Tower crane
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A tower crane is a lifting machine ( crane ) for the vertical lifting of loads, which can usually also be moved horizontally by means of a trolley . A tower crane , TDK for short , can also swivel its boom to the side with the aid of a slewing ring and thus move the load in all three dimensions. The structure and boom of the crane are often designed as trusses .
Tower cranes are particularly at construction sites in construction and civil engineering used. A distinction is made between top and bottom rotating tower cranes with trolley and luffing jibs.
history
The first tower crane designs were developed around 1910. The manufacturers from the very beginning include companies such as Heinrich Rieche from Kassel and Carl Peschke ( Pekazett ) from Zweibrücken (today KSD Kransysteme GmbH). The company Kaiser & Schlaudecker (later Otto Kaiser KG Maschinenfabrik ) from St. Ingbert followed in 1912 with a pioneering and previously widespread development in the field of building cranes and, from 1913, the Heilbronn company Julius Wolff (later Wolffkran) with its first overhead crane Construction crane in "bell jib design". All crane constructions from the aforementioned manufacturers still had a so-called crane portal as a rail-bound substructure.
After the Second World War, self-erecting tower cranes that could be moved quickly came onto the market. For example, the Kirchdorf master builder Hans Liebherr , founder of the construction machinery manufacturer of the same name , developed a tower crane that could be quickly transported and assembled in 1949. Other manufacturers also dedicated themselves to the production of tower cranes during this time and tried to meet the constantly increasing demand. With the advent of the climbing crane in the 1960s, the uses of tower cranes were expanded even further. Radio remote control and electronically programmable crane control systems were added later.
Lower rotating tower cranes
Bottom rotating tower cranes (bottom slewing ) consist of an undercarriage with a slewing ring on which the crane tower is rotatably attached. The jib is firmly connected to the crane tower and is mostly guyed over the top of the tower and very short counter jib up to the counterweight using pulling ropes. The required counterweight ( ballast ) is attached to the side of the base of the crane tower and rotates with it. A lateral movement of the boom is only possible by rotating the entire crane tower. The counterweight usually rotates within the support surface of the undercarriage. A crane that is bolted directly to a base plate or set in concrete does not require any special installation space. In this case, a larger area must be kept free for the swinging counterweight of the crane that is rotating below, compared to that of the top slewing crane.
The world's largest tower crane Kroll K-10000 is a bottom-slewing crane with a high load torque of 10,000 meters by ton, which means that it can lift a load of 100 tons on the jib at a distance of 100 meters from the crane tower. Its ballast weight is located at the end of the counter jib like a top-slewing machine.
The acquisition and storage costs of bottom-slewing tower cranes are lower than those of top-slewing tower. Assembly and dismantling are also easier. They are often also offered as self-erecting cranes. These are brought to the construction site pre-assembled, placed on stable ground and automatically erected within a few minutes. Bottom slewing machines are mainly used on small and medium-sized construction sites.
In the case of larger tower heights and load moments , there are disadvantages with the bottom slewing system, since the increasing space requirement due to longer booms on the ground quickly leads to problems, while the booms with the top slewing system at the upper end of the crane usually don't bother much. If bottom rotating tower cranes are mounted on vehicles, these are referred to as mobile construction cranes.
Top-slewing tower cranes
The crane tower of the top slewing tower cranes (top slewing crane ) is permanently mounted on the tower or foundation cross on which the central ballast is also located. Alternatively, the tower can be connected to a foundation plate, for example using foundation anchors embedded in concrete. Up to a manufacturer- and type-dependent tower height, these cranes can also be mounted on corresponding undercarriages so that they can travel on rails.
The slewing gear is at the top of the crane tower. When rotating, only the jib and the counter jib opposite it are moved, which can be braced at the crane tip. The counter jib is weighted down with ballast so that no moment occurs when the jib is half loaded in the slewing gear.
Particularly in the case of larger tower heights and loads, it has an advantageous effect that the slewing ring is less stressed by overhead cranes because
- the weight of the crane tower is not on him and
- the torque caused by the load and the wind is reduced due to the shorter lever arm.
Further advantages of the top slewing device are the small space required in the area of the installation site and the large tower heights that are achieved when the tower is anchored to the structure. Due to the small footprint, top-slewing heads can also be anchored in the middle of the building, e.g. B. in a future stairwell or elevator shaft.
Top-slewing cranes are also designed as climbing cranes , which, thanks to climbing devices, are able to lengthen or shorten their tower by installing new tower joints without the aid of other lifting equipment.
Trolley jib
Most of the tower cranes used in Central Europe are cranes with a trolley jib. A trolley jib is mounted horizontally on the crane tower and usually its height cannot be changed (with the exception of some bottom-slewing units, which can also be set up with a steep jib incline). The loads are transported with the help of a trolley that can move along the boom and carries the hoist rope with it.
A special form of the trolley jib is the so-called bending beam jib , which is installed in so-called topless cranes. The rigid jib, which is connected to the counter jib, does not need to be braced over a tower top, so that it occupies less height overall. With this type of crane, however, the load limit is reached sooner than with cranes with a tower top.
The bending beam construction is one of the oldest types of jib. As early as 1912, one of the first crane designs with a bending beam boom was carried out. Hans Liebherr, founder of the construction machinery company of the same name, took up this boom design in 1949 for his first crane developments.
Another variant is the telescopic boom, in which the boom is divided into two parts that can either be pushed one below the other or one inside the other. This is particularly advantageous when panning past obstacles.
Luffing jib
Luffing booms are also known as adjustable booms. In luffing jib cranes, the jib is attached to the crane tower below the top of the tower with a joint and the height can be changed using the jib hoisting rope that runs over the top of the crane. Cranes with luffing jibs usually do not have a trolley and the load is moved in the direction of the jib by raising and lowering the jib.
The luffing jib construction offers advantages in tight spaces, as the jib can be pulled up when approaching obstacles such as neighboring buildings in order to avoid a collision. This is also useful where the law prohibits the boom from crossing neighboring properties, such as in the UK and Japan. By erecting the boom, hook heights that go far beyond the height of the crane tower can be achieved, which may save tower height.
Moving the load in the direction of the jib requires a much more powerful drive than with trolley jibs, as the jib and load must be raised. Luffing jib cranes are mainly used in Asia, Great Britain, the USA, Australia and Russia. In Germany they can be found in building construction.
Luffing and topless cranes
With luffing or topless cranes (also known as flat-top cranes), the jib does not need to be braced over a tower top, as it is rigidly connected to the counter jib. With the luffing jib, the entire jib can be raised like a luffing jib. Topless cranes correspond to trolley jib cranes, but do not require a tower top over which the jib is guyed. On large construction sites, this allows other cranes to swivel over more easily. Topless cranes can be assembled quickly and are therefore becoming increasingly popular in the construction industry.
Wolff original construction crane, AG-KBM museum crane
Top-slewing tower crane with trolley jib
Topless topless crane
Use of two cranes with luffing jibs for the construction of the One World Trade Center in New York (photo from July 2010)
Overturned crane
A mobile folding crane (Potain)
See also
- Mobile crane
- Fire engine
- Aerial work platform
- Slewing rail crane
- Floating crane or crane ship
- Telescopic tube
literature
- Johannes Karl Westermann: Tower cranes in building construction: Investigations into automatic load handling devices . Thesis. Ed .: Universität Karlsruhe [TH]. Karlsruhe 2005.
- Dirk P. Moeller: Crane and Construction Machinery Museum: From Idea to Reality . In: Steel construction . tape 82 , no. 4 . Ernst & Sohn, April 3, 2013, ISSN 0932-6375 , p. 302–308 , doi : 10.1002 / stab.201320047 .
- Stephan Bergerhoff, Heinz-Gert Kessel, Pius Meyer: Tower cranes: 100 years on construction sites all over the world . Podszun, Brilon 2010, ISBN 978-3-86133-560-3 .
- Stefanie Ehmann, Alexandra Waldenmaier, Erik Bohr (photos): Between heaven and earth . Ed .: Wolffkran . Motorbuch, Stuttgart 2007, ISBN 978-3-613-02724-4 .
- Martin J. Dougherty: Cranes: The Most Spectacular Construction Equipment in the World . Parragon, Bath UK 2008, ISBN 978-1-4075-2396-5 .
- Karl-Eugen Kurrer : From the archetype of a tower crane . In: VDI nachrichten No. 18/2013, May 3, 2013, p. 6.
Web links
Individual evidence
- ↑ K-10000 tower crane - 100 tons at 100 meter hook radius. Tower Cranes of America, accessed April 15, 2016 .