Discussion on safety technology of grid earth meth

2022-08-16
  • Detail

Talking about the safety technology of the installation and construction of the earth erection method

I. Introduction to the installation and construction process of the earth erection method

the frame structure is being gradually popularized and adopted in the field of steel structure at present, and the installation of the frame is the key and difficult point of the whole frame construction. Rack installation is generally divided into integral installation method and bulk installation method. Using bulk method, mobile or full scaffold is generally required. The overall installation is divided into mechanical installation and indigenous installation. Generally, large tonnage hoisting equipment is used for mechanical installation, which will cause large equipment investment, long installation period, and there are many potential safety hazards in high-altitude assembly; The derrick can be used as the lifting and installation equipment for local installation. The derrick adopts the standard section of tower crane, which is easy to use, safe and reliable, but it is technically difficult and requires high requirements

the construction process of the earth method integral installation frame mainly includes the following steps:

1 A certain number of lifting derricks are set in the frame installation area. The standard section of tower crane can be used to lift the derrick. The height of lifting derrick is determined according to the actual installation height of the frame

2. Two steel beams are installed on the top of the lifting derrick, and one chain block is hung at each of the four corners of the beam. The size of the beam and the hoist is determined according to the calculation

3. Concrete is poured on the ground and is only applicable to the overall assembly of the frame after the pier is leveled

4. The chain block is fixed on the lower chord ball node of the frame with steel wire rope as the lifting point, and the selection of the lifting point should be determined by calculation

5. A corresponding number of workers synchronously operate the chain block for overall lifting

6. According to the lifting height, change the chain block in the middle and lift it in place as a whole

II. Key factors affecting the success of the process and treatment methods

the overall installation and construction of the scaffolding method has high requirements for the construction scheme and operators. In terms of safety management, we must carefully do a good job in the preparation and approval of the construction scheme, safety technical disclosure, personnel training and education, safety inspection and acceptance, etc. In particular, the overall lifting and installation of the frame must be refined and improved in advance from the scheme, and all possible problems should be considered, and corresponding preventive measures should be taken

unified coordination and command and the overall cooperation of all operators are very critical. Targeted training and training should be carried out before the implementation of the process

in terms of technology, perfect measures should be taken for the difficulties and hazards of the construction process, mainly including the following points:

1 Lifting support instability

the stability of the lifting support during the lifting process is the foundation to ensure the success of the whole construction scheme, and we must ensure that everything is safe

in view of the above situation, the following measures are taken in the construction:

(1) select the appropriate number of lifting brackets: according to the weight of the frame, after calculation, select the appropriate number of lifting brackets to lift the frame as a whole

(2) reasonably arrange the lifting support: the layout of the lifting support is very critical. If the layout is unreasonable, it will cause uneven stress of the lifting support and large deformation of the frame. Through the checking calculation of the overall weight of the frame and the distribution of the weight, determine the position of the lifting support, so that the support basically divides the weight of the frame. In addition, pay attention to the influence of the lifting point position on the stress of the frame members and joints, so as to avoid deformation or even damage beyond the allowable range

(3) correctly erect the cable wind rope: the angle of cable wind rope erection shall be controlled between 30 ~ 45 degrees, and it shall be tensioned with 5T chain block. During the lifting process, the frame member may interfere with the cable wind rope. At this time, the spare cable wind rope should be erected and fastened first, and then the original cable wind rope should be loosened

(4) select a suitable lifting support: considering the installation height and stability of the support, we selected the standard section of QTZ125 tower crane as the lifting support. The lifting support composed of the standard section of the tower crane far meets the lifting needs of the frame in terms of strength and bending resistance. It is simple and safe, ensuring the stability of the lifting bracket

(5) the ground resistance of the lifting support foundation should meet the requirements to avoid uneven settlement after stress, and the foundation should be determined by calculation

2. Broken chain block

chain block is the key facility of the whole process. It is necessary to ensure that there are no problems in the lifting of the chain block

to this end, the following measures are taken:

reasonably arrange the position of the hoist to ensure that the hoist is evenly stressed

select an appropriate number of gourds, and the laboratory of building materials testing ensures that there is a certain safety factor when lifting the gourd

choose a reasonable tonnage of gourd plastic as an important 3D printing raw material to ensure that the gourd will not be damaged when lifted

the hoist should be strictly inspected and carefully maintained before use, and it has normal use conditions

regularly check the quality changes of the hoist during the lifting process to ensure the smooth lifting

3. Work at heights

the installation of the scaffold should be placed on the ground as far as possible to reduce work at heights and increase the construction safety factor. Due to the shrinkage resistance of stiffeners, holes, bosses, sculptures and other shapes,. When lifting the scaffold, the lifting area should be set up with a warning to prevent irrelevant personnel from entering the operation area

III Engineering example

1 Project Overview:

the aircraft maintenance hangar project of Shenzhen Airlines base is located in Shenzhen Bao'an Huangtian International Airport. This project consists of hangar hall, tail hangar and annex building, covering an area of 12249.60 square meters, a building area of 7591 square meters, a building base axis area of 4768 square meters, and a total height of 30.3 meters

the roof frame area of the aircraft maintenance hangar in Shenzhen aviation base is 4403m2, purlins and wall frame beams are set on the top and sides, and 0.8mm aluminum-plated zinc profiled steel plate is paved on it. The center elevation of the lower chord is 21m, and the frame is welded with Q345B seamless steel pipe and hollow ball. The loss height of the frame varies from 4 to 8m, and the overall weight of the frame is about 180t

2. Key points of engineering technology

(1) selection of lifting bracket

after calculation, 12 lifting brackets composed of standard sections of QTZ125 tower crane are used to lift the bracket as a whole. The weight of the bracket is 180t, and the average stress of each lifting bracket is 15t, which far meets the lifting needs

(2) layout of lifting brackets

through the checking calculation of the overall weight of the bracket and the distribution of the weight, the positions of 12 lifting brackets are determined, so that the bracket basically divides the weight of the bracket

(3) the chain block adopts

48 10t chain blocks for the overall lifting frame, with a weight of 180t. The average force of each of the 48 chain blocks is 3.75t, and the safety factor is 2.7, which meets the needs

according to the process and safety technical measures introduced in this paper, the installation and construction of the roof frame of the aircraft maintenance hangar in Shenzhen Airlines base was successfully completed, achieving safety, efficiency and economy

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