The construction of the first
World Trade Center
World Trade Centers are sites recognized by the World Trade Centers Association.
World Trade Center may refer to:
Buildings
* List of World Trade Centers
* World Trade Center (2001–present), a building complex that includes five skyscrapers, a ...
complex in
New York City
New York, often called New York City or NYC, is the most populous city in the United States. With a 2020 population of 8,804,190 distributed over , New York City is also the most densely populated major city in the Un ...
was conceived as an
urban renewal
Urban renewal (also called urban regeneration in the United Kingdom and urban redevelopment in the United States) is a program of land redevelopment often used to address urban decay in cities. Urban renewal involves the clearing out of blighte ...
project to help revitalize
Lower Manhattan spearheaded by
David Rockefeller
David Rockefeller (June 12, 1915 – March 20, 2017) was an American investment banker who served as chairman and chief executive of Chase Manhattan Corporation. He was the oldest living member of the third generation of the Rockefeller family, ...
. The project was developed by the
Port Authority of New York and New Jersey
The Port Authority of New York and New Jersey, PANYNJ; stylized, in logo since 2020, as Port Authority NY NJ, is a joint venture between the U.S. states of New York and New Jersey, established in 1921 through an interstate compact authorize ...
. The idea for the World Trade Center arose after
World War II
World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the vast majority of the world's countries—including all of the great powers—forming two opposing ...
as a way to supplement existing avenues of international commerce in the United States.
The World Trade Center was originally planned to be built on the east side of Lower Manhattan, but the
New Jersey
New Jersey is a state in the Mid-Atlantic and Northeastern regions of the United States. It is bordered on the north and east by the state of New York; on the east, southeast, and south by the Atlantic Ocean; on the west by the Delaware ...
and
New York state governments, which oversee the Port Authority, could not agree on this location. 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
Radio Row is a nickname for an urban street or district specializing in the sale of radio and electronic equipment and parts. Radio Rows arose in many cities with the 1920s rise of broadcasting and declined after the middle of the 20th century ...
in the
Lower West Side of
Manhattan
Manhattan (), known regionally as the City, is the most densely populated and geographically smallest of the five boroughs of New York City. The borough is also coextensive with New York County, one of the original counties of the U.S. state ...
, 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
A path is a route for physical travel – see Trail.
Path or PATH may also refer to:
Physical paths of different types
* Bicycle path
* Bridle path, used by people on horseback
* Course (navigation), the intended path of a vehicle
* Desire p ...
.
The Port Authority hired architect
Minoru Yamasaki
was an American architect, best known for designing the original World Trade Center in New York City and several other large-scale projects. Yamasaki was one of the most prominent architects of the 20th century. He and fellow architect Edward ...
, 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. 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
An elevator or lift is a cable-assisted, hydraulic cylinder-assisted, or roller-track assisted machine that vertically transports people or freight between floors, levels, or decks of a building, vessel, or other structure. They a ...
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
A slurry wall is a civil engineering technique used to build reinforced concrete walls in areas of soft earth close to open water, or with a high groundwater table.
This technique is typically used to build diaphragm (water-blocking) walls surro ...
for digging the
foundation
Foundation may refer to:
* Foundation (nonprofit), a type of charitable organization
** Foundation (United States law), a type of charitable organization in the U.S.
** Private foundation, a charitable organization that, while serving a good cause ...
, and
wind tunnel
Wind tunnels are large tubes with air blowing through them which are used to replicate the interaction between air and an object flying through the air or moving along the ground. Researchers use wind tunnels to learn more about how an aircraft ...
experiments.
Construction of the World Trade Center's North Tower began in August 1968, and the South Tower in 1969. Extensive use of prefabricated components helped to speed up the construction process. The first tenants moved into the North Tower in December 1970 and into the South Tower in January 1972. Four other low-level buildings were constructed as part of the World Trade Center in the early 1970s, and the complex was mostly complete by 1973. A seventh building,
7 World Trade Center, was opened in 1987.
Planning
Context
In 1942,
Austin J. Tobin
Austin Joseph Tobin (May 25, 1903 – February 8, 1978) was an American businessman who served as the executive director of the Port of New York Authority, the precursor to the Port Authority of New York and New Jersey, from 1942 until 1972.
To ...
became the Executive Director of the
Port Authority, beginning a 30-year career during which he oversaw the planning and development of the World Trade Center.
The concept of establishing a "
world trade center
World Trade Centers are sites recognized by the World Trade Centers Association.
World Trade Center may refer to:
Buildings
* List of World Trade Centers
* World Trade Center (2001–present), a building complex that includes five skyscrapers, a ...
" was conceived during the post–
World War II
World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the vast majority of the world's countries—including all of the great powers—forming two opposing ...
period, when the United States thrived economically and international trade was increasing. At the time, economic growth was concentrated in
Midtown Manhattan, in part stimulated by
Rockefeller Center
Rockefeller Center is a large complex consisting of 19 commercial buildings covering between 48th Street and 51st Street in Midtown Manhattan, New York City. The 14 original Art Deco buildings, commissioned by the Rockefeller family, span th ...
, which had been
developed in the 1930s.
In 1946, a year after the war formally ended, the
New York State Legislature
The New York State Legislature consists of the two houses that act as the state legislature of the U.S. state of New York: The New York State Senate and the New York State Assembly. The Constitution of New York does not designate an officia ...
passed a bill that called for a "world trade center" to be established. This trade center would increase New York City's role in transatlantic trade.
The World Trade Corporation was founded, and a board was appointed by New York Governor
Thomas E. Dewey to develop plans for the project.
Less than four months after the board was named, plans for a "world trade center" were put on hold. By then, architect
John Eberson and his son Drew had devised a plan that included 21 buildings over a ten-block area, at an estimated cost of $150 million. However, projections determined that such a complex would not be profitable due to a lack of demand; one estimated that the World Trade Center project would only be successful if at least 4,800 of the United States' largest 6,000 companies were involved. In 1949, the World Trade Corporation was dissolved by the New York State Legislature.
Original plans
Meanwhile, the
Financial District
A financial district is usually a central area in a city where financial services firms such as banks, insurance companies and other related finance corporations have their head offices. In major cities, financial districts are often home to s ...
of Lower Manhattan was left out of the
economic boom
An economic expansion is an increase in the level of economic activity, and of the goods and services available. It is a period of economic growth as measured by a rise in real GDP. The explanation of fluctuations in aggregate economic activit ...
of financial industries there. Lower Manhattan also saw less economic growth than Midtown because many workers moved to the suburbs, and they found it easier to commute to midtown than to downtown. The writer
Paul Goldberger
Paul Goldberger (born in 1950) is an American author, architecture critic and lecturer. He is known for his "Sky Line" column in ''The New Yorker''.
Biography
Shortly after starting as a reporter at ''The New York Times'' in 1972, he was assign ...
states that the Financial District, in particular, was devoid of "almost any kind of urban amenity", including entertainment, cultural hubs, or housing. Commercial industries along the ports of Lower Manhattan were also being replaced with industries elsewhere.
David Rockefeller
David Rockefeller (June 12, 1915 – March 20, 2017) was an American investment banker who served as chairman and chief executive of Chase Manhattan Corporation. He was the oldest living member of the third generation of the Rockefeller family, ...
, who led
urban renewal
Urban renewal (also called urban regeneration in the United Kingdom and urban redevelopment in the United States) is a program of land redevelopment often used to address urban decay in cities. Urban renewal involves the clearing out of blighte ...
efforts in Lower Manhattan, constructed the
One Chase Manhattan Plaza
28 Liberty Street, formerly known as One Chase Manhattan Plaza, is a 60-story International style skyscraper in the Financial District of Manhattan in New York City, between Nassau, Liberty, William, and Pine Streets. The building was designed ...
in a bid to bring jobs back. Rockefeller believed that the area would lose its status as the nation's financial hub if it were not redeveloped. However, the skyscraper, which opened in 1960, attracted far fewer tenants than expected.
In 1958, Rockefeller established the Downtown-Lower Manhattan Association (DLMA), which commissioned
Skidmore, Owings and Merrill
Skidmore, Owings & Merrill (SOM) is an American architectural, urban planning and engineering firm. It was founded in 1936 by Louis Skidmore and Nathaniel Owings in Chicago, Illinois. In 1939, they were joined by engineer John Merrill. The fir ...
to draw up plans for revitalizing Lower Manhattan. The plans, made public in late June 1960, called for a World Trade Center to be built on a site along the
East River
The East River is a saltwater tidal estuary in New York City. The waterway, which is actually not a river despite its name, connects Upper New York Bay on its south end to Long Island Sound on its north end. It separates the borough of Quee ...
, at the
South Street Seaport
The South Street Seaport is a historic area in the New York City borough of Manhattan, centered where Fulton Street meets the East River, and adjacent to the Financial District, in Lower Manhattan. The Seaport is a designated historic district ...
, one of the Lower Manhattan ports that had seen a continuous decline in business over the past decade. The site would be bounded clockwise from the south by
Old Slip,
Water Street,
Fulton Street, and
South Street,
and the complex itself would be located on "a two-story platform that would supersede and displace the conventional street grid". The proposed complex included a
exhibition hall
A convention center (American English; or conference centre in British English) is a large building that is designed to hold a convention, where individuals and groups gather to promote and share common interests. Convention centers typica ...
, as well as a 50- to 70-story building with a hotel located on some of its upper floors. Other amenities would include a theater, shops, and restaurants.
The plan also called for a new
securities
A security is a tradable financial asset. The term commonly refers to any form of financial instrument, but its legal definition varies by jurisdiction. In some countries and languages people commonly use the term "security" to refer to any for ...
exchange building, which the Downtown-Lower Manhattan Association hoped would house the
New York Stock Exchange
The New York Stock Exchange (NYSE, nicknamed "The Big Board") is an American stock exchange in the Financial District of Lower Manhattan in New York City. It is by far the world's largest stock exchange by market capitalization of its listed ...
.
David Rockefeller suggested that the Port Authority would be a logical choice for taking on the project
because it had experience with similar large engineering projects, and also because the Port Authority, rather than Rockefeller, would be paying for the complex's construction. Rockefeller argued that the Trade Center would provide great benefits in facilitating and increasing volume of international commerce coming through the
Port of New York and New Jersey
The Port of New York and New Jersey is the port district of the New York-Newark metropolitan area, encompassing the region within approximately a radius of the Statue of Liberty National Monument.
It includes the system of navigable water ...
.
David's brother, New York Governor
Nelson Rockefeller, formally asked the Port Authority to investigate the feasibility of this proposal. Given the importance of New York City in global commerce, Port Authority director Austin J. Tobin remarked that the proposed project should be ''the'' World Trade Center, and not just a generic "world trade center". Tobin commissioned an aide, Richard Sullivan, to lead a study on the feasibility of building a World Trade Center.
Sullivan published his study, "A World Trade Center in the Port of New York", on March 10, 1961. The report recommended building a trade center along the waterfront to facilitate commerce within the Port of New York. The study also stated that Rockefeller's suggested site near the South Street Seaport was the most ideal location for the trade center, but did not take locals' possible objections into account. The Port Authority formally backed the project the next day.
Agreement
![Wtc locator map](https://upload.wikimedia.org/wikipedia/commons/5/5b/Wtc_locator_map.png)
The States of
New York and
New Jersey
New Jersey is a state in the Mid-Atlantic and Northeastern regions of the United States. It is bordered on the north and east by the state of New York; on the east, southeast, and south by the Atlantic Ocean; on the west by the Delaware ...
also needed to approve the project, given their control and oversight role of the Port Authority. Objections to the plan came from
New Jersey Governor
The governor of New Jersey is the head of government of New Jersey. The office of governor is an elected position with a four-year term. There is a two consecutive term term limit, with no limitation on non-consecutive terms. The official res ...
Robert B. Meyner
Robert Baumle Meyner (July 3, 1908 – May 27, 1990) was an American Democratic Party politician and attorney who served as the 44th governor of New Jersey from 1954 to 1962. Before being elected governor, Meyner represented Warren County in t ...
, who resented that New York would be getting the $355 million project. Meyner would only agree if his own state were able to benefit. He was particularly concerned about ridership on New Jersey's
Hudson and Manhattan Railroad
Port Authority Trans-Hudson (PATH) is a rapid transit system in the northeastern New Jersey cities of Newark, Harrison, Jersey City, and Hoboken, as well as Lower and Midtown Manhattan in New York City. It is operated as a wholly owned sub ...
(H&M). The H&M's ridership had declined substantially from a high of 113 million riders in 1927 to 26 million in 1958, after new automobile tunnels and bridges opened across the
Hudson River
The Hudson River is a river that flows from north to south primarily through eastern New York. It originates in the Adirondack Mountains of Upstate New York and flows southward through the Hudson Valley to the New York Harbor between N ...
. The H&M's
Hudson Terminal
Hudson Terminal was a rapid transit station and office-tower complex in the Radio Row neighborhood of Lower Manhattan in New York City. Opened during 1908 and 1909, it was composed of a terminal station for the Hudson & Manhattan Railroad (H&M), ...
, a large and mostly decrepit office-building complex along Manhattan's Lower West Side, was located in a neighborhood referred to as the
Radio Row
Radio Row is a nickname for an urban street or district specializing in the sale of radio and electronic equipment and parts. Radio Rows arose in many cities with the 1920s rise of broadcasting and declined after the middle of the 20th century ...
, which was also seeing a general decline due to a loss of transportation options. The ferries across the Hudson River, which had seen 51 million annual riders in 1920, had stopped running, while the area's elevated lines were being dismantled in favor of high-speed subways. For many years, New Jersey residents and elected officials had proposed that the Port Authority purchase the H&M Railroad, but each time, the Port Authority had refused. Meyner suggested that he would support the plans for the World Trade Center project if the Port Authority took over the H&M. The Port Authority then started conducting another study on Meyner's suggestion of a H&M takeover.
In February 1961, Governor Rockefeller introduced a bill that would combine the H&M's $70 million acquisition with the $335 million trade center at South Street. Even though Nelson Rockefeller had been warned of the hastiness of the deal, owing to the fact that it highlighted the price disparity between the two agreements, the New York state legislature approved the bill anyway. Subsequently, negotiations with Governor Meyner regarding the World Trade Center project reached a stalemate. Months later, Sullivan was contacted by a colleague, Sidney Schachter, who had surveyed Hudson Terminal. After taking a walk around the Radio Row neighborhood, Schachter concluded that the site could be used for the World Trade Center. This would carry multiple benefits: the obsolete Hudson Terminal could be replaced with more modern office buildings; the H&M would get a new railway terminal; and the World Trade Center could be built without objections from New Jersey. Through the end of the year, the Port Authority continued to investigate the feasibility of taking over the H&M.
In December 1961, Tobin had several meetings with newly elected New Jersey Governor
Richard J. Hughes.
They ultimately agreed to a proposal to shift the World Trade Center project to the site of the H&M's Hudson Terminal. The new location not only was closer to New Jersey, but also was able to utilize the unused
air rights
Air rights are the property interest in the "space" above the earth's surface. Generally speaking, owning, or renting, land or a building includes the right to use and build in the space above the land without interference by others.
This lega ...
above the Hudson Terminal: although other developers were theoretically allowed to build atop the terminal, none had done so. In acquiring the Hudson & Manhattan Railroad, the Port Authority would also acquire the Hudson Terminal and other buildings, which were deemed obsolete.
On January 22, 1962, the two states reached an agreement to allow the Port Authority to take over the railroad and to build the World Trade Center on Manhattan's lower west side. As part of the deal, the Port Authority renamed the H&M "Port Authority Trans-Hudson", or PATH for short. The New Jersey state legislature approved this deal in February 1962. After the World Trade Center legislation was approved by the New Jersey legislature, Chairman Tobin formed the World Trade Office to develop and operate the trade center, appointing
Guy F. Tozzoli to lead the new office.
The new site constituted a mostly trapezoidal plot of land, with an extension on the north that resembled a "cork". The bulk of the land was a twelve-block area bounded by Vesey, Church, Liberty, and West Streets on the north, east, south, and west, respectively.
All of these blocks would be combined to form the
superblock upon which the World Trade Center was built.
The "cork" was a smaller trapezoid bounded clockwise from the north by Barclay Street, West Broadway, Vesey Street, and Washington Street. This would become the site of
7 World Trade Center, although that building was not added until much later. The two blocks to the west and east of the "cork" were occupied by the
New York Telephone Company Building and the Federal Building, respectively.
Eviction controversy
The site for the World Trade Center was the location of Radio Row, which was home to 323 commercial or industrial tenants, over one thousand offices, many small businesses, and approximately 100 residents. Estimates indicated that either 17,200 or 30,000 employees worked within the area that was to be occupied by the World Trade Center, and that the businesses employing them made a combined $300 million in profits every year. The World Trade Center plans involved evicting these business owners, some of whom strongly dissented to the forced relocation. The group protesting against the evictions was led by Oscar Nadel, one of the business owners who was facing eviction. Newspapers published stories about small-business owners who would be affected by the evictions, while residents and tenants went around the neighborhood, carrying the effigy of a "Mr. Small Businessman" in a mock funeral.
The Port Authority opened an office to assist tenants with relocation; although this offer was accepted by some tenants, it was protested by others. The agency refused to meet with large groups of merchants, instead saying that concerned tenants meet with Port Authority officials one-by-one. Nadel believed that this would allow the Port Authority to convince individual tenants to move out, thus causing an exodus of merchants from the area. As the merchants' ''de facto'' spokesperson, he requested a meeting with Tobin directly. However, when the meeting did occur in mid-June 1962, Nadel immediately rejected Tobin's proposal to give him a storefront space in the World Trade Center. Two weeks later, a group representing approximately 325 shops and 1,000 other affected small businesses filed an
injunction, challenging the Port Authority's power of
eminent domain
Eminent domain (United States, Philippines), land acquisition (India, Malaysia, Singapore), compulsory purchase/acquisition (Australia, New Zealand, Ireland, United Kingdom), resumption (Hong Kong, Uganda), resumption/compulsory acquisition (Austr ...
, or the takeover of private property for public use.
The dispute with local business owners went through the court system to the
New York State Court of Appeals
The New York Court of Appeals is the highest court in the Unified Court System of the State of New York. The Court of Appeals consists of seven judges: the Chief Judge and six Associate Judges who are appointed by the Governor and confirmed by ...
. Although several lower courts refused to hear the merchants' cases, they also ruled that the World Trade Center did not serve a "public purpose" and that the plan had caused harm to Radio Row merchants, contrary to what Tobin had claimed. In response, Tobin announced that the lower courts had ruled on the constitutional question of "public purpose", prompting an appellate judge to issue a public rebuke for Tobin's "extramural misrepresentation" of the outcome. Tobin changed his offer to the merchants, offering to relocate them to a new electronics complex and delay demolition until 1964. However, in public, he acted as though the judges had already ruled in his favor on the constitutional question. In February 1963, the New York Court of Appeals ruled that the World Trade Center did not constitute a "public purpose", thereby nullifying the Port Authority's land acquisition. The Port Authority immediately appealed, and in April, the same court reversed its previous decision, upholding the Port Authority's right of eminent domain and saying that the project had a "public purpose". The merchants then appealed to the
United States Supreme Court
The Supreme Court of the United States (SCOTUS) is the highest court in the federal judiciary of the United States. It has ultimate appellate jurisdiction over all U.S. federal court cases, and over state court cases that involve a point o ...
. On November 12, 1963, the Supreme Court rejected the case, stating that it lacked proof of needing
federal action.
Under the state law, the Port Authority was required to assist business owners in relocating, something it had been doing since 1962. However, many business owners regarded what the Port Authority offered as inadequate.
Questions continued while the World Trade Center was constructed, as to whether the Port Authority really ought to take on the project, described by some as a "mistaken social priority."
Design process
After New Jersey approved of the World Trade Center project, the Port Authority started looking for tenants. First, the agency approached the
United States Customs Service
The United States Customs Service was the very first federal law enforcement agency of the U.S. federal government. Established on July 31, 1789, it collected import tariffs, performed other selected border security duties, as well as conducted c ...
because the Customs Service had been dissatisfied with its current headquarters, the
Alexander Hamilton U.S. Custom House
The Alexander Hamilton U.S. Custom House (originally the New York Custom House) is a government building, museum, and former custom house at 1 Bowling Green, near the southern end of Manhattan in New York City, United States. Designed by Cas ...
on the tip of Lower Manhattan. The Port Authority then solicited the New York state government, since there were too few private companies willing to move to the World Trade Center. The World Trade Center's planners were concerned that the World Trade Center would be underused, because at the time, less than 3.8% of the United States'
gross national product
The gross national income (GNI), previously known as gross national product (GNP), is the total domestic and foreign output claimed by residents of a country, consisting of gross domestic product (GDP), plus factor incomes earned by foreign ...
came from international trade, and corporations with a worldwide presence comprised four-fifths of that sector. In January 1964, the Port Authority certified a deal with the New York state government to relocate some offices to the World Trade Center. The Port Authority began signing commercial tenants in the spring and summer of 1964, including several banks. The Port Authority signed the United States Customs Service as a tenant a year later.
After considering these facts, Tobin and Tozzoli determined that the only way to make the World Trade Center appealing to private entities was to make the trade center the world's largest. This resulted in an enlargement of plans for the entire trade center, which was originally supposed to include only of floor space. After the release of the feasibility report for the new site, this figure increased to at least of floor space, making the World Trade Center about as large as
the Pentagon
The Pentagon is the headquarters building of the United States Department of Defense. It was constructed on an accelerated schedule during World War II. As a symbol of the U.S. military, the phrase ''The Pentagon'' is often used as a meton ...
, the world's largest office building at the time. However, after directing his staff to inspect the proposed trade center's new site at Radio Row, Tobin decided to increase the amount of floor space further, to at least . Fearing controversy, Tobin kept this plan secret from the public.
Search for an architect
Tozzoli dismissed the three planners who had worked on the original World Trade Center study, due to their lack of creative designs for the World Trade Center complex. He then went to Seattle to meet with architect
Minoru Yamasaki
was an American architect, best known for designing the original World Trade Center in New York City and several other large-scale projects. Yamasaki was one of the most prominent architects of the 20th century. He and fellow architect Edward ...
. Tozzoli had a general idea of what should be in the trade center, but had not yet devised the specific details of the design. Prior to this meeting, Yamasaki's only high-rise construction project was the
Michigan Consolidated Gas Company's 30-story tower in Detroit. As a result, Yamasaki initially thought that the offer for him to build a $280,000,000 world trade center in New York City was a typo. After it was clarified that the offer was not made in error, Yamasaki presented his "big and unmistakable, yet intimate and humane" proposal for the trade center to the Port Authority board in June 1962. The author Paul Goldberger wrote that Yamasaki "presented himself as an aesthete" to the Port Authority board, which was mostly composed of engineers. Following this meeting, a group of Port Authority planners began looking through Yamasaki's prior projects.
On September 20, 1962,
[ after an exhaustive search for architects, the Port Authority announced the selection of Yamasaki as lead architect, and ]Emery Roth
Emery Roth ( hu, Róth Imre, July 17, 1871 – August 20, 1948) was an American architect of Hungarian-Jewish descent who designed many of the definitive New York City hotels and apartment buildings of the 1920s and 1930s, incorporating Beaux ...
& 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."
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. 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.
Another major limiting factor in the buildings' designs was elevator
An elevator or lift is a cable-assisted, hydraulic cylinder-assisted, or roller-track assisted machine that vertically transports people or freight between floors, levels, or decks of a building, vessel, or other structure. They a ...
s. As the building got taller, more elevators were needed to service the building, which required more elevator banks that in turn took up space. 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. Thus, the local elevators can be stacked within the same elevator shaft. Located on the 44th and 78th floors of each tower, the sky lobbies enabled the elevators to be used efficiently, while also increasing the amount of usable space on each floor from 62 to 75 percent by reducing the number of required elevator shafts. The World Trade Center towers were the second supertall
A supertall building is an occupied "supertall" structure higher than and beneath . A form of skyscraper, it falls midway between a common minimum definition of "skyscraper" (a building taller ) and a " megatall" building (taller than ).
Diff ...
buildings to use sky lobbies, after the John Hancock Center
The John Hancock Center is a 100- story, 1,128-foot supertall skyscraper located in Chicago, Illinois. Located in the Magnificent Mile district, the building was officially renamed 875 North Michigan Avenue in 2018.
The skyscraper was designed ...
in Chicago. This system was inspired by the New York City Subway, whose lines include local stations, where only local trains stop, and express stations, where all trains stop. This allowed the towers' heights to be increased to 110 floors without the top floors being economically unfeasible.
Design revealed
Yamasaki's final design for the World Trade Center was unveiled to the public on January 18, 1964, with an eight-foot model. The towers had a square plan, approximately 207 feet (63 m) in dimension on each side. The buildings were designed with narrow office windows, only 18 inches (45 cm) wide, which reflected on Yamasaki's fear of heights
Acrophobia is an extreme or irrational fear or phobia of heights, especially when one is not particularly high up. It belongs to a category of specific phobias, called space and motion discomfort, that share both similar causes and options for ...
and desire to make building occupants feel secure. The windows only covered 30% of the buildings' exteriors, making them look like solid metal slabs from a distance, though this was also a byproduct of the structural systems that held up the towers. Yamasaki's design called for the building facades to be sheathed in aluminum-alloy.
Yamasaki, who had previously designed Saudi Arabia
Saudi Arabia, officially the Kingdom of Saudi Arabia (KSA), is a country in Western Asia. It covers the bulk of the Arabian Peninsula, and has a land area of about , making it the fifth-largest country in Asia, the second-largest in the A ...
's Dhahran International Airport with the Saudi Binladin Group
Saudi Binladin Group (SBG) is a Saudi construction company headquartered in Jeddah, Hejaz. It is the largest construction company of the Middle East. The company is owned primarily by the Bin Laden family.
Founded by Muhammad Binladin in 1931, ...
, incorporated features of Arabic architecture
Islamic architecture comprises the architectural styles of buildings associated with Islam. It encompasses both secular and religious styles from the early history of Islam to the present day. The Islamic world encompasses a wide geographic ar ...
into the design of the World Trade Center. The plaza
A town square (or square, plaza, public square, city square, urban square, or ''piazza'') is an open public space, commonly found in the heart of a traditional town but not necessarily a true geometric square, used for community gatherings. ...
was modelled after Mecca
Mecca (; officially Makkah al-Mukarramah, commonly shortened to Makkah ()) is a city and administrative center of the Mecca Province of Saudi Arabia, and the holiest city in Islam. It is inland from Jeddah on the Red Sea, in a narrow ...
, incorporating features such as a vast delineated square, a fountain
A fountain, from the Latin "fons" (genitive "fontis"), meaning source or spring, is a decorative reservoir used for discharging water. It is also a structure that jets water into the air for a decorative or dramatic effect.
Fountains were ori ...
, and a radial circular pattern. Yamasaki described the plaza as "a mecca, a great relief from the narrow streets and sidewalks of the Wall Street area." He also incorporated other features of Arabic architecture into the building design, including pointed arch
A pointed arch, ogival arch, or Gothic arch is an arch with a pointed crown, whose two curving sides meet at a relatively sharp angle at the top of the arch. This architectural element was particularly important in Gothic architecture. The earlie ...
es, interweaving tracery of prefabricated concrete, a minaret like flight tower, and arabesque
The arabesque is a form of artistic decoration consisting of "surface decorations based on rhythmic linear patterns of scrolling and interlacing foliage, tendrils" or plain lines, often combined with other elements. Another definition is "Foli ...
patterns.
The World Trade Center design brought criticism of its aesthetics from the American Institute of Architects
The American Institute of Architects (AIA) is a professional organization for architects in the United States. Headquartered in Washington, D.C., the AIA offers education, government advocacy, community redevelopment, and public outreach to su ...
and other groups. Lewis Mumford
Lewis Mumford (October 19, 1895 – January 26, 1990) was an American historian, sociologist, philosopher of technology, and literary critic. Particularly noted for his study of cities and urban architecture, he had a broad career as a w ...
, author of '' The City in History'' and other works on urban planning
Urban planning, also known as town planning, city planning, regional planning, or rural planning, is a technical and political process that is focused on the development and design of land use and the built environment, including air, water, ...
, 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
The New York metropolitan area, also commonly referred to as the Tri-State area, is the largest metropolitan area in the world by urban landmass, at , and one of the most populous urban agglomerations in the world. The vast metropolitan are ...
, 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. The Linnaean Society
The Linnean Society of London is a learned society dedicated to the study and dissemination of information concerning natural history, evolution, and taxonomy. It possesses several important biological specimen, manuscript and literature colle ...
of the American Museum of Natural History also opposed the Trade Center project, citing hazards the buildings would impose on migrating birds.
The structural engineering firm Worthington, Skilling, Helle & Jackson worked to implement Yamasaki's design, developing a framed-tube structural system that was used in the buildings. The Port Authority's Engineering Department served as foundation engineers, Joseph R. Loring & Associates as electrical engineers
Electrical engineering is an engineering discipline concerned with the study, design, and application of equipment, devices, and systems which use electricity, electronics, and electromagnetism. It emerged as an identifiable occupation in the ...
, and Jaros, Baum & Bolles (JB&B) Jaros, Baum & Bolles (JB&B) is an American MEP (Mechanical, electrical, and plumbing) and consulting engineering firm founded in 1915 by Alfred L. Jaros, Jr. and Albert L. Baum. The firm is best known for high-rise projects, including One World Trad ...
as mechanical engineers
Mechanical engineering is the study of physical machines that may involve force and movement. It is an engineering branch that combines engineering physics and mathematics principles with materials science, to design, analyze, manufacture, an ...
. Tishman Realty & Construction
Tishman Realty & Construction Co., Inc. is an American corporation founded in 1898 that owns and develops real estate. The company is known for being the contractor that built the original World Trade Center in New York City. Tishman Constructio ...
Company 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.
Design of the towers
Structural design elements
As an interstate agency, the Port Authority was not subject to local laws and regulations of the City of New York, including building code
A building code (also building control or building regulations) is a set of rules that specify the standards for constructed objects such as buildings and non-building structures. Buildings must conform to the code to obtain planning permiss ...
s. Nonetheless, the Port Authority required architects and structural engineers to follow the New York City building codes. At the time when the World Trade Center was planned, new building codes were being devised to replace the 1938 version that was still in place. The structural engineers ended up following draft versions of the new 1968 building codes, which incorporated "advanced techniques" in building design
Building design refers to the broadly based architectural, engineering and technical applications to the design of buildings. All building projects require the services of a building designer, typically a licensed architect. Smaller, less complica ...
.
The World Trade Center towers included many structural engineering
Structural engineering is a sub-discipline of civil engineering in which structural engineers are trained to design the 'bones and muscles' that create the form and shape of man-made structures. Structural engineers also must understand and cal ...
innovations in skyscraper design and construction
The design and construction of skyscrapers involves creating safe, habitable spaces in very high buildings. The buildings must support their weight, resist wind and earthquakes, and protect occupants from fire. Yet they must also be convenientl ...
, which allowed the buildings to reach new heights and become the tallest in the world. Traditionally, skyscrapers used a skeleton of columns distributed throughout the interior to support building loads, with interior columns disrupting the floor space. The framed-tube concept, earlier introduced by Bangladeshi-American
Bangladeshi Americans ( bn, বাংলাদেশী মার্কিনী, Bangladeshī Markinī) are Americans of Bangladeshi descent. The majority of Bangladeshi Americans are Bengalis and form the largest group of Bengali Americans. Ba ...
structural engineer Fazlur Rahman Khan
Fazlur Rahman Khan ( bn, ফজলুর রহমান খান, ''Fozlur Rôhman Khan''; 3 April 1929 – 27 March 1982) was a Bangladeshi-American structural engineer and architect, who initiated important structural systems for skyscrape ...
, was a major innovation, allowing open floor plans and more space to rent.The tube-frame design required 40 percent less structural steel than conventional building designs. The buildings used high-strength, load-bearing perimeter steel columns which acted as Vierendeel trusses. Although the columns themselves were lightweight, they were spaced closely together, forming a strong, rigid wall structure. There were 59 perimeter columns, narrowly spaced, on each side of the buildings. In all, the perimeter walls of the towers were on each side, and the corners were beveled. The perimeter columns were designed to provide support for virtually all lateral loads (such as wind loads) and to share the gravity loads with the core columns. Structural analysis of major portions of the World Trade Center were computed on an IBM 1620
The IBM 1620 was announced by IBM on October 21, 1959, and marketed as an inexpensive scientific computer. After a total production of about two thousand machines, it was withdrawn on November 19, 1970. Modified versions of the 1620 were used as ...
.
Perimeter
The perimeter structure was constructed of prefabricated modular pieces, which consisted of three columns, three stories tall, connected by spandrel
A spandrel is a roughly triangular space, usually found in pairs, between the top of an arch and a rectangular frame; between the tops of two adjacent arches or one of the four spaces between a circle within a square. They are frequently fill ...
plates. The perimeter columns had a square cross section, on a side, and were constructed of welded steel plate. The thickness of the plates and grade of structural steel varied over the height of the tower, ranging from 36,000 to 100,000 pounds per square inch (260 to 670 MPa). The thickness of the steel plates decreased with height because they were required to support lesser amounts of building mass and wind loads on higher floors. However, the steel grade increased with height. Columns were made of higher grades than spandrels. Steel grade was higher near the corner. From the 7th floor to the ground level, and down to the foundation, the columns were spaced 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.
The spandrel plates, typically deep, were welded to the exterior columns to create the modular pieces off-site at the fabrication shop. Each of the modular pieces weigh 22 tons, was wide and tall, and extended for two full floors and half of two more floors. Adjacent modules were bolted together, with the splices occurring at mid-span of the columns and spandrels. The spandrel plates were located at each floor, transmitting shear stress
Shear stress, often denoted by (Greek: tau), is the component of stress coplanar with a material cross section. It arises from the shear force, the component of force vector parallel to the material cross section. ''Normal stress'', on the ...
between columns, allowing them to work together in resisting lateral loads. Other than at the mechanical floors, the joints between modules were staggered vertically, so the column splices between adjacent modules were not at the same floor.
Core
The building's core housed the elevator and utility shafts, restrooms, three stairwells, and other support spaces. The core of each tower was a rectangular area 87 by 135 feet (27 by 41 m), and contained 47 steel columns running from the bedrock to the top of the tower. The North Tower's structural core was oriented with the long axis east to west, while the South Tower's was oriented north to south.
The core columns supported about half the towers' weight. The core was surrounded by a girder to which were connected the inner ends of the floor trusses. The 16 columns which supported the long span trusses were particularly large, accounting for half of the core's loads. Of this, 40 percent came from the corner columns which supported the transfer trusses. Conversely, the seven innermost columns were quite small, carrying only about 3 percent.
The columns were made almost exclusively of 36ksi or 42ksi steel, and gradually switched from rectangular box sections to tapering box sections to wide flange sections at higher floors. Typical columns were box columns for most of their height. Box columns maintained a constant width of predominantly , , or . In the lower third of the building, they also maintained a constant depth of predominantly . The smallest columns were wide flange sections for most of their height. Wide flange sections were mostly 14 inch, followed by 12 inch sections. 42ksi and higher steel grades were predominantly present in these columns.
All elevators were located in the core. Each building had three stairwells, also in the core, except on the mechanical floor
A mechanical floor, mechanical penthouse, mechanical layer or mechanical level is a story of a high-rise building that is dedicated to mechanical and electronics equipment. "Mechanical" is the most commonly used term, but words such as ''utilit ...
s where the two outside stairwells temporarily left the core in order to avoid the express elevator machine rooms, and then rejoined the core by means of a transfer corridor. It was this arrangement that allowed Stairwell A of the South Tower to remain passable after the aircraft impact on September 11, 2001.
Floors
The large, column-free space between the perimeter and core was bridged by prefabricated floor trusses. The floors supported their own weight, as well as live loads, provided lateral stability to the exterior walls, and distributed wind loads among the exterior walls. The floors consisted of thick lightweight concrete slabs laid on a fluted steel deck with shear connections for composite action
Composite or compositing may refer to:
Materials
* Composite material, a material that is made from several different substances
** Metal matrix composite, composed of metal and other parts
** Cermet, a composite of ceramic and metallic material ...
. A grid of lightweight bridging trusses and main trusses supported the floors. The trusses had a span of in the long-span areas and in the short span area. The trusses connected to the perimeter at alternate columns, and were on centers. The top chords of the trusses were bolted to seats welded to the spandrels on the exterior side and a channel welded to the core columns on the interior side. The floors were connected to the perimeter spandrel plates with viscoelastic
In materials science and continuum mechanics, viscoelasticity is the property of materials that exhibit both viscous and elastic characteristics when undergoing deformation. Viscous materials, like water, resist shear flow and strain linearly ...
dampers, which helped reduce the amount of sway felt by building occupants.
File:WTC typical floor framing.jpg, Typical Twin Tower floor framing
File:WTC1 core floor 96 structure.jpg, 96th floor core of WTC 1. This floor structure configuration is typical.
File:Wtc floor truss system.png, Schematic of composite floor truss system
Hat truss
Hat truss
A truss is an assembly of ''members'' such as beams, connected by ''nodes'', that creates a rigid structure.
In engineering, a truss is a structure that "consists of two-force members only, where the members are organized so that the assembl ...
es (or "outrigger truss") located from the 107th floor to the top of the buildings were designed to support a tall communication antenna on top of each building. Only the north tower, 1 World Trade Center, actually had an antenna fitted, which was added in 1978. The truss system consisted of six trusses along the long axis of the core and four along the short axis. This truss system allowed some load redistribution between the perimeter and core columns and supported the transmission tower.
Wind effects
The framed-tube design using steel core and perimeter columns protected with sprayed-on fire resistant material created a relatively lightweight structure that would sway more in response to the wind, compared to traditional structures such as the Empire State Building that have thick, heavy masonry
Masonry is the building of structures from individual units, which are often laid in and bound together by mortar; the term ''masonry'' can also refer to the units themselves. The common materials of masonry construction are bricks, building ...
for fireproofing
Fireproofing is rendering something (structures, materials, etc.) resistant to fire, or incombustible; or material for use in making anything fire-proof. It is a passive fire protection measure. "Fireproof" or "fireproofing" can be used as a ...
of steel structural elements. During the design process, wind tunnel
Wind tunnels are large tubes with air blowing through them which are used to replicate the interaction between air and an object flying through the air or moving along the ground. Researchers use wind tunnels to learn more about how an aircraft ...
tests were done at Colorado State University and at the National Physical Laboratory in the United Kingdom to establish design wind pressures that the World Trade Center towers could be subjected to and structural response to those forces. Experiments were also done to evaluate how much sway occupants could tolerate. Subjects were recruited for "free eye exams," while the real purpose of the experiment was to subject them to simulated building sway and find out how much they could comfortably tolerate. Many subjects did not respond well, experiencing dizziness
Dizziness is an imprecise term that can refer to a sense of disorientation in space, vertigo, or lightheadedness. It can also refer to disequilibrium or a non-specific feeling, such as giddiness or foolishness.
Dizziness is a common medical c ...
and other ill effects. One of the chief engineers Leslie Robertson worked with Canadian engineer Alan G. Davenport to develop viscoelastic
In materials science and continuum mechanics, viscoelasticity is the property of materials that exhibit both viscous and elastic characteristics when undergoing deformation. Viscous materials, like water, resist shear flow and strain linearly ...
dampers to absorb some of the sway. These viscoelastic dampers, used throughout the structures at the joints between floor trusses and perimeter columns, along with some other structural modifications reduced the building sway to an acceptable level.
Aircraft impact
The structural engineers on the project also considered the possibility that an aircraft could crash into the building. In July 1945, a B-25 bomber that was lost in the fog had crashed
"Crashed" is the third U.S. rock Single (music), single, (the fifth overall), from the band Daughtry (band), Daughtry's debut album. It was released only to U.S. rock stations on September 5, 2007. Upon its release the song got adds at those stat ...
into the 78th and 79th floors of the Empire State Building. A year later, another airplane crashed into the 40 Wall Street
40 Wall Street, also known as the Trump Building, is a Gothic Revival architecture, neo-Gothic skyscraper on Wall Street between Nassau Street (Manhattan), Nassau and William Street (Manhattan), William streets in the Financial District, Manh ...
building, and there was another close call at the Empire State Building. In designing the World Trade Center, Leslie Robertson considered the scenario of the impact of a jet airliner, the Boeing 707, which might be lost in the fog, seeking to land at JFK or at Newark airports. The National Institute of Standards and Technology
The National Institute of Standards and Technology (NIST) is an agency of the United States Department of Commerce whose mission is to promote American innovation and industrial competitiveness. NIST's activities are organized into physical s ...
(NIST) found a three-page white paper
A white paper is a report or guide that informs readers concisely about a complex issue and presents the issuing body's philosophy on the matter. It is meant to help readers understand an issue, solve a problem, or make a decision. A white pape ...
that mentioned another aircraft impact analysis, involving impact of a jet at , was indeed considered, but NIST could not locate the documentary evidence of the aircraft impact analysis.
Fire protection
Sprayed-fire resistant materials (SFRMs) were used to protect some structural steel elements in the towers, including all floor trusses and beams. Gypsum
Gypsum is a soft sulfate mineral composed of calcium sulfate dihydrate, with the chemical formula . It is widely mined and is used as a fertilizer and as the main constituent in many forms of plaster, blackboard or sidewalk chalk, and drywal ...
wallboard
Drywall (also called plasterboard, dry lining, wallboard, sheet rock, gypsum board, buster board, custard board, and gypsum panel) is a panel made of calcium sulfate dihydrate (gypsum), with or without additives, typically extruded between thic ...
in combination with SFRMs, or in some cases gypsum wallboard alone, was used to protect core columns. Vermiculite
Vermiculite is a hydrous phyllosilicate mineral which undergoes significant expansion when heated. Exfoliation occurs when the mineral is heated sufficiently, and commercial furnaces can routinely produce this effect. Vermiculite forms by the we ...
plaster was used on the interior-side and SFRMs on the other three sides of the perimeter columns for fire protection. The 1968 New York City building codes were more lenient in some aspects of fire protection, such as allowing three exit stairwells in the World Trade Center towers, instead of six as required under older building codes. In April 1970, the New York City Department of Air Resources ordered the World Trade Center's contractors to stop the spraying of asbestos as an insulating material.
More fireproofing was added after a fire in February 1975 that spread to six floors before being extinguished. After the 1993 bombing, inspections found fireproofing to be deficient. The Port Authority was in the process of replacing it, but replacement had been completed on only 18 floors in the North Tower, including all the floors affected by the aircraft impact and fires on September 11, and on 13 floors in the South Tower, although only three of these floors (77, 78, and 85) were directly affected by the aircraft impact.
The 1968 New York City building codes did not require sprinklers for high-rise buildings, except for underground spaces. In accordance with building codes, sprinklers were originally installed only in the underground parking structures of the World Trade Center. Following a major fire in February 1975, the Port Authority decided to start installing sprinklers throughout the buildings. By 1993, nearly all of the South Tower and 85 percent of the North Tower had sprinklers installed and the entire complex was retrofitted by 2001.
Controversies during design process
Even once the agreement between the states of New Jersey, New York, and the Port Authority had been finalized in 1962, the World Trade Center plan faced continued controversy. New York City Mayor Robert F. Wagner Jr.
Robert Ferdinand Wagner II (April 20, 1910 – February 12, 1991) was an American politician who served three terms as the mayor of New York City from 1954 through 1965. When running for his third term, he broke with the Tammany Hall leadership ...
did not like that the city had a very small stake in the trade center's planning process. Wagner had heard of the revised West Side site through the ''Newark Evening News'', and he stated that the Port Authority had regarded the city as an "outsider rather than the central figure" during the planning process. Wagner wanted the agreement to be delayed until the city could express its opinion regarding the deal. The city and Port Authority hosted a series of meetings to discuss the details of the World Trade Center. However, the city was at a disadvantage since it only had jurisdiction over the streets in the World Trade Center site, but had no say in the site's condemnations. The city used this fact as leverage once private developers announced their opposition to the project.
By 1964, by which time the intended scale of the scheme had been made public with plans for twin 110-story towers, private real estate developers and members of the Real Estate Board of New York also expressed concerns about the World Trade Center's much-"subsidized" office space going on the open market, competing with the many vacancies in the private sector. One notable critic was Lawrence Wien
Lawrence Arthur Wien (May 30, 1905 – December 10, 1988) was an American lawyer, philanthropist, and real estate investor.[tallest building in the world
This list of tallest buildings includes skyscrapers with continuously occupiable floors and a height of at least . Nonbuilding structure, Non-building structures, such as towers, are not included in this list (for these, see ''List of tallest ...]
. Wien organized a group of builders into a group called the "Committee for a Reasonable World Trade Center" to demand that the project be scaled down. This group approached the city for assistance in trying to reduce the size of the World Trade Center project. They claimed that the large amount of floor space in the World Trade Center would create an excess of real estate, causing a reduction in other developers' profits. The city and developers used a myriad of arguments to stall construction for two years.
Wagner's successor, John Lindsay
John Vliet Lindsay (; November 24, 1921 – December 19, 2000) was an American politician and lawyer. During his political career, Lindsay was a U.S. congressman, mayor of New York City, and candidate for U.S. president. He was also a regular ...
, and the New York City Council raised concerns about the limited extent that the Port Authority involved the city in the negotiations and deliberations. Negotiations between the New York City government and the Port Authority were centered on tax issues: the Port Authority offered to pay the city an extra $4 million per year in exchange for foregoing tax payments, while the city wanted four times the amount the Port Authority was offering. This dispute went on for two years, during which time the projected price of the World Trade Center increased sharply. The original estimates put forth by the Port Authority had the costs for construction of the World Trade Center at $350 million—an optimistic figure. In December 1966, the Port Authority announced increased cost estimates, bringing the estimated total to $575 million. This announcement brought criticism of the project from private real estate developers, ''The New York Times'', and others in New York City. The critics stated that the Port Authority figure was an unrealistically low estimate, and they estimated the project would end up costing $750 million. By the time the World Trade Center twin towers were ultimately completed, the total costs to the Port Authority had reached $900 million.
By July 1966, neither the city or the Port Authority were able to come to an agreement. However, negotiations soon resumed, and a final agreement was made on August 3, 1966.[ As part of the agreement, the Port Authority would make annual payments to the City, in lieu of taxes, for the portion of the World Trade Center leased to private tenants.] As part of the agreement, the city would build the New York Passenger Ship Terminal in Hell's Kitchen, Manhattan
Hell's Kitchen, also known as Clinton, is a neighborhood on the West Side of Midtown Manhattan in New York City. It is considered to be bordered by 34th Street (or 41st Street) to the south, 59th Street to the north, Eighth Avenue to the ea ...
, while the Port Authority would build the South Brooklyn Marine Terminal
The South Brooklyn Marine Terminal (SBMT) is an intermodal shipping, warehousing, and manufacturing complex in the Port of New York and New Jersey. It is located along the Upper New York Bay, between 29th and 39th Streets in the Sunset Park and ...
. In subsequent years, the payments would rise as the real estate tax rate increased. The project would be financed through tax-exempt
Tax exemption is the reduction or removal of a liability to make a compulsory payment that would otherwise be imposed by a ruling power upon persons, property, income, or transactions. Tax-exempt status may provide complete relief from taxes, redu ...
bond
Bond or bonds may refer to:
Common meanings
* Bond (finance), a type of debt security
* Bail bond, a commercial third-party guarantor of surety bonds in the United States
* Chemical bond, the attraction of atoms, ions or molecules to form chemica ...
s issued by the Port Authority.
Construction
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.
The Bathtub
Groundbreaking was on August 5, 1966, marking the beginning of construction of the World Trade Center's foundations. The site of the World Trade Center was located on landfill, with the bedrock located below grade. In order to construct the World Trade Center, it was necessary to build "The Bathtub", with the slurry wall
A slurry wall is a civil engineering technique used to build reinforced concrete walls in areas of soft earth close to open water, or with a high groundwater table.
This technique is typically used to build diaphragm (water-blocking) walls surro ...
along the West Street side of the site, to keep water from the Hudson River
The Hudson River is a river that flows from north to south primarily through eastern New York. It originates in the Adirondack Mountains of Upstate New York and flows southward through the Hudson Valley to the New York Harbor between N ...
out. This method was used in place of conventional dewatering methods because lowering the groundwater table would cause large settlements of nearby buildings not built on deep foundation
A deep foundation is a type of foundation that transfers building loads to the earth farther down from the surface than a shallow foundation does to a subsurface layer or a range of depths. A pile or piling is a vertical structural eleme ...
s.
The slurry method involved digging a trench
A trench is a type of excavation or in the ground that is generally deeper than it is wide (as opposed to a wider gully, or ditch), and narrow compared with its length (as opposed to a simple hole or pit).
In geology, trenches result from ero ...
, and as excavation proceeded, filling the space with a slurry mixture. The mixture, composed of bentonite
Bentonite () is an absorbent swelling clay consisting mostly of montmorillonite (a type of smectite) which can either be Na-montmorillonite or Ca-montmorillonite. Na-montmorillonite has a considerably greater swelling capacity than Ca-m ...
, plugged holes and kept water out. When the trench was dug out, a steel cage was inserted and concrete was poured in, forcing the slurry out. The slurry method was devised by Port Authority chief engineer John M. Kyle Jr. Towards the end of 1966, work began on building the slurry wall, led by Montreal
Montreal ( ; officially Montréal, ) is the second-most populous city in Canada and most populous city in the Canadian province of Quebec. Founded in 1642 as '' Ville-Marie'', or "City of Mary", it is named after Mount Royal, the triple ...
-based Icanda, a subsidiary of an Italian engineering firm, Impresa Costruzioni Opere Specializzate (I.C.O.S.). It took fourteen months for the slurry wall to be completed, which was necessary before excavation of material from the interior of the site could begin. The original Hudson Tubes
Port Authority Trans-Hudson (PATH) is a rapid transit system in the northeastern New Jersey cities of Newark, Harrison, Jersey City, and Hoboken, as well as Lower and Midtown Manhattan in New York City. It is operated as a wholly owned su ...
, which carried PATH trains into Hudson Terminal, remained in service as elevated tunnels until 1971 when a new PATH station was built.
Twin Towers
Construction work on the North Tower began in August 1968 with construction beginning on the South Tower by January 1969. In January 1967, the Pacific Car and Foundry Company, Laclede Steel Company Alton Steel is a steel manufacturer, based in Alton, Illinois, United States. The company is a reincarnation of the Laclede Steel Company, which halted operations of its mill in 1998. The company entered bankruptcy in 2001, but emerged in 2003 wit ...
, Granite City Steel Company, and Karl Koch Erecting Company were awarded $74 million in contracts 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
The Bethlehem Steel Corporation was an American steelmaking company headquartered in Bethlehem, Pennsylvania. For most of the 20th century, it was one of the world's largest steel producing and shipbuilding companies. At the height of its succe ...
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
Alcoa Corporation (an acronym for Aluminum Company of America) is a Pittsburgh-based industrial corporation. It is the world's eighth-largest producer of aluminum. Alcoa conducts operations in 10 countries. Alcoa is a major producer of primary ...
. Tishman Realty & Construction
Tishman Realty & Construction Co., Inc. is an American corporation founded in 1898 that owns and develops real estate. The company is known for being the contractor that built the original World Trade Center in New York City. Tishman Constructio ...
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
The Penn Central Transportation Company, commonly abbreviated to Penn Central, was an American class I railroad that operated from 1968 to 1976. Penn Central combined three traditional corporate rivals (the Pennsylvania, New York Central and the ...
(later Conrail and now CSX
CSX Transportation , known colloquially as simply CSX, is a Class I freight railroad operating in the Eastern United States and the Canadian provinces of Ontario and Quebec. The railroad operates approximately 21,000 route miles () of track. ...
) yard in Jersey City. From there, they were brought in the early morning hours through the Holland Tunnel
The Holland Tunnel is a vehicular tunnel under the Hudson River that connects the New York City neighborhood of Hudson Square in Lower Manhattan to the east with Jersey City in New Jersey to the west. The tunnel is operated by the Port Author ...
to the construction site, then lifted into place by a crane. Larger pieces were brought to the construction site by tugboat
A tugboat or tug is a marine vessel that manoeuvres other vessels by pushing or pulling them, with direct contact or a tow line. These boats typically tug ships in circumstances where they cannot or should not move under their own power, su ...
s. A special type of crane, suitable for constructing such tall buildings, that used hydraulics
Hydraulics (from Greek: Υδραυλική) is a technology and applied science using engineering, chemistry, and other sciences involving the mechanical properties and use of liquids. At a very basic level, hydraulics is the liquid counte ...
to lift components and provided its own power was used in construction of the World Trade Center. The Favco Standard 2700 Crane, manufactured by Favelle Mort Ltd. of New South Wales
)
, nickname =
, image_map = New South Wales in Australia.svg
, map_caption = Location of New South Wales in AustraliaCoordinates:
, subdivision_type = Country
, subdivision_name = Australia
, established_title = Before federation
, es ...
, Australia was informally called a " kangaroo crane."
In 1970, tugboat workers went on strike
Strike may refer to:
People
* Strike (surname)
Physical confrontation or removal
*Strike (attack), attack with an inanimate object or a part of the human body intended to cause harm
*Airstrike, military strike by air forces on either a suspected ...
, halting the transport of material to the construction site. The Port Authority attempted other means of transporting material, including via helicopter
A helicopter is a type of rotorcraft in which lift and thrust are supplied by horizontally spinning rotors. This allows the helicopter to take off and land vertically, to hover, and to fly forward, backward and laterally. These attributes ...
. 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. In all, 60 workers were killed in construction accidents while the World Trade Center was being built.
The topping out
In building construction, topping out (sometimes referred to as topping off) is a builders' rite traditionally held when the last beam (or its equivalent) is placed atop a structure during its construction. Nowadays, the ceremony is often parlaye ...
ceremony of the North Tower (1 World Trade Center) took place on December 23, 1970, while the South Tower (2 World Trade Center)'s ceremony occurred on July 19, 1971. The first tenants moved into the North Tower on December 15, 1970, and into the South Tower in January 1972. The buildings were dedicated on April 4, 1973; Tobin, who had resigned the year before, was absent from the ceremonies.[Darton, Eric (1999) ''Divided We Stand: A Biography of New York's World Trade Center'', Chapter 6, Basic Books.]
Building the World Trade Center involved excavating of material. Rather than transporting this material at great costs out to sea or to landfills in New Jersey, the fill material was used to expand the Manhattan
Manhattan (), known regionally as the City, is the most densely populated and geographically smallest of the five boroughs of New York City. The borough is also coextensive with New York County, one of the original counties of the U.S. state ...
shoreline across West Street. Work to demolish the piers began on January 5, 1967, including Pier 7 to Pier 11 which were all constructed around 1910. The demolition work moved forward, despite conflicts between David Rockefeller, Governor Nelson Rockefeller, and Mayor John Lindsay regarding plans for Battery Park City
Battery Park City is a mainly residential planned community and neighborhood on the west side of the southern tip of the island of Manhattan in New York City. It is bounded by the Hudson River on the west, the Hudson River shoreline on the north ...
. Landfill material from the World Trade Center
World Trade Centers are sites recognized by the World Trade Centers Association.
World Trade Center may refer to:
Buildings
* List of World Trade Centers
* World Trade Center (2001–present), a building complex that includes five skyscrapers, a ...
was used to add land, and a cellular cofferdam
A cofferdam is an enclosure built within a body of water to allow the enclosed area to be pumped out. This pumping creates a dry working environment so that the work can be carried out safely. Cofferdams are commonly used for construction or re ...
was constructed to retain the material.[ ] The result was a extension into the Hudson River, running six blocks or . This land was a "gift" to New York City, allowing more tax-generating developments in Battery Park City.
Other buildings
The World Trade Center complex included four other smaller buildings constructed during the 1970s and early 1980s. 3 World Trade Center
3 World Trade Center (3 WTC; also known as 175 Greenwich Street) is a skyscraper constructed as part of the new World Trade Center in Lower Manhattan, New York City. The tower is located on Greenwich Street along the eastern side of the World ...
was a 22-story building, which was home to the Marriott World Trade Center
The Marriott World Trade Center was a 22-story, 825-room hotel at 3 World Trade Center within the World Trade Center complex in Manhattan, New York City. It opened in April 1981 as the Vista International Hotel and was the first major hotel t ...
. It was designed by Skidmore, Owings and Merrill in 1978–79. 4 World Trade Center
4 World Trade Center (4 WTC; also known as 150 Greenwich Street) is a skyscraper constructed as part of the new World Trade Center in Lower Manhattan, New York City. The tower is located on Greenwich Street at the southeastern corner of the ...
, 5 World Trade Center
5 World Trade Center (5 WTC; also referred to as 130 Liberty Street) is a planned skyscraper at the World Trade Center in Lower Manhattan, New York City. The site is across Liberty Street, to the south of the main World Trade Center site. ...
, and 6 World Trade Center
Six World Trade Center was an eight-story building in Lower Manhattan in New York City. It opened in 1974 and was the building in the World Trade Center complex that had the fewest stories. The building served as the U.S. Customs House for N ...
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. The 47-story building was designed by Emery, Roth & Sons, and constructed on top of a Con Edison
Consolidated Edison, Inc., commonly known as Con Edison (stylized as conEdison) or ConEd, is one of the largest investor-owned energy companies in the United States, with approximately $12 billion in annual revenues as of 2017, and over $62 ...
power substation.
Modifications
Over time, numerous structural modifications were made to suit the needs of tenants in the Twin Towers. Modifications were made in accordance with the Port Authority's ''Tenant Alteration Review Manual'' and were reviewed by the Port Authority to ensure the changes did not compromise structural integrity of the buildings. In many instances, openings were cut in the floors to accommodate new stairways to connect tenant floors. Some steel beams in the core were reinforced and strengthened to accommodate heavy live loads, such as large amounts of heavy files that tenants had on their floors.
Repairs to structural elements on the lower levels of 1 WTC were made following the 1993 bombing. The greatest damage occurred on levels B1 and B2, with significant structural damage also on level B3. Primary structural columns were not damaged, but secondary steel members experienced some damage. Floors that were blown out needed to be repaired to restore the structural support they provided to columns. The slurry wall was in peril following the bombing and loss of the floor slabs which provided lateral support to counteract pressure from Hudson River water on the other side. The refrigeration
The term refrigeration refers to the process of removing heat from an enclosed space or substance for the purpose of lowering the temperature.International Dictionary of Refrigeration, http://dictionary.iifiir.org/search.phpASHRAE Terminology, ht ...
plant on sublevel B5, which provided air conditioning
Air conditioning, often abbreviated as A/C or AC, is the process of removing heat from an enclosed space to achieve a more comfortable interior environment (sometimes referred to as 'comfort cooling') and in some cases also strictly controlling ...
to the entire World Trade Center complex, was heavily damaged and replaced with a temporary system for the summer of 1993. The fire alarm
A fire alarm system warns people when smoke, fire, carbon monoxide or other fire-related or general notification emergency, emergencies are detected. These alarms may be activated automatically from smoke detectors and heat detectors or may also ...
system for the entire complex needed to be replaced, after critical wiring and signaling in the original system was destroyed in the 1993 bombing. Installation of the new system took years to complete; replacement of some components was still underway in September 2001, at the time of the attacks that ultimately destroyed the complex.
Gallery
File:World Trade Center twin towers, under construction, New York City - LCCN2020736822.jpg, Twin Towers under construction. Circa 1970s
File:Aerial pix of lower Manhattan with World Trade Center & other construction.jpg, Construction on 11 January 1971
File:View of the New World Trade Center, 1971.jpg, Construction on 12 January 1971. View from below
See also
*Construction of One World Trade Center
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 reach ...
*Collapse of the World Trade Center
The collapse of the World Trade Center occurred during the terrorist attacks of September 11, 2001, after the Twin Towers were struck by two hijacked commercial airliners. One World Trade Center (WTC 1, or the North Tower) was hit at 8:46&nb ...
*World Trade Center (2001–present)
The World Trade Center (WTC) is a mostly completed complex of buildings in the Lower Manhattan neighborhood of New York City, U.S., replacing the original seven buildings on the same site that were destroyed in the September 11 attacks. The s ...
*One World Trade Center
One World Trade Center (also known as One World Trade, One WTC, and formerly Freedom Tower) is the main building of the rebuilt World Trade Center complex in Lower Manhattan, New York City. Designed by David Childs of Skidmore, Owings & Mer ...
*2 World Trade Center
2 World Trade Center (2 WTC; also known as 200 Greenwich Street) is a planned skyscraper as part of the World Trade Center complex in Manhattan, New York City. It will replace the original 2 World Trade Center, which was completed in 1972 and ...
*3 World Trade Center
3 World Trade Center (3 WTC; also known as 175 Greenwich Street) is a skyscraper constructed as part of the new World Trade Center in Lower Manhattan, New York City. The tower is located on Greenwich Street along the eastern side of the World ...
*4 World Trade Center
4 World Trade Center (4 WTC; also known as 150 Greenwich Street) is a skyscraper constructed as part of the new World Trade Center in Lower Manhattan, New York City. The tower is located on Greenwich Street at the southeastern corner of the ...
*5 World Trade Center
5 World Trade Center (5 WTC; also referred to as 130 Liberty Street) is a planned skyscraper at the World Trade Center in Lower Manhattan, New York City. The site is across Liberty Street, to the south of the main World Trade Center site. ...
* 7 World Trade Center
Notes and references
Notes
References
Sources
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External links
New York: A Documentary Film – The Center of the World
– ''Building the World Trade Center'', an 18-minute film, with construction footage, produced by the Port Authority in 1983
– Skyscraper Museum
{{WTC navigation
World Trade Center
Construction in the United States
1960s in Manhattan
1980s in Manhattan
1970s in Manhattan