Skyscrapers are known to be super tall building either residential, work place or of mix use. They are now tends to coincide with major downturns in the economy. Today the number of skyscrapers that are being built all around the world are increasing where the land is highly expensive (as in big / metropolitan cities) as they provide high ratio of floor space to be used to per unit area of available land. They are not built just for the economy of space, they are considered to be symbol of citys economic power. They do not only define the skyline but also defines the citys identity. In many places exceptionally tall skyscrapers have been built not just because of necessity of space but to define the citys identity and presence of power as a city.
The first skyscrapers would have been typically an office building of more than 10 storeys. The concept was undoubtedly originated in the USA, in Chicago and in New York, where space was limited and where the best option was to increase the height of the buildings. The crucial developments for skyscrapers were steel, reinforced concrete, water pumps, and elevators. Until the 19th century, buildings of over six stories were rare. So many flights of stairs were impractical for inhabitants, and water pressure was usually insufficient to supply running water above about 15 metres (50 feet). The weight-bearing components of skyscrapers differ substantially from those of other buildings. Buildings up to about four stories can be supported by their walls, while skyscrapers are larger buildings that must be supported by a skeletal frame.
In the late 19th century, the first skyscrapers would have been typically an office building of more than 10 storeys. The concept was undoubtedly originated in the USA, in Chicago and in New York, where space was limited and where the best option was to increase the height of the buildings. The Home Insurance Building in Chicago was perhaps the first skyscraper in the world. Built in 1884-1885 its height was 42 m/10 storeys. Designed by Major William Le Baron Jenney, a graduate of l’EcoleCentrale des Arts et Manufactures de Paris, the structural skeleton was a bolted steel frame without bracing supporting the loads coming from the walls and the slabs, founded on a raft. This led to what is known as the “Chicago Skeleton.
Skyscraper foundations are considerably more complex than those for normal buildings. The complexity brought is just because of their height and weight and can be further depend on the certain specific factors such as nature of soil, exposure to wind , earthquake and their location in relation to surrounding property. Depending on the nature of the structure, the type of foundation and the characteristics of the ground, the value of the foundation / excavation can be as much as the 7.5% of the total project value.
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