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Introduction to scaffolding

by:Shizhan     2020-09-19
Scaffold refers to the various supports erected on the construction site for workers to operate and solve vertical and horizontal transportation. A general term in the construction industry, refers to the construction site used for external walls, internal decoration or high-rise places where direct construction is impossible. Mainly for construction personnel to work up and down or to protect the outer safety net and high-altitude installation of components. To put it bluntly, it is to build scaffolding. Scaffolding materials usually include bamboo, wood, steel pipe or synthetic materials. Some projects also use scaffolding as templates, and are also widely used in the advertising industry, municipal administration, traffic roads and bridges, mining and other departments.

development path

In China before 1949 and the early 1950s, bamboo or wood erection methods were used for construction scaffolding. Since the 1960s, fastener-type steel pipe scaffolding has been promoted.
Since the 1980s, China has made remarkable achievements in the development of advanced and multi-functional scaffolding series, such as portal scaffolding series and bowl-buckle steel pipe scaffolding series. The annual output has reached tens of thousands of tons, and there are already a certain number of Export.

For a long time, the erection tool itself, its construction technology and the use of safety management work are in a relatively backward state, resulting in a higher incidence of accidents. Relevant statistics show that about one-third of the casualties that occur in China's construction system every year are directly or indirectly related to the problems of erection tools and their use.

With the increasing maturity and improvement of the Chinese construction market, bamboo-wood scaffolding has gradually been phased out of the construction market, and is only still used in some remote and backward areas; while portal scaffolding and bowl-buckle scaffolding are only used in municipalities and bridges. Used in projects, ordinary fastener steel scaffolding occupies more than 70% of China's domestic market due to its simple maintenance, long service life, and low investment cost, and has a large development space.

classification

1. Whether it is movable: divided into two types: mobile and fixed;

2. Material: Divided into wood, steel and soft ladder;

3. Tower connection form and usage:

① Formwork support-used to support the formwork, using scaffolding materials to erect the shelf

②Single-row scaffolding-referred to as single-row scaffolding, that is, a type of scaffolding with only one row of vertical poles and one end of the horizontal horizontal pole resting on the wall

③Double-row scaffolding-referred to as double-row scaffolding, that is, a scaffold composed of two rows of vertical rods and horizontal rods inside and outside

④Decoration scaffolding-used for decoration engineering construction work

⑤Structural scaffolding-used for masonry and structural engineering construction work

⑥Overhanging scaffolding-used in equipment installation or overhauling overhanging operations

4. Construction nature: divided into construction scaffolding and installation scaffolding

5. Block size

①Open type: There are only railings and toe boards on the working floor, and no scaffolding for other shielding facilities. It is a hot spot for scaffolding rental in Tianjin.

②Fully enclosed: scaffold that is enclosed along the full length and height of the outside of the scaffold.

③Semi-enclosed: scaffolding covering 30% to 70% of the area.

④Partially closed: the sheltered area is less than 30%.

6. Other

① Soft ladder: Hangqian uses short wooden sticks or steel pipes. The rope is tied to the crossbar. It is fixed on the top when used. It is often used for maintenance of large catalytic flue, reactor, regenerator, inclined pipe, etc.

②Mobile hanging ladders and hanging baskets: fixed ladders or hanging baskets that can be moved. Generally, hooks or slides are set on the top to hang on a firm place.

Features

Different types of construction use scaffolding and formwork support for different purposes. Most bridge support frames use bowl buckle scaffolding, and some use portal scaffolding. The main structure construction floor scaffolds mostly use fastener scaffolds. The vertical distance of the scaffold poles is generally 1.2~1.8m; the horizontal distance is generally 0.9~1.5m.

Compared with the general structure, the working conditions of scaffolding have the following characteristics:

1. The load has great variability;

2. The fastener connection node is semi-rigid, and the rigidity of the node is related to the quality of the fastener and the installation quality, and the performance of the node has a large variation;

3. There are initial defects in the structure and components of the scaffolding, such as the initial bending and corrosion of the rods, the erection size error, and the load eccentricity.

4. The connection point with the wall has a large constraint variation on the scaffolding. The research on the above problems lacks systematic accumulation and statistical data, and does not have the conditions for independent probability analysis. Therefore, the adjustment coefficient of structural resistance multiplied by less than 1 is determined by calibration with the previously adopted safety factor. Therefore, the design method adopted in this specification is essentially half-probability and half-empirical. It is the basic condition of design calculation that the scaffold meets the structural requirements specified in this code.

Process flow

1. The technological process of shelf erection:

Position the bounce line and pole on a solid foundation → place the sweeping pole → erect the pole and fasten it to the sweeping pole → install the sweeping small crossbar, and fasten it to the vertical pole and the sweeping rod → install the first large crossbar and Fasten each vertical rod → install the small crossbar of the first step → install the large crossbar of the second step → install the small crossbar of the second step → add temporary diagonal braces, and fasten the upper end with the large crossbar of the second step (installation After removing the connecting rod with the column) → install the third and fourth step large and small cross bars → install the second layer and column tie rods → connect the vertical rods → add shear braces → lay the scaffold board, lash the protection and the foot board, stand Hang a safety net.

2. The tie between the frame and the building (flexible tie)

It adopts Φ6 steel bars, top braces, steel pipes and other components, in which the steel bars bear tensile force, and the pressure is transmitted by the top braces, steel pipes, etc.

3. Safety net

(1) Hooking requirements: The safety net should be hung tightly, tied firmly with plastic, and must not be lashed out. The connection between the two nets should be tied to the same rod. The safety net should be hung inside the scaffold.

(2) A closed flat net should be set up between the scaffold and the construction layer according to the acceptance standard to prevent the debris from falling.
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