Skyscraper

A skyscraper is a very tall building or otherwise permanently habitable structure, typically defined as reaching a minimum height of either 100 metres (328 ft) or 150 metres (492 ft) in height; however, there remains no universally accepted definition of a skyscraper, other than being a high-rise. Skyscrapers can host a variety of spaces, typically including office, commercial, hotel, and residential space. Skyscrapers are a common feature in the downtown or central business districts (CBD) of major cities, especially in the Americas, Asia, and Australia, often due to a high demand for space and limited availability of land.

The majority of skyscrapers are designed with a steel frame and shear walls that support 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 those made of reinforced concrete. Modern skyscraper walls are not load-bearing, and are characterized 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 are built with setbacks, which in some cases is also structurally required.