Scaffolding is a working platform set up to ensure the smooth progress of each construction process. According to the location of the scaffolding, it can be divided into external scaffolding and internal scaffolding; according to different materials, it can be divided into wooden scaffolding, bamboo scaffolding, and steel pipe scaffolding; according to the structural form, it can be divided into vertical pole scaffolding, bridge scaffolding, door scaffolding, suspended scaffolding, hanging scaffolding, cantilever scaffolding, and climbing scaffolding.
The development history and trend of scaffolding in China
In the early 1980s, China successively introduced various types of scaffolding such as portal scaffolding and cup-hook scaffolding from abroad. 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 scaffolding has not been widely promoted and applied. A number of portal scaffolding manufacturers have been built in China, and most of their products are processed according to foreign drawings. Cup-hook scaffolding is the most popular type of scaffolding among new scaffoldings, but its use is not widespread. It is only used in some areas and some projects.
Since the 1990s, some domestic enterprises have introduced foreign technology and developed a variety of new scaffoldings, such as pin-type scaffolding, CRAB module scaffolding, disc scaffolding, square tower scaffolding, and various types of climbing frames. Technically speaking, domestic scaffolding companies have the ability to process and produce various new scaffoldings.
Practice has proved that the use of new scaffolding is not only safe and reliable in construction, and the assembly and disassembly speed is fast, but also the amount of steel used in the scaffolding can be reduced by 33%, the assembly and disassembly efficiency can be more than doubled, the construction cost can be significantly reduced, and the construction site is civilized and tidy.
Scaffolding characteristics
Different types of engineering construction use scaffolds for different purposes. Most bridge support frames use cup-hook scaffolds, and some use portal scaffolds. Most ground-type scaffolds used in main structure construction use fastener scaffolds, and the vertical distance of the scaffolding poles is generally 1.2~1.8m; the horizontal distance is generally 0.9~1.5m.
Compared with general structures, the working conditions of scaffolds have the following characteristics:
1. The load variability is large;
2. The fastener connection nodes are semi-rigid, and the node rigidity is related to the fastener quality and installation quality, and the node performance has a large variation;
3. The scaffolding structure and components have initial defects, such as initial bending and rust of the rods, erection size errors, load eccentricity, etc.;
4. The connection points with the wall have a large variation in the constraints on the scaffolding. The research on the above issues lacks systematic accumulation and statistical data, and does not have the conditions for independent probability analysis. Therefore, the value of the adjustment coefficient of the structural resistance multiplied by less than 1 is determined by calibration with the safety factor used in the past. Therefore, the design method adopted in this specification is semi-probabilistic and semi-empirical in nature. It is a basic condition for design calculation that the scaffolding meets the structural requirements specified in this specification.
