The cup-lock steel tubular scaffolding system has gained widespread application in building construction and municipal infrastructure projects, owing to its superior node load-bearing capacity, high erection and dismantling efficiency, and high degree of component standardization. However, superior structural performance does not equate to operational safety-improper erection procedures, disorganized dismantling sequences, or inadequate process control may still lead to scaffold collapse, falls from height, and other safety incidents. This article, based on JGJ/T 231-2021 Safety Technical Standard for Cup-lock Steel Tubular Scaffolding in Building Construction and various local construction safety implementation rules, systematically outlines the key technical requirements for the erection and dismantling of cup-lock scaffolding systems, for the reference of site management and operational personnel.
I. Preparatory Work Before Erection
1. Special Construction Plan and Safety Briefing
The erection of cup-lock scaffolding must be carried out in accordance with an approved special construction plan. The plan shall specify key parameters including longitudinal and transverse spacing of uprights, step height of horizontal members, arrangement of tie-in connections, and bracing configurations, and must be reviewed and approved. For ultra-risk major hazard projects-such as those with erection height of 8m or above, or span of 18m or above-the plan must undergo expert review.
Prior to erection, the technical responsible person shall provide a written safety technical briefing to the operating personnel, covering operational procedures, hazard identification, and emergency response measures. Both parties shall sign to confirm receipt and understanding.
2. Component Inspection and Acceptance
All components delivered to site shall be accompanied by product certificates, type test reports, and quality inspection reports. Uprights, horizontal members, diagonal members, and other components shall be inspected individually, with particular attention to:
- Wall thickness and specifications: B-type uprights shall have an outer diameter of 48.3mm and wall thickness of 3.2mm; Z-type uprights shall have an outer diameter of 60.3mm and wall thickness of 3.2mm. Tolerances shall be controlled within ±0.15mm;
- Welding quality: The welds connecting the disc node to the upright shall be full and free from cracks;
- Surface defects: Components with deformation, corrosion, or cracks are strictly prohibited.
3. Foundation Preparation
The foundation shall be leveled and compacted, with bearing capacity not less than the design requirement specified in the special plan (generally not less than 150kPa). Adjustable bases or base plates shall be placed under each upright to ensure uniform load transfer to the foundation and prevent differential settlement.
II.Technical Essentials for Erection Operations
1. Erection Sequence
Cup-lock scaffolding erection shall follow the fundamental principle of "from bottom to top, layer by layer." The typical sequence is:-2
Layout and positioning → Placement of adjustable bases and base plates → Insertion of first-tier uprights → Installation of first-tier horizontal and diagonal members → Formation of the basic frame unit → Outward expansion → Layer-by-layer upward progression → Simultaneous installation of tie-in connections → Installation of working platform protection
2. Key Points for Frame Unit Erection
At the commencement, adjustable bases shall be positioned according to the upright layout specified in the plan. After inserting four uprights, the horizontal and diagonal members shall be connected to the connection discs on the uprights via the wedge-shaped pins on the coupler heads, forming a stable basic unit, from which outward expansion proceeds.
The connection between horizontal member coupler heads and the upright connection discs shall be secured by driving the pins tight with a specialized hammer, ensuring proper wedging. Upon completion, each pin shall be inspected to confirm full insertion and absence of looseness.
3. Verticality and Levelness Control
After each tier is completed, timely correction shall be made for:
- Upright verticality deviation shall not exceed 1/500 of the scaffold height, and shall in no case exceed 50mm;
- Horizontal member levelness deviation shall be controlled within allowable tolerances;
- The positions of adjacent upright connecting sleeve joints shall be staggered within the same horizontal level.
4. Tie-in Connections and Diagonal Bracing
Tie-in connections are critical components for ensuring lateral stability of the scaffold and shall be installed simultaneously with the scaffold erection. Retroactive installation after scaffold completion is strictly prohibited.
Diagonal bracing shall be provided in accordance with the plan, with the angle to the ground preferably controlled between 45° and 60°, to ensure the formation of a stable triangular load-transfer system.
5. Working Platform Protection
The working platform shall be fully covered with scaffold boards, with guardrails not less than 1.2m high and toe boards provided on the outer side. Safety nets shall be installed as required. Horizontal catch nets shall be provided below to prevent falls of personnel or materials.
III. Technical Essentials for Dismantling Operations
1. Dismantling Sequence
The dismantling of cup-lock scaffolding shall strictly follow the principle of "from top to bottom, dismantle in reverse order of erection-first installed, last removed; last installed, first removed."
Dismantling sequence: Establishment of safety cordon → Layer-by-layer removal of working platform protection → Removal of horizontal members → Removal of diagonal members → Removal of uprights → Layer-by-layer downward progression → Removal of tie-in connections (progressing with the scaffold layer by layer) → Removal of base-tier components
2. Key Safety Control Measures
- Safety cordon: A safety cordon shall be established beneath the dismantling area, with conspicuous warning signs posted and dedicated personnel assigned to monitor the area. Unauthorized personnel are strictly prohibited from entering;
- No throwing: Dismantled components shall be lowered vertically using hoisting equipment or ropes, one piece at a time. Throwing components from height is strictly prohibited;
- Tie-in removal with progression: Tie-in connections shall be removed only when the scaffold has been dismantled down to that tier. Removing tie-in connections on lower tiers before the upper tiers have been dismantled is strictly prohibited;
- Adverse weather suspension: In the event of high winds (Force 6 or above), rain, snow, fog, or other adverse weather conditions, dismantling operations shall be immediately suspended.
3. Post-dismantling Handling
Dismantled components shall be sorted and stacked by category, and promptly removed from site or stored in designated areas. Uprights, horizontal members, and other components shall be cleaned and inspected for damage or deformation. Only components in good condition may be cycled back into service. Wear-prone parts such as pins and coupler heads shall be given special attention, and those with excessive wear shall be replaced.
IV. Critical Safety Bottom Lines
- Certification required: Personnel performing erection and dismantling operations must hold a Special Operation Certificate for Scaffold Erectors issued by the competent construction administrative authority;
- No overloading: The construction load on working scaffolding shall not exceed the design value (structural scaffolding ≤3kN/m², finishing scaffolding ≤2kN/m²);
- No unauthorized modification or removal: During the service period of the scaffold, no load-bearing members shall be removed without authorization. If temporary removal is unavoidable, it must be approved by the project technical responsible person and accompanied by appropriate reinforcement measures;
- Acceptance required before use: Upon completion of erection, the scaffold shall be inspected and accepted by the project technical responsible person and relevant parties, with acceptance records completed, before being put into service.