290HC Mast Section Four factors of tower crane selection: basic parameters, installation mode, starting height and surrounding environment
1. Determination of basic parameters of tower crane
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The basic parameters of the tower crane refer to the height, arm length and the maximum lifting weight of the arm end (that is, the farthest end of the big arm of the tower crane). In general, the maximum lifting weight of tower crane does not need to be considered except in very special cases. According to the length, width and height of the building, the length of the tower crane arm can be preliminarily determined. The arm length is suitable to cover the whole project with a little margin. At present, the commonly seen tower cranes are generally 30m, 40m, 50m, 55m, 60m, 70m in length. Tower cranes with longer arms are seldom used due to the limitations of other conditions on site, so they should be selected carefully. The height of the tower crane is only 10-15m higher than the maximum height of the building. The lifting weight of the boom end is determined by the weight of the object to be lifted given by the civil construction personnel. For general frame structure buildings, because the tower crane needs to lift the concrete bucket, the lifting weight of the arm end is large; but now for high-rise buildings with concrete structure, the requirement is low. After the above three parameters are determined, the type of tower crane can be preliminarily determined.
2. Determination of tower crane installation mode
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Tower crane is the equipment used on the ground, its own weight (1ot ~ 200t) is far greater than the general engineering machinery, so the installation method of tower crane foundation is also one of the main problems to be considered in selection. At present, the commonly used jack up tower crane has three basic installation methods: the installation of fixed feet in large concrete blocks, the installation of pressurized weight on large chassis and the installation of walking type. Different installation methods have different requirements on the ground pressure of foundation soil (15-20t / m2), and different types of tower cranes have different pressures on the ground. In addition, the foundation depth and slope type of the project also affect the installation method of tower crane foundation, and then affect the selection of tower crane. This can only be determined after the user has some practical experience and carefully read the chapter about the foundation part of the product specification of the proposed tower crane.
3 Determination of starting height
The commonly used self elevating tower crane can rise with the rise of the building. When the height of the tower crane exceeds the "free height", if it rises again, the measures of "attaching the wall" shall be adopted, that is to "anchor" the tower crane with the project under construction. The height of the first attached wall of different types of tower cranes is different, and the distance force between each two attached walls is also different. The attached wall of tower crane has extra outside pulling force on the construction project, which requires that the completed part of the project can reach a certain strength. If the construction speed is fast, the wall attached part has not reached the predetermined strength, which will affect the construction progress. In this case, the type of tower crane with larger free height should be considered. And it is particularly important in winter construction.
4 impact of surrounding environment
The surrounding environment includes transportation road, underground pipeline, height of surrounding buildings and whether there is high-voltage line, etc. Tower crane structural parts are long and heavy, generally 10m long. Large transport vehicles and large tonnage truck cranes are required for installation. After the completion of the project, the same equipment shall be used to remove it. Therefore, the surrounding environment also has a certain restriction on the selection of tower crane. Sometimes, only one large tonnage tower crane is needed for construction. However, due to the constraints of the surrounding environment, it is necessary to select two smaller tonnage tower cranes for construction; on the contrary, sometimes only one smaller tonnage tower crane is needed. If you want to solve this problem well, after the preliminary determination of tower crane type selection, find a professional tower crane dismantling unit (with the qualification approved by the local construction committee) to conduct field survey before finalizing the design.
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