GB 55023-2022General code for scaffold in construction (English PDF)

4.1 General design

4.1.1 The design of scaffolding shall adopt the limit state design method based on probability theory, and the calculation shall be carried out with partial factor design expressions.

4.1.2 The scaffolding structure should be designed according to the limit state of bearing capacity and the limit state of normal use.

4.1.3 Scaffold foundations shall meet the following requirements:

1 It should be flat and solid, and should meet the requirements of bearing capacity and deformation;

2 Drainage measures should be set up, and the erection site should not be waterlogged;

3 Frost-heave prevention measures shall be taken during winter construction.

4.1.4 The strength and deformation of the engineering structure supporting the scaffold and the engineering structure attached to the scaffold shall be checked and calculated. When the checking calculation cannot meet the requirements for safe bearing, corresponding reinforcement measures shall be taken according to the checking calculation results.

4.2 Loads

4.2.1 The loads borne by a scaffold shall include permanent loads and variable loads.

4.2.2 The permanent loads of a scaffold shall include the following:

1 Self-weight of scaffolding structural parts;

2 Self-weight of scaffold boards, safety nets, railings and other accessories;

3 Self-weight of the objects supported by the scaffold;

4 Other permanent loads.

4.2.3 The variable loads of a scaffold shall include the following:

1 Construction load;

2 Wind load;

3 Other variable loads.

4.2.4 The standard values of the variable loads on scaffolding shall meet the following requirements:

1 The standard value of the construction load on the working scaffold shall be determined according to the actual situation, and shall not be lower than the provisions in Table 4.2.4-1;

2 When two or more working layers on the scaffolding are in use at the same time, the sum of the standard construction loads of the working layers within the same span shall not be less than 5.0 kN/m2;

3 The standard value of the construction load on the supporting scaffold shall be determined according to the actual situation, and shall not be lower than the provisions in Table 4.2.4-2;

4 For moving equipment, tools and other items supported on the scaffold, the standard value of the variable load shall be calculated from their self-weight.

4.2.5 When calculating the standard value of the horizontal wind load on special scaffold structures, such as high tower-type structures and cantilevered structures, the amplifying effect of wind load fluctuation shall be taken into account.

4.2.6 For the dynamic load on the scaffold, the self-weight of the vibrating and impacting object should be multiplied by the dynamic coefficient 1.35 and then included in the variable load standard value.

4.2.7 In scaffolding design, loads shall be combined according to the calculation needs of the ultimate limit state and the serviceability limit state, and the most unfavourable combination of the loads that may act on the scaffold at the same time during normal erection, use or dismantling shall be taken.

4.3 Structural Design

4.3.1 Scaffolding design and calculation should be carried out according to the actual construction conditions of the project, and the results should meet the requirements for scaffolding strength, stiffness and stability.

4.3.2 Scaffold structural design and calculation shall select, according to the construction conditions, the most unfavourable representative rods and components, taking the most unfavourable cross-section and working condition as the calculation condition. The calculation units shall be selected as follows:

1 The rods and structural parts with the largest force should be selected;

2 The rods and structural parts at the positions where the span, spacing change, geometric shape and load-bearing characteristics change shall be selected;

3 The rods and structural parts at the structural changes or weak points of the frame body should be selected;

4 When there is a concentrated load on the scaffold, the rods and components with the largest force within the concentrated load range should be selected.

4.3.3 The strength of scaffold rods and structural parts shall be calculated on the net section; their stability and deformation shall be calculated on the gross cross-section.

4.3.4 When the scaffolding is designed for the ultimate limit state, the basic combination of loads and the design values of material strength shall be used. When it is designed for the serviceability limit state, the characteristic combination of loads and the deformation limits shall be used.

4.3.5 The allowable deflection of the flexural members of the scaffold shall meet the requirements in Table 4.3.5.

4.3.6 The formwork support scaffold shall be designed and calculated for the continuous support according to the construction conditions, and the number of support layers shall be determined according to the most unfavorable conditions.

4.4 Construction requirements

4.4.1 The construction measures of scaffolds shall be reasonable and complete, so that the frame has a clear load path and a uniform distribution of forces.

4.4.2 The connecting nodes of the scaffold rods should have sufficient strength and rotational rigidity, and the nodes of the frame body should not be loose during the service period.

4.4.3 The spacing and step distance of scaffold poles shall be determined by design.

4.4.4 Safety protection measures shall be taken on the working layer of scaffolding and shall comply with the following:

1 Scaffold boards shall be fully laid on the working layer of working scaffolds, full-height supporting scaffolds and attached lifting scaffolds, and shall be stable and reliable. When the distance between the edge of the working layer and the outer surface of the structure is greater than 150 mm, protective measures shall be taken;

2 Steel scaffold boards connected by hooks shall have self-locking devices and be locked to the horizontal bar of the working layer;

3 Wooden scaffold boards, bamboo string boards and bamboo mat boards shall be supported by reliable horizontal rods and bound firmly;

4 Protective railings and toe boards shall be provided on the outer edge of the working layer;

5 The bottom layer of scaffold boards of a working scaffold shall be closed;

6 A layer of horizontal protection shall be provided at every 3 floors of the building under construction or at a height not greater than 10 m. The outside of the working layer shall be closed with a safety net; when a dense-mesh safety net is used, it shall meet the flame-retardant requirements;

8 The part of the scaffold board protruding beyond the horizontal bar shall not be greater than 200 mm.

4.4.5 The poles at the bottom of a scaffold shall be provided with longitudinal and transverse sweeping poles, firmly connected to the adjacent poles.

4.4.6 Working scaffolds shall be provided with wall ties according to the design calculation and the construction requirements, and shall meet the following requirements:

1 Wall ties shall be rigid members able to withstand both compression and tension, and shall be firmly connected to the engineering structure and to the frame;

2 The horizontal spacing of wall ties shall not exceed 3 spans and the vertical spacing shall not exceed 3 steps; the cantilever height of the frame above the top wall tie shall not exceed 2 steps;

3 Additional wall ties shall be provided at the corners of the frame and at the ends of open-type scaffolds, with a vertical spacing not greater than the storey height of the building and not greater than 4 m.

4.4.7 Vertical scissor braces shall be provided on the longitudinal outer facade of working scaffolds and shall meet the following requirements:

1 Each scissor brace shall span 4 to 6 bays, with a width of not less than 6 m and not greater than 9 m; the angle between the scissor brace and the horizontal plane shall be between 45° and 60°;

2 When the erection height is below 24 m, a pair of scissor braces shall be provided at both ends and corners of the frame and in the middle at intervals of not more than 15 m, set continuously from bottom to top; when the erection height is 24 m or more, they shall be set continuously from bottom to top over the entire outer facade;

3 On cantilevered scaffolds and attached lifting scaffolds they shall be set continuously from bottom to top over the entire outer facade.

4.4.8 The bottom of the poles of a cantilevered scaffold shall be reliably connected to the cantilever support structure; a longitudinal sweeping pole shall be installed at the bottom of the poles, and horizontal scissor braces or horizontal diagonal braces shall be provided at intervals.

4.4.9 Attached lifting scaffolds shall meet the following requirements:

1 The vertical main frame and horizontal supporting truss shall adopt truss or rigid frame structure, and the rods shall be connected by welding or bolts;

2 They shall have anti-tilting, anti-falling, floor-stopping, load control and synchronous lifting control devices, and all devices shall be sensitive and reliable;

3 A wall-attached support shall be provided on each floor covered by the vertical main frame; each wall-attached support shall be able to bear all the loads of the vertical main frame;

4 When electric lifting equipment is used, its continuous lifting distance shall be greater than the height of one floor, and it shall have braking and positioning functions.

4.4.10 Reliable structural strengthening measures shall be taken at the following locations of working scaffolds:

1 Where the scaffold is attached to or supported on the junction of engineering structures;

2 Corners of the plan layout;

3 Where the scaffold is interrupted or opened for facilities such as tower cranes, construction hoists and material platforms;

4 Where the storey height is greater than the vertical spacing of the wall ties;

5 Where protruding parts of the engineering structure affect the normal layout of the frame.

4.4.11 Effective rigid protection measures shall be taken on the outer facade and corners of scaffolding facing a street.

4.4.12 The height-to-width ratio of a free-standing supporting scaffold frame shall not be greater than 3.0.

4.4.13 Supporting scaffolds shall be provided with vertical and horizontal scissor braces, which shall meet the following requirements:

1 Scissor braces shall be arranged uniformly and symmetrically;

2 The width of each vertical scissor brace shall be 6 m to 9 m, and the angle of its diagonal bar with the horizontal shall be between 45° and 60°.

4.4.14 The horizontal rods of supporting scaffolds shall be arranged continuously in both the longitudinal and the transverse direction at each step, and firmly connected to the adjacent poles.

4.4.15 The length of the adjusting screw of adjustable bases and adjustable supports inserted into the scaffold pole shall not be less than 150 mm. The extension length of the adjusting screw shall be determined by calculation and shall meet the following requirements:

1 When the steel pipe of the pole has a diameter of 42 mm, the extension length shall not be greater than 200 mm;

2 When the steel pipe of the pole has a diameter of 48.3 mm or more, the extension length shall not exceed 500 mm.

4.4.16 The gap between the adjusting screw of adjustable bases and adjustable supports and the steel pipe of the pole into which it is inserted shall not be greater than 2.5 mm.

5.1 Personal protection

5.1.1 Corresponding safety measures shall be in place for the erection and dismantling of scaffolding, and operators shall wear personal protective equipment and non-slip shoes.

5.1.2 During the erection and dismantling of scaffolding, safety warning lines and warning signs shall be set up and supervised by designated personnel; entry of non-operating personnel is strictly prohibited.

5.1.3 When temporary construction power lines are laid on scaffolding, insulation measures shall be taken and operators shall wear insulating non-slip shoes; a safe distance shall be kept between the scaffolding and overhead transmission lines, and grounding and lightning protection shall be provided.

5.1.4 When erecting, using and dismantling scaffolding in a narrow space or a space with no air circulation, measures should be taken to ensure sufficient oxygen supply, and the accumulation of toxic, harmful, flammable and explosive substances should be prevented.

5.2 Set up

5.2.1 Scaffolding shall be erected in sequence and shall meet the following requirements:

1 Ground-supported working scaffolds and cantilevered scaffolds shall be erected in step with the construction of the main structure; each lift shall not exceed 2 steps above the uppermost wall tie, and the free height shall not be greater than 4 m;

2 Reinforcing rods such as scissor braces and diagonal braces shall be erected together with the frame;

3 Component-assembled scaffolding shall be erected from one end to the other and step by step from bottom to top, changing the direction of erection at each layer;

4 After each step of the frame is erected, the spacing of the poles, the step distance, the verticality of the poles and the levelness of the horizontal bars shall be corrected in time.

5.2.2 The installation of wall ties shall meet the following requirements:

1 Wall ties shall be installed at the same time as the scaffolding is erected;

2 When the working layer of the scaffold is 2 or more steps above the adjacent wall tie, temporary tie measures shall be taken until the upper wall ties are installed.

5.2.3 When erecting cantilevered scaffolds and attached lifting scaffolds, the anchorage of the cantilever support structure and of the attached supports shall be stable and reliable.

5.2.4 Protective facilities such as safety nets and protective railings shall be installed in place at the same time as the scaffold is erected.

5.3 Use

5.3.1 The load on the working layer of the scaffold shall not exceed the design value of the load.

5.3.2 Work on scaffolding shall be stopped in thunderstorms and in winds of force 6 and above; the erection and dismantling of scaffolding shall be stopped in rain, snow and fog. After rain, snow or frost, effective anti-slip measures shall be taken before working on the scaffold, and snow shall be removed.

5.3.3 It is strictly forbidden to fix supporting scaffolds, guy ropes, concrete pump delivery pipes, unloading platforms or supports for large equipment to working scaffolds, and to hang lifting equipment on the scaffolding.

5.3.4 During the use of scaffolding, it shall be checked regularly and the checks recorded; the working condition of the scaffolding shall meet the following requirements:

1 Main load-bearing members, scissor braces and other reinforcing members, and wall ties shall not be missing or loose, and the frame shall show no obvious deformation;

2 There shall be no water accumulation on the site, and the bottom of the poles shall not be loose or suspended;

3 The safety protection facilities shall be complete and effective, without damage or missing parts;

4 The supports of attached lifting scaffolds shall be stable; the anti-tilting, anti-falling, floor-stopping, load control and synchronous lifting control devices shall be in good working order, and lifting and lowering of the frame shall be normal and steady;

5 The cantilevered support structure of the cantilevered scaffold should be stable.

5.3.5 In any of the following situations the scaffolding shall be inspected and the inspection recorded, and it may continue to be used only after its safety has been confirmed:

1 After bearing an accidental load;

2 After winds of force 6 and above;

3 After heavy rain or heavier precipitation;

4 After frozen foundation soil has thawed;

5 After being out of use for more than 1 month;

6 After partial dismantling of the frame;

7 Other special circumstances.

5.3.6 A safety hazard found during the use of the scaffold shall be eliminated in time; when any of the following occurs, operators shall be evacuated immediately and inspection and handling shall be organized in time:

1 Rods or connecting parts are damaged because the material strength is exceeded, slip at connection nodes, or are unfit for continued loading because of excessive deformation;

2 Part of the scaffold structure loses its equilibrium;

3 Scaffold structural members lose stability;

4 The scaffolding tilts as a whole;

5 The foundation loses its bearing capacity.

5.3.7 While concrete is being poured or engineering structural parts and other loads are being installed on a supporting scaffold, no one is allowed under the scaffold.

5.3.8 Electric welding, gas welding and other hot work on the scaffold shall be carried out only after the hot work application has been approved; fire protection measures such as fire buckets, fire extinguishers and removal of combustible materials shall be taken, and designated personnel shall keep watch.

5.3.9 During the use of scaffolding, excavation under or near the foundation of the scaffold poles is strictly forbidden.

5.3.10 The anti-tilting, anti-falling, floor-stopping, load control and synchronous lifting control devices of attached lifting scaffolds shall not be removed during use.

5.3.11 While an attached lifting scaffold or an external protective frame is being lifted or lowered, no one is allowed on the frame, and no work is allowed below it at the same time.

5.4 Demolition

5.4.1 Before the scaffolding is dismantled, materials left on the working layer shall be removed.

5.4.2 The dismantling of scaffolding shall comply with the following:

1 The frame shall be dismantled step by step from top to bottom, and upper and lower levels shall not be worked on at the same time;

2 Rods and structural parts on the same level shall be removed outside first, then inside; reinforcing rods such as scissor braces and diagonal braces shall be removed when the rods at that position are dismantled;

3 The wall ties of working scaffolds shall be removed layer by layer together with the frame; a whole layer or several layers of wall ties shall not be removed before the frame is dismantled;

4 During dismantling, when the cantilever height of the frame exceeds 2 steps, a temporary tie shall be added.

5.4.3 When scaffolding is dismantled in sections, the parts not yet removed shall be reinforced before dismantling starts.

5.4.4 The dismantling of the frame shall be organized as a single operation directed by a designated person, and no cross operations are allowed.

5.4.5 It is strictly forbidden to throw dismantled scaffolding materials and components down from height.