autosurflog

Sunday, December 17, 2006

Skyscraper
A skyscraper is a very tall, continuously habitable building. Although there is no official definition, a minimum height of approximately 150 meters or 500 feet is often used as a criterion for a building to qualify as a skyscraper. Other criteria like shape and appearance may also affect whether or not a building is considered a skyscraper. The city of Chicago is widely credited as the birth place of the skyscraper.
The word skyscraper was first applied to such buildings in the late 19th century, reflecting public amazement at the tall buildings being built in Chicago and New York City. The structural definition of the word skyscraper was refined later by architectural historians, based on engineering developments of the 1880s that had enabled construction of tall multi-story buildings. This definition was based on the steel skeleton—as opposed to constructions of load-bearing masonry, which passed their practical limit in 1891 with Chicago's Monadnock Building. Philadelphia's City Hall, completed in 1901, still holds claim as the world's tallest load-bearing masonry structure. The steel frame developed in stages of increasing self-sufficiency, with several buildings in Chicago and New York advancing the technology that allowed the steel frame to carry a building on its own. Today, however, many of the tallest skyscrapers are built more or less entirely with reinforced concrete. In the United States today, it is a loose convention to draw the lower limit on what is a skyscraper at 150 meters. Elsewhere, though, a shorter building will sometimes be referred to as a skyscraper, especially if it is said to "dominate" its surroundings. Thus, calling a building a skyscraper will usually, but not always, imply pride and achievement.
Originally, skyscraper was a nautical term for a tall mast or sail on a sailing ship. A skyscraper taller than 300 meters may sometimes be referred to as a super tall.
The somewhat arbitrary term skyscraper should not be confused with the slightly less arbitrary term high-rise, defined by the Emporis Data Committee as "a building which is 35 meters or greater in height, and is divided at regular intervals into occupiable floors" . All skyscrapers are high-rises, but only the tallest high-rises are skyscrapers. Habitability separates skyscrapers from towers and masts. Some structural engineers define a high-rise as any vertical construction for which wind is a more significant load factor than weight is.

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