How did a 100-meter tower crane grow taller?

In our daily life, we often see tower cranes being used in many construction projects. As the buildings get taller, the tower cranes seem to "grow taller" as well.

So, what are tower cranes made of? How do they grow taller? Some people have even seen tower cranes spinning in the wind during a typhoon. Normally, construction sites should be shut down during a typhoon, so why are tower cranes still spinning? Are they damaged by the wind?

Today, let us learn some knowledge about tower cranes.

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The composition of tower crane

The full name of tower crane is tower crane, which is also the abbreviation of tower crane. It is essentially a crane. Cranes have a long history. As early as the ancient Egyptian period, people used cranes to move huge stones to build pyramids. Whether it is a tower crane or a crane, they all use Archimedes' lever principle . That is, the product of the force at both ends and the lever arm is equal. The longer the lever arm, the smaller the force required.

Leverage Principle

The tower crane consists of three parts: metal structure, working mechanism and electrical system.

Metal structure: including tower body, boom, base, attachment rod, etc.

Working mechanism: It has four parts: lifting, boom lengthening, rotation and traveling.

Electrical system: including motors, controllers, distribution boxes, signal and lighting devices, etc.

How do tower cranes grow taller?

The reason why the tower crane can grow taller is very simple. It is a bit like a common toy: Lego. It is assembled section by section , which involves three very important parts: standard section, climbing section and hydraulic jack.

The standard section is the metal support of the tower crane; the second is the "climbing section", which is the part that allows the tower crane to rise. The "climbing section" is a climbing frame installed at the top of the tower. The height and size of the climbing section are larger than the standard section , so the "climbing section" is like a hat, which is put on the standard section to make room for upward movement.

Finally, there is the hydraulic jack . A hydraulic jack is installed inside the climbing section. The operator will operate the hydraulic system to raise the climbing frame to make room for the installation of the new standard section.

When the climbing frame rises to a certain height, the operator aligns the new standard section with the main structure of the tower crane and fixes it with bolts. Finally, the operator lowers the climbing frame so that it wraps around the bottom of the tower crane again, completing a "heightening" cycle.

Why doesn’t the tower crane fall down?

The tower crane is so tall and so thin, won't it be blown down by the wind? In fact , the stability of the tower crane requires a stable tower crane foundation, which is very critical. The factor related to the stability of the tower crane is a large concrete platform. Before the tower crane is delivered, the construction team will spend several weeks pouring this platform, which is the tower crane foundation .

Secondly, the structural design of the tower crane makes it highly stable. Its own weight and the counterweight on the balance arm work together to maintain the balance of the tower crane.

Furthermore, a large amount of counterweights are usually installed at the end of the tower crane's balance arm . These counterweights can offset the torque generated when lifting materials, thereby maintaining the stability of the tower crane.

How can a tower crane stay standing in a typhoon? As mentioned at the beginning, according to the operating specifications, when a tower crane encounters strong winds, the brake of the slewing mechanism must be released to allow the boom to rotate with the wind, so as to release the kinetic energy of the wind load to the maximum extent, enhance the wind resistance, and resist strong typhoon attacks. Therefore, we can see tower cranes rotating with the wind in typhoon weather.

How heavy can a tower crane carry?

As an important construction machinery at the construction site, the safe construction of tower cranes is very important, so there are not only clear operating procedures for tower cranes, but also clear regulations for operators, inspection systems, troubleshooting, etc. For example, you cannot lift at an angle or overload, you cannot lift if the bulk material is too full or not tied firmly, you cannot lift components buried underground, and you cannot lift in strong winds above level 6. Among them, not lifting in overload is a very important rule. So how much weight can a tower crane generally bear?

The load-bearing capacity of a tower crane depends on many factors, including its design parameters, structural strength, working conditions, and installation method. Generally speaking, the load-bearing capacity of a tower crane is usually described in terms of static load and dynamic load.

1

Static load capacity

It refers to the maximum weight that a tower crane can bear when it is stationary . This weight is calculated by the tower crane manufacturer based on its design parameters and structural strength, and is marked on the equipment. The size of the static load capacity is affected by factors such as the tower crane's own weight, counterweight, arm length, and foundation stability. Generally speaking, the greater the static load capacity of a tower crane, the stronger its carrying capacity.

2

Dynamic load capacity

It refers to the maximum weight that a tower crane can bear when in operation. Compared with the static load capacity, the dynamic load capacity takes into account the inertia factor of the tower crane when lifting and lowering materials, so it is usually smaller than the static load capacity. In actual construction, construction personnel need to arrange the lifting operation reasonably according to the specific situation to ensure that the load capacity of the tower crane is not exceeded to prevent accidents.

References

[1] Liu Zhisheng, Yin Haibo. On the use and safety management of tower cranes[. Heilongjiang Science and Technology Information, 2009(28):302.

[2]https://mp.weixin.qq.com/s/DzOE-ub-eifNF33GUijnMA

[3]https://mp.weixin.qq.com/s/AP3se3kY6Col9kQa0ngKtw

[4]https://mp.weixin.qq.com/s/guTvv0w7dbikNOUB2qVXaw

[5]https://mp.weixin.qq.com/s/ZIbqD_KNjL7_JUy-JRcQdw

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Source丨Like Popular Science (ID: lxkp_cstam)

Editor: Zhong Yanping

Proofread by Xu Lailinlin