Skyscraper

Background

There is no precise definition of how many stories or what height makes a building a skyscraper. "I don't think it is how many floors you have. I think it is attitude," architect T. J. Gottesdiener told the Christian Science Monitor. Gottesdiener, a partner in the firm of Skidmore, Owings & Merrill, designers of numerous tall buildings including the Sears Tower in Chicago, Illinois, continued, "What is a skyscraper? It is anything that makes you stop, stand, crane your neck back, and look up."

Some observers apply the word "skyscraper" to buildings of at least 20 stories. Others reserve the term for structures of at least 50 stories. But it is widely accepted that a skyscraper fits buildings with 100 or more stories. At 102 stories, the Empire State Building's in New York occupied height reaches 1,224 ft (373 m), and its spire, which is the tapered portion atop a building's roof, rises another 230 ft (70 m). Only 25 buildings around the world stand taller than 1,000 ft (300 m), counting their spires, but not antennas rising above them.

The tallest freestanding structure in the world is the CN Tower in Toronto, Canada, which rises to a height of 1,815 ft (553 m); constructed to support a television antenna, the tower is not designed for human occupation, except for a restaurant and observation deck perched at 1,100 ft (335 m). The world's tallest occupied structure is the Petronas Twin Towers in Kuala Lumpur, Malaysia, which reach a height of 1,483 ft (452 m), including spires. The Sears Tower in Chicago boasts the highest occupied level; the roof of its 110th story stands at 1,453 ft (443 m).

In some ways, super-tall buildings are not practical. It is cheaper to build two half-height buildings than one very tall one. Developers must find tenants for huge amounts of space at one location; for example, the Sears Tower encloses 4.5 million square feet (415,000 square meters). On the other hand, developers in crowded cities must make the fullest possible use of limited amounts of available land. Nonetheless, the decision to build a dramatically tall building is usually based not on economics, but on the desire to attract attention and gain prestige.

History

Several technological advances occurred in the late nineteenth century that combined to make skyscraper design and construction possible. Among them were the ability to mass produce steel, the invention of safe and efficient elevators, and the development of improved techniques for measuring and analyzing structural loads and stresses. During the 1920s and 1930s, skyscraper development was further spurred by invention of electric arc welding and fluorescent light bulbs (their bright light allowed people to work farther from windows and generated less heat than incandescent bulbs).

Traditionally, the walls of a building supported the structure; the taller the structure, the thicker the walls had to be. A 16-story building constructed in Chicago in 1891 had walls 6 ft (1.8 m) thick at the base. The need for very thick walls was eliminated with the invention of steel-frame construction, in which a rigid steel skeleton supports the building's weight, and the outer walls are merely hung from the frame almost like curtains. The first building to use this design was the 10-story Home Insurance Company Building, which was constructed in Chicago in 1885.

The 792-ft (242-m) tall Woolworth Building, erected in New York City in 1913, first combined all of the components of a true skyscraper. Its steel skeleton rose from a foundation supported on concrete pillars that extended down to bedrock (a layer of solid rock strong enough to support the building), its frame was braced to resist expected wind forces, and its high-speed elevators provided both local and express service to its 60 floors.

In 1931, the Empire State Building rose in New York City like a 1,250-ft (381-m) exclamation point. It would remain the world's tallest office building for 41 years. By 2000, only six other buildings in the world would surpass its height.

Raw Materials

Reinforced concrete is one important component of skyscrapers. It consists of concrete (a mixture of water, cement powder, and aggregate consisting of gravel or sand) poured around a gridwork of steel rods (called rebar) that will strengthen the dried concrete against bending motion caused by the wind. Concrete is inherently strong under compressive forces; however, the enormous projected weight of the Petronas Towers led designers to specify a new type of concrete that was more than twice as strong as usual. This high-strength material was achieved by adding very fine particles to the usual concrete ingredients; the increased surface area of these tiny particles produced a stronger bond.

The other primary raw material for skyscraper construction is steel, which is an alloy of iron and carbon. Nearby buildings often limit the amount of space available for construction activity and supply storage, so steel beams of specified sizes and shapes are delivered to the site just as they are needed for placement. Before delivery, the beams are coated with a mixture of plaster and vermiculite (mica that has been heat-expanded to form sponge-like particles) to protect them from corrosion and heat. After each beam is welded into place, the fresh joints are sprayed with the same coating material. An additional layer of insulation, such as fiberglass batting covered with aluminum foil, may then be wrapped around the beams.

To maximize the best qualities of concrete and steel, they are often used together in skyscraper construction. For example, a support column may be formed by pouring concrete around a steel beam.

A variety of materials are used to cover the skyscraper's frame. Known as "cladding," the sheets that form the exterior walls may consist of glass, metals, such as aluminum or stainless steel, or masonry materials, such as granite, marble, or limestone.

Design

Design engineers translate the architect's vision of the building into a detailed plan that will be structurally sound and possible to construct.

Designing a low-rise building involves creating a structure that will support its own weight (called the dead load) and the weight of the people and furniture that it will contain (the live load). For a skyscraper, the sideways force of wind affects the structure more than the weight of the building and its contents. The designer must ensure that the building will not be toppled by a strong wind, and also that it will not sway enough to cause the occupants physical or emotional discomfort.

Each skyscraper design is unique. Major structural elements that may be used alone or in combination include a steel skeleton hidden behind non-load-bearing curtain walls, a reinforced concrete skeleton that is in-filled with cladding panels to form the exterior walls, a central concrete core (open column) large enough to contain elevator shafts and other mechanical components, and an array of support columns around the perimeter of the building that are connected by horizontal beams to one another and to the core.

Because each design is innovative, models of proposed super tall buildings are tested in wind tunnels to determine the effect of high wind on them, and also the effect on surrounding buildings of wind patterns caused by the new building. If tests show the building will sway excessively in strong winds, designers may add mechanical devices that counteract or restrict motion.

In addition to the superstructure, designers must also plan appropriate mechanical systems such as elevators that move people quickly and comfortably, air circulation systems, and plumbing.

The Construction Process

Each skyscraper is a unique structure designed to conform to physical constraints imposed by factors like geology and climate, meet the needs of the tenants, and satisfy the aesthetic objectives of the owner and the architect. The construction process for each building is also unique. The following steps give a general idea of the most common construction techniques.

The substructure

• 1 Construction usually begins with digging a pit that will hold the foundation. The depth of the pit depends on how far down the bedrock lies and how many basement levels the building will have. To prevent movement of the surrounding soil and to seal out water from around the foundation site, a diaphragm wall may be constructed before the pit is dug. This is done by digging a deep, narrow trench around the perimeter of the planned pit; as the trench is dug, it is filled with slurry (watery clay) to keep its walls from collapsing. When a section of trench reaches the desired depth, a cage of reinforcing steel is lowered into it. Concrete is then pumped into the trench, displacing the lighter slurry. The slurry is recovered and used again in other sections of the trench.
• 2 In some cases, bedrock lies close to the surface. The soil on top of the bedrock is removed, and enough of the bedrock surface is removed to form a smooth, level platform on which to construct the building's foundation. Footings (holes into which the building's support columns can be anchored) are blasted or drilled in the bedrock. Steel or reinforced concrete columns are placed in the footings.
• 3 If the bedrock lies very deep, piles (vertical beams) are sunk through the soil until they are embedded in the bedrock. One technique involves driving steel piles into place by repeatedly dropping a heavy weight on their tops. Another technique involves drilling shafts through the soil and into the bedrock, inserting steel reinforcing rods, and then filling the shafts with concrete.
• 4 A foundation platform of reinforced concrete is poured on top of the support columns.

The superstructure and core

Once construction of a skyscraper is underway, work on several phases of the structure proceeds simultaneously. For example, by the time the support columns are several stories high, workers begin building floors for the lower stories. As the columns reach higher, the flooring crews move to higher stories, as well, and finishing crews begin working on the lowest levels. Overlapping these phases not only makes the most efficient use of time, but it also ensures that the structure remains stable during construction.

• 5 If steel columns and cross-bracing are used in the building, each beam is lifted into place by a crane. Initially, the crane sits on the ground; later it may be positioned on the highest existing level of the steel skeleton itself. Skilled workers either bolt or weld the end of the beam into place (rivets have not been used since the 1950s). The beam is then wrapped with an insulating jacket to keep it from overheating and being weakened in the event of a fire. As an alternative heat-protection measure in some buildings, the steel beams consist of hollow tubes; when the superstructure is completed, the tubes are filled with water, which is circulated continuously throughout the lifetime of the building.
• 6 Concrete is often used for constructing a building's core, and it may also be used to construct support columns. A technique called "slip forming" is commonly used. Wooden forms of the desired shape are attached to a steel frame, which is connected to a climbing jack that grips a vertical rod. Workers prepare a section of reinforcing steel that is taller than the wooden forms. Then they begin pouring concrete into the forms. As the concrete is poured, the climbing jack slowly and continuously raises the formwork. The composition of the concrete mixture and the rate of climbing are coordinated so that the concrete at the lower range of the form has set before the form rises above it. As the process continues, workers extend the reinforcing steel grid that extends above the formwork and add extensions to the vertical rod that the climbing jack grips. In this way, the entire concrete column is built as a continuous vertical element without joints.
• 7 In a steel-skeleton building, floors are constructed on the layers of horizontal bracing. In other building designs, floors are supported by horizontal steel beams attached to the building's core and/or support columns. Steel decking (panels of thin, corrugated steel) is laid on the beams and welded in place. A layer of concrete, about 2-4 in (5-10 cm) thick, is poured on the decking to complete the floor.

The Empire State Building was intended to end the competition for tallest building. It was to tower 102 stories, 1,250 ft (381 m) above Manhattan's streets. Its developers, John J. Raskob and Pierre Samuel Du Pont, along with former New York Governor Alfred E. Smith, announced in August 1929 their intention to build the world's tallest building. They chose the construction firm Starrett Brothers and Eken, and the architectural firm Shreve, Lamb, and Harmon for the project with William F. Lamb as the chief designer. If is set back from the street above the fifth floor and then soars uninterrupted for more than 1,000 ft (305 m) to the 86th floor. The exterior is limestone and granite and vertical chrome-nickel-steel alloy columns extend from the sixth floor to the top. The building contained 67 elevators and 6,500 glass windows, topped with a 200-ft (61-m) mooring mast for dirigibles.

The Empire State Building was completed on April 11, 1931, 12 days ahead of schedule and officially opened on May 1, 1931. The building took its place in history as the tallest building ever built, holding this title for more than 40 years. It was not until 1972, when the 1,348-ft-(411-m-) tall twin towers of the World Trade Center were completed that the Empire State Building was surpassed in height. The World Trade Center in turn was surpassed in 1974 by the Sears Tower in Chicago, which at 1,453 ft (443 mj became the tallest building in the world.

The exterior

• 8 In most tall buildings, the weight of the structure and its contents is borne by the support columns and the building's core. The exterior walls themselves merely enclose the structure. They are constructed by attaching panels of such materials as glass, metal, and stone to the building's framework. A common technique is to bolt them to angle brackets secured to floor slabs or support columns.

Finishing

• 9 When a story of the building has been enclosed by exterior walls, it is ready for interior finishing. This includes installation of such elements as electrical wires, telephone wires, plumbing pipes, interior walls, ceiling panels, bathroom fixtures, lighting fixtures, and sprinkler systems for fire control. It also includes installation of mechanical components like elevators and systems for air circulation, cooling, and heating.
• 10 When the entire superstructure has been completed, the top of the building is finished by installing a roof. This may be built much like a floor, and then waterproofed with a layer of rubber or plastic before being covered with an attractive, weather—resistant layer of tiles or metal.

Quality Control

Various factors are taken into consideration when assuring quality control. Because of the huge scale of skyscrapers, a small positioning error at the base will be magnified when extended to the roof. In addition to normal surveying instruments, unusual devices like global positioning system (GPS) sensors and aircraft bombsights may be used to verify the placement and alignment of structural members.

Soil sensors around the building site are used to detect any unexpected earth movement caused by the construction activity.

Byproducts/Waste

Excavation of the foundation pit and basement levels require the removal of enormous amounts of dirt. When the 110-story World Trade Center towers were built in New York in the early 1970s, more than I million cubic yards (765,000 cubic meters) of soil and rock were removed and dumped in the Hudson River to create 23.5 acres (95,100 square meters) of new land, on which another skyscraper was later constructed.

The Future

Plans have been developed for several new skyscrapers that would break existing height records. For example, a 108-story building at 7 South Dearborn Street in Chicago, expected to be completed by 2004, will be 1,550 ft (473 m) tall. It will provide 43 acres (174,000 square meters) of enclosed space on a lot only 200 ft (61 m) square.

In 1956, American architect Frank Lloyd Wright announced plans for a mile-high (1.6-km tall) skyscraper in which 100,000 people could work. In 1991, another American architect, Dr. Eugene Tsui, designed a 2-mile (3,220-m) tall building that would provide space for living, working, and recreation for 1,000,000 people. Although such buildings may be theoretically constructable, they are currently impractical. For example, human comfort levels limit elevator speeds to no more than 3,000 ft/min (915 m/min). To accommodate the 100,000 people working in Wright's proposed structure, the number of elevator shafts would have taken up too large a portion of the building's area.

Improvements in elevator technology will be important for future skyscraper designs. Self-propelled, cableless elevator cars that move horizontally, as well as vertically, have been proposed, but are still under development. Computerized car dispatching systems using fuzzy logic could be refined to carry people more efficiently by grouping passengers whose destinations are near each other.

Where to Learn More

Books

Books Dunn, Andrew. Structures: Skyscrapers. New York: Thomson Learning, 1993.

Michael, Duncan. How Skyscrapers Are Made. New York: Facts on File Publications, 1987.

Periodicals

Hayashi, Alden M. "The Sky's the Limit." Scientific American Presents: Extreme Engineering (Winter 1999): 66 ff.

Richey, Warren. "New Rush of Buildings Reaching for the Clouds." The Christian Science Monitor (July 8, 1998): 1.

Other

Dankwa, E. T. New York Skyscrapers.http://mx3.xoom.com/iNetwork/NYC (March 2000).

"Ultima's Tower, Two-Mile High Sky City." Tsui Design & Research.http://www.tdrinc.com/ultima.html (March 2000).

—LorettaHall

Skyscraper

The ten-story Home Insurance Company Building, built in Chicago, Illinois, in 1885, is considered to be the first modern skyscraper.

A skyscraper is a very tall building with many stories. Skyscrapers usually refer to structures that serve as residences or work places for thousands of people. The term "skyscraper" was first used in the United States in the 1880s, where the form of the structure originated. Originally used to describe a building with at least ten stories, today it refers to buildings with forty to more than one hundred floors. Its height is measured from the street level where the main entrance is located to the top of the structure, which includes spires (the tapered portion on top of a building's roof). However flagpoles, television antennas, and radio antennas are not included.

The tallest skyscrapers in the world are a pair of office buildings in Kuala Lumpur, Malaysia. The Petronas Twin Towers stand 1,483 feet (452 meters) tall, including spires. Completed in 1997, each of the towers holds eighty-eight stories. The Sears Tower in Chicago, Illinois, at 1,454 feet (443 meters), is the second tallest skyscraper. It opened in 1974. (The television antenna on top of the 110-story building adds an additional 253 feet [77 meters] to its height.) The third tallest skyscraper, the Jin Mao Tower in Shanghai, China, rises to 1,381 feet (421 meters). It was constructed in 1998 and has eighty-eight stories.

The Empire State Building in New York, New York, completed in 1931, held the title of the world's tallest skyscraper for more than forty years. In 1972, the twin towers of the World Trade Center surpassed the Empire State Building in height. The twin towers, which collapsed due to damage sustained from a terrorist attack on September 11, 2001, each had 110 floors and rose to 1,362 feet (415 meters) and 1,368 (417 meters), respectively.

Building up instead of out

During the 1850s, the need for more office spaces in big cities, where land was expensive or scarce, gave rise to the construction of buildings that could hold several stories. The walls of a building typically support its structure; therefore, a tall building would require very thick stone or brick walls on the lower stories to hold up the higher levels. The earliest tall buildings in the United States consisted of about five stories, with the lower floors losing plenty of space to the thick walls. In later years, architects used cast iron (a metal composed of a mixture of iron, carbon, and silicon) frames to bear the weight of the upper floors. The walls remained of stone and brick construction.

Rising to new heights

In the late 1880s, major technological advances made possible the design and construction of buildings with more stories. The invention of steel-frame construction, in which a rigid steel skeleton supported the building's weight, eliminated the need for very thick walls. The outer walls, made of bricks or stones, held only their own weight and were then supported by the steel frame. The first skyscraper to use this design was the ten-story Home Insurance Company Building, which was built in Chicago, Illinois, in 1885 by William Le Baron Jenney (1832–1907). This was considered the first skyscraper.

Steel (an alloy of iron and carbon), being stronger and weighing less than iron, was the ideal material for the framework because it allowed for additional stories. The ability to mass-produce steel further increased the construction of skyscrapers.

The invention of the safety elevator in 1852 by Elisha Otis (1811–1861) created the ability to reach the upper stories of tall buildings with ease and safety. This steam-powered rope elevator had an automatic safety device that kept it from falling if the lifting rope broke. Nearly forty years later, in 1889, the high-speed, electric-powered, roped elevator enabled the construction of higher structures.

Raw Materials

Reinforced concrete is an important component (part) of skyscrapers. It is made from concrete poured around a framework of steel rods, strengthening the resulting dried concrete against bending movement caused by the wind. A type of high-strength concrete has been developed by adding very fine particles to the regular concrete ingredients. The increased surface area of these tiny particles produces a stronger bond. This type of concrete was used in Petronas Twin Towers.

The other important material for skyscraper construction is steel. Different sizes of steel beams (long pieces of steel) are delivered to the construction site as they are needed. Before delivery, the beams are coated with a substance that protects them from rust and heat. After each beam is welded into place, the same coating substance is used to cover the fresh joints. Another layer of insulation, such as fiberglass batting covered with aluminum foil, may then be wrapped around the beams.

The exterior walls of a skyscraper are called curtain walls because they hang from the frames like curtains. A variety of materials, called claddings, make up these exterior walls. They may be glass; metal, such as aluminum or stainless steel; or masonry materials, such as granite, marble, or limestone.

Design

The architect designs the skyscraper, determining the shape and height as well as its inside and outside appearances. Some architects use a computer program that helps them see how the skyscraper will look when completed, or how the building will fit into its surroundings.

Next, structural engineers put the architect's ideas into a detailed plan. The engineers make sure the structure will support not only the weight of the skyscraper, but also the weight of the people and furniture the skyscraper will contain.

THE TALLEST STRUCTURES MAY NOT BE SKYSCRAPERS

Some of the world's tallest structures are not necessarily skyscrapers because they do not house offices or living quarters. The world's tallest freestanding (standing unsupported or with attachment) structure is not a skyscraper. The CN tower in Toronto, Canada, was erected in 1975 to support a huge television antenna. It measures 1,815 feet (553 meters), with the Skypod (comprised of a restaurant, nightclub, and an observation viewing deck) at around 1,100 feet (335 meters) from the street. The world's second largest freestanding structure is also a television tower that was built in 1967. The Ostankino Tower in Moscow, Russia, has an observation deck located almost two-thirds up the tower's total height of 1,771 feet (540 meters). A restaurant called the Seventh Heaven, with three dining areas, is located below the observation deck.

Tall buildings, especially their top levels, can sway anywhere from two inches to more than two feet in strong winds. The engineers have to make sure the structure is sound enough that it will not be toppled by the sideways force of wind, or that it will not sway too much to cause the occupants physical or emotional discomfort. Models of the planned building are tested in wind tunnels to determine the effects of high winds.

If tests show the building will sway excessively in strong winds, designers may add a central core. They may also incorporate devices to counteract the motion or restrict motion. One such device is called the tuned mass damper, which is a heavy weight in the top level of the building. When the building starts to sway, the computer system moves this heavy weight in the opposite direction, thereby reducing the amount of sway.

Tall buildings also affect the wind patterns of surrounding areas. The wind between skyscrapers that are built near one another is known to be stronger.

Each skyscraper design is different. Major structural designs that may be used alone or combined with others include a steel skeleton hidden behind curtain walls that do not support the structure's weight and a reinforced concrete skeleton that is in-filled with cladding panels to form exterior walls. The design may also include a central concrete core to hold the elevators, as well as the air conditioning, water pipes, and ducts for electrical wirings. Still another design includes support columns around the perimeter of the building that are connected by horizontal beams to one another and to the core.

The Construction Process

Each skyscraper is designed to suit the needs of its future occupants, whether they are apartment dwellers or office workers. The owner and the architect have to approve what the final structure will look like. The structure of the building also has to take into consideration the layout of the land and the type of climate in the area. For example, in Japan, designers have to allow for the occurrence of earthquakes when they design the structure. The construction process for each building differs. However, all skyscrapers follow basic methods.

The substructure

1 Construction usually begins with digging a hole that will hold the foundation. The depth of the hole depends on how far down the bedrock (solid rock deep underground) is and how many basement levels will be built.

Digging a deep hole can cause movement of the surrounding soil. To prevent this from happening and to seal out water from around the foundation site, a diaphragm wall is constructed. This is done by digging a deep narrow ditch around the boundary of the planned hole. As the ditch is dug, it is filled with slurry (watery clay) to keep its sides from collapsing. As each section of the ditch reaches the desired depth, a cage of reinforced steel is lowered into it. Concrete is pumped into the ditch, displacing the slurry. The slurry is reused in other sections of the ditch. The concrete hardens, forming the wall.

2 If the bedrock lies close to the surface, the soil on top of it is removed. The bedrock surface is smoothed to form a leveled surface for the foundation. Footings (holes into which the building's support columns will be held in place) are drilled in the bedrock. Then the support columns made of steel or reinforced concrete are placed in the footings.

3 If the bedrock lies very deep, long steel columns or reinforced concrete columns called piles are sunk through the soil until they are embedded in the bedrock. This can be done using one of two methods. Steel piles may be embedded in the bedrock by repeatedly dropping a heavy weight on their tops. The second method involves drilling shafts (large tubes) through the soil and into the bedrock. Steel rods are inserted through the shafts and concrete is poured around them, resulting in reinforced concrete columns.

4 Finally, a foundation platform of reinforced concrete is poured on top of the support columns.

The superstructure and core

Once construction of a skyscraper has started, work on several phases of the structure generally takes place at the same time. For example, when the support columns are several stories high, workers begin building floors for the lower stories. As the columns are built higher, the flooring crews move to higher stories. In the meantime, the finishing crews start work on the lowest level. This process not only saves time but also ensures that the structure stays safe during construction.

5 If steel columns and beams are used in the building, each piece is lifted into place by tall cranes (machines that lift and move heavy materials). While the lowest stories are under construction, the cranes stay on the ground. As the structure rises higher, the cranes may be placed on the highest completed level of the steel skeleton.

Workers either bolt or weld the ends of the beams into place.

6 Many skyscrapers have a core (middle section) made of concrete. The core serves to keep the structure from swaying too much from strong winds. The core usually contains the elevator shafts, as well as the pipes for transporting water and the ducts (large pipes) for electrical wirings. Concrete may also be used to construct support columns.

Concrete cores and support columns are constructed using a technique called slip-forming. Steel rods are put inside a metal or wooden form called a formwork, which is made to the desired shape. The formwork is constructed so that it moves upward. As concrete is poured around the rods inside the formwork, the formwork rises. The speed of the climbing formwork is timed so that the concrete at the lower part has set before the formwork moves upward. The concrete mixture has to be such that it has hardened by the time the formwork is raised. In this way, the entire concrete core or column is made as one continuous piece.

7 In some skyscrapers, the floors are made of reinforced concrete. In others, the floors are supported by horizontal steel beams that are attached to the core and/or support columns. Steel decks (panels of thin, corrugated steel) are laid on the beams and welded in place. Then, concrete is poured over the steel decks.

The exterior

8 In most skyscrapers, the core and support columns bear the weight of the structure and its contents. The outer walls simply enclose the structure. The walls are constructed by attaching panels of materials, such as glass, metal, and stone, to the building's framework. These materials are called claddings.

Finishing

9 After a story has been enclosed by exterior walls, it is ready for interior finishing. This includes installation of electrical wires, telephone wires, plumbing pipes, interior walls, ceiling panels, bathroom fixtures, lighting fixtures, water tanks, and sprinkler systems for fire control. Mechanical components, such as elevators, air conditioners, heating systems, and electricity generators are also put in place.

10 After completion of the superstructure, a roof is installed. This may be constructed like a floor and then waterproofed with a layer of rubber or plastic. Finally, the roof is covered with attractive weather-resistant tiles or metal.

The Future

The race is always on for constructing the highest skyscraper. The building at 7 South Dearborn Street in Chicago, Illinois, due for completion by 2004, will surpass the Petronas Twin Towers. It will rise 1,550 feet (471 meters) and contain 108 stories. Two television antennas will make the total height 2,000 feet.

Plans for other skyscrapers are being developed. In India, two pyramid-shaped buildings are being proposed. The taller of the two would reach 2,222 feet (677 meters). Japan, faced with scarce land to house its growing population, has proposed the X-Seed 4000, its name designating its height in meters. The 12,000-foot building is designed to accommodate about one million people. Another idea involves a skyscraper called the Millennium Tower (2,438 feet, or 800 meters) to be constructed in the Bay of Tokyo.

While building these skyscrapers is possible, they are just ideas. Such projects would cost a lot of money because extremely tall structures require very strong foundations and materials. The task of getting materials up to the highest stories would also require more expenses. Additional stories would require more elevators that would take up more spaces in the building core. One solution is to group passengers according to a common destination. Another solution is to have two sets of elevators—one elevator to take passengers partway up the building and another elevator to take these passengers the rest of the way.

alloy:

A mixture of a metal and a nonmetal or a mixture of two or more metals. For example, steel is an alloy made of the metal iron and the nonmetal carbon. Brass is an alloy made of two metals, copper and zinc.

architect:

A person who designs a building, determining the shape and height as well as its inside and outside appearances.

beam:

Horizontal piece of a frame.

bolt:

A threaded metal pin with a head. It is inserted through a hole in a building piece and is secured with a nut. The nut, a small piece of metal, has a threaded hole that fits around the bolt to keep it in place.

cladding:

Material that makes up the exterior wall of a skyscraper.

column:

Vertical piece of a frame.

concrete:

A mixture of cement powder, water, gravel, and sand.

corrugated steel:

A steel sheet, shaped into folds for rigidity.

masonry:

Stonework or brickwork.

reinforced concrete:

Concrete that is made stronger by having steel rods embedded in it.

spire:

The tapered portion on top of a building's roof.

weld:

To unite metal pieces by applying heat, which melts the edges of the pieces, joining them together.

For More Information

Books

Macaulay, David. Building Big. Boston, MA: Houghton Mifflin Company, 2000.

Oxlade, Chris. Skyscrapers. Chicago, IL: Reed Educational & Professional Publishing, 2001.

Severance, John B. Skyscrapers: How America Grew Up. New York, NY: Holiday House, 2000.

Web Sites

Harris, Tom. "How Skyscrapers Work." How Stuff Works.http://howstuffworks.com/skyscraper.htm (accessed on July 22, 2002).

The Skyscraper Museum.http://www.skyscraper.org (accessed July 22, 2002).

SkyscraperPage.com.http://www.skyscraperpage.com (accessed July 22, 2002).

SKYSCRAPERS

SKYSCRAPERS entered American parlance around 1890, describing ten-to fifteen-story commercial buildings mostly in Chicago and New York. Dependent on the passenger elevator, telephone, and incandescent bulb for internal circulation, communication, and illumination, the structural potential of its steel frame ensured that the economic benefit of multiplying lot size twenty, fifty, or one hundred times would render municipal height restrictions obsolete. Well before New York's 1913 Woolworth Building opened at 792 feet (54 stories), the world's tallest edifice excepting the Eiffel Tower in Paris, it was a social convention to wonder if the only limit to upward growth were the heavens themselves.

Artistic hesitation characterized skyscraper design from the beginning, less so in Chicago than in New York. Although skyscrapers' determining features were steel and height, architects were inclined to hide steel inside highly decorated, thick masonry walls. In addition, they negated height by wrapping every few stories with a protruding cornice interrupting vertical flow or by periodically shifting styles, so, as a building ascended, it resembled a stack of small structures. Those willing to embrace height tended to base form on historical analogies, usually French gothic cathedrals or Italian medieval towers.

In Chicago, Louis Sullivan referred to the classical column, but in his pioneering search for a self-referential skyscraper aesthetic, he transformed base, shaft, and capital into commercial ground floor, office tier, and attic for ancillary services, each function indicated externally. By recessing windows and walls a few inches behind columns and mullions, he privileged vertical elements of the frame to create, he wrote in 1896, "a proud and soaring thing" that was "every inch of it tall." Although highly regarded by critics, Sullivan's "system of vertical construction" was not widely adopted by architects, not even his Chicago School (c. 1885–1915) colleagues, whose so-called "utilitarian" building facades, less ornamented and more fenestrated than Sullivan's, closely followed in composition the grid pattern of the frame, which in reality is nondirectional.

Chicago School buildings were America's principal contribution to the formative stages of what was soon labeled "modern architecture." The implication, which might be encapsulated in the phrase "form follows structure," was disregarded in the United States during the 1920s, but it was taken up in Europe, particularly in Germany,

where in 1921 and 1922 Ludwig Mies van der Rohe proposed free-form skyscrapers entirely encased with glass panels clipped to the edges of floor slabs. Of the 265 entries from 23 countries to the 1922 Chicago Tribune headquarters competition, 37 were German, notable among them Walter Gropius and Adolf Meyer's grid of reinforced concrete completely filled with windows. These and other European designs conclusively demonstrated what Chicagoans had almost perceived. Since load-bearing walls were structurally unnecessary, a skyscraper's facade could be reduced to little more than frame and glazing. The lesson was ignored when the Tribune Company selected Raymond Hood and John Mead Howells's decidedly unglassy, neogothic cousin to the Woolworth Building.

Until large-scale private sector construction halted during the Great Depression, American skyscrapers were either historical pastiches or tips of the hat to European art deco. Most famous were New York's Chrysler, Empire State, and Rockefeller Center buildings (of 1930 and 1931), featuring diagonal or zigzag "jazz age" ornament and equal amounts of glass and masonry in alternating vertical or horizontal strips forming crisp, rectilinear facades that nonetheless hide the frame. Two exceptions were noteworthy: Hood's 1929–1931 McGraw-Hill Building, designed with André Fouilhoux, in New York; and William Lescaze's 1929–1932 Philadelphia Savings Fund Society Building, designed with George Howe. Both were in what was labeled "the international style," which made structurally determined form something of a fetish.

It was fitting that the European émigrés Fouilhoux (from Paris) and Lescaze (from Zurich) figured prominently in the reconfiguration of American skyscrapers, because a third European, Mies van der Rohe, who arrived in Chicago in 1938, almost single-handedly completed the process, beginning with his 1946–1949 Promontory Apartments. More than any other edifice, his 1954–1958 Seagram Building in New York made the flatroofed, glass-walled, steel-or concrete-framed, minimally ornamented box a corporate signature as well as an indication that derivations of European modernism had captured the mainstream of American architecture.

A comparison of the two McGraw-Hill Buildings in New York suggests how much had changed since 1929. The first, by Hood with Fouilhoux, is bluish-green glazed terra-cotta and steps back five times before reaching its penthouse, which is sided with huge firm-name graphics. Its thirty-five richly textured, horizontally articulated stories complement the vertical thrust of the elevator shafts and stairwell. Although resolutely international in style, it resembles no other building. The four identical facades of the second McGraw-Hill Building, built in 1973 by Harrison, Abramovitz, and Harris, soar without interruption or variation through forty-five stories of closely spaced reddish granite columns. Devoid of graphics, it is a clone of the flanking Celanese and Exxon Buildings by the same architects. In less than half a century, collective anonymity replaced architectural individuality in every American city.

The low profile adopted by American corporations after World War II gave way in the 1980s to a more assertive public posture expressed architecturally in post-modernism (POMO): the return of polychrome, ornament, and historical reference enlivened by mixtures of nonorthogonal with rectilinear geometries. Rejecting the Mies-inspired modernist box and companion frame-based aesthetic, POMO recaptured a spirit of experimentation akin to that of the European 1920s but enhanced by an array of new materials and technologies, including computer-assisted design. The sky was again the limit in terms not of height but of artistic possibility.

Globalization of capital internationalized the profession. For example, four architects were invited in 2000 to submit proposals for a new New York Times headquarters: Norman Foster of London; Renzo Piano with offices in Paris and Genoa; Cesar Pelli, the Argentina-born dean of the Yale School of Art and Architecture; and Frank Gehry, a Toronto native residing in California. Gehry produced a twisting, undulating, concave and convex agglomeration of sinewy, computer-generated, non-Euclidean shapes that appears to be one tower or three, depending on the viewer's vantage point. Like the other submissions, it makes no reference except for signage to site or function, suggesting that any one of the four could be erected anywhere to serve any purpose. Sharing only the absence of similarity, they are as far removed from the modernist box as that was from the Woolworth Building.

During the course of a century, an American commercial building type, stylistically conditioned by historical precedent or by the steel frame, became an omnifunctional symbol of globalization conditioned only by architectural imagination. Technical limits to skyscraper height may be approaching, but form has no limits at all.

BIBLIOGRAPHY

Goldberger, Paul. The Skyscraper. New York: Knopf, 1981.

Scuri, Piera. Late-Twentieth-Century Skyscrapers. New York: Van Nostrand Reinhold, 1990.

Twombly, Robert. Power and Style: A Critique of Twentieth-Century Architecture in the United States. New York: Hill and Wang, 1995.

Van Leeuwen, Thomas A. P. The Skyward Trend of Thought: The Metaphysics of the American Skyscraper. Cambridge, Mass.: MIT Press, 1988.

RobertTwombly

See alsoArchitecture ; World Trade Center .

skyscraper. High multi-storey building based on a steel- or concrete-framed or skeleton structure, evolved in the USA in the late 1880s after the limitations of traditional load-bearing construction had been reached with ten- or twelve-storey buildings. While it would be possible to build higher load-bearing walls, the huge amounts of material needed would be uneconomic. Important in the evolution of the skyscraper was Post's Equitable Life Assurance Building, NYC (1868–70—designed with a passenger-lift (or elevator) ). The lift had been invented in the late 1850s, and from c.1880 its speed and reliability were greatly improved, enabling the building-type to further develop. William Le Baron Jenney's Home Insurance Building in Chicago, IL (1883–5—demolished— which incorporated iron columns, lintels, girders, and steel beams), was the model for later architecture of the Chicago School. Steel and iron, with traditional loadbearing brick, were also used by Holabird & Roche in the 22 storey Tacoma Building in Chicago (1887–8— demolished 1929), although L. S. Buffington claimed to have originated the whole system on which skyscraper construction was based, and there were earlier experiments by Loudon, Paxton, Saulnier, and others that pointed the way forward. Later important skyscrapers include Cass Gilbert's Woolworth Building, NYC (1911–13), Shreve, Lamb, & Harmon's Empire State Building, NYC (designed 1928–9, built 1930–2), SOM's John Hancock Center (1969–70) and Sears Tower (1972–4), both in Chicago, and Pelli's Petronas Twin Towers, Kuala Lumpur, Malaysia (1991–7). However, the rapid collapse (11 Sept. 2001) of the twin towers of the World Trade Center, NYC (designed by Yamasaki with Emery Roth, 1964–74), following the deliberate attack using passenger-carrying aeroplanes, may cause questions to be asked about the future of steel frames and large areas of glass, although, as Carol Willis observed, ‘Form follows Finance’.

Bibliography

Bletter & and Robinson (1975);
Condit (1952, 1960, 1961, 1964, 1968, 1973);
Goldberger (1981);
H H Sturgis (1985);
D. Hoffmann (1988);
S. Landau & and Condit (1996);
Leeuwen (1988);
C. Willis (1995);
Yeang (1997);
Zukowsky (ed.) (1987)

sky·scrap·er / ˈskīˌskrāpər/ • n. 1. a very tall building of many stories.2. another term for skysail.