سؤال قراءة ستيب محلول — فهم التفاصيل (تدريب 7035)

(1) A skyscraper is a very tall, multistoried building. The term skyscraper was first used during the 1880s, when the first tall buildings were constructed in the United States. These original skyscrapers were about 10 to 20 stories high. By the late 20th century, however, the term skyscraper was used to describe high-rise buildings of unusual height, generally greater than 40 or 50 stories. (2) The increase in urban commerce in the United States in the second half of the 19th century augmented the need for city business space, and the installation of the first safe passenger elevator (in the Haughwout Department Store, New York City) in 1857 made practical the erection of buildings more than four or five stories tall. (3) As the population density of urban areas has increased, so has the need for buildings that rise rather than spread. The skyscraper, which was originally a form of commercial architecture, has increasingly been used for residential purposes as well. (4) The earliest skyscrapers rested on extremely thick masonry walls at the ground level. However, architects soon began to use a cast-iron and wrought-iron framework to support the weight of the upper floors. In New York City, New York, in 1848, James Bogardus built the Cast Iron Building with a rigid frame of iron providing the main support for the upper floors and the roof. (5) In the 1860s, steel became widely available in the United States. Since it is stronger and lighter than iron, the use of a steel frame made it possible to construct truly tall buildings. Generally considered the world’s first skyscraper, the first building to use steel-girder construction was William Le Baron Jenney’s 10-story Home Insurance Company Building (1884-85) in Chicago, Illinois. Jenney’s skyscrapers also were the first to use the curtain wall, an outer covering of masonry or other material that is affixed to and supported by the steel skeleton. Structurally, skyscrapers consist of a substructure of piers beneath the ground, a superstructure of columns and girders above the ground, and a curtain wall hung on the girders. (6)The design and decoration of skyscrapers have changed over time. Jenney and his protégé Louis Sullivan styled their buildings with delineated columns rising from the ground to the top. By the early 20th century, previous architectural styles influenced builders. The Metropolitan Life Insurance Building in New York City (1909), for example, was modeled by Napoleon Le Brun after the Campanile of St. Mark’s in Venice, Italy. The Woolworth Building (1913), by Cass Gilbert, is a prime example of neo-Gothic decoration. Even the Art Deco carvings on such towers as the Chrysler Building (1930), the Empire State Building (1931), and the RCA Building (1931) in New York City, which were then considered as modern as the new technology, are now viewed as more related to the old ornate decorations than to truly modern lines. (7) After World War II, skyscrapers were mostly designed in the International Style, with simple lines and lack of ornamentation. Notable early examples of this style are the Seagram Building (1958) in New York City and the Lake Shore Drive Apartments (1951) in Chicago. During the 1970s, urban architecture began to incorporate the human element by designing plazas and parks into and around the bases of skyscrapers. Office towers, such as the Sears Tower (1973; now called Willis Tower) in Chicago, continued to be built, but most of them featured space for shopping and entertainment at the street level. By the late 20th century. energy conservation began to influence skyscraper design and construction. For example, sealed windows that required continuous forced-air cooling gave way in mid-rise buildings to operable windows and glass walls that were tinted to reflect the sun’s rays. (8)In 1996 the Petronas Twin Towers, in Kuala Lumpur, Malaysia, surpassed the Sears Tower to become the world’s tallest buildings. Since then, many skyscrapers have been built in Asia. At 2,717 feet (828 meters), the 162-story Burj Khalifa, in Dubai, United Arab Emirates, was hundreds of feet taller than any other structure when it opened in 2010. The title of tallest building in the United States was claimed by One World Trade Center in 2014. The building, initially called Freedom Tower when its design was announced, is 1,776 feet (541 meters) in height. It is located in New York City, near the site of the World Trade Center towers that fell in the terrorist attacks of September 11, 2001. Burj Khalifa, One World Trade Center, and many other new skyscrapers have spires that extend the measured height far above the highest occupied floor. Which two materials were used to build tall buildings in the 19th century?