World Trade Center

:This article is about the World Trade Center complex in New York City; see this article for the many other buildings around the world that have also been called "world trade centers".

The Twin Towers

Each of the WTC towers had 110 stories. Tower One (the North Tower, which featured a massive antenna) stood 1,368 ft (417 m) high and Tower Two (the South Tower, which contained the observation deck) was 1,362 ft (415 m) tall. The length and breadth of the towers were 208 ft (63.4 m) x 208 ft (63.4 m). When the towers were completed in 1972 and 1973, respectively, they were the tallest buildings on Earth, 100 feet (30 m) taller than the Empire State Building. Their size was the subject of a joke during a press conference unveiling the landmarks. Minoru Yamasaki was asked: "Why two 110-story buildings? Why not one 220-story building?" His response was: "I didn't want to lose the human scale."

Related Topics:
Ft - M - Empire State Building - Minoru Yamasaki

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Another joke was that the towers looked like the boxes that the Chrysler Building and Empire State Building came out of.

Related Topics:
Chrysler Building - Empire State Building

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For a time the local television station on Channel 11 used the towers as a graphic representation of its channel number.

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The WTC towers held the height record only briefly. As the building neared completion in 1973, work had already begun on Chicago's Sears Tower, which ultimately reached 1,450 ft (442 m). With the World Trade Center's destruction, the Empire State Building again became the tallest building in New York, after spending almost 30 years as the third-tallest.

Related Topics:
Chicago - Sears Tower - Empire State Building

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To solve the problem of wind sway or vibration in the construction of the towers, chief engineer Leslie Robertson took a then unusual approach - instead of bracing the buildings corner-to-corner or using internal walls, the towers were essentially hollow steel tubes. Each tower thus contained 240 vertical steel columns called Vierendeel trusses around the outside of the building, which were bound to each other using ordinary steel trusses. In addition, 10,000 dampers were included in the structure. With a strong shell such as this, the internal floors could be simply light steel and concrete with internal walls not needed for structural integrity, creating a tower that was extremely light for its size. This method of construction also meant that the twin towers had the world's highest load-bearing walls. The exterior steel supports were spaced 22 inches (559 mm) apart, and narrow windows filled the gaps in between.

Related Topics:
Wind - Leslie Robertson - Steel - Vierendeel trusses

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Of the 110 stories, eight were set aside for technical services (mechanical floors), in four two-floor areas evenly spread up the building. All the remaining floors were free for open-plan offices. Each tower had 350,000 m² (3.8 million ft²) of office space, ample room for companies to set up shop. Altogether the entire complex of seven buildings had 1.04 km² (11.2 million ft²) of space. During the 1990s some 500 companies, especially financial firms, had offices in the complex, including Morgan Stanley, Aon Corporation, Salomon Brothers, and the Port Authority itself.

Related Topics:
Mechanical floor - Morgan Stanley

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The twin towers were also the first supertall buildings to use sky lobbies, spaces where commuters can switch from one local elevator to another. Located on the 44th and 78th floors of each tower, those sky lobbies enabled the elevators (each tower had 104) to be used efficiently while taking up a minimum of valuable office space.

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Five smaller buildings stood around the 16 acre (65,000 m²) block. One was the 22-floor Vista Hotel, later a Marriott Hotel, that was squeezed between the two towers. Three low-rise buildings in the same hollow tube design as the towers also stood around the plaza; they housed the US Customs Service and the US Commodities Exchange. In 1987, a 46-floor office building called 7 WTC was built north of the block. Under the block was a highly profitable underground shopping mall, which in turn led to various mass transit facilities, particularly the New York City subway system and the Port Authority's own PATH trains connecting Manhattan to Jersey City.

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The excavation of the foundations of the building, known as the Bathtub, located on the former Radio Row, was particularly complicated since there were two subway tubes close by needing protection without service interruption. A six-level basement was built in the foundations. The excavation of about 1 million cubic yards (760,000 m³) of earth and rock created a $90 million real estate asset for the project owner, the Port Authority of New York and New Jersey, which helped offset the enormous loss in revenues which came from the tax breaks given to the Trade Center itself. The soil was used to create 23 acres (93,000 m²) of landfill in the Hudson river next to the World Trade Center site, which became the site of Battery Park City (still under development).

Related Topics:
The Bathtub - Radio Row - Subway - Hudson river - Battery Park City

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One of the world's largest gold depositories was stored underneath the World Trade Center, owned by a group of commercial banks. The 1993 bomb detonated close to the vault, but it withstood the explosion, as did the towers. One source estimates the 1993 value of the gold at one billion dollars, believed to be owned by Kuwaiti interests. That same source claims that when the World Trade Center was destroyed, the amount of gold "far exceed the 1993 levels." The gold was finally recovered in its entirety in late 2001.

Related Topics:
Gold - 1993 - Billion - 2001

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See World Trade Center site for reconstruction news.

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