Skyscraper:
A skyscraper is a high-rise, livable building that has more than 40 floors and is taller than approximately 150 m (492 ft). Historically, the term first referred to buildings with 10 to 20 floors in the 1880s. The definition changed with the advancement of construction technology during the 20th century. [1] Skyscrapers can house commercial offices or residential spaces, or both. For buildings with a height greater than 300 m (984 ft), the term "supertall" can be used, while skyscrapers that reach more than 600 m (1,969 ft) are classified as "mega tall".
A common feature of skyscrapers is having a steel frame that supports curtain walls. These curtain walls rest on the lower frame or are suspended from the upper frame, instead of leaning on load-bearing walls of conventional construction. Some of the first skyscrapers have a steel structure that allows the construction of load-bearing walls higher than those of reinforced concrete.
The modern walls of skyscrapers do not support loads, and most skyscrapers are characterized by large areas of windows made possible by steel frames and curtain walls. However, skyscrapers may have curtain walls that mimic conventional walls with a small window area. Modern skyscrapers often have a tubular structure and are designed to act as a hollow cylinder to withstand wind, seismic and other lateral loads. To look more slender, allow less exposure to the wind and transmit more daylight to the ground, many skylines have a design with setbacks, which are sometimes also structurally required.
