Skyscraper

A skyscraper is a tall continuously habitable building having multiple floors. Modern sources currently define skyscrapers as being at least 100 metres[1] or 150 metres[2] in height, though there is no universally accepted definition. Skyscrapers are very tall high-rise buildings. Historically, the term first referred to buildings with between 10 and 20 stories when these types of buildings began to be constructed in the 1880s.[3] Skyscrapers may host offices, hotels, residential spaces, and retail spaces.

Completed in 2009, the Burj Khalifa, in Dubai, United Arab Emirates, is currently the tallest building in the world, with a height of 829.8 metres (2,722 ft). The setbacks at various heights are a typical skyscraper feature.

One common feature of skyscrapers is having a steel framework that supports curtain walls. These curtain walls either bear on the framework below or are suspended from the framework above, rather than resting on load-bearing walls of conventional construction. Some early skyscrapers have a steel frame that enables the construction of load-bearing walls taller than of those made of reinforced concrete.

Modern skyscrapers' walls are not load-bearing, and most skyscrapers are characterised by large surface areas of windows made possible by steel frames and curtain walls. However, skyscrapers can have curtain walls that mimic conventional walls with a small surface area of windows. Modern skyscrapers often have a tubular structure, and are designed to act like a hollow cylinder to resist wind, seismic, and other lateral loads. To appear more slender, allow less wind exposure and transmit more daylight to the ground, many skyscrapers have a design with setbacks, which in some cases is also structurally required.

As of January 2020, only nine cities in the world have more than 100 skyscrapers that are 150 m (492 ft) or taller: Hong Kong (355), Shenzhen (289), New York (284), Dubai (201), Shanghai (163), Tokyo (158), Mumbai (151), Chicago (130), Chongqing (127), and Guangzhou (118).[4]