What Is Steel Scaffolding?

Scaffolding is a working platform set up to ensure the smooth progress of each construction process. It is divided into external scaffolding and internal scaffolding according to the erected position; it can be divided into wooden scaffolding, bamboo scaffolding, and steel pipe scaffolding according to different materials; it can be divided into vertical scaffolding, bridge scaffolding, door scaffolding, hanging scaffolding, Hanging scaffolding, picking scaffolding, climbing scaffolding.

In the early 1980s, China has introduced various types of scaffolding, such as door scaffolding and bowl buckle scaffolding. Portal scaffolding has also been widely used in many domestic projects and achieved good results. Due to the product quality problems of portal scaffolding, this type of scaffolding has not been widely promoted and applied. A number of portal scaffolding factories have been established in China, and most of their products are processed according to foreign business plans. Bowl buckle scaffolding is the most popular type of scaffolding in the new type of scaffolding.

Since the 1990s, some domestic companies have introduced advanced foreign technologies and developed a variety of new scaffolding, such as pin-type scaffolding, CRAB module scaffolding, disc scaffolding, square tower scaffolding, and various types of climbing frames. By 2013, there were more than 100 domestic professional scaffolding manufacturers, mainly in Wuxi, Guangzhou, Qingdao and other places. Technically speaking, China's scaffolding enterprises have the ability to process and produce various new scaffolding. However, the domestic market has not yet formed, and the construction enterprises' understanding of the new scaffolding is still insufficient.

With the emergence of a large number of modern large-scale building systems in our country, fastener-type steel pipe scaffolds can no longer meet the needs of the development of building construction. It is imperative to vigorously develop and promote new scaffolding. Practice has proved that the new type of scaffolding is not only safe and reliable in construction, fast in assembly and disassembly, but also reduces the amount of steel used in scaffolding by 33%, and improves the efficiency of assembly and disassembly by more than twice. The construction cost can be significantly reduced, and the construction site is civilized and clean. ^[1]

Different types of engineering construction use scaffolding for different purposes. Most of the bridge supports use bowl-shaped scaffolding, and some use door scaffolding.

Scaffolding design

(1) There should be a clear understanding of heavy scaffolding. Generally, if the floor thickness exceeds 300mm, the design of heavy scaffolding should be considered. If the scaffolding load exceeds 15KN / , the design scheme should be organized by experts. It is necessary to distinguish clearly that the change in the length of the steel pipe in those parts has a greater impact on the load. For the formwork support, the length a of the center line of the top horizontal bar from the support point of the formwork should not be too long, and it is generally less than 400mm (in the new code) It may be revised). Generally, the uppermost step and the lowermost step are subjected to the most stress during the calculation of the pole, and should be used as the main calculation point. When the bearing capacity is not satisfied with the requirements of the group, increase the vertical rod to reduce the vertical and horizontal spacing, or increase the horizontal rod to reduce the step distance.

(2) The domestic scaffolding generally has unqualified materials such as steel pipes, fasteners, top brackets and bottom brackets, which are not taken into account in theoretical calculations in actual construction. It is best to take a certain safety factor in the design calculation process. ^[5]

Scaffolding construction

The sweep bar is missing, the vertical and horizontal junctions are not connected, the sweep bar is too large or too small from the ground; the scaffold is cracked, the thickness is insufficient, and the overlap does not meet the requirements of the specification; after the large formwork is removed, there is no protection between the inner pole and the wall. Falling nets; scissor braces are not continuous in the plane; open scaffolds are not provided with diagonal braces; the distance between the small crossbars under the scaffolding board is too large; the wall parts are not rigidly connected inside and outside; the distance between the protective railings is greater than 600mm; Fastener slip, etc.

Scaffold deformation accident

(1) Local deformation of scaffolding caused by foundation settlement. On the cross section of the double-row frame, splayed stilettoes or scissor braces are set up, and a set of columns is erected every other row until the deformation area is lined up outside. The stilt or scissors must be placed on a solid and reliable foundation.

(2) The deflection of the cantilevered steel beam on which the scaffolding takes root exceeds the prescribed value. The anchorage point of the cantilevered steel beam should be reinforced. The steel beam is supported by a steel support and a U-shaped bracket and screwed against the roof. There is a gap between the embedded steel ring and the steel beam, and it must be prepared with a horse wedge. The steel wire ropes at the outer end of the hanging steel beam are inspected one by one, and all are tightened to ensure uniform force.

(3) The scaffolding unloading and tensioning system caused local damage. It should be immediately restored according to the unloading and tensioning method established in the original plan, and the deformed parts and members must be corrected. To correct the outward deformation of the scaffold, first set a 5t reverse chain for each opening, tighten the structure, loosen the rigid pull joints, and tighten the reverse chain inward at the same time until the deformation is corrected, and do the rigid pull. Then, tighten the steel wire rope at each unloading point to make the force uniform, and finally release the inverted chain.