measures must be taken after installation to prevent electric shock. A dedicated person should connect large formworks in series and link them to the lightning protection system to prevent leakage and injuries.
(9) Ensure protective measures against electric shock are in place after installation. Connect large formworks in series and link them to the lightning protection network.
(10) Large formwork must include auxiliary facilities such as operating platforms, stairs, walkways, and protective railings.
Key Points for Dismantling Large Formwork
(1) When dismantling, remove vertical wall formwork first, followed by horizontal wall formwork and door opening formwork. Detach connecting components such as flower basket bolts, upper mouth clips, and wall penetrating bolts, and store them in a toolbox. Then loosen foundation bolts gradually to detach the formwork from the wall.
(2) For hinged cylindrical formwork, after removing connectors, rotate the demoulding device to lift it away from the wall. Due to the heavy weight and close wall contact, hooks must be securely attached and lifting must be steady to avoid wall damage.
(3) When dismantling corner formwork, remove concrete from the surface first, then pry from the bottom to remove the corner formwork. Take care during door opening formwork removal to avoid cracks from vibration in concrete beams above the door opening.
(4) Promptly chisel protruding concrete, repair concave parts or corners with cement mortar, and install supports or delay formwork removal for prefabricated openings with spans exceeding 1 meter.
(5) Before lifting large formwork post-demoulding, ensure all through-wall bolts are removed and the formwork is fully detached. When removing external formwork, hang the hook first, tighten the rope, then remove pin rods.
(6) Erect fences around dismantling and assembly areas with clear signage to prohibit unauthorized access. Connect adjacent flat formworks promptly using fixtures or basket screws.
(7) Personnel responsible for commanding, dismantling, and hooking must operate from safe, reliable locations. Lifting with personnel attached to the formwork is strictly forbidden.
(8) Hooks must remain perpendicular during lifting and not lifted diagonally. Do not release hooks until they are lifted above head height. Only after exceeding the allowable clearance should vehicles move or crane arms rotate. Cable wind ropes must be installed during dismantling.
(9) After formwork removal, promptly clean residual concrete and apply release agent. Secure the formwork temporarily during cleaning and coating. Leave a 50–60 cm-wide walkway between parked formwork surfaces, and use tie rods to secure stacked formwork.
Key Points for Storing Large Formwork
(1) When storing flat formwork, ensure it meets regional self-stabilizing angle requirements. Store two large formworks face-to-face. For long-term storage, connect formworks as a whole. Store large formworks at elevated locations with reliable anti-tip measures, positioned perpendicular to the outer wall and not along its edge.
(2) Unsupported or insufficiently stabilized large formwork should be stored on dedicated stacking racks or stacked flat, avoiding leaning against other formworks or objects.
(3) Before lifting, inspect ropes, fixtures, and lifting rings for completeness and reliability. Remove all temporary supports before lifting. Adjust crane position to ensure stable lifting and precise placement.
(4) Cylindrical molds can be transported whole by trailer or disassembled into flat molds for horizontal stacking and transport. When stacking flat molds, align wooden pads vertically and tie securely. No one is allowed to ride on the vehicle during transport.
(5) High-altitude transportation is prohibited during strong winds.
Source: Architectural Technology Magazine
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