The erection of cantilever scaffolding is related to construction safety and efficiency. The following is a detailed analysis of the key points in the erection process from scheme design to acceptance.
First, the preparation of special construction plans for cantilever scaffolding and the control of erection height
(I) Preparation of scaffolding plans and expert demonstration
1. Plan requirements: A special construction plan must be prepared for cantilever scaffolding, covering structural verification, node details, load transfer path analysis, and emergency response measures.
2. Approval and demonstration: The plan must be approved by the technical person in charge of the construction unit. When the height of the cantilever exceeds 20m, an expert demonstration must be organized.
3. Clarification of key parameters: The special plan should clarify key parameters such as the number of cantilevers, the spacing of I-beams (usually consistent with the vertical distance of the poles, which is 1.5m), and the installation nodes of the wire rope.
(II) Height limit for erecting scaffolding
1. Height regulation: The height of the cantilever at one time shall not exceed 20m. If it exceeds this height, it is necessary to adopt a segmented cantilever or pass an expert demonstration.
2. Wall ties and tie measures: When the frame is erected, wall ties should be set up simultaneously. When the working layer is 2 steps higher than the adjacent wall ties, temporary tie measures must be taken.
Second, the selection and construction requirements of I-beams for cantilever scaffolding
(I) Profile specifications and layout of cantilever scaffolding
1. Profile selection: I-beams must adopt a biaxial symmetrical section. It is recommended to use models 16 and above, and the section height is ≥160mm.
2. Spacing arrangement: The spacing of cantilever beams is consistent with the longitudinal spacing of the vertical poles, which is generally 1.5m. At the corners, a fan-shaped arrangement or steel tripod reinforcement can be adopted.
3. Overhang length: The overhang length of the cantilever end should not exceed 3m. For special overlong parts, separate design verification is required.
(II) The ratio of the fixed end to the cantilever end of the cantilever scaffolding
1. Length ratio: The length of the fixed end must be ≥1.25 times the length of the cantilever end. For example, when the cantilever is 1m, the fixed end is ≥1.25m.
2. Positioning and anchoring: The end of the I-beam needs to be welded with φ20mm×150mm positioning steel bars to ensure accurate alignment of the vertical pole axis. The anchoring end is fixed with double bolts, the steel pressure plate size is ≥100mm×10mm, and the angle steel specification is ≥63mm×63mm×6mm.
Third, the U-shaped ring pre-embedding and installation process of the cantilever scaffolding
(I) Anchor setting specifications for cantilever scaffolding
1. The number and position of U-shaped rings: 3 U-shaped rings are set for each I-beam, 1 at the front end, 200mm from the end of the I-beam; 2 at the rear end, with a spacing of 200mm.
2. Materials and installation: The U-shaped ring is pre-buried with HPB300 grade φ16mm round steel, the anchor depth is ≥180mm, and the gap with the I-beam is tightened with wooden wedges.
(II) Anti-rust and acceptance of nodes of cantilever scaffolding
1. Anti-rust treatment: I-beams and U-shaped rings need to be rust-proofed, and the anchor bolts should expose the nuts ≥3 buckles.
2. Acceptance items: During concealed acceptance, it is necessary to check the pre-buried position deviation (≤10mm), weld quality (weld height ≥6mm), and concrete strength (≥C20).
Fourth, the wire rope safety reserve system of cantilever scaffolding
(I) Design of the tie system of cantilever scaffolding
1. Wire rope and lifting ring: The cantilevered end is equipped with a wire rope of φ14mm or more to tie with the upper structure, with ≥3 rope clips and a spacing of ≥6 times the rope diameter. The upper embedded lifting ring adopts φ20mm round steel, the anchor length is ≥30d, and a 180° hook is set.
2. Installation conditions: The installation of wire rope needs to wait until the concrete strength is ≥80%.
(II) Key points of force control of cantilever scaffolding
1. Force positioning: The wire rope is only used as a safety reserve and does not participate in the structural force calculation.
2. Installation requirements: The basket bolts need to be tightened to uniform force, and the angle between the diagonal rod and the I-beam should be ＞45°. In special parts, such as the outer corner and the super-long cantilever, it is necessary to add diagonal wire rope or steel support rod.
Fifth, the construction process control and acceptance standards of cantilever scaffolding
(I) Construction stage control of cantilever scaffolding
1. Sample acceptance: Sample acceptance is required before erection.
2. Process control: Correct the verticality of the vertical pole (deviation ≤1/200) and the straightness of the horizontal pole at each step. The wall connection parts are set up in two steps and three spans, the span of the scissor brace is ≥6m, and the inclination is 45°-60°.
(II) Key indicators for the acceptance of cantilever scaffolding
1. Quantitative indicators: vertical deviation of the frame ≤50mm, cantilever beam deflection ≤L/250, fastener tightening torque 40-65N·m.
2. Data retention: The acceptance needs to retain the image data, focusing on checking the tightness of the wire rope, the weld of the anchor end of the I-beam, and the tightening state of the U-shaped ring.
By accurately controlling the above technical points, the structural safety and construction efficiency of the cantilever scaffolding can be ensured. During the implementation of the project, it is necessary to combine the “Safety Technical Specifications for Fastener-Type Steel Pipe Scaffolding in Building Construction” (JGJ130) and local standards to form a complete closed loop of quality and safety management.
Post time: Jun-23-2025