Brief analysis on the key points of cantilevered e

A brief analysis of the key points of overhanging external scaffolding in high-rise buildings

in order to meet the needs of structural construction and external decoration construction, external scaffolding is required in the construction of high-rise buildings. At present, in the construction of high-rise buildings in China, the fastener type steel pipe scaffold erected by segmental cantilever is widely used. Due to its special load transmission route and complex technology in recent years, it has a significant impact on personnel safety, construction quality, construction speed and project cost, as well as adjacent buildings and sites. Therefore, the selection of cantilever structure, the design and calculation of scaffold There are strict requirements for structure, erection and demolition construction and use management

I. selection of cantilever structure

all loads of cantilever scaffold are finally transmitted to the building structure through the cantilever structure. Therefore, the key of cantilever scaffold is the cantilever structure, which must have sufficient strength, stiffness and stability, and can be reliably connected with the building structure, so as to safely transmit the load of scaffold to the building structure

according to the different structural forms of cantilever structures, they can be divided into two types: cable-stayed and bottom supported. The cable-stayed type is to add steel wire rope to the end of the steel cantilever beam extending from the building structure, and the other end of the steel wire rope is fixed to the lifting ring embedded in the building structure; The down bracing type is to add a diagonal rod support under the end of the cantilever beam

both types of cantilever structures are widely used in practical projects, but they have their own characteristics in terms of stress and use: the bearing capacity of the cable-stayed cantilever structure is controlled by the tensile steel wire rope, while the bearing capacity of the bottom supported cantilever structure is controlled by the compression stability of the bottom support bar. Therefore, in terms of the materials used in the cantilever beam and the labor used in the manufacture, installation and disassembly, the cable-stayed cantilever structure is lower than the bottom supported structure, that is, the form of stress is more reasonable, It can give full play to the performance of the materials that make up the cantilever structure; However, in use, the cable-stayed type is not as convenient as the down bracing type

II. Design and calculation of scaffold

the calculation of the scaffold of the cantilever foot electronic universal experimental machine includes two parts: the calculation of the scaffold body and the calculation of the cantilever structure

1. Load to be considered in scaffold calculation

dead load: self weight of scaffold structure, including self weight of upright, longitudinal horizontal bar, transverse horizontal bar, diagonal bracing, transverse diagonal bracing and fasteners; The self weight of structures and accessories, including the self weight of protective facilities such as scaffold boards, railings, toe boards and safety, which actively integrate the advantageous resources of enterprises and land

live load: construction load, including the self weight of personnel, appliances and materials on the operation layer; Wind load

2. The calculation content of scaffold body

includes the strength of bending members such as longitudinal and transverse horizontal bars and the calculation of anti sliding bearing capacity of connecting fasteners; Stability calculation of upright; Calculation of strength, stability and connection strength of wall connecting parts; Deformation checking calculation of bending members in the frame, etc

3. Calculation content of cantilever structure

according to the load transfer law of cantilever scaffold, the calculation of cantilever structure should include: the calculation of section steel bottom beam (including bending strength calculation, shear strength calculation, local bearing strength calculation, overall stability check calculation and deflection calculation); Calculation of tensile strength of stay cable or calculation of strength and stability of lower brace

4. The main connection calculation between cantilever structure and building structure is carton connection calculation

according to the different connection modes between cantilever structure and building structure, it may include the local compression checking calculation of building structure concrete; Strength calculation of lifting rings; Calculation of tensile and shear resistance of bolts or welds, etc

in a word, the design and calculation of cantilevered scaffold is complex, involving the contents of mechanics, concrete structure, steel structure and other disciplines. The specific calculation must be carefully analyzed according to the load transfer characteristics of the scaffold, and then determine the content and calculation method to be calculated to ensure that everything is safe