1.Introduction
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1.Introduction The original idea for a world trade center in New York is generally credited to David Rockefeller, one of industrialist John D. Rockefeller's many grandsons. In fact, the idea was proposed soon after World War II, a decade before Rockefeller ever got involved, but he was the one who actually got the ball rolling. In the 1950s and '60s, while serving as chairman of Chase Manhattan Bank, Rockefeller was dedicated to revitalizing lower Manhattan. He hoped to energize the area with new construction, in much the same way his father revitalized midtown Manhattan in the 1930s with Rockefeller Center. As part of his plan, David Rockefeller proposed a complex dedicated to international trade, to be constructed at the east end of Wall Street. Rockefeller believed that the trade center, which would include office and hotel space, an exhibit hall, a securities and exchange center and numerous shops, would be just the thing to spur economic growth in the area. The original World Trade Center featured landmark twin towers(1 WTC and 2 WTC), which opened on April 4, 1973. The North Tower (left), with antenna spire, is 1 WTC. The South Tower (right) is 2 WTC 33 2.Contruction of the World Trade Center The construction of the World Trade Center was conceived as an urban renewal project, spearheaded by David Rockefeller, to help revitalize Lower Manhattan. On September 20, 1962, the Port Authority announced the selection of Minoru Yamasaki as lead architect, and Emery Roth & Sons as associate architects. Originally, Yamasaki submitted to the Port Authority a concept incorporating twin towers, but with each building only 80 stories tall. Yamasaki remarked that the "obvious alternative, a group of several large buildings, would have looked like a housing project." To meet the Port Authority's requirement to build 10 million square feet (930,000 m²) of office space, the buildings would each need to be 110 stories tall. A major limiting factor in building heights is elevators; the taller the building, the more elevators are needed to service the building, requiring more space-consuming elevator banks. Yamasaki and the engineers decided to use a new system that included sky lobbies, which are floors where people can switch from a large-capacity express elevator, which goes only to the sky lobbies, to a local elevator that goes to each floor in a section (the local elevators can be stacked within the same elevator shaft) 44 Demolition work began on March 21, 1966, to clear thirteen square blocks of low rise buildings in Radio Row for construction of the World Trade Center. Groundbreaking for the construction of the World Trade Center took place on August 5, 1966. (WTC model skyscraper) The topping out ceremony of 1 WTC (North Tower) took place on December 23, 1970, while 2 WTC's ceremony (South Tower) occurred later on July 19, 1971.The first tenants moved into the North Tower in December 1970; the South Tower accepted tenants in January 1972. When the World Trade Center twin towers were completed, the total costs to the Port Authority had reached $900 million. The ribbon cutting ceremony was on April 4, 1973. Over 200,000 tons of steel, 425,000 cubic yards of concrete, a total of 10,000 workers and 7 years, 2 buildings were created known as the World Trade Centers. It's more than its signature twin towers: it was a complex of seven buildings on 16-acres with its own zip code (10048). The twin towers consist of 110 floors, and were ranked as the tallest buildings in the world until the Sears Towers was built in 1974. The towers were built downtown-lower Manhattan Development Association by Chase Manhattan Bank chairman David Rockefeller who believed that the towers would benefit the city. Although the towers were a complete accomplishment 60 workers died during the construction. There were 43,600 windows and 99 elevators that can carry about 55 people with a 10,000 pound capacity and can travel up to 27 feet per second. The towers contained 430 businesses from 26 different countries and held up to 5,000 office workers. It had 6 basements and 3 Subway railway stations. Five different channel news stations were also in the Towers along with medical centers and banks. 5 3. September 11 Attacks The September 11 attacks (also referred to as September 11, September 11th, or 9/11) were a series of four coordinated terrorist attacks launched by the Islamic terrorist group al-Qaeda upon the United States in New York City and the Washington, D.C. area on September 11, 2001. Four passenger airliners were hijacked by 19 al-Qaeda terrorists so they could be flown into buildings in suicide attacks. Two of those planes, American Airlines Flight 11 and United Airlines Flight 175, were crashed into the North and South towers, respectively, of the World Trade Center complex in New York City. Within two hours, both towers collapsed with debris and the resulting fires causing partial or complete collapse of all other buildings in the WTC complex, as well as major damage to ten other large surrounding structures. A third plane, American Airlines Flight 77, was crashed into the Pentagon (the headquarters of the United States Department of Defense), leading to a partial collapse in its western side. The fourth plane, United Airlines Flight 93, was targeted at the United States Capitol in Washington, D.C., but crashed into a field near Shanksville, Pennsylvania after its passengers tried to overcome the hijackers. 6 Flight paths of hijacked planes-September 11 attacks Within 30 minutes of two planes hitting the World Trade Center twin towers, American Airlines Flight 77 departed Dulles International Airport bound for Los Angeles. The Boeing 757 was hijacked and crashed, loaded with 10,000 gallons of fuel, at 345 mph into the west side of the Pentagon. The five-story Pentagon is made up of five pentagonal structures arranged in concentric rings. These rings surround a five-acre open courtyard and are connected by 10 spike-like corridors. The plane took out light poles in the parking lot, hit the ground just outside the outermost ring of the Pentagon, turned up on its wing, and penetrated the E ring (outermost) midway between corridors 4 and 5 as shown below. The Pentagon after the attack 7 Along with the 110-floor Twin Towers, numerous other buildings at the World Trade Center site were destroyed or badly damaged, including WTC buildings 3 through 7 and St. Nicholas Greek Orthodox Church.The North Tower, South Tower, the Marriott Hotel (3 WTC) and 7 WTC were completely destroyed. The U.S. Customs House (6 World Trade Center), 4 World Trade Center, 5 World Trade Center, and both pedestrian bridges connecting buildings were severely damaged. The Deutsche Bank Building on 130 Liberty Street was partially damaged and demolished later. The two buildings of the World Financial Center also suffered damage. The Deutsche Bank Building across Liberty Street from the World Trade Center complex was later condemned as uninhabitable because of toxic conditions inside the office tower, and was deconstructed. The Borough of Manhattan Community College's Fiterman Hall at 30 West Broadway was condemned due to extensive damage in the attacks, and is being rebuilt. Other neighboring buildings including 90 West Street and the Verizon Building suffered major damage but have been restored. World Financial Center buildings, One Liberty Plaza, the Millenium Hilton, and 90 Church Street had moderate damage and have since been restored. Communications equipment on top of the North Tower was also destroyed, but media stations were quickly able to reroute signals and resume broadcasts. The attacks resulted in the deaths of 2,996 people, including the 19 hijackers and 2,977 victims. The victims included 246 on the four planes (from which there were no survivors), 2,606 in New York City in the towers and on the ground, and 125 at the Pentagon. Nearly all of the victims were civilians; 55 military personnel were among those killed at the Pentagon. 8 4. Attacks on the Twin Towers On September 11, 2001, Islamist terrorists hijacked American Airlines Flight 11 and crashed it into the northern façade of the North Tower at 8:46:40 a.m., the aircraft striking between the 93rd and 99th floors. Seventeen minutes later, at 9:03:11 a.m., a second team of terrorists crashed the similarly hijacked United Airlines Flight 175 into the South Tower, striking it between the 77th and 85th floors. The damage caused to the North Tower by Flight 11 destroyed any means of escape from above the impact zone, trapping 1,344 people.Flight 175 had a much more off-centered impact compared to Flight 11, and a single stairwell 9 was left intact; however, only a few people managed to pass through it successfully before the tower collapsed. Although the South Tower was struck lower than the North Tower, thus affecting more floors, a smaller number, fewer than 700, were killed instantly or trapped. At 9:59 a.m., the South Tower collapsed after burning for approximately 56 minutes. The fire caused steel structural elements, already weakened from the plane impact, to fail. The North Tower collapsed at 10:28 a.m., after burning for approximately 102 minutes. At 5:20 p.m.[ on September 11, 2001, 7 World Trade Center started to collapse with the crumble of the east penthouse, and it collapsed completely at 5:21 p.m. owing to uncontrolled fires causing structural failure. The 3 World Trade Center, a Marriott hotel, was destroyed during the collapse of the two towers.