Tower crane (hereinafter referred to as tower crane) is one of the necessary construction machinery in construction. Because of its characteristics of tower crane and the special working mode, the choice of it is very different from other construction machinery, according to the determined in the construction process of building structure and the different ways of choosing different type of tower crane, tower crane is the main principle of selection. In addition, the transportation, roads, soil conditions, underground structures and other surrounding environment also have a certain impact on the selection.
1. determination of basic parameters
The basic parameters of a tower crane are the height of the tower crane, the length of the arm and the maximum lifting weight at the end of the arm (the most distal end of the big arm of the tower crane). Except for the special case, the maximum lifting weight of tower crane should not be considered. According to the length, width and height of the building, the arm length of the tower crane can be preliminarily determined. Arm length to ensure that all works can be covered and a little allowance is appropriate. At present, the tower cranes commonly seen are usually 40m, 50m, 55m, 60m, 70m and several kinds of cranes. The tower cranes with larger arm length are rarely used by other conditions in the field, so they should be carefully chosen. Tower crane height as long as the maximum height of the building is 10 to 15m higher. The lifting weight at the end of the arm shall be determined by the construction personnel and the weight of the object to be lifted. The general frame structure of the building, because tower crane need to lift concrete bucket, the arm end of heavy lifting; and now the concrete structure of high-rise building, this requirement is lower. After the above 3 parameters are determined, the type of tower crane can be preliminarily determined.
2. determination of installation methods
Tower crane is the equipment used on the ground, and its weight (1Ot to 200t) is much larger than the general construction machinery, so the tower crane foundation installation method is also one of the main problems that should be considered when selecting. At present, there are three basic installation methods for self lifting tower cranes: large concrete block, fixed foot, big chassis, heavy weight and walking type. On the basis of different installation requirements of different soil ground pressure (15 - 20t / m2, different types of tower crane on the ground pressure is different, in addition to the engineering foundation depth, slope type also affects the foundation of tower crane installation, thereby affecting the selection of tower crane. This point requires the applicant to have certain practical experience, and seriously read the tower crane product manual, the basic section of the chapter can be determined.
3. start by height
Tower crane can be increased with the increase of the common buildings, when the tower height exceeds the "free height", if the increase is needed "wall" measures is put in the tower crane and under construction in the project "anchoring" together. Different types of tower cranes have different wall heights for the first time, and the distance between two walls is also different. The attached walls of the tower crane have extra lateral tensile force on the works, which requires that the completed part of the project can reach a certain strength. If the construction speed is rapid, the wall part has not reached the predetermined intensity, this will affect the construction schedule. In this case, the tower crane type with higher free height should be considered. And in winter construction is particularly important.
4, the impact of the surrounding environment
The surrounding environment includes transportation roads, underground pipelines, the height of the surrounding buildings and whether there is any high-voltage line. Tower crane structure parts are longer and heavier, usually 10m long, and need large transport vehicles and large tonnage truck crane when installation. When the project is completed, it will be dismantled with the same equipment. Therefore, the surrounding environment has some restrictions on the tower crane type selection. Sometimes it takes only a large tonnage of tower cranes to complete the project. But due to the constraints of the surrounding environment, the last resort with two sets of small tonnage crane before construction; on the other hand, the tower crane sometimes only a small tonnage. If you want to solve this problem well, after the initial selection of tower cranes, find professional tower crane dismantling units (need to have the qualifications approved by the local construction committee), the site investigation can be finalized
5. other considerations
The above aspects are the selection principle of independent construction of single tower crane. When the height of the building is very high (more than 150m) should be used in climbing tower crane; when the building covers an area of large and irregular shape should be selected with multiple sizes of different height configuration of tower crane, configuration principle both to cover completely, and not interfere with each other, should also be based on the workload and work cycle different, the tower is placed in the most appropriate location.
In addition, should also pay attention to the tower crane large power consumption, generally tens of kV transformer installation site, as close as possible to the site, but also should avoid too close to power lines. In a word, the selection principle of tower crane has great uncertainty. In fact, the specific project should determine the corresponding tower crane type, can not be small generation, and can not be big generation small. It is possible to draw a satisfactory result by using the three aspects of construction, machinery and installation which are suitable for the tower crane in the project. Selection if there is an error, it may cause significant economic losses, and even accidents. Therefore, the selection of tower crane is very important