World's tallest buildings.Two new buildings scrape the sky at world-record-breaking height. What keeps these tall towers from tumbling down? Talk about being on top of the world! Construction workers in Kuala Lumpur Kuala Lumpur (kwä`lə l  m`pr), city (1990 est. pop. , Malaysia, recently stood a dizzying 427 meters (1,400 feet) above the ground and bolted steel pinnacles to the top of the Petronas Towers Petronas Towers, twin skyscrapers in Kuala Lumpur, Malaysia, that are the world's tallest twin towers. Standing 1,483 ft (452 m) high, they were designed by the Argentinean-American architect Cesar Pelli. . With the pinnacles in place, the towers stand 451.9 meters (1,483 feet) high. That makes the buildings 8.9 meters (29 feet) taller than Chicago s Sears Tower--and the newest tallest buildings in the world These are lists of skyscrapers, ranked by:
Designing super tall buildings isn't easy. So how do engineers keep the towers from tumbling down? BENEATH THE BASEMENT A solid building begins width a strong foundation--the part of the structure that is underground, says Christian Meyer Christian Meyer (born December 12, 1969 in Freiburg) is a retired track cyclist from Germany, who won the gold medal for his native country in the men's team time trial (100 km) at the 1992 Summer Olympics in Barcelona, Spain. of Columbia University's School of Engineering. The foundation's job, Meyer explains? is to make sure the soil under the building can support the enormous load, or weight, of the building and its contents. "A building--especially a tall building--weighs a lot," Meyer says. He's not joking. The Sears Tower Sears Tower, Chicago, the world's third tallest building. Until the opening of the 1,483-ft (452-m) Petronas Towers (1997) in Kuala Lumpur, Malaysia, it was the world's tallest building. Constructed from 1970 to 1974 for Sears, Roebuck & Co. weighs about 225,500 tons. The taller Petronas Towers are even heavier. The best material for supporting that kind of enormous weight is solid rock or bedrock. Bedrock is good at resisting the force of compression created by the weight of the building pushing down. In other words Adv. 1. in other words - otherwise stated; "in other words, we are broke" put differently , the rock holds its shape under the force. Result: A building on bedrock won't sink. But reaching bedrock isn't always easy. To get to the solid rock under New York New York, state, United States New York, Middle Atlantic state of the United States. It is bordered by Vermont, Massachusetts, Connecticut, and the Atlantic Ocean (E), New Jersey and Pennsylvania (S), Lakes Erie and Ontario and the Canadian province of City's World Trade Center, for instance, workers dug down 21 meters (70 feet) and scooped up, enough dirt and loose rock to build a 23-acre land extension on Manhattan's West Side! The bedrock under the Petronas Towers is buried even deeper. After workers hauled out enough soil to create a hole 20 meters (65 feet) deep for the buildings' three basements, they still hadn't come close to hitting solid rock. Removing even more soil would have been expensive. So instead of supporting the building on bedrock, the Petronas Towers engineers took a different approach. MATERIAL MATTERS Construction workers dug 210 narrow vertical holes--some as deep as 105 meters (344 feet)--into the soil. Then they filled the holes with reinforced concrete--long steel rods surrounded by concrete, says Udom Hungspruke, one of the structural engineers who helped design the buildings. These long concrete-and-steel tubes are called barrettes. Friction between the barrettes and the soil around them keeps the barrettes in place so they can support the building. Concrete alone couldn't have done the job, explains Rustum Roy Rustum Roy (born July 3, 1924) is a materials scientist, science policy analyst, advocate of interdisciplinary education and alternative medicine, and science and religion. , a materials scientist at Penn State University. Concrete--which is made of small stones, sand, and cement--tends to develop pores, which are weak, Roy explains. Those weak spots make concrete likely to break when exposed to a bending or pulling force called tension. The steel bars in reinforced concrete reinforced concrete Concrete in which steel is embedded in such a manner that the two materials act together in resisting forces. The reinforcing steel—rods, bars, or mesh—absorbs the tensile, shear, and sometimes the compressive stresses in a concrete give the composite material composite material or composite, any material made from at least two discrete substances, such as concrete. Many materials are produced as composites, such as the fiberglass-reinforced plastics used for automobile bodies and boat hulls, but the greater strength against tension, because steel has fewer weak spots, Roy says. FROM THE GROUND UP Reinforced concrete was also the perfect material for the next layer of the foundation. This 4.5-meter (14.8-foot) thick concrete slab Concrete slab A shallow, reinforced-concrete structural member that is very wide compared with depth. Spanning between beams, girders, or columns, slabs are used for floors, roofs, and bridge decks. distributes the building's weight evenly to the barrettes. On top of the slab, workers constructed the columns and floor beams that make up the building's frame, or supporting structure. Most skyscrapers have steel frames. In fact, the invention of steel helped make some of the first tall buildings possible (see timeline, p. 14). Because steel is very strong, you don't need much of it to support the weight of a building, Meyer says. In New York City's World Trade Center, for example, the exterior columns are made of hollow steel tubes with walls only 7.5 centimeters (3 inches) thick. But steel also costs a lot. So the Petronas Towers' frame is made of cheaper--and weaker--reinforced concrete, which is easier to get in Malaysia, Hungspruke says. To make up for the difference in strength, the Petronas Towers' builders had to use a lot of reinforced concrete. The towers' largest columns are 2.4 meters (7.8 feet) in diameter and solid. One of the building's engineers compares these massive columns to the trunks of giant redwood giant redwood n. See giant sequoia. trees. WIND WILLIES wil·lies pl.n. Slang Feelings of uneasiness. Often used with the: The dark, dank cave gave me the willies. [Origin unknown. Like trees, tall buildings must be able to sway in the wind. If they didn't, the wind would literally push them over. Still, you don't want to let the building sway too much. The motion might make people who work inside sick! The concrete in the Petronas Towers makes the frame stiff enough to minimize swaying. And the reinforcing steel helps the building resist the wind's bending force. But the building still moves in a strong wind. Hungspruke won't say how much. But, in the United States United States, officially United States of America, republic (2005 est. pop. 295,734,000), 3,539,227 sq mi (9,166,598 sq km), North America. The United States is the world's third largest country in population and the fourth largest country in area. , tall buildings are allowed to sway 1/500th of their height. That means that if the Petronas Towers were built here, the tops of the buildings could sway about one full meter (3 feet) in each direction! SKY'S THE LIMIT So, are the Petronas Towers about as tall as buildings can get? Not even close, Meyer says. Reinforced concrete buildings could be about twice as tall as the new record holder. And buildings made with stronger steel frames could I'll be about three times as tall! Engineers will take another step toward those heights this year when workers begin digging the foundation of a new skyscraper: the World Financial Center in Shanghai, China, which is set to open in 2001. With a planned height of 460 meters (1,509 feet), that building will soon become the world's tallest--at least for a while! RELATED ARTICLE: TALL, TALLER, TALLEST? See how buildings have grown over time. 2550 B.C. Great Pyramid Great Pyramid, the Cheops’ tomb, built 4,600 years ago, nearly 500 feet high, with bases 755 feet long. [Egypt. Arch.: Brewer Dictionary, 735] See : Wonders, Architectural at Giza, Egypt At 147 meters (481 feet), the tomb for King Khufu was the tallest structure on Earth for more than 4,000 years. The pyramid still holds the record for the largest stone structure ever built. 1885 A.D. Home Insurance Company Building, Chicago, Illinois Experts consider this building the world's first skycraper because of its use of steel framing. It stood roughly 46 meters (150 feet) high. The building was torn down in 1931. 1889 Eiffel Tower Eiffel Tower, structure designed by A. G. Eiffel and erected in the Champ-de-Mars for the Paris exposition of 1889. The tower is 984 ft (300 m) high and consists of an iron framework supported on four masonry piers, from which rise four columns uniting to form one , Paris, France The record-breaking height of this 300-meter (1,000-foot) tower proved that steel would make ever-taller buildings possible. 1913 Woolworth Building Woolworth Building in New York City; erected by Frank Woolworth in 1913; tallest building until Empire State Building (1930-1931). [Architecture: NCE, 3004] See : Tallness , New York City New York City: see New York, city. New York City City (pop., 2000: 8,008,278), southeastern New York, at the mouth of the Hudson River. The largest city in the U.S. The first skyscraper in New York City rose to 241 meters (792 feet) and cost $13.5 million to build. F.W. Woolworth, owner of a chain of dime stores, paid for the building in cash. 1931 Empire State Building, New York City This 378-meter (1,239-foot) building was the world's tallest for 40 years. Workmen erected the tower in just 18 months. Clouds often float below tourists on the 86th-floor observation deck Ob`ser`va´tion deck 1. A room or platform at a high point in a tall building with a broad view of the surrounding area. It is often an outdoor platform, but is sometimes indoors in a room with large windows to accommodate viewing. . 1971 World Trade Center, New York City These two enormous towers, which soar 412 meters (1,350 feet) over lower Manhattan Lower Manhattan is the southernmost part of the island of Manhattan, the main island and center of business and government of the City of New York. Lower Manhattan is generally defined as the area delineated on the north by Chambers Street, on the west by the Hudson River (North , stole the world record from the Empire State Building. 1974 Sears Tower, Chicago At 443 meters (1,454 feet), this building ranked as the tallest in the world for more than 20 years. The height of the building is measured to the top of its highest roof. 1996 Petronas Towers, Kuala Lumpur, Malaysia These towers, which stand 451.9 meters (1,483 feet) tall, including the spires, now hold the record as the world's tallest. Total construction time: 3 1/2 years. 2001 World Financial Center, Shanghai, China Construction will begin on this 460-meter (1,509-foot) mega-structure in late 1996. When complete in 2001, the building will become the tallest in the world--at least for a while! RELATED ARTICLE: Build Your Own Skyscraper! Try this design challenge to see if you can make a structure that will stand strong through windy weather. WHAT YOU NEED: A group of friends (or your science class) organized into several "engineering teams" * electric fan * meter stick * a set of building materials for each team Each set of building materials should contain: Ten index cords * sheet of sand paper * five plastic drinking straws * small ball of clay * scissors scissors Cutting instrument or tool consisting of a pair of opposed metal blades that meet and cut when the handles at their ends are brought together. Modern scissors are of two types: the more usual pivoted blades have a rivet or screw connection between the cutting ends * tape WHAT TO DO: 1. After reading this article, each team should build a "skyscraper" at least 25 centimeters (10 inches) tall using only the materials listed above. Concentrate on making a structure that will be strong enough to stand against the force of wind. Remember to use some of your materials to "anchor" the building to the ground. 2. After all the teams have finished, measure the completed structures to make sure each is tall enough. 3. Position a fan 30 centimeters (one foot) from one of the finished structures. Turn the fan on low. If the building stays standing, turn the fan on medium. Then try high. 4. Test each structure in the same way. CONCLUSIONS: Which design was strongest against the "wind"? Can you explain why? DON'T STOP NOW! Do some research to learn more about how buildings are designed to withstand wind. |
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