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Some common problems of scaffolding

by:Shizhan     2020-09-19
(1) There should be a clear understanding of heavy-duty scaffolding. Generally, if the thickness of the floor slab exceeds 300mm, the design of heavy-duty scaffolding should be changed. The scaffolding load exceeds 15KN/㎡, and the design plan should be organized by experts to demonstrate. It is necessary to distinguish the steel pipe length changes in those parts which have a greater impact on the load bearing. For the formwork support, it should be considered: the length a between the center line of the top horizontal rod and the formwork support point should not be too long, generally less than 400mm (in the new specification) May need to be revised). Generally, the top and bottom steps are the most stressed when calculating the pole, and should be used as the main calculation point. When the bearing capacity is not satisfied with the requirements of the group, the vertical pole should be increased to reduce the vertical and horizontal spacing, or the horizontal pole should be increased to reduce the step distance.

(2) Domestic scaffolding generally has unqualified materials such as steel pipes, fasteners, top brackets and bottom brackets. The theoretical calculations in actual construction did not take these into account. It is best to take a certain safety factor in the design calculation process.


Construction

The sweeping pole is missing, the vertical and horizontal junctions are not connected, the distance between the sweeping pole and the ground is too large or too small, etc.; the scaffold board is cracked, the thickness is not enough, and the overlap does not meet the specification requirements; there is no protection between the inner pole and the wall after the large formwork is removed Falling net; the scissors support is not continuous in the plane; the open scaffolding is not equipped with diagonal supports; the spacing of the small crossbars under the scaffold board is too large; the wall parts are not rigidly connected inside and outside; the distance between the protective railings is greater than 600mm; the fasteners are not tightly connected, Fastener slippage, etc.

Allowable deviation of verticality and horizontality of scaffolding

Item (verticality)
Allowable deviation (mm)
Item (Level)
Allowable deviation (mm)
Frame per step
h/1000 and ±2.0
The height difference between the two ends of the horizontal frame in one span
±l/600 and ±3.0
Scaffolding as a whole
H/600±50
Scaffolding as a whole
±L/600 and ±50
Note: h——step distance; H——scaffold height; l——span; L scaffold length.

Deformation accident

(1) Local deformation of scaffold caused by foundation settlement. On the transverse section of the double-breasted frame, set up a stilt or scissor brace, and set up a set of vertical rods every other row until the deformation zone is outside. The horoscope or scissor support foot must be set on a solid and reliable foundation.

(2) The deflection and deformation of the cantilever steel beam on which the scaffolding is rooted exceeds the specified value, and the anchor point at the rear of the cantilever steel beam should be reinforced. The top of the steel beam should be tightened with steel supports and U-shaped brackets to withstand the roof. There is a gap between the pre-embedded reinforcement ring and the steel beam, which must be secured with a horse wedge. The steel wire ropes at the outer ends of the hanging steel beams are checked one by one, and all are tightened to ensure uniform force.

(3) The scaffolding unloading and pulling connection system is partially damaged. It must be restored immediately according to the unloading pulling method formulated in the original plan, and the deformed parts and members shall be corrected. If correcting the deformation of the scaffolding outwards, first set a 5t rewinding chain for each bay, tighten the structure, loosen the rigid pull contact, and tighten the rewinding chain inward at all points at the same time, until the deformation is corrected, and the rigid pull is done. Connect and tighten the wire ropes at each unloading point to make it evenly stressed, and finally release the chain.
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