The Crane

There are many different operation sites, therefore there are many different construction types and designs of cranes. They are for example used for loading and unloading ships, railway wagons and trucks. Inside assembly halls, production shops and warehouses they move heavy goods from one place to another. In structural engineering, this construction machinery for vertical and horizontal loading is essential on any construction site.



There are two construction types of revolving tower cranes: the bottom-slewing and the top-slewing tower crane. Both types are equipped with a slewing ring. The bottom-slewing tower crane consists of an undercarriage with slewing ring onto which the crane tower is mounted. Since the whole structure moves during operation, it requires a lot of space and is therefore used on small and medium-sized construction sites. For higher towers and loads, the top-slewing tower crane is suitable. It is mounted onto a solid base or a corresponding undercarriage. The slewing gearbox is located at the top end of the crane tower. In case of rotation only the boom is moved. It not only requires less space than the bottom-slewing. The top-slewing crane can for example be anchored to buildings and therefore grow with the building by installing additional crane elements. The loads are either transported via a trolley jib or a fly-jib. A trolley jib is mounted horizontally to the crane tower and can't be changed in height. The load is transported by means of a trolley that is able to move along the jib carrying the hoist rope with it. Cranes with a fly jib don't have a trolley. The load is transported in direction of the orientation of the jib just by lifting and lowering the jib.


Scientists believe that the first crane featuring a winch and a pulley for lifting heavy loads was used in the 6th century before Christ, thus about 2,600 years ago in Ancient Greece. Until then, the people used the so-called "ramp technique" for building large structures. They used to raise huge ramps of soil in order to be able to transport the construction material frequently including stone blocks weighing up to 20 tonnes to their destination. Today, in structural engineering, mainly revolving tower cranes are used that have been developed in the 20th century.



During the construction of the highest building in the world, the "Burj Khalifa" in Dubai, five tower cranes with fly-jibs were used, the latter being anchored and self-climbing. The highest revolving tower crane is the "K 10000" of the Danish manufacturer Kroll. The 100 metres long jib is able to still bear more than 100 tonnes at its tip. At the end of the 1970s, the 15 units produced were used at first in the USA and in the former Sovjet Union for building nuclear power plants. Today, the functional cranes left are mainly used in shipbuilding.


Photo: Wikimedia