How do tower cranes grow taller?

In our daily life, we often see tower cranes used in many construction projects. As the buildings get taller, the tower cranes seem to grow taller as well. So what are the components of a tower crane? How do they grow taller? How are the slender tower cranes fixed?

In April, when spring comes, more than 100 kilometers south of Beijing, the Baiyangdian Lake is rippling with blue waves, the "Millennium Forest" is lush and green, and construction in the start-up area is in full swing... The outline of a modern new city is emerging.

Today, there are 14 pairs of intercity trains running between Beijing and Xiong'an every day. With the accelerated construction of external backbone transportation networks, the ancient capital and the city of the future are becoming increasingly closely connected and integrated. About 30 kilometers west of Xiong'an Station, tower cranes are everywhere in the core area of ​​the Xiong'an New Area's startup area. Builders are sweating on this hot land, constantly refreshing "Chinese quality" and "Chinese speed".

Xiongan New Area is full of cranes. Image source: Great Wall Network

01

The origin 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.

When talking about cranes, we have to mention one person, Archimedes.

Archimedes Image source: Sohu.com

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, and the longer the lever arm, the smaller the force required. With this knowledge, even a 10-ton elephant can be lifted. Archimedes even boasted that if he was given a fulcrum, he could move the earth.

Leverage Principle

02

How does a tower crane work?

So, what is the structure of a modern tower crane, and how does it “grow taller” to adapt to the height requirements of a building?

Tower crane image source: Sohu.com

The tower crane is a bit like a common toy: Lego. It is assembled section by section, involving three very important parts: the ordinary section, the climbing section, and the hydraulic jack.

Ordinary section: It is easy to understand, it is the metal support of the tower crane.

Tower crane ordinary section Source: Zoomlion

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 ordinary section, so the "climbing section" is like a hat, which is put on the ordinary section to make room for upward movement.

Tower crane climbing section Source: Zoomlion

Finally, there is the hydraulic jack. A hydraulic jack is installed inside the climbing section.

Hydraulic jack source: Baidu Encyclopedia

The role of this hydraulic jack is crucial. The tower crane is raised by the hydraulic jack . Its role is to temporarily replace the standard section to perform support work. The standard sections are connected by bolts, so as long as one section is disassembled, N standard sections can be filled in. At the beginning, the most basic structure can be completed with a crane, and the subsequent raising is all handed over to the jacking hydraulic frame.

The tower crane is growing taller. Source: Sohu.com

03

Why is the tower crane so stable?

The tower crane stands tall in the clouds, standing firm on the construction site. Faced with such a tall piece of machinery, one can't help but wonder: how does such a slender tower crane stay stable?

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 foundation of the tower crane.

This concrete platform usually has corresponding dimensions. Taking a tower crane with a lifting weight of 10 tons as an example, the concrete platform that needs to be poured is approximately 10x10x1.3 meters and weighs 182,000 kilograms. Inside the concrete platform are large anchor bolts deeply embedded. These large anchor bolts deeply embedded in the concrete slab can support the bottom of the tower crane. Therefore, the tower crane is actually connected to the ground by bolts to ensure its stability.

Schematic diagram of tower crane foundation Source: Sina.com

Of course, when designing a concrete platform, it is necessary to comprehensively consider factors such as the geological environment and engineering design, conduct a good job in tower crane foundation force and load analysis, tower crane foundation strength calculation, anti-overturning stability calculation, foundation shear bearing capacity calculation, etc., and comprehensively determine the tower crane selection and construction requirements.

Schematic diagram of tower crane foundation stability calculation Source: Reference 1

04

If you want to see the tower crane, please pay attention to safety

Tower cranes are important lifting equipment in construction. During operation, accidents such as equipment collapse, falling from heights, being hit by objects, and lifting injuries are prone to occur. The operation is dangerous and there are great safety risks.

According to the current "Safety Regulations for Tower Cranes" (GB5144-2006), "In places with buildings, the distance between the tail of the crane and the building and the construction facilities outside the building should be no less than 0.5m." However, there are no normative standards for the safety of pedestrians approaching tower cranes.

Source of construction sign: Technical Specification for Construction Site Signage JGJ348-2014

Therefore, if you want to stop and observe the "growing" process of the tower crane, remember to choose a time when the weather is good and the wind is light, and observe from a distance. Never get close to it and do not enter the construction site at will.

Source: People's Daily, Intuitive Mechanical

References:

[1] Mei Bin. Design of independent tower crane scheme and calculation and analysis of tower crane foundation in strong wind area[J]. Journal of Shijiazhuang Railway Vocational and Technical College, 2021, 20(03): 26-31.

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

[3] Wang Yishan. Analysis of safety accidents and protection measures of tower cranes in construction[J]. Engineering Technology Research, 2022, 7(21): 139-141. DOI: 10.19537/j.cnki.2096-2789.2022.21.047.

[4] Yang Shan. Do not rely solely on visual inspection to determine safety distance[J]. Rural Electrician, 2011, 19(04): 39.

[5] JGJ 196-2010, Safety technical regulations for installation, use and disassembly of tower cranes in construction[S].

Author: Chen Yangping Hunan Science and Technology Museum