First, an overview of scaffolding engineering
1. Construction and erection of double-row ground scaffolding
1) Construction of double-row ground scaffolding: Double-row ground scaffolding is erected with φ48×3.5 steel pipes, with a maximum erection height of 24m, a vertical distance of 1.5m between vertical poles, a row distance of 1.05m between vertical poles, a step distance of 1.8m between large horizontal poles, and an inner row of vertical poles 0.3m away from the wall. The bottom of the ground scaffolding is compacted with plain soil, a 100mm thick C15 concrete cushion layer is cast in place, a full-length scaffolding board is laid at the root of the vertical pole, and a vertical and horizontal sweeping pole is set 200mm above the ground. Bamboo fences are laid on each small horizontal pole, a kicking pole is set on the outside at a height of 250mm on each small horizontal pole, and two handrails are set at 600mm and 1200mm. A green dense safety net is hung on the outside. A 180mm high footboard is set on the top three steps. The scaffolding tie points are set in two steps and three spans and are connected by double fasteners.
(1) During erection, the joint positions of adjacent vertical poles should be staggered and arranged in different step distances, and the distance from the adjacent large crossbars should not be greater than one-third of the step distance. The vertical poles and large crossbars must be fastened with right-angle fasteners, and no steps should be set or omitted. Except for the top of the top layer, the vertical pole extension is connected by butt fasteners at all other levels. The distance from the edge of the end fastener cover plate to the rod end is not less than 100mm. The vertical deviation of the vertical pole should not be greater than 1/300 of the frame height, and at the same time, its absolute deviation should be controlled to be no more than 50mm.
(2) The large crossbar is set on the inside of the vertical pole, and the length of a single pole shall not be less than 3 spans. The large crossbar is set according to the floor height, and two steps are set on each floor. The spacing is not more than 1500mm, and it meets the design requirements. The rods are connected by butt joints or overlap. When erecting, the joint positions of the crossbars should be staggered in different vertical distances of the vertical poles, with a staggered distance of not less than 500mm and a rod overlap length of not less than 1m. The distance from the adjacent vertical poles should not be greater than 1/3 of the vertical distance.
(3) Arrange close to the vertical poles, erected on the large crossbars and fastened with right-angle fasteners. A small crossbar must be set at the main node, fastened with right-angle fasteners, and strictly prohibited from being removed. The center distance between the two right-angle fasteners at the main node should not be greater than 150mm. The length of the erected small crossbar extending from the side of the external pole should not be different, and it is best to control it within 150 to 300mm to facilitate the hanging of the dense safety net and ensure the facade effect of the entire external frame. The extension length of the small crossbar against the wall should not be less than 100mm and should not be greater than 300mm, and the distance from the small crossbar against the wall to the decorative surface should not be greater than 100mm. The small crossbars at non-main nodes on the working layer should be set at equal distances according to the needs of supporting the scaffolding board, and the maximum spacing should not be greater than 1/2 of the vertical distance of the vertical poles. Between adjacent vertical poles, 1 to 2 small crossbars should be added as needed. Under no circumstances should the small crossbars that serve as basic structural members be removed.
(4) The scissors braces on the facade of the scaffolding are set continuously and are set continuously from the bottom to the top. The scissors braces must be erected synchronously with the vertical poles, longitudinal and transverse horizontal poles, etc. The diagonal rods of the scissors braces are fixed to the vertical poles or large crossbars that intersect with them with rotating fasteners, and the distance from the center of the rotating fastener to the main node is not more than 150mm. The angle between the diagonal rods of the scissors braces and the ground is 45 to 60 degrees, and the diagonal rods of the scissors braces should be reliably connected to the basic structural members of the scaffolding. The connection of the nodes is reliable. The tightening torque of the fastener bolts is 40N.m to 65N.m.
(5) The verticality deviation of the scaffolding poles should be ≤1/300, and at the same time, the maximum verticality deviation value should be controlled to be no more than 50mm.
(6) The horizontal pole deviation of the scaffolding should be ≤1/250, and the horizontal deviation value of the entire frame length should not be greater than 50mm.
(7) When the scaffolding is in use, it must be re-inspected and qualified before it can be put into use: continuous use for 6 months; stop using for more than 15 days during construction, and it should be checked before it can be used; after being subjected to strong factors such as storms, heavy rains, earthquakes, etc.; during use, when significant deformation, settlement, removal of rods and knots, and safety hazards are found.
(8) The safety net should be hung with the erection of the external frame. The safety net should be tied and fixed to the steel pipe with nylon rope and must not be loosened at will.
Second, unloading platform structure design and material selection.
1) Unloading platform structure design: To ensure the turnover and transportation of materials, the ground structure construction sets up an unloading platform on each floor from the second floor upwards. The plane size of the unloading platform is 5000mm×3000mm. The bottom uses I-beams as the main beam structure of the receiving platform with a spacing of 1500mm. Angle steel is used as support between I-beams with a spacing of 500mm. The angle steel and I-beams are welded into a whole, and the surface is covered with wooden plywood. On the I-beams on both sides 800mm away from the outer end of the receiving platform, a steel plate is welded for threading steel wire ropes. On the I-beams on both sides, steel pipes with a height of 1200mm and a spacing of 1500mm are welded as handrails.
2) Material selection:
Cantilever beam: Use I-beam specification 126×74×5.0;
Angle steel: Use ∟50×6 angle steel;
Wire rope: Use 6×19 wire rope, diameter 18.5mm, the total breaking force of wire rope 180.0kN (according to the nominal tensile strength of steel wire 1400N/mm2);
Through-beam screw: Use Φ20 round steel for processing;
Connecting steel plate: Use a 20mm thick steel plate,
3) Installation, acceptance, and use of the unloading platform
(1) When installing the unloading platform, weld the unloading platform with angle steel on the outside of the floor slab to prevent the receiving platform from sliding inward due to axial pressure. The unloading platform overlaps the floor slab by 300mm. A hole with a diameter of 250mm is reserved on the top beam of the floor. During installation, the through-beam screw is fixed in the reserved hole. The receiving platform and the bolt are connected with the selected steel plate and wire rope. The wire rope forms a 45° angle with the receiving platform. The unloading platform wire rope adopts φ19 wire rope, 4 in total, 2 of which are used as safety ropes. The wire rope is adjusted with a basket bolt to ensure that the wire rope is evenly stressed. The wire rope connection adopts rope clamps, and each wire rope has no less than 6. The three sides of the platform are enclosed with a height of 1200mm. It is welded with φ48×3.5 steel pipes, and a safety-dense mesh is hung inside. The unloading platform shall not be connected to the external scaffolding.
(2) The unloading platform can only be hoisted after it has been processed and accepted. When hoisting, first hang the hooks at the four corners and send the initial signal, but only slightly lift the platform and loosen the inclined wire rope before formal hoisting. The four guide ropes of the hook should be of equal length to ensure that the platform is stable during the hoisting process. After hoisting to the predetermined position, first, fix the platform I-beam and embedded parts, then fix the wire rope, tighten the nuts and wire rope clips, and then loosen the tower crane hook. The unloading platform can only be used after it has been installed and accepted. It is required to be hoisted and accepted once.
(3) When the unloading platform is in use, a weight limit sign should be hung in a conspicuous position near the platform, and it shall not be used overweight.
Third, safety technical requirements for scaffolding
1. Safety technical requirements for scaffolding erection and use
1) Lightning rods should be installed on the steel pipe frame, which is placed on the corner poles of the outer frame and connected to the large crossbar to form a lightning protection network, and the grounding resistance should be detected to be no more than 30Ω.
2) Regularly check the scaffolding, find problems and hidden dangers, and repair and reinforce it in time before construction to achieve firmness and stability to ensure construction safety.
3) Personnel who erect external scaffolding must be certified to work and use safety helmets, safety belts, and non-slip shoes correctly.
4) It is strictly forbidden to have probe boards on scaffolding boards. When laying scaffolding boards and multi-layer operations, the internal and external transmission of construction loads should be balanced as much as possible.
5) Ensure the integrity of the scaffolding body, do not tie it together with the elevator, and do not cut off the frame.
6) Each layer of the external scaffolding of the structure is erected. After the erection is completed, it can be used only after acceptance by the safety officer of the project department. Any team leader and individual shall not arbitrarily remove scaffolding components without consent.
7) Strictly control the construction load, the scaffolding board shall not be concentrated and loaded, and the construction load shall not be greater than 3kN/m2 to ensure a large safety reserve.
8) During structural construction, multiple layers are not allowed to be operated simultaneously. During decoration construction, the number of layers to be operated simultaneously shall not exceed two layers. The number of layers to be operated simultaneously on temporary cantilever frames shall not exceed the number of layers.
9) When the operating layer is more than 3.0m higher than the wall connection below it and there is no wall connection above it, appropriate temporary support measures should be taken.
10) Reliable protective fences should be set up between each operating layer to prevent falling objects from injuring people.
11) Drainage ditches should be dug outside the foundation of the scaffolding poles to prevent rainwater from soaking the foundation.
Fourth, safety technical requirements for scaffolding removal
1) Before dismantling the scaffolding, a comprehensive inspection should be carried out on the scaffolding to be dismantled. According to the inspection results, an operation plan should be drawn up and submitted for approval. Work can only be carried out after a technical explanation.
2) When dismantling the scaffolding, the operation area should be divided, and rope-tied fences or warning signs should be erected around it. A special person should be assigned to command on the ground, and non-operating personnel should be prohibited from entering.
3) The dismantling procedure should follow the principle of top-down, first erection and then dismantling, that is, first dismantle the tie rod, scaffolding board, scissor brace, diagonal brace, and then dismantle the small crossbar, large crossbar, vertical pole, etc., and proceed in sequence according to the principle of one step and one clear. It is strictly forbidden to dismantle the frame at the same time.
4) When dismantling the vertical pole, hold the vertical pole first and then dismantle the last two buckles. When dismantling the large crossbar, diagonal brace, and scissor brace, the middle buckle should be removed first, then hold the middle, and then untie the end buckle.
5) The wall connecting rod (tie point) should be dismantled layer by layer as the dismantling progresses. When dismantling the throwing brace, should be supported by temporary support before dismantling.
6) During dismantling, unified command should be given, and the upper and lower parts should respond to each other and coordinate the movements. When untying the knot related to another person, the other party should be notified first to prevent falling.
7) When dismantling the frame, no person should be replaced in the middle. If a person must be replaced, the dismantling situation should be explained clearly before leaving.
8) The dismantled materials should be transported down slowly, and throwing is strictly prohibited. The materials transported to the ground shall be transported and dismantled at the designated location, classified and stacked, and dismantled and cleared on the same day.
9) When leaving the post on the same day, the unremoved parts shall be reinforced in time to prevent hidden dangers from causing man-made accidents after returning to work.
10) In case of special weather such as strong wind, rain, snow, etc., the scaffolding shall not be dismantled, and it is strictly forbidden to dismantle it at night.
Post time: Nov-19-2024