skyscraper, modern building of great height, constructed on a steel skeleton. The form originated in the United States.

Development of the Form

Many mechanical and structural developments in the last quarter of the 19th cent. contributed to its evolution. With the perfection of the high-speed elevator after 1887, skyscrapers were able to attain any desired height. The earliest tall buildings were of solid masonry construction, with the thick walls of the lower stories usurping a disproportionate amount of floor space. In order to permit thinner walls through the entire height of the building, architects began to use cast iron in conjunction with masonry. This was followed by cage construction, in which the iron frame supported the floors and the masonry walls bore their own weight.

The next step was the invention of a system in which the metal framework would support not only the floors but also the walls. This innovation appeared in the Home Insurance Building in Chicago, designed in 1883 by William Le Baron Jenney—the first building to employ steel skeleton construction and embody the general characteristics of a modern skyscraper. The subsequent erection in Chicago of a number of similar buildings made it the center of the early skyscraper architecture. In the 1890s the steel frame was formed into a completely riveted skeleton bearing all the structural loads, with the exterior or thin curtain walls serving merely as an enclosing screen.

Legal and Aesthetic Refinements

In 1892 the New York Building Law made its first provisions for skeleton constructions. There followed a period of experimentation to devise efficient floor plans and aesthetically satisfying forms. In New York City the Flatiron Building by D. H. Burnham was constructed in 1902, the Metropolitan Life Insurance Tower in 1909, and the Woolworth Building, 60 stories high, by Cass Gilbert, in 1913. The last, with Gothic ornamentation, exemplifies the general tendency at that time to adapt earlier architectural styles to modern construction. The radical innovator Louis Henry Sullivan gave impetus to a new, bold aesthetic for skyscrapers. An excellent example is his design for the Wainwright building in St. Louis (1890-91). Frank Lloyd Wright also contributed his unorthodox vision to such structures as the Price Tower (1953) in Bartlesville, Okla.

In 1916, New York City adopted the Building Zone Resolution, establishing legal control over the height and plan of buildings and over the factors relating to health, fire hazard, and assurance of adequate light and air to buildings and streets. Regulations regarding the setting back of exterior walls above a determined height, largely intended to allow light to reach the streets, gave rise to buildings whose stepped profiles characterize the American skyscraper of subsequent years.

With the complex structural and planning problems solved, architects still seek solutions to the difficulties of integrating skyscrapers with community requirements of hygiene, transportation, and commercial interest. In New York during the 1950s, public plazas were incorporated into the designs of the Lever House by Gordon Bunshaft and the Seagram Building of Mies van der Rohe. These International style buildings are also examples of the effective use of vast expanses of glass in skyscrapers. More recently, numerous skyscrapers have been constructed in a number of postmodern modes.

Outstanding Skyscrapers

The tallest skyscrapers are freestanding structures such as the CN Tower in Toronto (opened 1976), which measures 1,815 ft (553 m), and the Ostankino Tower in Moscow (opened 1967), which is 1,771 ft (540 m) high. By convention, however, a building is defined as being primarily for human habitation with the greatest majority of its height divided into occupiable floors. The height of a building is measured from the sidewalk level of the main entrance to the structural top of the building. This includes spires but does not include television antennas, radio antennas, or flagpoles. By this definition the tallest building is Taipei 101, Taipei, Taiwan, which was topped off at 1,671 ft (509 m) and 101 stories in 2003. The twin Petronas Towers (opened 1997) in Kuala Lumpur, Malaysia, are the second tallest; 88 stories high and topped by twin spires, they stand 1,483 ft (456 m) tall. Third highest is the Sears Tower (opened 1974) in Chicago; its 110 stories rise 1,454 ft (443 m) with an additional 253 ft (77 m) for the television antenna on top, making it the world's third tallest freestanding structure at 1,707 ft (520 m). The next tallest building, the 1,380 ft (420 m) tall Jin Mao Building (opened 1998) in Shanghai, China, is another example of leadership in skyscraper construction shifting from the United States.

Among the highest New York City skyscrapers are the Empire State Building, with 102 stories, 1,250 ft (381 m) high; the Chrysler Building, with 77 stories, 1,048 ft (319 m) high; 60 Wall Tower, with 67 stories, 950 ft (290 m) high; and the GE (formerly RCA) Building in Rockefeller Center, with 70 stories, 850 ft (259 m) high. The former World Trade Center, which was the tallest building in the city until it was destroyed (Sept., 2001) by a terrorist attack, had two unstepped, rectangular towers of 110 stories each, one 1,362 ft (415 m) and the other 1,368 ft (417 m) high.

Very tall multistoried building. The term originally applied to buildings of 10–20 stories, but now generally describes high-rises of more than 40–50 stories. James Bogardus (1800–1874) built the pioneering Cast Iron Building, New York (1848), with a rigid iron frame providing the main support for upper-floor and roof loads. The refinement of the Bessemer process for making steel (lighter and stronger than iron) made extremely tall buildings possible. Chicago's Home Insurance Co. Building (1884–85), by William Le Baron Jenney (1832–1907), was the first tall building to use a steel skeleton. Structurally, skyscrapers consist of a substructure supported by a deep foundation of piles or caissons beneath the ground, an aboveground superstructure of columns and girders, and a curtain wall hung on the structural framework. Tube structures, braced tubes, and trussed tubes were developed to give skyscrapers the ability to resist lateral wind and seismic forces. The bundled-tube system, developed by Fazlur Khan (1928–1982), uses narrow steel tubes clustered together to form exceptionally rigid columns, and has been used to build some of the world's tallest skyscrapers (e.g., Sears Tower). Skyscraper design and decoration have passed through several stages: Louis Sullivan emphasized verticality; the firm of McKim, Mead, & White (see Charles F. McKim, Stanford White) stressed Neoclassicism. The International Style was ideally suited to skyscraper design. Originally a form of commercial architecture, skyscrapers have increasingly been used for residential purposes as well. Seealso setback.

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