Planning and construction
In 1943, the idea of establishing a World Trade Center in New York City was first proposed. The New York State Legislature authorized Thomas E. Dewey, then Governor of New York, to begin developing plans for the project,[10] but those plans were put on hold in 1949.[11] During the late 1950s and 1960s, New York's economic growth was concentrated in the center of the city, Manhattan, while Lower Manhattan was pushed into the background. To stimulate urban renewal, David Rockefeller suggested that the Port Authority build the World Trade Center in Lower Manhattan.[12].
Initial plans, made public in 1961, identified a site on the East River "East River (New York)") as the construction zone for the World Trade Center. As a bi-state agency, the Port Authority required approval from both the Governors of New York and New Jersey for new projects. Robert B. Meyner, then Governor of New Jersey, opposed New York receiving a $335 million project.[14] Towards the end of 1961, negotiations with Meyner, the outgoing Governor of New Jersey, stalled.[15]
By then, ridership on New Jersey's Hudson and Manhattan Railroad (H&M) had dropped sharply from a peak of 113 million passengers in 1927 to 26 million in 1958, after new tunnels and automobile bridges opened across the Hudson River.[16] In a December 1961 meeting between Astin J. Tobin, director of the Port Authority, and Richard J. Hughes, recently elected Governor of New Jersey, the Port Authority offered to take the Hudson and Manhattan Railroad and transform it into the Port Authority Trans-Hudson (PATH). The Port Authority also decided to move the World Trade Center project to the site of the Hudson Terminal building on the west side of Lower Manhattan, a more convenient location for New Jersey passengers arriving via the PATH.[15] With the new location and the Port Authority's acquisition of the H&M Railroad, New Jersey agreed to support the World Trade Center project.[17].
Approval from New York City Mayor John Lindsay and the New York City Council was also required. Disagreements with the city centered on tax issues. On August 3, 1966, an agreement was reached under which the Port Authority would make annual payments to the city in lieu of paying taxes on the portion of the World Trade Center bid out to private tenants.[18] In later years, payments increased as the real estate tax rate increased.[19]
On September 20, 1962, the Port Authority of New York and New Jersey announced the selection of Minoru Yamasaki as principal architect and Emery Roth and Sons as associate architects.[20] Yamasaki devised a plan that incorporated two twin towers into the complex; In Yamasaki's original plan, each was 80 stories high.[21] To meet the Port Authority's requirement for 930,000 m² of office space, each tower was to be 110 stories high.[22]
An important limitation in this type of construction is the issue of elevators; The taller the building, the more elevators are needed to serve it, which consumes a lot of space. Yamasaki and the engineers decided to use a new system with two special lobbies, which allowed users to go from high-capacity express elevators (stopping only on certain floors) to a local elevator (stopping on all floors in a section). This allowed the design to stack local elevators within a single elevator shaft. Located on the 44th and 78th floors of each tower, the special lobbies allowed the elevators to be used efficiently, increasing the amount of usable space on each floor by 62-75%, by reducing the number of elevator shafts.[23][24] Altogether, the World Trade Center had 95 elevators, including express and local.[25] This system was inspired by that used by the New York Subway, whose lines include express stations, where both express and local trains stop, and local stations, where only local trains stop.[26].
Minoru Yamasaki's design for the World Trade Center, revealed to the public on January 18, 1964, showed for the towers a square base of approximately 63 meters on each side.[27][28] The buildings were designed with narrow, 18-inch-wide windows in the offices, which reflected Yamasaki's fear of heights as well as his desire for tenants to feel safe within the buildings. buildings.[3][29] The design of each tower featured facades clad in aluminum alloy, the pieces of which were assembled one by one as the towers gained height.[30] The World Trade Center was one of the most important implementations of Le Corbusier's architectural ethics, as well as the greatest expression of Yamasaki's Gothic modernist tendencies.[31].
In addition to the twin towers, the plan for the World Trade Center complex included four other low-rise buildings, which were built in the early 1970s. The 47-story 7 World Trade Center building was built in the 1980s, north of the main complex. Altogether, the World Trade Center complex occupied a 65,000 m² superblock.[32].
The structural engineering company Worthington, Skilling, Helle & Jackson worked to put Yamasaki's design into practice, developing the structural tube frame used in the facade of the Twin Towers. The Port Authority's engineering department served as the founding engineers, Joseph R. Loring & Associates as the electrical engineers, and Jaros, Baum & Bolles as the project's mechanical engineers. Tishman Realty & Construction was the general contractor on the World Trade Center project. Guy F. Tozzoli, director of the World Trade Department at the Port Authority, and Rino M. Monti, the Port Authority's chief engineer, oversaw the project.[33] As an interstate agency, the Port Authority was not subject to local laws or New York City regulations, including building codes. However, the World Trade Center's structural engineers ended up following drafts of the new building codes of 1968.[34] The tube frame design, previously introduced by Fazlur Khan, was a new approach that allowed for more open floor plans than the traditional design, which distributed columns through the interior to support the building's loads. The World Trade Center towers used strong and resistant perimeter steel columns, known as Vierendeel trusses, which were located a short distance from each other, thus forming a strong and rigid wall structure, supporting virtually all lateral loads, such as wind, and sharing the load of gravity with the central columns. The perimeter structure, which contained 59 columns per side, was built with extensive use of prefabricated modular pieces, each composed of three columns, three stories high, connected by spandrel plates. These plates were welded to the columns to create the modular pieces off-site, in the manufacturing workshop. parapet plates. The plates were located on each floor, transmitting the shear stress between the columns, allowing them to work together to resist lateral loads. The joints between modules were staggered vertically, so that the column joints between adjacent modules were not on the same floor.[34].
The center of the towers stored the elevator and service shafts, toilets, three staircases and other support spaces. The center of each tower was a rectangular area measuring 27 by 41 meters and contained 47 steel columns that ran from the base to the top of the tower. The large space between the perimeter and the center, free of columns, was segmented vertically by prefabricated floor beams. The floors supported their own weight, as well as live loads, providing lateral stability to the exterior walls and distributing wind loads between these walls.[37] The floors consisted of lightweight concrete slabs 10 centimeters thick, located on a corrugated steel deck. A network of light bridge beams and main beams served as support for the floors.[38] The beams were connected to the perimeter in alternating columns and stood on 2.03 meter bases. The top lines of the beams were bolted to seats welded to the spandrel plates on the exterior side and to a channel welded to the center columns on the interior side. The floors were connected to the perimeter sill plates with viscoelastic dampers that helped reduce the sway perceived by building occupants.
Between the 107th floor and the top of each tower, a large beam was arranged, designed to support a tall communications antenna on the top of each tower.[38] However, only WTC 1 (North Tower) had an antenna, which was added in 1978.[39] The truss system consisted of six trusses arranged on the long side of the core "Core (architecture)"), and four on the short side, which They joined the central core with the perimeter framework of the building. This framing system allowed the redistribution of the load between the perimeter and the central columns, helping to stabilize the efforts caused by the transmission antenna.[38].
The tube frame design, which used a steel core and perimeter columns covered with a fire-resistant material, created a relatively lightweight structure that would sway more in response to wind than traditional structures, such as the Empire State Building, which feature thick, heavy masonry with steel structural elements to protect against fire.[40] During the design process, wind tunnel testing was performed to establish the wind stresses at which the World Trade Center buildings could [41] Experiments were also conducted to assess how much sway the occupants could comfortably tolerate; however, many subjects experienced dizziness and other adverse effects.[42] One of the lead engineers, Leslie Robertson, worked with Canadian engineer Alan G. Davenport to develop viscoelastic shock absorbers to absorb some of the sway. These dampers, used in the structures at the joints between the floor beams and the perimeter columns, together with other structural modifications, reduced the sway of the building to an acceptable level.[43].
In March 1965, the Port Authority began acquiring property at the World Trade Center site. Demolition work began on March 21, 1966 to clear thirteen blocks of low-rise buildings on Radio Row for the construction of the World Trade Center. The cornerstone for the complex's construction was laid on August 5, 1966.
The World Trade Center site was located in a landfill with the bedrock located 20 meters below.[47] To build the WTC, it was necessary to make a "bathtub" with a diaphragm wall around the West Street side of the site, to keep out water from the Hudson River.[48] The containment method, selected by John M. Kyle, Jr., chief engineer of the Port Authority, included the excavation of a trench, which was then filled with a pasty mixture composed of bentonite and water, which plugged the holes and kept groundwater out. When the trench was dug, a steel box was inserted into the site and concrete was poured, forcing the mixture out. It took fourteen months to complete the diaphragm wall, which was necessary to begin excavating material from within the site.[49] The 917,000 m³ of excavated material was used (along with other fill material) to expand the Manhattan waterfront across West Street, thus forming Battery Park City.[50][51].
In January 1967, the Port Authority awarded $74 million in contracts to various steel suppliers, and Karl Koch was hired to erect the steel. Tishman Realty & Construction was hired in February 1967 to oversee construction of the project. Construction work began on the North Tower in August 1968; Construction of the South Tower was already underway in January 1969.[54] The original Hudson Tubes, which carried PATH trains to Hudson Terminal, remained in service as elevated tunnels during the construction process, until 1971, when a new PATH station opened.[55].
The completion ceremony for WTC 1 (North Tower) was on December 23, 1970, while the ceremony for WTC 2 (South Tower) occurred later, on July 19, 1971.[54] The first tenants moved into the North Tower in December 1970; the South Tower accepted tenants in January 1972.[56] By the time the Twin Towers of the World Trade Center were completed, total costs to the Port Authority had reached $900 million.[1] The groundbreaking ceremony was held on April 4, 1973.[57].
Plans to build the World Trade Center were controversial. The site where the World Trade Center was built was previously located Radio Row, a place specializing in the sale of radio equipment and parts,[58] which was also home to hundreds of commercial and industrial tenants, property owners, small businesses and approximately 100 residents, many of whom presented strong resistance to the forced relocation.[59] A group of affected small businesses filed an injunction challenging the Port Authority's power of expropriation.[60] The case made its way through the judicial system until it reached the Supreme Court of the United States, which refused to accept it.[61][62] In February 1964, a group of “anti-Twin Towers” merchants and activists reported that there was a danger to the safety of the future towers in the event of an explosion or plane crash.[62].
Some private real estate developers and members of the New York Real Estate Board, led by Lawrence A. Wien, owner of the Empire State Building, expressed concern about this large amount of "subsidized" office space, which was on the open market, competing with the private sector when there was already a glut of vacancies.[63][64][62] The World Trade Center itself was not fully leased until after 1979.[65] Others They questioned whether the Port Authority should really accept a project described by some as a "misguided social priority".[66]
The World Trade Center design brought criticism for its aesthetics from the American Institute of Architects and other groups.[30][67] Lewis Mumford, author of The City in History and other books on urban planning, criticized the project and described it and other new skyscrapers as "mere filing cabinets of glass and metal."[68]The narrow office windows of the Twin Towers, just 18 inches wide and framed with pillars Activist and sociologist Jane Jacobs also criticized the plans for the construction of the WTC, arguing that the coastline should be left open for the enjoyment of New Yorkers.[69]
The commercial center superblock, replacing the dense, more traditional neighborhood, was seen by some critics as an inhospitable environment that disrupted Manhattan's complicated traffic network. For example, in his book The Pentagon of Power, Lewis Mumford denounced the center as an "example of the purposeless gigantism and technological exhibitionism that today eviscerate the living fabric of every great city."[70]
For many years, the immense Austin J. Tobin Plaza (also known as World Trade Center Plaza) was frequently beset by strong winds at ground level.[71] In fact, some gusts were so strong that pedestrians had to be assisted by ropes to walk.[72] In 1999, the outer plaza reopened after undergoing some $12 million in renovations, which included replacing marble pavers with gray stones and granite roses, the addition of new benches, flower pots, new restaurants, food kiosks and outdoor dining areas.[73].
Complex
In the 1980s, with the construction of 7 World Trade Center, the World Trade Center had a total of seven buildings, but the most notable were the two main towers. Each rose to a height of 410 meters, and occupied about one of the 16 acres (65,000 m²) of land occupied by the complex. During a press conference in 1973, a journalist asked Yamasaki, "Why two 110-story buildings?" Why not a 220-story building? His response was: "I didn't want to lose the human scale."[74].
When it was completed in 1972, 1 World Trade Center (the North Tower) became, for two years, the tallest building in the world, surpassing the Empire State Building, which had held the title for 40 years. The North Tower was 417 meters high and featured a telecommunications antenna or mast that was added to the roof in 1978 and was 110 meters high. With this antenna, the highest point of the North Tower reached 527 meters. World Trade Center 2 (the South Tower) became the second tallest building in the world when it was completed in 1973. The observation deck on the roof of the South Tower was 415 meters high and the observation deck inside the tower was 400 meters high.[75] The World Trade Center towers held the height title for only a brief time: the Willis Tower in Chicago, completed in May 1973, reached 440 meters to the roof.[76] Throughout their existence, however, the WTC towers had more floors (110) than any other building. This number was not surpassed until the construction of the Burj Khalifa in Dubai, which opened in 2010.
Of the 110 floors, eight were kept aside for technical services on the B5/B6 level technical floors (floors 7/8, 41/42, 75/76 and 108/109), which are four two-story areas spaced evenly in the building. All remaining floors were free for open plan offices. Each floor of the towers had 3,700 m² of space to be occupied.[25] Each tower had 350,000 m² of office space. Altogether, the entire complex of seven buildings had 1,040,000 m² of space.
Initially conceived as a complex dedicated to companies and organizations that directly took part in the "world of commerce", it was initially unsuccessful in attracting the expected clients. During the first years, several government organizations became key tenants of the World Trade Center, including the State of New York. It was not until the 1980s that the city's perilous financial state improved, after which a growing number of private companies, mainly financial firms associated with Wall Street, became tenants. During the 1990s, approximately 500 companies had offices in the complex, including many financial companies, such as Morgan Stanley, Aon Corporation, Salomon Brothers, and the Port Authority itself. The World Trade Center basement confluence included the World Trade Center Mall along with a PATH station "World Trade Center (PATH station)". The North Tower became the corporate headquarters of Cantor Fitzgerald,[77] as well as the headquarters of the Port Authority of New York and New Jersey.[78].
History, events and occurrences
On a typical weekday, 50,000 people worked at the Twin Towers,[90] with another 200,000 stopping by as visitors.[91] The complex was so large that it had its own ZIP code: 10048.[92] The towers offered a great view from the Top of the World Trade Center Observatories observation deck, atop the South Tower, and from the Windows on the World restaurant, atop of the North Tower. The Twin Towers became known around the world, appearing in numerous films and television shows, as well as on postcards and other marketing media, and began to be seen as an icon of New York, on the same level as the Empire State Building, the Chrysler Building, and the Statue of Liberty.[93]
French tightrope walker Philippe Petit walked between the towers on a tightrope in 1974, as shown in the film On the Tightrope "The Walk (film)"). He crossed the 43 meters that separated the two buildings eight times. In total it was a 45-minute adventure more than 400 meters above the ground.[94].
George Willing, a Brooklyn toy maker, scaled the outside of the South Tower in 1977.[95] In 1983, on Memorial Day, high-rise activist, firefighter, and rescuer Dan Goodwin successfully scaled the outside of the WTC's North Tower. Their action was intended to draw attention to the impossibility of rescuing people potentially trapped on upper floors of skyscrapers.[96][97].
The 1995 World Chess Championship "1995 World Chess Championship (Classical)") was played on the 107th floor of the South Tower.[98].
On February 13, 1975, a fire broke out in the North Tower of the WTC, which spread throughout the 11th floor. This fire spread through the core to the 9th and 14th floors after the insulation of the telephone cables located in a service shaft that ran vertically between the floors caught fire. The fire that reached other areas was extinguished almost immediately, and the original fire was put out within a few hours. Most of the damage was concentrated on the 11th floor, as the fire was fueled by cabinets filled with paper, alcohol-based office machine fluid and other office supplies. There was no structural damage to the tower, as the steel was covered by a fire-resistant material. Other than the damage caused by the fire, some floors below suffered damage caused by the water used to extinguish the fire above. At that time, the World Trade Center did not have fire sprinkler systems.[99][100].
On February 26, 1993, at 12:17, a Ryder truck containing 680 kilograms of explosives, parked by Ramzi Yousef, exploded in the underground parking lot of the North Tower. Throughout the tower's 110 floors, six people died and another 50,000 workers and visitors were left without enough air to breathe normally. Many people inside the North Tower were forced to descend stairs in the dark that did not have emergency lighting, some taking more than two hours to reach safety.[103][104].
Destruction
On Tuesday, September 11, 2001, a group of terrorists, belonging to Al-Qaeda, hijacked 2 commercial flights: American Airlines Flight 11 and crashed it into the north façade of the North Tower, at 8:46:40 a.m.; The plane impacted between the 93rd and 99th floors. 17 minutes later, at 9:02:54, a second team of terrorists crashed the also hijacked (and in a similar manner to the previous one) United Airlines Flight 175 into the South Tower; the impact occurred between the 77th and 85th floors.[124][2] The damage caused to the North Tower by Flight 11 destroyed all means of escape from above the impact area, trapping 1,344 people.[125] Flight 175, compared to that of Flight 11, had a much less centered impact, and a single staircase was left intact; However, only 18 people managed to pass through it successfully before the tower collapsed. Although the South Tower was hit lower than the North Tower, thus affecting more floors, a smaller number of people, just under 700, died instantly or were trapped.[126]
At 9:59, the South Tower collapsed, after burning for approximately 56 minutes. The fire caused steel structural elements, already weakened by the plane's impact, to fail. The North Tower collapsed at 10:28, after burning for approximately 102 minutes.[2][127] At 5:20 pm[128] on September 11, 2001, 7 World Trade Center began to collapse, with the east eave falling, and completely collapsed at 5:21 pm,[128] due to the uncontrolled fire. caused a structural failure.[129].
The 3 World Trade Center, a Marriott hotel, was destroyed during the collapse of the two towers. The three remaining buildings in WTC Plaza were severely damaged by debris and were later demolished.[130] The Deutsche Bank building, across Liberty Street (Manhattan) from the World Trade Center complex, was later condemned due to the uninhabitable toxic conditions inside; It was deconstructed, with work completed in early 2011.[131][132] The Fiterman Hall of the Manhattan Township Community College, located at 30 West Broadway, was also condemned, due to serious damage received in the attacks, and is scheduled for deconstruction.[133].
Immediately after the attacks, press reports suggested that tens of thousands of people could have been killed in the attacks, as more than 50,000 could be inside the towers. Recently, 2,753 death certificates (excluding those of the hijackers) were submitted in connection with the 9/11 attacks in New York, including one submitted for Felicia Dunn-Jones), who was added to the official death toll in May 2007; Dunn-Jones") died five months later from a lung condition "connected with his exposure to dust during the World Trade Center collapse. Three other victims were later added to the official death toll by the city coroner's office: Dr. Sneha Anne Philip, last seen the day before the attacks, Len Heyward"), a man who developed lymphoma and later died in 2008 as a result of breathing in dust during the attacks. events following the attacks on the Twin Towers,[135][136] and Jerry Borg, who died in December 2010 of pulmonary sarcoidosis, which was determined in June 2011 to be a result of dust from the attacks.[9] Cantor Fitzgerald L.P., an investment bank located on floors 101 to 105 of the North Tower, lost 658 employees, considerably more than any other company,[137] while Marsh & McLennan Companies, located immediately below Cantor Fitzgerald, on floors 93 to 100 (the impact site of Flight 11), lost 295 employees, and 175 Aon Corporation employees died in the South Tower.[138] Additionally, 343 of the dead were New York City firefighters, 84 were Port Authority workers, of whom 37 were members of the Department of Port Authority Police, and 23 others were New York City Police Department officers.[139][140][141] Ten years after the attacks, in 2011 only 1,629 victims have been identified.[142] Of all the people who were still in the towers when they collapsed, only 20 were rescued alive. McLoughlin, Port Authority police officers, were the 18th and 19th survivors.[143] The last person rescued after the collapse was found after 27 hours of rescue work.[144] After these 20 survivors, it is estimated that an undetermined number of people may have survived for a time in the rubble, but lost their lives when their rescue was not possible.