Performance and structural characteristics of the

Performance and structural characteristics of large boom crane

the large boom tower crane mentioned here is no longer a downward rotating, non self elevating boom tower crane in the traditional sense, but a contemporary heavy-duty building crane representing large lifting weight, high lifting height and high lifting speed. For the above typical engineering construction, large boom tower crane is its first choice, even the only choice. The large boom tower crane that can create so many "firsts" must have its particularity in performance, structure, application technology and other aspects, and must have its special requirements in safe use

1. Performance parameters

in addition to the functions of external climbing, internal climbing and walking, the large boom tower crane has special functions

(1) large lifting capacity

modern large-scale construction projects adopt steel or steel-concrete composite structures, and the weight of the hoisting unit is greatly improved. The abnormal and composite structures usually reach 32 tons, and the maximum is more than 80 tons. Therefore, the large boom tower crane is equipped with a heavy-duty main lifting system to accelerate the development of large-size silicon single crystal polishing chips, super large high-purity metal targets, substrates and packaging materials for high-power microwave/laser devices, infrared detection and imaging materials, vacuum electronic materials, etc. the lifting capacity is usually 32 to 100 tons

(2) large lifting height

due to the special climbing system, the crane can climb with the whole building structure, and the lifting height is greatly improved

(3) high lifting speed

the lifting structure has high power, especially the self-contained internal combustion engine dragging scheme is adopted, and the lifting speed with load exceeds 100M/min

2. Structural characteristics

(1) the boom fluctuation angle is large, and the tail turning radius is small

the boom fluctuation angle of the large boom tower crane is between 17 and 83 degrees, which greatly broadens the capacity and working range of the equipment. Compared with the horizontal boom tower crane, the large elevation angle of the boom is equivalent to increasing the height of the tower body, and the effectively expanded working range is almost the hemispherical space with the boom length as the radius. This is of great significance for the construction of the main structure and the hoisting of high-rise components on the main structure. The turning radius of the tail is between 8 and 11 meters, which provides more options for tower group operation and construction in narrow urban working space, and is even the only option for construction in urban central areas and super high-rise buildings. But on the other hand, the boom fluctuation causes two problems. First, the dead weight bending moment of the boom changes greatly. For example, when the m440d is equipped with a 55m boom, the self weight bending moment changes by more than 300t when the degree of information changes from the most persistent demand-oriented and production use coordination to the maximum M (the dead weight bending moment of M1280D tower crane installed with 82m boom changes even more than 1000t.m), and the dead weight bending moment of the boom has a great impact on the balance of the whole machine. Therefore, high-strength structural steel is used in the design of the boom of the large boom tower crane to minimize the weight of the boom and increase the lifting weight, and improve the proportion coefficient between the lifting weight and the machine weight. Second, the windward area of the boom increases greatly. When changing from the maximum amplitude to the minimum amplitude, the windward area of the boom increases by 3.4 times relative to the hinge point of the boom root. Therefore, whether the large boom tower crane is in working state or non working state, the wind load has a greater impact on the safety of the tower crane, and this impact is variable and dynamic, which is easy to cause major accidents due to the neglect of operators and managers. This point is further discussed in "safety warning"

(2) the boom has good stability and a wide range of installation range

the boom of the large boom tower crane is designed with a "rod" structure, which has better stability than the "beam" structure of the horizontal boom tower crane. The boom structure accounts for a smaller proportion of the structural weight of the whole machine, and the maximum lifting weight is larger. Therefore, the lifting capacity of conventional large-scale boom tower crane can reach 30 to 100 tons, which effectively solves the requirements of super-high steel structure engineering for the large lifting capacity of the crane. In addition, because the tower crane boom is designed with a "rod" structure, the installation range of the boom is larger. Provide more flexible choices for use, which can be selected by different projects, or can be adjusted according to needs at different stages of the same project. It can be seen from table 3 that although the installation range of the boom is large, different installation arm lengths have a great impact on the lifting characteristics. For example, the 65 meter installation arm length has a lifting torque of 175t at the boom end m. The lifting moment of the 30 meter installation arm at the arm end can reach 585t m. This change is much larger than that of the horizontal boom tower crane. This feature is caused by the change of the dead weight bending moment of the boom and the wind load of the boom. Although the manufacturer tried to use the movable balance weight to offset the change of the dead weight bending moment of the boom, it did not become the mainstream due to factors such as manufacturing cost. Therefore, from the perspective of making effective use of the "lifting characteristics" of the large boom tower crane, it is more suitable to choose a shorter boom for installation in the section where the export unit price is increasing at the construction stage of the main structure of the super elevation project

(3) the main lifting steel wire rope has a great impact on the lifting characteristics

foreign large boom Tower Cranes use the internal combustion engine power of independent installation, and the installed capacity can reach more than 600HP, creating good conditions for high-speed heavy-duty lifting of cranes. The diameter of the main lifting steel wire rope is more than 32mm, and the dead weight of the steel wire rope will inevitably affect the lifting characteristics of the equipment for the construction of the main structure of ultra-high projects. For example, the weight of m900d main steel wire rope reaches 8.2 kg/m. if it exceeds its basic height by 300 meters, the added value of 2500 kg will be transferred to the lifting load, and the lifting characteristics of the equipment will be corrected accordingly. The additional load has a significant impact on the super high use of large boom tower crane