Construction work began on the North Tower in August 1968 with construction beginning on the South Tower by January 1969. In January 1967, $74 million in contracts were awarded to the Pacific Car and Foundry Company, Laclede Steel Company, Granite City Steel Company, and Karl Koch Erecting Company to supply steel for the project. The Port Authority chose to use many different steel suppliers, bidding on smaller portions of steel, rather than buy larger amounts from a single source such as Bethlehem Steel or U.S. Steel as a cost-saving measure. Karl Koch was also hired to do all the work of erecting the steel, and a contract for work on the aluminum facade was awarded to the Aluminum Company of America.
Twin Towers
Construction of the World Trade Center
Construction of the World Trade Center | Twin Towers
August 1968 The North Tower in August 1968 and the South Tower by January 1969. 21 March 1965. Construction work began on the North Tower in August 1968 with construction beginning on the South Tower by January 1969
when did construction start on the twin towers
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At the time of their completion the "Twin Towers"—the original 1 World Trade Center (the North Tower), at 1,368 ft (417 metres), and 2 World Trade Center (the South Tower)—were the tallest buildings in the world. The other buildings in the complex included the Marriott World Trade Center (3 WTC), 4 WTC, 5 WTC, 6 WTC, and 7 WTC. All of these buildings were built between 1975 and 1985, with a construction cost of $400 million (equivalent to $ in dollars). The complex was located in New York City's Financial District and contained of office space. The World Trade Center experienced a fire on , 1975, a bombing on , 1993 and a robbery on , 1998.
World Trade Center site | Original buildings
The original twin towers took less than three years from start of construction to be finished and five years from the beginning planning stages. However, given the complexity and highly political nature of the rebuilding efforts, they are often cited as an example of a successful public-private collaboration and are taught as a case study in successful negotiations.
World Trade Center site | Planning for the new World Trade Center
Construction resumed in August 2014, and the building opened on June 11, 2018.
World Trade Center site | Towers
There was much debate regarding the future of Ground Zero following the destruction of the World Trade Center. Disagreement and controversy regarding who owned the property and what would be built there hindered construction at the site for several years. Many wanted the Twin Towers to be rebuilt, but at a taller height than before. The project for the new Twin Towers was called Twin Towers II, which was led by an informal organization called the Twin Towers Alliance. Others did not want anything built there at all or wanted the entire site to become a memorial. Finally, a master plan was agreed upon, which would feature a memorial and museum where the original Twin Towers stood and six new skyscrapers surrounding it.
World Trade Center (2001–present) | Controversy and criticism
After a two-year stoppage in above-ground construction, the tower project itself started in August 2014, and the building opened on June 11, 2018.
World Trade Center (2001–present) | Towers
Tishman Realty & Construction was hired in February 1967 to oversee construction of the project. Extensive use of prefabricated parts for the perimeter framing and floor truss systems helped speed up the construction process and reduce costs, while providing greater quality control. Steel components were freighted into a Penn Central (later Conrail) yard in Jersey City. From there, they were brought in the early morning hours through the Holland Tunnel to the construction site, then lifted into place by a crane. Larger pieces were brought to the construction site by tugboats. A special type of crane, suitable for constructing such tall buildings, that used hydraulics to lift components and provided its own power was used in construction of the World Trade Center.
Construction of the World Trade Center | Twin Towers
Construction work began on the North Tower in August 1968 with construction beginning on the South Tower by January 1969. In January 1967, $74 million in contracts were awarded to the Pacific Car and Foundry Company, Laclede Steel Company, Granite City Steel Company, and Karl Koch Erecting Company to supply steel for the project. The Port Authority chose to use many different steel suppliers, bidding on smaller portions of steel, rather than buy larger amounts from a single source such as Bethlehem Steel or U.S. Steel as a cost-saving measure. Karl Koch was also hired to do all the work of erecting the steel, and a contract for work on the aluminum facade was awarded to the Aluminum Company of America.
Construction of the World Trade Center | Twin Towers
In all, 60 workers were killed in construction accidents while the World Trade Center was being built.
Construction of the World Trade Center | Twin Towers
One World Trade Center and Two World Trade Center, commonly referred to as the Twin Towers, were designed by architect Minoru Yamasaki as framed tube structures, which provided tenants with open floor plans, uninterrupted by columns or walls. They were the main buildings of the World Trade Center. Construction of the North Tower at One World Trade Center began in 1966 with the South Tower at Two World Trade Center. When completed in 1972, 1 World Trade Center became the tallest building in the world for two years, surpassing the Empire State Building after its 40-year reign. The North Tower stood tall and featured a telecommunications antenna or mast that was built on the roof in 1978.
World Trade Center (1973–2001) | North and South Towers
Their floor counts were not matched until the construction of the Sears Tower, and they were not surpassed until the construction of the Burj Khalifa, which opened in 2010. Each tower had a total mass of around 500,000 tons.
World Trade Center (1973–2001) | North and South Towers
When the World Trade Center twin towers were completed, the total costs to the Port Authority had reached $900 million. The ribbon cutting ceremony took place on , 1973.
World Trade Center (1973–2001) | Construction
The original World Trade Center was a large complex of seven buildings in the Financial District of Lower Manhattan, New York City, United States. It opened on April 4, 1973, and was destroyed in 2001 during the September 11 attacks. At the time of their completion, the Twin Towers—the original 1 World Trade Center (the North Tower), at ; and 2 World Trade Center (the South Tower), at —were the tallest buildings in the world. Other buildings in the complex included the Marriott World Trade Center (3 WTC), 4 WTC, 5 WTC, 6 WTC, and 7 WTC. The complex contained of office space.
World Trade Center (1973–2001) | Introduction
He favored the 80-story twin-tower plan, but found that it did not meet the Port Authority's requirements. At the time, it was not considered economical to build an office building with more than 80 floors.
Construction of the World Trade Center | Search for an architect
The buildings are among many created by the World Trade Centers Association. The original World Trade Center comprised the Twin Towers, which opened in 1973 and were the tallest buildings in the world at the time of their completion. They were destroyed on the morning of September 11, 2001, when al-Qaeda-affiliated hijackers flew two Boeing 767 jets into the complex in a coordinated act of terrorism. The attacks on the World Trade Center killed 2,753 people. The resulting collapse of the World Trade Center caused structural failure in the surrounding buildings as well. The process of cleaning up and recovery at the World Trade Center site took eight months, after which rebuilding of the site commenced.
World Trade Center (2001–present) | Introduction
By the end of 2007, the tower's footings and foundations were nearly complete.
Construction of One World Trade Center | 2004–2007
A seventh building was built in the mid-1980s.
One World Trade Center | Construction
After Seven World Trade Center was built in the 1980s, the World Trade Center complex had a total of seven buildings; however, the most notable ones were the main Twin Towers built in the 1970s—One World Trade Center was the North Tower, and Two World Trade Center was the South Tower. Each tower was over high, and occupied about of the total of the site's land. During a press conference in 1973, 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." When it was topped out on October, 1971, One World Trade Center became the tallest building in the world, surpassing the Empire State Building, which had held the record for 40 years.
One World Trade Center | Specifications and operations
The World Trade Center complex included four other smaller buildings constructed during the 1970s. 3 World Trade Center was a 22-story building, which was home to the Marriott World Trade Center. It was designed by Skidmore, Owings and Merrill in 1978–79. 4 World Trade Center, 5 World Trade Center, and 6 World Trade Center were all 8–9 story buildings that were designed by the same team as the Twin Towers, including Minoru Yamasaki; Emery Roth & Sons; and Skilling, Helle, Christiansen, Robertson. 7 World Trade Center was built in the mid-1980s, just north of the main World Trade Center site.
Construction of the World Trade Center | Other buildings
After the September 11 attacks in 2001, several ideas about building new twin towers were discussed online and in the media. After the Lower Manhattan Development Corporation (LMDC) launched the World Trade Center Site Memorial Competition in 2002, seven architectural groups were commissioned by the organization to create a proposal to restore the Manhattan skyline. Out of the seven, four groups proposed building twin towers though they were not identical to the original design by Minoru Yamasaki. After Daniel Libeskind's Memory Foundations design was favored and then chosen by the Lower Manhattan Development Corporation in 2003, the proposed twin-towered designs were rejected.
Twin Towers 2 | Background (2001–2003)
Beside the towers, an above-ground memorial would have occupied the footprints of the original towers. The new site would also have featured three 12-story buildings, replacing the original 3, 4 and 5 World Trade Center. The complex was designed and developed by American architect Herbert Belton and American engineer Kenneth Gardner, and sponsored by Donald Trump.
Twin Towers 2 | Introduction
In June 1975 a coalition of labor unions distributed a pamphlet to arriving visitors, warning them to stay away. The opening of the mammoth World Trade Center complex in 1972, however, was one of the few high points of the city's history at that time. Conceived by David Rockefeller and built by the Port Authority of New York and New Jersey on the site of the Radio Row electronics district in Lower Manhattan, the Twin Towers displaced the Empire State Building in Midtown as the world's tallest building; it was displaced in turn by Chicago's Sears Tower in 1973.
History of New York City (1946–1977) | 1970s
The design and construction of the towers involved many other innovative techniques, such as wind tunnel experiments and the slurry wall for digging the foundation. Yamasaki also incorporated elements of Islamic architecture in the building's design, having previously designed Saudi Arabia's Dhahran International Airport with the Saudi Binladin Group. Construction of the North Tower (One World Trade Center) began in August 1966; extensive use of prefabricated components sped up the construction process. The first tenants moved into the North Tower in October 1971. In the 1970s, four other low-level buildings were built as part of the World Trade Center complex.
One World Trade Center | Construction
Since its construction began, One World Trade Center has been seen in many films, TV series and video games, while under construction. The tower began construction in 2006 and lasted until 2013. Films, TV shows and video games released from 2006 to 2013 will show the tower under construction, unless they were released during this period but set at a later date; e.g. "", which shows the tower completed.
One World Trade Center in popular culture | Introduction
The construction of the World Trade Center, of which the Twin Towers (One and Two World Trade Center) were the centerpieces, was conceived as an urban renewal project and spearheaded by David Rockefeller. The project was intended to help revitalize Lower Manhattan. The project was planned by the Port Authority of New York and New Jersey, which hired architect Minoru Yamasaki. He came up with the idea of building twin towers. After extensive negotiations, the New Jersey and New York State governments, which supervise the Port Authority, consented to the construction of the World Trade Center at the Radio Row site, located in the lower-west area of Manhattan.
One World Trade Center | Construction
With this addition, the highest point of the North Tower reached . Chicago's Sears Tower, finished in , reached at the rooftop. When completed in 1973, the South Tower became the second tallest building in the world at . Its rooftop observation deck was high and its indoor observation deck was high. Each tower stood over high, and occupied about of the total of the site's land. During a press conference in 1973, Yamasaki was asked, "Why two 110-story buildings? Why not one 220-story building?" His tongue-in-cheek response was: "I didn't want to lose the human scale." Throughout their existence, the twin towers had more floors (at 110) than any other building.
World Trade Center (1973–2001) | North and South Towers
Details about proposals for the site, or construction timelines have yet to emerge.
5 World Trade Center | Introduction
The Favco Standard 2700 Crane, manufactured by Favelle Mort Ltd. of New South Wales, Australia was informally called a "kangaroo crane." In 1970, tugboat workers went on strike, halting the transport of material to the construction site. The Port Authority attempted other means of transporting material, including via helicopter. When this method was tried, the helicopter lost its load of steel into the Kill Van Kull. Some other mishaps occurred during the construction process, including disruption of telephone service in Lower Manhattan when telephone cables were crushed by pile drivers. On March 16, 1970, an explosion injured six workers when a truck hit a propane tank.
Construction of the World Trade Center | Twin Towers
The result of the competition and the design chosen by the LMDC was criticized by the public, including architectural critic Herbert Muschamp as well as Donald Trump. The twin-towered Team Twin Towers design was planned to be entered into the World Trade Center Site Memorial Competition, but was unable to complete the design before the competition closed.
Twin Towers 2 | Background (2001–2003)
Criticism arose in 2008 that the rebuilding of the World Trade Center was taking longer than expected. Though now-renamed One World Trade Center (formerly Freedom Tower) was under construction as well as the National September 11 Memorial & Museum, it was still proposed to halt One World Trade Center and build the Twin Towers II project. "Seeing them go up could be as powerful as seeing them go down." Ken Gardner stated, engineer of the project. Members of the Twin Towers Alliance, an organization supporting the rebuilding of new twin towers, gathered in July 2008 in Central Park to rally for the cause.
Twin Towers 2 | Later development (2008–2009)
It is the opinion of scientific skeptics that mediumship is a con, and the claimed paranormal powers of the twins is no exception. The Jamisons widely claim to have predicted the September 11 attacks on the World Trade Center during a November 2, 1999 interview on the Art Bell radio show. However, according to show transcripts, their actual statement was: "We are seeing terrorist attacks on Federal Government, excuse me, federal buildings. Particularly South Carolina or Georgia, by July 2002 and also the New York Trade Center, the World Trade Center in 2002." The September 11 attack occurred in 2001, not 2002, and it was common knowledge that the buildings had been previously attacked by terrorists in the 1993 World Trade Center bombing, calling into question the Jamisons' claims.
Linda and Terry Jamison | Critical analysis
Upon completion, the Twin Towers were briefly the tallest buildings in the world, and at the time of the terrorist attacks they were still in the top five. One World Trade Center (WTC 1) the "North Tower" was, at , six feet taller than Two World Trade Center (WTC 2) the "South Tower", which stood tall. At the time of the attacks only the then recently completed Petronas Towers in Kuala Lumpur, Malaysia and the Willis Tower (known then as the Sears Tower) in Chicago were taller. Built with a novel design that maximized interior space, the towers had a high strength to weight ratio as they utilized a new "framed tube" design that required 40 percent less steel than more traditional steel framed skyscrapers.
Collapse of the World Trade Center | Background
The initial planning of the project first surfaced in the media in 2004 with the group behind the project called Team Twin Towers, Inc., composed of activists and designers collaborating on the early design of the model. The team was initially led by television producer and co-founder of the team Randy Warner, and the design led by engineer Kenneth "Ken" Gardner and architect Herbert Belton, who was an architect for the original World Trade Center. Their spokesman was Jonathan Hakala, a venture capitalist who had been a tenant on the 77th floor of the original North Tower. The project design was called the "Plan of the People", and would be identical to the original Yamasaki design.
Twin Towers 2 | Initial emergence (2004)
In September 2005, the National Institute of Standards and Technology (NIST) published the results of its investigation into the collapse. The investigators did not find anything substandard in the design of the twin towers, noting that the severity of the attacks was beyond anything experienced in buildings in the past. They determined the fires to be the main cause of the collapses, finding that sagging floors pulled inward on the perimeter columns, causing them to bow and then to buckle. Once the upper section of the building began to move downwards, a total progressive collapse was unavoidable.
Collapse of the World Trade Center | Introduction
Lewis Mumford, author of "The City in History" and other works on urban planning, criticized the project, describing it and other new skyscrapers as "just glass-and-metal filing cabinets". The Twin Towers were described as looking similar to "the boxes that the Empire State Building and the Chrysler Building came in". Many disliked the twin towers' narrow office windows, which were only wide and framed by pillars that restricted views on each side to narrow slots. Activist and sociologist Jane Jacobs argued the waterfront should be kept open for New Yorkers to enjoy.
World Trade Center (1973–2001) | Criticism
This had been considered a priority since restoring Con Edison's electrical substation in the building's lower floors was necessary to meet power demands of Lower Manhattan.
World Trade Center (2001–present) | Early construction and final planning
This marked the official start of construction of the National September 11 Memorial & Museum, though not without controversy and concerns from some family members. In , the Port Authority and Larry Silverstein reached an agreement in which Silverstein ceded rights to develop Towers One and Five in exchange for financing with Liberty Bonds for Towers Two, Three, and Four. On , 2006, a ground-breaking ceremony was held for the Freedom Tower. The building was designed to be tall, the height of the original World Trade Center north tower, and its spire rises to the symbolic height of 1,776 feet (541 m), a reference to the year in which the United States Declaration of Independence was signed.
World Trade Center (2001–present) | Early construction and final planning
Phase 1 of construction was completed in 1990. Phase 2 was completed in 1999, and Phase 3 started in 2005. Phase 3A was completed in August 2010. The original construction was designed by architects Robert Sobel/Emery Roth & Sons with associate architect Nikken Sekkei. Phase 3 was designed by architects Skidmore, Owings and Merrill.
The China World Trade Center | Introduction
The core complex was built between 1966 and 1975, at a cost of $400 million (equivalent to $2.27 billion in 2018). During its existence, the World Trade Center experienced several major incidents, including a fire on , 1975, a bombing on , 1993, and a bank robbery on , 1998. In 1998, the Port Authority of New York and New Jersey decided to privatize it by leasing the buildings to a private company to manage. It awarded the lease to Silverstein Properties in . On the morning of September 11, 2001, Al-Qaeda-affiliated hijackers flew two Boeing 767 jets into the Twin Towers within minutes of each other; two hours later, both towers collapsed.
World Trade Center (1973–2001) | Introduction
The World Trade Center design brought criticism of its aesthetics from the American Institute of Architects and other groups. Lewis Mumford, author of "The City in History" and other works on urban planning, criticized the project and described it and other new skyscrapers as "just glass-and-metal filing cabinets." Television broadcasters raised concerns that the World Trade Center twin towers would cause interference in television reception for viewers in the New York City area, who were getting their broadcasts from the Empire State Building at that time. In response to these concerns, the Port Authority offered to provide new television transmission facilities at the World Trade Center.
Construction of the World Trade Center | Design revealed
A federal technical building and fire safety investigation of the collapses of the Twin Towers was conducted by the United States Department of Commerce's National Institute of Standards and Technology (NIST). The goals of this investigation, completed on April 6, 2005, were to investigate the building construction, the materials used, and the technical conditions that contributed to the outcome of the WTC disaster. The investigation was to serve as the basis for: The report concludes that the fireproofing on the Twin Towers' steel infrastructures was blown off by the initial impact of the planes and that, if this had not occurred, the towers would likely have remained standing.
U.S. government response to the September 11 attacks | Collapse of the World Trade Center
In January 1967, the Port Authority awarded $74 million in contracts to various steel suppliers. Construction work began on the North Tower in , and construction on the South Tower was under way by . The original Hudson Tubes, which carried PATH trains into Hudson Terminal, remained in service during the construction process until 1971, when a new station opened. The topping out ceremony of 1 WTC (North Tower) took place on , 1970, while 2 WTC's ceremony (South Tower) occurred on , 1971. Extensive use of prefabricated components helped to speed up the construction process, and the first tenants moved into the North Tower in , while it was still under construction, while the South Tower began accepting tenants in .
World Trade Center (1973–2001) | Construction
Since 2008, news of the project, as well as if it could still be built, had not been mentioned. Due to the completion of One World Trade Center and Four World Trade Center, as well as the National September 11 Memorial & Museum since then, it is unlikely that the project will ever be built at the World Trade Center site. Since the project had been considered moot, Ken Gardner, the engineer of the project, made a comment that he considered voting for Donald Trump, who is now the 45th President of the United States. Bjarke Ingels, who was selected as the architect for Two World Trade Center's new design, stated that he would have rebuilt the World Trade Center if it were up to him.
Twin Towers 2 | Project abandonment (2010)
The design was finalized in 2004, but was revised extensively after the NYPD raised security concerns, which delayed the start of the construction by two years. In 2006, the Port Authority took over from Silverstein Properties. The project's developer Tishman Construction Corporation was the construction manager at the time. Construction began in April 2006. Digging the foundation and installing tower-foundation steel columns, concrete, and rebar took twice as long as it normally would due to the existence of the subway line under West Broadway nearby. The building reached grade level by 2010, progressed at a pace of one floor a week, topped out in August 2012, and was structurally completed in May 2013.
World Trade Center site | Towers
Construction slowed again from late June till mid July due to high temperatures which caused the building to remain at roof level, leading to a delay in the installation of the antenna spire. With temperatures easing by July 16, construction crews began installing parapet steel at the top of 1 WTC. On July 18, the first node steel was installed. On July 31, 2012, all corner parapet columns, also called "node steel", were installed around the perimeter of the tower. A special beam, signed by the U.S. President Barack Obama, local officials and the construction workers, was raised on August 2, 2012.
Construction of One World Trade Center | 2012
Six towers, a 9/11 memorial and museum, a mall, a transportation hub, a parking lot, a park, a church, and a performing arts venue are to eventually occupy the new World Trade Center. As of March 2020, progress on the construction of the redesigned site was as follows:
World Trade Center (2001–present) | Structures
It's a living memorial, and I think it's more powerful than pretending 9/11 never happened." The main twin towers originally would feature a 500-foot-high mast on top of the North Tower, which would bring its total height to 1,888 feet, which at the time would have made it the tallest building in the world surpassing the 1,667-foot-high Taipei 101 in Taipei, Taiwan. The two towers were planned to be 112 stories tall. Team Twin Towers was one of several groups pressuring government and development officials to alter the reconstruction plans of the Daniel Libeskind master plan chosen by the Lower Manhattan Development Corporation.
Twin Towers 2 | Initial emergence (2004)
The original World Trade Center had a massive, five-acre plaza which all other buildings, including the Twin Towers centered around. In 1982, the immense plaza between the twin towers was renamed after the man who authorized the construction of the original World Trade Center. Port Authority's late chairman, Austin J. Tobin. During the summer, the Port Authority installed a portable stage, typically backed up against the North Tower within Tobin Plaza for performers. The odd layout for performances was due to the installation of a sculpture in the center of the plaza, which only allowed for about 6,000 fans. For many years, the Plaza was often beset by brisk winds at ground level owing to the Venturi effect between the two towers.
World Trade Center (1973–2001) | Austin J. Tobin Plaza
In addition, The Port Authority of New York and New Jersey reported in their 2009 Q3 Annual Report that steel erection should commence by January 2010, and that the typical floor construction could begin.
Construction of One World Trade Center | 2009
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." The Port Authority mandated that of office space be included in the new World Trade Center, but tasked Yamasaki with determining how to arrange that space. As a result, Yamasaki tested out different possible designs, including spreading out the space across three or four towers, as well as condensing the space within two 80-story towers. His other plans included a single, very large tower and ten moderately large buildings.
Construction of the World Trade Center | Search for an architect
It had a roof height of . Construction began in 1979 and it opened in July 1981 as the Vista International Hotel. The entire World Trade Center complex was destroyed during the September 11 attacks in 2001. Construction originally began in 2010, but was delayed until 2014 because of a lack of an anchor tenant. The building's concrete core was topped out to maximum height in August 2016, with the perimeter steel structure following on October 6, 2016. The building opened on June 11, 2018. The building was designed by Rogers Stirk Harbour + Partners, and is managed by Silverstein Properties through a ground lease with the Port Authority of New York and New Jersey, the landowner.
3 World Trade Center | Introduction
The World Trade Center was built using prefabricated parts which were bolted or welded together at the site. This process dramatically reduced construction time and costs. Using this process, t-beams and other types of cross beams were created and used in each of the World Trade Center buildings. The Twin Towers' collapse sent debris down onto Six World Trade Center, and gutted the interior of that building; the intact cross beam later found in 6 World Trade Center's debris is believed to have come from the North Tower. Following the terrorist attacks, a massive operation was launched to clear the site and attempt to find any survivors amongst the rubble.
World Trade Center cross | Context
The World Trade Center complex housed more than 430 companies that were engaged in various commercial activities. On a typical weekday, an estimated 50,000 people worked in the complex and another 140,000 passed through as visitors. The complex hosted of office space, and was so large that it had its own zip code: 10048. The towers offered expansive views from the observation deck atop the South Tower and the Windows on the World restaurant on top of the North Tower. The Twin Towers became known worldwide, appearing in numerous movies and television shows as well as on postcards and other merchandise.
World Trade Center (1973–2001) | Complex
After extensive negotiations, the New Jersey and New York state governments agreed to support the World Trade Center project, which was built at the site of Radio Row in the Lower West Side of Manhattan, New York City. To make the agreement acceptable to New Jersey, the Port Authority agreed to take over the bankrupt Hudson & Manhattan Railroad, which brought commuters from New Jersey to the Lower Manhattan site and, upon the Port Authority's takeover of the railroad, was renamed PATH. The Port Authority hired architect Minoru Yamasaki, who came up with the specific idea for twin towers. The towers were designed as framed tube structures, which provided tenants with open floor plans, uninterrupted by columns or walls.
Construction of the World Trade Center | Introduction
This was accomplished using numerous closely spaced perimeter columns to provide much of the strength to the structure, along with gravity load shared with the core columns. The elevator system, which made use of sky lobbies and a system of express and local elevators, allowed substantial floor space to be freed up for use as office space by making the structural core smaller. The design and construction of the World Trade Center, most centrally its twin towers, involved many other innovative techniques, such as the slurry wall for digging the foundation, and wind tunnel experiments.
Construction of the World Trade Center | Introduction
After years of delay and controversy, reconstruction at the World Trade Center site started. The new complex includes One World Trade Center, 3 World Trade Center, 4 World Trade Center, 7 World Trade Center, and one other high-rise office building being planned at 2 World Trade Center. The new World Trade Center complex also includes a museum and memorial, and a transportation hub building that is similar in size to Grand Central Terminal. 7 World Trade Center opened on May 23, 2006, making it the first of five skyscrapers to have been completed in the World Trade Center complex. 4 World Trade Center, the first building completed as part of the site's master plan, opened on November 12, 2013.
World Trade Center (2001–present) | Introduction
In January 2008, two construction cranes were moved into the construction site. The tower's concrete core began rising in the first months of 2008. By February 22, 2008, 9,400 of the nearly of steel necessary had been ordered. By March 13, 2008, the steel for the tower had reached high, below street level. From late March through early April, a tall mockup of a section of the tower's wall with twenty-four windows was tested by Construction Consulting Laboratory West in Ontario, California. The purpose of the testing was to ensure that the all-glass exterior of the tower will be able to withstand earthquakes and extreme weather conditions.
Construction of One World Trade Center | 2008
That story was the basis for a book he would co-author with James Glanz, published in 2003, "City in the Sky, the Rise and Fall of the World Trade Center", which examined the conception, design, construction, life and ultimate destruction of the twin towers, tracing the story back to the 1950s when the project was first proposed by David Rockefeller. A second story, titled "Fighting to Live as the Towers Died", examined the fate of the unlucky individuals who were stuck above the point of impact in the two towers after the planes hit, a piece based on hundreds of hours or work collecting random emails, text messages and recollections of phone calls with those victims, all of which were assembled into a single narrative.
Eric Lipton | World Trade Center coverage
One World Trade Center (previously coined the "Freedom Tower" by Governor Pataki) is the centerpiece of Daniel Libeskind's design. The building rises to , the height of the original 1 World Trade Center (The North Tower), and its spire rises to the symbolic height of 1,776 feet (541 m). This height refers to 1776, the year in which the United States Declaration of Independence was signed. The tower was a collaboration between Studio Daniel Libeskind and Skidmore, Owings & Merrill architect David Childs. Childs acted as the design architect and project manager for the tower, and Daniel Libeskind collaborated on the concept and schematic design.
World Trade Center (2001–present) | Towers
In 1949, the World Trade Corporation was dissolved by the New York State Legislature.
Construction of the World Trade Center | Context
The first of the towers was finished in 1970. Many of his buildings feature superficial details inspired by the pointed arches of Gothic architecture, and make use of extremely narrow vertical windows. This narrow-windowed style arose from his own personal fear of heights. One particular design challenge of the World Trade Center's design related to the efficacy of the elevator system, which was unique in the world. Yamasaki integrated the fastest elevators at the time, running at 1,700 feet per minute. Instead of placing a large traditional elevator shaft in the core of each tower, Yamasaki created the Twin Towers' "Skylobby" system.
Minoru Yamasaki | Career
On , 1962, the Port Authority announced the selection of Minoru Yamasaki as lead architect and Emery Roth & Sons as associate architects. Yamasaki devised the plan to incorporate twin towers. His original plan called for the towers to be 80 stories tall, but to meet the Port Authority's requirement for of office space, the buildings would each have to be 110 stories tall. Yamasaki's design for the World Trade Center, unveiled to the public on , 1964, called for a square plan approximately in dimension on each side. The buildings were designed with narrow office windows wide, which reflected Yamasaki's fear of heights as well as his desire to make building occupants feel secure.
World Trade Center (1973–2001) | Design
The design for the World Trade Center was finalized in 2005, but was revised extensively after the NYPD raised security concerns regarding various sites in the complex, which delayed the start of the construction of the entire complex by two years. The new plans for the World Trade Center Transportation Hub, which involved doubling the number of support columns, pushed back the construction timeline. In the original plan, the construction of the National September 11 Memorial & Museum would have begun after the Transportation Hub had been completed because the roof of the Transportation Hub provided the foundation on which the memorial rested upon and the walls of the museum.
World Trade Center (2001–present) | Early construction and final planning
It was demolished following the destruction of the World Trade Center during the September 11 attacks, when 10 al-Qaeda participants hijacked American Airlines Flight 11 and United Airlines Flight 175, crashing them into the Twin Towers. After burning for less than two hours, both 110-story towers collapsed. The collapse of the North Tower destroyed large sections of the Six World Trade Center beyond repair, and the remnants of the building were pulled down using cables.
Six World Trade Center | Original building (1973–2001)
The strength of the steel and thickness of the steel plates decreased with height because they were required to support lesser amounts of building mass on higher floors. The tube-frame design required 40 percent less structural steel than conventional building designs. From the 7th floor to the ground level, and down to the foundation, the columns were spaced 10 feet (3 m) apart to accommodate doorways. All columns were placed on bedrock, which, unlike that in Midtown Manhattan, where the bedrock is shallow, is at 65–85 feet (20–26 m) below the surface.
Construction of the World Trade Center | Structural design
In the following weeks, Skidmore, Owings & Merrill withdrew its entry from the competition. Days before the announcement of the two finalists in February 2003, Larry Silverstein wrote to LMDC Chair John Whitehead to express his disapproval of all of the semifinalists' designs. As the Twin Towers' insurance money recipient, Silverstein claimed that he had the sole right to decide what would be built. He announced that he had already picked Skidmore, Owings & Merrill as his master planner for the site.
World Trade Center site | 2002 World Trade Center site design competition
Margaret Donovan, a graphic designer and organizer for the Twin Towers Alliance, criticized the city for allegedly "not paying attention to New Yorkers' wishes for redevelopment designs." Donovan worked in the South Tower the year before the attacks. Though One World Trade Center was under construction, she stated that "We can still have the World Trade Center we deserve", adding that "It's not wishful thinking. It's just common sense, and it's not too late."
Twin Towers 2 | Later development (2008–2009)
An additional section of the ship was found on the site in August 2011, giving historians more information about the vessel, which was active around the 1770s.
Construction of One World Trade Center | 2010
Twin Towers is a 2002 short documentary film directed by Bill Guttentag and Robert David Port, depicting the September 11, 2001 attacks on the World Trade Center. It is about two brothers, policeman Joseph Vigiano and fireman John Vigiano Jr., and their actions during the attacks. The film was awarded an Oscar for Best Documentary Short at the 2003 Academy Awards honoring films released in the year 2002.
Twin Towers (film) | Introduction
Prior to the September 11, 2001 attacks in New York City, the twin towers of the first World Trade Center occupied the second and third positions on the list below, behind Willis Tower. The North Tower(1 WTC) stood at , while the South Tower(2WTC) was tall. If they were still standing today, they would occupy the seventh and eighth positions on the list below, with their replacement—the new One World Trade Center—being excluded.
List of tallest buildings in the United States | Introduction
The original World Trade Center, which featured the landmark Twin Towers (1 WTC and 2 WTC), was a building complex in the Financial District in Lower Manhattan, New York City. 1 and 2 World Trade Center – the North and South Tower – stood at 1,368 feet and 1,362 feet with 110-stories, respectively, becoming the tallest buildings in the world from 1971–1973. The North Tower, with its antenna included, was the tallest building in the world by pinnacle height until the towers were destroyed in the September 11 attacks in 2001. An iconic feature of the New York City skyline for nearly three decades, the World Trade Center has been featured in cartoons, comic books, computer games, video games, television, films, photographs, artwork and music videos.
World Trade Center in popular culture | Introduction
The construction phase of the new 7 World Trade Center began on May 7, 2002, with the installation of a fence around the construction site. Tishman Construction Corporation of New York began work at the new 7 World Trade Center in 2002, soon after the site was cleared of debris. Restoring the Con Ed electrical substation was an urgent priority to meet power demands of Lower Manhattan. Because 7 World Trade Center is separate from the main World Trade Center site, Larry Silverstein required approval from only the Port Authority, and rebuilding was able to proceed quickly. Building Seven was not included in the original World Trade Center master plan by Daniel Libeskind, but was designed by Skidmore, Owings & Merrill under the leadership of David Childs, who largely redesigned One World Trade Center.
7 World Trade Center | Construction
By February 11, 2009, the tower was above street level. On July 2, 2009, over of concrete were poured to form parts of the street-level plaza. On August 13, the builders of 1 WTC set a piece of steel into place—the largest column installed yet at the building. Each steel column, made at a factory in Luxembourg, was about long. The columns at the bottom of the tower's foundation were about long. By November 1, 2009, the twenty-four perimeter columns of 1 WTC were all erected, and construction of the second floor (the first floor above ground level) was nearly complete.
Construction of One World Trade Center | 2009
The ship, believed to be a Hudson River sloop, was found just south of where the Twin Towers used to stand, about 20 feet below the surface. The area that was cleared for construction of the original World Trade Center complex was previously occupied by various electronics stores in what was called Radio Row. These streets and stores were demolished in the 1960s to make way for the World Trade Center.
World Trade Center site | Before the World Trade Center
Groundbreaking took place in 2008. The building reached street level in November 2009. The safety cocoon was installed December 2010. The first glass was installed May 2011. In November 2010, three PureCell fuel cells were delivered at the World Trade Center site which together will provide about 30% of the tower's power. The structural engineer for the building is Leslie E. Robertson Associates, New York City. On February 16, 2012, one of the building's construction crane cables snapped while lifting steel, causing the steel to fall 40 stories from the building, landing on a flat bed truck. No injuries were reported.
4 World Trade Center | Construction
In September, 2001 the CMT Association was in the World Trade Center when the Twin Towers fell.
CMT Association | History
The original World Trade Center contained the Twin Towers, which were the tallest buildings in the world after they opened on April 4, 1973. The other buildings in the complex included the Marriott World Trade Center (3 WTC), as well as 4 WTC, 5 WTC, 6 WTC, and 7 WTC. Despite high financial expectations for the original complex, it did not become profitable until the 1980s. On July 24, 2001, the Port Authority finalized an agreement that leased the complex to Larry Silverstein, who already owned 7 WTC. For $3.2 billion, Silverstein received the legal right to operate the complex and site for 99 years.
World Trade Center (2001–present) | Original complex and 9/11
The Twin Towers II (also known as Twin Towers 2, New Twin Towers, Trump Twin Towers and World Trade Center Phoenix) was a proposed twin-towered skyscraper complex which would have been located at the World Trade Center site in Manhattan, New York City. The proposed complex would have replaced the former Twin Towers of the World Trade Center destroyed in the September 11 attacks, restoring the skyline of the city to its former state. The main design for the proposed complex would feature new landmark twin towers, nearly identical to the originals designed by Minoru Yamasaki, though it would feature 115 stories—5 floors taller than the originals, among other differences.
Twin Towers 2 | Introduction
Construction on the building eventually resumed after the accident. On June 25, 2012, steel topped out at floor 72. Structural steel and concrete completed by June 1, 2013, followed by the removal of construction fencing in September 2013 and the building's opening on November 13, 2013. Cost of construction of 4 World Trade Center was US$1.67 billion, funded by insurance funds and Liberty bonds. The first tenants to move in were two government agencies, and , the building is 62% leased.
4 World Trade Center | Construction
These trusses were installed in each building to support future transmission towers but only the north tower was ultimately fitted with one.
Collapse of the World Trade Center | Structural design
The building was constructed by the architectural group: Skidmore, Owings, and Merrill - the same company that is credited with the construction of One World Trade Center in New York City, which was constructed after the September 11 terrorist attacks.
China World Trade Center Tower III | Introduction
Six World Trade Center was first proposed in 1968 as part of the original World Trade Center complex. The building was designed by Emery Roth & Sons, along with Yamasaki Associates. Construction was completed in 1973. The original Six World Trade Center was home to the U.S. Customs Service for the state of New York, from 1974 to 2001. It was a 537,693-square-foot (49,953-square-meter), eight-story building, the shortest in the World Trade Center complex. From the Austin J. Tobin Plaza level, on which the main structure was built, it had a height of 92 feet (28 m) but was 105 feet (32 m) above the actual ground level.
Six World Trade Center | Original building (1973–2001)
An advanced "cocoon" scaffolding system was installed to protect workers from falling, and was the first such safety system installed on a steel structure in the city. The tower reached 52 floors and was over tall by December 2010. The tower's steel frame was halfway complete by then, but grew to 82 floors by the tenth anniversary of the September 11 attacks, at which time its concrete flooring had reached 72 floors and the glass cladding had reached 56 floors.
One World Trade Center | Construction and later development
The construction of One World Trade Center began on April 27, 2006, and reached its full height on May 20, 2013. The spire was installed atop the building at that date, putting 1 WTC's height at 1,776 feet (541 m) and thus claiming the title of the tallest building in the Western Hemisphere. One WTC finished construction and opened on November 3, 2014. On the World Trade Center site, three more office towers were to be built one block east of where the original towers stood. 4 WTC, meanwhile, opened in November 2013, making it the second tower on the site to open behind 7 World Trade Center, as well as the first building on the Port Authority property.
September 11 attacks | Rebuilding
In January 2012, with Silverstein still unable to find tenants for 4 WTC, construction on the above-ground levels was delayed indefinitely, with plans for only 7 stories. Meanwhile One World Trade Center topped out in August 2012, and its spire was then shipped from Quebec to New York, with the first section of the spire being hoisted to the top of the tower on December 12, 2012. The September 11 Museum was supposed to open that year. However, construction was halted in December 2011 to September 2012 due to cost disputes, and further delays were caused when Hurricane Sandy significantly damaged the site in November 2012.
World Trade Center (2001–present) | Significant progress
At the time, the World Trade Center only had a few notable tenants, and Silverstein wanted to improve the complex to make it more attractive to potential tenants. These plans for improvement were never realized. On the morning of September 11, 2001, Al-Qaeda-affiliated hijackers flew two Boeing 767 jets into the Twin Towers in a coordinated act of terrorism. At 8:46 a.m. Eastern Time (ET), a team of five hijackers intentionally crashed American Airlines Flight 11 into the northern facade of the North Tower. At 9:03 a.m. ET, a second team of five hijackers intentionally crashed United Airlines Flight 175 into the southern facade of the South Tower.
World Trade Center (2001–present) | Original complex and 9/11
In March 1965, the Port Authority began acquiring property at the World Trade Center site. The Ajax Wrecking and Lumber Corporation was hired for the demolition work, which began on March 21, 1965 to clear the site for construction of the World Trade Center.
Construction of the World Trade Center | Construction
Once construction of the power substation was completed in October 2003, work proceeded on building the office tower. An unusual approach was used in constructing the building; erecting the steel frame before adding the concrete core. This approach allowed the construction schedule to be shortened by a few months. Construction was completed in 2006 at a cost of $700 million. Though Silverstein received $861 million from insurance on the old building, he owed more than $400 million on its mortgage. Costs to rebuild were covered by $475 million in Liberty Bonds, which provide tax-exempt financing to help stimulate rebuilding in Lower Manhattan and insurance money that remained after other expenses.
7 World Trade Center | Construction
One World Trade Center (previously coined the "Freedom Tower" by Governor Pataki) is the centerpiece of Libeskind's design. The building rises to , the height of the original World Trade Center north tower, and its antenna rises to the symbolic height of 1,776 feet (541 m). This height refers to 1776, the year in which the United States Declaration of Independence was signed. The tower was a collaboration between Studio Daniel Libeskind and Skidmore, Owings & Merrill architect David Childs. Childs acted as the design architect and project manager for the tower, and Daniel Libeskind collaborated on the concept and schematic design.
World Trade Center site | Towers
The South Tower (also known as Tower 2, Building Two or 2 WTC) was one of the original Twin Towers in the original World Trade Center in New York City, New York. The Tower was completed and opened in 1973 at a height of 415 meters (1,362 ft) to the roof, distinguishable from its twin, the North Tower by its outdoor observation deck and the absence of a television antenna. Both the South Tower and the North Tower had mechanical floors, and the same type of walls. The new 2 World Trade Center (currently on hold) has the same flat roof, with no observation deck, and no mechanical floors.
List of tenants in Two World Trade Center | Introduction
The building opened on November 3, 2014, and the first 170 employees of anchor tenant Conde Nast began their work there. Danish architect Bjarke Ingels designed Two World Trade Center, also known as 200 Greenwich Street. The building's gardens integrate Tribeca with the Financial District at the World Trade Center. As part of a 2010 lease deal to finance 4 WTC, there were plans to build 2 and 3 World Trade Center to ground level. Construction of everything up to street level was completed in mid-2013. The rest of the building, however, has yet to be built until tenants for Tower 2 can be found.
World Trade Center site | Towers
The 47-story building was designed by Emery, Roth & Sons, and constructed on top of a Con Edison power substation.
Construction of the World Trade Center | Other buildings
The following is a list of structures that have historically held the title as the tallest towers in the world.
List of tallest buildings and structures | History of tallest tower
These architecture firms were then invited to compete to be the master plan architect for the World Trade Center:
World Trade Center (2001–present) | Planning
Plans for the World Trade Center rebuilding started in July 2002 which was headed by the Lower Manhattan Development Corporation. There were many proposals on how to build the World Trade Center back however many lacked creativity. Several architects were chosen throughout this construction process, but all of them ran into many problems with the design. The financial crisis in 2008 also forced the construction process over to the Port Authority; however, the Port Authority construction is not going as smoothly as planned. City officials are looking for better ways to lower the problems and delays. The World Trade Center completion of construction was scheduled for 2016.
Rescue and recovery effort after the September 11 attacks on the World Trade Center | Reconstruction
In the September 11 attacks, two commercial airliners were deliberately crashed into the Twin Towers of the World Trade Center in New York City. The impact and resulting fires caused both towers to collapse within less than two hours. The impacts severed exterior columns and damaged core columns, redistributing the loads that these columns had carried. This redistribution of loads was greatly influenced by the hat trusses at the top of each building. The impacts dislodged some of the fireproofing from the steel, increasing its exposure to the heat of the fires. Temperatures became high enough to weaken the core columns to the point of creep and plastic deformation under the weight of higher floors.
Structural integrity and failure | World Trade Center Towers 1, 2, and 7
Almost all the deaths in the Twin Towers occurred in the zones above the points of aircraft impact. As the North Tower had been struck directly midway into the structure, the three stairways in the tower core were all damaged or blocked by debris preventing escape to lower floors. In the South Tower, the impact was slightly off center to the central section of the tower and stairway A in the northwest portion of the central core was only partially blocked, and 14 to 18 civilians managed to escape from the point of aircraft impact and the floors above that.
Collapse of the World Trade Center | Emergency response and evacuation
Construction of New York City's One World Trade Center was deferred until 2006 because of disputes between the Port Authority of New York and New Jersey and the developer. Tishman Realty & Construction is the selected builder. The building reached ground level on May 17, 2008, and was topped out on May 10, 2013. One World Trade Center opened to tenants on November 3, 2014, and One World Observatory opened to the public on May 28, 2015.
Construction of One World Trade Center | Introduction
The tower was originally designed by Foster and Partners in 2006, then redesigned by the Bjarke Ingels Group (BIG), before finally being given back to Foster and Partners for a redesign of the original concept in 2020.
2 World Trade Center | Designs
In 2015, the design was modified and the height reduced by , from to its current height of . , 3 World Trade Center's core had risen to the 19th floor and steel to the 14th floor. On June 28, 2015, one more tower crane was built on the site. Another crane arrived in July, bringing the total to four cranes. On May 20, 2016, the tower's concrete core reached the symbolic height of , thus officially reaching supertall status and exceeding the roof height of neighboring 4 World Trade Center. On June 23, 2016, 3 World Trade Center's core was topped out.
3 World Trade Center | Resumption of construction
That story formed the basis of a 2004 book called "102 Minutes: The Untold Story of the Fight to Survive Inside the Twin Towers", written by Jim Dwyer and Kevin Flynn, who were co-authors on the original "New York Times" story. Archival materials from the Lipton and Glanz research effort—the most comprehensive history ever written about the World Trade Center—are now maintained at the New York Public Library. The materials are separated into five chronological categories: Conception (1945-1970), Construction (1966-1973), Life in the Towers (1972-2001), 9/11, and Post 9/11 (2001-2003) The research was also featured in an episode of the documentary series "American Experience", "New York: The Center of the World".
Eric Lipton | World Trade Center coverage