Problems needing attention in the design of the ho

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Problems that should be paid attention to in the design of attached lifting scaffold

attached lifting scaffold, as an advanced auxiliary construction technology for the construction of high-rise and super high-rise buildings, has been accepted and popularized by more and more construction enterprises; Compared with the traditional floor scaffold and cantilever scaffold, it has the advantages of less material occupation, less labor consumption, no impact on the project construction progress, highlighting the CI image of the construction site, especially its low cost and reusable features, making all kinds of "attached lifting scaffolding" visible everywhere in domestic construction sites. However, there are different degrees of safety defects in the design of many frames. Now we are talking about our views on the problems in the design of the new attached lifting scaffold

1. feasibility evaluation

the attached lifting scaffold serves the main civil construction. Its principle is generally the same, but the specific form is ever-changing. In addition, there are many forms of civil construction for high-rise and super high-rise buildings, such as hanging frames, cantilever frames, etc. When designing the attached lifting scaffold, we must give full play to its advantages and improve its disadvantages, so as to truly achieve the significance of the design. According to the working principle of attached lifting scaffold, it is mainly applicable to those continuous high-rise and super high-rise buildings with simple shape, without too much section change in the middle, and the standard number of floors accounts for the majority of the total number of floors. The standard floor height should be ≤ 4.5m, without the frame shear wall of balcony, canopy and air conditioning board with large cantilever length, and tube in tube building. In addition, when the number of standard floors is greater than 16, under the normal construction progress; In order to better reflect its advantages of saving materials. In addition to the above situations, the economic benefits of using attached lifting scaffolds in other projects are not obvious. In particular, the state stipulates to adopt finalized products to erect attached lifting scaffolds, which increases the investment of the construction unit and the cost accordingly

2. Specific requirements for design layout and erection

the design of attached lifting scaffold includes many aspects. Here we mainly talk about some problems of arranging bearing points. Whether the load-bearing points are properly arranged fundamentally determines the safety factor and convenience of the attached lifting scaffold in the future. The location of the bearing point is determined by the maximum span distance between the two lifting points and whether there is a reasonable embedded point. The maximum span distance between lifting points is a combination of factors such as the lower frame per unit length and self weight load, the material specification and mechanical properties of the erection materials, the coefficient of rigging and lifting appliances, and the difficulty of manual erection. According to the statistics, the electronic experimental machine below 30t has more advantages, and the selection of embedded points has greater personal randomness, which reflects whether a designer has a full understanding of the attached lifting scaffold, Whether you have a full understanding of the mechanical performance of concrete, whether you know the situation of the construction site, and whether you are familiar with the erection steps of attached lifting scaffold is the best answer. A good plane layout concept can provide a good operation surface and sufficient safety for the civil construction team to the greatest extent, give full play to the working capacity of each set of equipment, facilitate the daily work of lifting operators to the greatest extent, and reduce costs to the greatest extent. In view of the different uses of buildings, shear walls, frame beams and frame columns may appear on the boundary, which are more favorable parts for the layout of embedded points. However, it is also very common for the embedded points to appear in balconies, awnings, air-conditioning panels and special-shaped beams. Generally, we should carefully study the standard floor structural plan and profile of the building, understand the specific construction steps of the civil engineering team, and find out the floor and location of the tower crane attachment and installation, and the location of the construction elevator and material hoist. These disconnects are often the starting and ending positions of the attached lifting scaffold; In case of continuous construction, the construction scheme can also be formulated in advance for future use. For the cantilevered part of the outline, such as balcony, canopy, etc., a part of load-bearing cantilever beam with special size can be made to expand the distance from the wall of the attached lifting scaffold, or a compact multi row frame can be set up with a small spacing of poles to wrap the special part. The construction of secondary shape can also be changed to post pouring through consultation with the project department, that is, the main structure construction is completed after the attached lifting scaffold. 5. The compressed air pipeline should be treated during the descent process after the air tightness test under the working pressure. Generally, it is used when the amount of post pouring parts left by the civil engineering is small and does not affect the overall appearance. For the construction of inner patio in some buildings, it may be necessary to set up several points separately to control the rise and fall separately, but we must pay attention to the balance of forces on each point; For the construction of large-area shear wall, it is necessary to reserve reinforcement points at reasonable positions to prevent the frame from overturning and deformation. After the bearing points are arranged, the finalized bottom truss and main frame can be installed after landing; Since the finalized products adopted by various construction units are different, we will not discuss them in detail here

3. Several doubts about design calculation

(1) Jian No. 230 stipulates that "the safety factor of riggings and slings used in lifting mechanisms shall not be less than 6.0", and the definition of lifting mechanism in the appendix - "nouns and terms" is "the mechanism that controls the lifting operation of the frame". I don't quite understand this definition, and there is no clear definition of rigging and slings. (the concept of the specification is very clear, that is, riggings and slings, like other lifting appliances editor) as a complete set of products provided by manufacturers, it is also difficult to have the performance specification parameters of their spare parts. At this time, the design checking calculation is a difficult problem that should not be determined

(2) there are no guiding provisions on the stress of reinforced concrete as the embedded part that ultimately bears the attached lifting scaffold itself and the load, and the quality of concrete construction greatly affects the safety of the entire attached lifting scaffold, which is by no means as simple as "the strength of concrete shall not be less than C10" in Article 23, paragraph 6, of Jian Jian No. 230 document

the above are just some personal opinions on the design of attached lifting scaffold. I hope to get the criticism and guidance of authoritative experts, and I also hope that my colleagues can discuss it, so as to promote the construction technology of attached lifting scaffold to a more perfect and safer 3 To ensure a new height of clear imaging! (Wang Min, Du Kai)

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