Difference between revisions of "World Trade Center" - New World Encyclopedia

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{{CoorHeader|40|42|42|N|74|00|45|W|type:landmark}}
 
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{{about|the former World Trade Center (Twin Towers) in [[New York City]]}}
 
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{{redirect|WTC}}
 
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{{Redirect6|World Trade Center|World Trade Center, second version, Tower 1|Freedom Tower|World Trade Center, second version, Tower 2|200 Greenwich Street}}
 
 
{{Infobox Skyscraper
 
{{Infobox Skyscraper
 
|building_name=World Trade Center  
 
|building_name=World Trade Center  
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|image=[[Image:World Trade Center Ground View 1999.jpg|225px]]  
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|image=[[Image:World Trade Center Ground View 1999.jpg|200px]]  
 
|previous_building=[[Empire State Building]]
 
|previous_building=[[Empire State Building]]
 
|year_built= 1972
 
|year_built= 1972
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|year_highest=1972
 
|year_highest=1972
 
|year_end=1973
 
|year_end=1973
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|location=[[Manhattan|New York City]], [[New York]], [[United States|USA]] ([[Lower Manhattan]]) [[Image:Flag of USA.svg|25px]]
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|location=[[Manhattan|New York City]], [[New York]], [[United States|USA]] (Lower Manhattan)  
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|height_meters=417
 
 
|height_feet=1,368
 
|height_feet=1,368
 
|height_stories=110
 
|height_stories=110
 
|construction_period=1966-1973
 
|construction_period=1966-1973
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|destroyed=September 11, 2001 ("[[9/11]]")
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|destroyed=[[September 11 attacks|September 11, 2001]]
 
|completed=1973
 
|completed=1973
 
|emporis_id=131020
 
|emporis_id=131020
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|antenna_spire=1,727 ft (526.3 m) [http://www.skyscraperpage.com/cities/?buildingID=15]
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|antenna_spire=1,727 feet <ref>Skyscraper Page, [http://www.skyscraperpage.com/cities/?buildingID=15 One World Trade Center.] Retrieved September 30, 2022.</ref>
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|roof=1,368 ft (417.0 m)
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|roof=1,368 feet
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|top_floor=1,355 ft (413.0 m)
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|top_floor=1,355 feet
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|floor_area=8.6 million&nbsp;sq&nbsp;ft<br/>800,000&nbsp;m²&nbsp;(1 & 2)
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|floor_area=8.6 million square feet (1 & 2)
 
|elevator_count=198 (1 & 2)
 
|elevator_count=198 (1 & 2)
 
|architect=[[Minoru Yamasaki]], [[Emery Roth & Sons]]
 
|architect=[[Minoru Yamasaki]], [[Emery Roth & Sons]]
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|owner= [[Port Authority of New York and New Jersey]]
 
|owner= [[Port Authority of New York and New Jersey]]
 
}}
 
}}
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The '''World Trade Center''' in [[New York City]] (sometimes informally referred to as the '''WTC''' or the '''Twin Towers''') was a complex of seven buildings, mostly designed by American architect [[Minoru Yamasaki]] and developed by the [[Port Authority of New York and New Jersey]]. It was initiated in 1960 by a Lower Manhattan Association created and chaired by [[David Rockefeller]], who had the original idea of building the Center, with strong backing from the then New York governor, his brother, [[Nelson Rockefeller]].<ref>[http://select.nytimes.com/search/restricted/article?res=F00813FC345B0C7B8CDDA00894DA404482 The Height of Ambition], ''[[New York Times]]'' September 8, 2002.</ref> [[Larry Silverstein]] held the most recent lease to the complex, the Port Authority having leased it to him in July of 2001.<ref>{{cite press release |publisher=[[Port of New York and New Jersey]]|date=July 21,2001 | url=http://www.panynj.gov/pr/pressrelease.php3?id=80 | title=Governor Pataki, Acting Governor DiFrancesco Laud Historic Port Authority Agreement To Privatize World Trade Center}}</ref> The complex, located in the heart of New York City's downtown financial district, contained 13.4 million square feet (1.24 million m²) of office space, almost four percent of Manhattan's entire office inventory.<ref>{{cite web|url=http://www.buildings.com/Articles/detail.asp?ArticleID=341 |author=Buildings.com |title= Four Percent of Manhattan's Total Office Space Was Destroyed in the World Trade Center Attack}}</ref>
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The '''World Trade Center''' in [[New York City]] (sometimes informally referred to as the '''WTC''' or the '''Twin Towers''') was a complex of seven buildings, mostly designed by American architect [[Minoru Yamasaki]] and developed by the [[Port Authority of New York and New Jersey]]. It was destroyed on [[September 11 attacks|September 11, 2001]], in an infamous [[terrorism|terrorist]] attack.
  
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Best known for its iconic 110-story twin towers, the World Trade Center was beset by a fire on February 13, 1975 and [[World Trade Center bombing|a bombing]] on February 26, 1993. All of the original buildings in the complex were destroyed in the [[September 11, 2001, attacks]], including [[One World Trade Center tenants|1 WTC]], [[Two World Trade Center tenants|2 WTC]] (North and South Towers) and [[7 World Trade Center|7 WTC]] which collapsed; [[Marriott World Trade Center (hotel)|3 WTC]] (Marriott Hotel) was crushed by the collapses of 1 WTC and 2 WTC; and [[4 World Trade Center|4 WTC]], [[5 World Trade Center|5 WTC]], and [[6 World Trade Center|6 WTC]] were damaged beyond repair and later demolished. In addition, [[St. Nicholas Greek Orthodox Church]] (not part of the complex) was destroyed by the collapse of 2 WTC.
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The center was initiated in 1960 by a Lower Manhattan Association created and chaired by [[David Rockefeller]], who had the original idea of building the Center, with strong backing from then New York governor, his brother, [[Nelson Rockefeller]]. The complex, located in the heart of New York City's downtown financial district, contained 13.4 million square feet of office space, almost four percent of Manhattan's entire office inventory.
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Best known for its iconic, 110-story twin towers, the World Trade Center was beset by a fire on February 13, 1975, and [[World Trade Center bombing|a bombing]] on February 26, 1993. All of the original buildings in the complex were destroyed in the September 11, 2001 attacks, including the famous North and South Towers and 7 WTC, which collapsed; 3 WTC (the Marriott Hotel) which was crushed by the collapse of the main towers; and 4 WTC, 5 WTC, and 6 WTC were damaged beyond repair and later demolished. In addition, nearby St. Nicholas Greek Orthodox Church (not part of the complex) was destroyed by the collapse of 2 WTC.
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{{toc}}
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The World Trade Center complex was rebuilt over a span of more than a decade. The site is being rebuilt with six new skyscrapers, while a memorial to those killed in the attacks and a new rapid transit hub have both opened. One World Trade Center, the tallest building in the United States, is the lead building for the new complex, reaching more than 100 stories upon its completion in November 2014.
  
 
==Planning and construction==
 
==Planning and construction==
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{{main|Design and construction of the World Trade Center}}
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During the post-[[World War II]] period, the [[United States]] thrived economically, with increasing [[international trade]]. At the time, economic growth in New York City was concentrated in Midtown Manhattan, with Lower Manhattan left out. To help stimulate [[urban renewal]], [[David Rockefeller]], with support from his brother, New York Governor [[Nelson Rockefeller]], suggested that the Port Authority should build a "world trade center" in Lower Manhattan.
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During the post-[[World War II]] period, the [[United States]] thrived economically, with increasing [[international trade]]. At the time, economic growth in New York City was concentrated in [[Midtown Manhattan]], with Lower Manhattan left out. To help stimulate [[urban renewal]], [[David Rockefeller]], with support from his brother, New York Governor [[Nelson Rockefeller]], suggested that the Port Authority should build a "[[World Trade Center (disambiguation)|world trade center]]" in [[Lower Manhattan]].<ref name="gillespie-ch1">Gillespie, Angus K. (1999) ''Twin Towers: The Life of New York City's World Trade Center'', Chapter 1, Rutgers University Press</ref>
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Initial plans, made public in 1961, identified a site along the [[East River]] for the World Trade Center. Meanwhile, New Jersey's Hudson and Manhattan Railroad (H&M) was facing bankruptcy. Port Authority executive director, Austin J. Tobin agreed to take over control of the H&M Railroad, in exchange for support from [[New Jersey]] for the World Trade Center project. With this acquisition, the Port Authority would obtain the Hudson Terminal, and decrepit buildings located above the terminal in Lower Manhattan. The Port Authority decided to demolish these buildings, and use the site along the [[Hudson River]] for the World Trade Center.
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[[Image:Wtc arial march2001.jpg|thumb|300px|Aerial view of the WTC.]]
  
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Initial plans, made public in 1961, identified a site along the [[East River]] for the World Trade Center.<ref name="gillespie-ch1"/> Objections to the plan came from New Jersey Governor [[Robert B. Meyner]], who resented that New York would be getting this $335 million project.<ref name="gillespie-ch1"/>  Meanwhile, New Jersey's [[Hudson and Manhattan Railroad]] (H&M) was facing bankruptcy.  Port Authority executive director, [[Austin J. Tobin]] agreed to take over control of the H&M Railroad, in exchange for support from New Jersey for the World Trade Center project.<ref name="gillespie-ch1"/>  With this acquisition, the Port Authority would obtain the Hudson Terminal, and decrepit buildings located above the terminal in Lower Manhattan.<ref name="gillespie-ch1"/>  The Port Authority decided to demolish these buildings, and use this site along the Hudson River for the World Trade Center.<ref name="gillespie-ch1"/>  The complex towers were designed by architect [[Minoru Yamasaki]] with [[Antonio Brittiochi]] and [[Emery Roth & Sons]] as associate architects. The World Trade Center was one of the most striking American implementations of the architectural ethic of [[Le Corbusier]], as well as the seminal expression of Yamasaki's gothic modernist tendencies.
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The complex towers were designed by architect [[Minoru Yamasaki]] with [[Antonio Brittiochi]] and [[Emery Roth & Sons]] as associate architects. The World Trade Center was one of the most striking American implementations of the architectural ethic of [[Le Corbusier]], as well as the seminal expression of Yamasaki's [[Gothic]] modernist tendencies.
  
 
===Structural design===
 
===Structural design===
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The World Trade Center included many structural engineering innovations in skyscraper design and construction. The towers were designed as framed tube structures, with columns grouped around the perimeter and within the core. The perimeter columns supported virtually all lateral loads, such as wind loads, and shared the gravity loads with the core columns.<ref name="NIST-chapter1">{{cite web |url=http://wtc.nist.gov/NISTNCSTAR1CollapseofTowers.pdf |title=Final Report on the Collapse of the World Trade Center (chapter 1) |publisher=National Institute of Standards and Technology (NIST) |date=September 2005}}</ref>  All columns were founded on [[bedrock]], which unlike Midtown Manhattan, where the bedrock is shallow, is at 65 feet (20m) below the surface.
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The World Trade Center included many structural engineering innovations in skyscraper design and construction. The towers were designed as framed tube structures, with columns grouped around the perimeter and within the core. The perimeter columns supported virtually all lateral loads, such as wind loads, and shared the gravity loads with the core columns. All columns were founded on [[bedrock]], which unlike Midtown Manhattan, where the bedrock is shallow, is at 65 feet below the surface.
  
 
====Perimeter columns====
 
====Perimeter columns====
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Above the seventh floor there were 59 perimeter columns along each face of the building. The perimeter columns had a square cross section, 14 inches on a side (36 cm), and were constructed of welded steel plate.<ref name="NIST-chapter1"/>  The thickness of the plates and grade of steel were varied over the height of the tower, ranging from 36 ksi to 100 ksi, with the steel strength and plate thickness decreasing with height.<ref name="NIST-chapter1"/>  The perimeter columns supported virtually all lateral loads such as wind loads and shared the gravity loads with the core columns. The perimeter structure was constructed with extensive use of prefabricated modular pieces, which consisted of three columns, three stories tall, connected together by spandrel plates. The spandrel plates were welded to the columns at the fabrication shop. The modular pieces were typically 52 inches (1.3 m) deep, and extended for two full floors and half of two more floors.<ref name="NIST-chapter1"/> 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, and served to transmit shear flow between columns, thus allowing them to work together in resisting lateral loads. The joints between modules were staggered vertically, so the column splices between adjacent modules were not at the same floor.<ref name="NIST-chapter1"/>
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Above the seventh floor there were 59 perimeter columns along each face of the building. The perimeter columns had a square cross section, 14 inches on a side, and were constructed of welded steel plate. The thickness of the plates and grade of steel were varied over the height of the tower, ranging from 36 kilogram per square inch (ksi) to 100 ksi, with the steel strength and plate thickness decreasing with height. The perimeter columns supported virtually all lateral loads such as wind loads and shared the gravity loads with the core columns. The perimeter structure was constructed with extensive use of prefabricated modular pieces, which consisted of three columns, three stories tall, connected together by spandrel plates.  
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The spandrel plates were welded to the columns at the fabrication shop. The modular pieces were typically 52 inches deep, 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, and served to transmit shear flow between columns, thus allowing them to work together in resisting lateral loads. The joints between modules were staggered vertically, so the column splices between adjacent modules were not at the same floor.
  
 
====Core====
 
====Core====
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The building's core housed the [[elevator]] and utility shafts, restrooms, three stairwells, and other support spaces. The core in 1 WTC was oriented with the long axis east to west, while that of 2 WTC was oriented north to south. 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.<ref name="NIST-chapter1"/> The columns tapered with height, and consisted of welded box-sections at lower floors and rolled wide-flange sections at upper floors. All of the elevators and stairwells were located in the core.
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The building's core housed the [[elevator]] and utility shafts, restrooms, three stairwells, and other support spaces. The core in 1 WTC was oriented with the long axis east to west, while that of 2 WTC was oriented north to south. The core of each tower was a rectangular area 87 by 135 feet and contained 47 steel columns running from the bedrock to the top of the tower. The columns tapered with height, and consisted of welded box-sections at lower floors and rolled wide-flange sections at upper floors. All of the elevators and stairwells were located in the core.
  
 
====Floor system====
 
====Floor system====
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[[Image:World Trade Center NYC Sander Lamme.jpg|225px|right|thumb|View from the WTC.]]The large, column-free space between the perimeter and core was bridged by pre-fabricated 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 4 inch (10 cm) thick lightweight [[concrete]] slabs laid on a fluted steel deck. A grid of lightweight bridging trusses and main trusses supported the floors. The trusses had a span of 60 feet (18.2 m) in the long-span areas and 35 feet (11.0 m) in the short span area.<ref name="NIST-chapter1"/>  The trusses connected to the perimeter at alternate columns, and were therefore on 6 foot 8 inch (2.03 m) 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 spandel plates with vicsoelastic dampers, which helped reduce the amount of sway felt by building occupants. The trusses supported a 4-inch-thick (10 cm) lightweight concrete floor slab, with shear connections for composite action.<ref name="NIST-chapter1"/>
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The large, column-free space between the perimeter and core was bridged by pre-fabricated, 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 4-inch-thick, lightweight [[concrete]] slabs laid on a fluted-steel deck. A grid of lightweight bridging trusses and main trusses supported the floors. The trusses had a span of 60 feet in the long-span areas and 35 feet in the short span area. The trusses connected to the perimeter at alternate columns, and were therefore on six-foot, eight-inch 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 spandel plates with viscoelastic dampers, which reduced building structural vibration and were first utilized in the Twin World Trade Center Towers in New York in 1969, for wind induced vibrations. VE damping system in the Twin Towers is a double-layer shear damper using a 3M material, which is a rubber derivative, glued to steel plate and angle irons.<ref>Design Community, [http://www.designcommunity.com/discussion/7595.html Viscoelastic dampers]. Retrieved September 30, 2022.</ref> This helped reduce the amount of sway felt by building occupants. The trusses supported a 4-inch-thick, lightweight-concrete floor slab, with shear connections for composite action.
  
 
====Hat trusses====
 
====Hat trusses====
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Hat trusses (or "outrigger truss") located from the 107th floor to the top of the buildings were designed to support a tall communications antenna on top of each building.<ref name="NIST-chapter1"/>  Though, only WTC1 (north tower) actually had an antenna. The truss system consisted of six trusses along the long axis of 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.
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Hat trusses (or "outrigger truss") located from the 107th floor to the top of the buildings were designed to support a tall communications antenna on top of each building. However, only WTC1 (north tower) actually had an antenna. The truss system consisted of six trusses along the long axis of 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.
  
 
====Design innovations====
 
====Design innovations====
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[[Image:World Trade Center Building Design with Floor and Elevator Arrangment.svg|thumb|250px|A typical floor layout and elevator arrangement of the WTC towers.]]
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[[Image:World Trade Center Building Design with Floor and Elevator Arrangment.svg|thumb|right|400px|A typical floor layout and elevator arrangement of the WTC towers.]]
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To solve the problem of [[wind]] sway or vibration in the construction of the towers, chief engineer [[Leslie Robertson]] took a then unusual approach — instead of bracing the buildings corner-to-corner or using internal walls, the towers were essentially hollow [[steel]] tubes surrounding a strong central core. The 208 feet (63.4 m) wide facade was, in effect, a prefabricated steel lattice, with columns on 39&nbsp;[[inch]] (100 [[centimetre|cm]]) centers acting as wind bracing to resist all overturning forces; the central core took the majority of the gravity loads of the building. A very light, economical structure was built by keeping the wind bracing in the most efficient area, the outside surface of the building, thus not transferring the forces through the floor membrane to the core, as in most curtain-wall structures. The core supported the weight of the entire building and the outer shell containing 240 vertical steel columns called  [[truss#Vierendeel truss|Vierendeel trusses]] around the outside of the building, which were bound to each other using ordinary steel trusses. In addition, 10,000 dampers were included in the structure. With a strong shell and core such as this, the exterior walls could be simply light steel and concrete.  With the massive core and lightweight shell for structural integrity, Robertson created a tower that was extremely light for its size. This method of construction also meant that the twin towers had high load-bearing walls.
 
  
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The buildings were also the second [[supertall]] buildings to use [[sky lobby|sky lobbies]], after the [[John Hancock Center]] in [[Chicago]].<ref>{{cite web |url= http://www.otis.com/otis150/section/1,2344,ARC3066_CLI1_RES1_SEC5,00.html|publisher=[[Otis Elevator Company]]|title= Otis History: The World Trade Center|accessdate=2006-12-07}}</ref>  Skylobbies are floors where commuters can switch from an express [[elevator]] that goes only to the sky lobbies to a local elevator that goes to each floor in a section.  The local elevators were stacked on top of each other, 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 taking up a minimum of valuable office space.<ref>{{cite book |last=Gillespie |first=Angus K. |title=Twin Towers: The Life of New York City's World Trade Center |year=1999 |publisher=Rutgers University Press |chapter=Chapter 2}}</ref>  Altogether, the World Trade Center had 95 express and local elevators.<ref name="ruchelman-p11">{{cite book |title=The World Trade Center: Politics and Policies of Skyscraper Development. |author=Ruchelman, Leonard I. |publisher=Syracuse University Press |year=1977 |pages=p. 11}}</ref>  This system was inspired by the [[New York City Subway]] system, whose lines include local stations where local trains stop and express stations where all trains stop.<ref name="gillespie-p76">{{cite book |author=Gillespie, Angus K. |year=1999 |title=Twin Towers: The Life of New York City's World Trade Center |publisher=Rutgers University Press |pages=p. 76}}</ref>
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To solve the problem of [[wind]] sway or vibration in the construction of the towers, chief engineer [[Leslie Robertson]] took a then unusual approach—instead of bracing the buildings corner-to-corner or using internal walls, the towers were essentially hollow [[steel]] tubes surrounding a strong central core. The 208-foot-wide facade was, in effect, a prefabricated steel lattice, with columns on 39-inch centers acting as wind bracing to resist all overturning forces; the central core took the majority of the gravity loads of the building. A very light, economical structure was built by keeping the wind bracing in the most efficient area, the outside surface of the building.  
  
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The site of the World Trade Center was located on landfill, with the bedrock located 65 feet below.<ref name="iglauer">{{cite news |url=http://www.newyorker.com/archive/content/articles/010924fr_archive02 |title=The Biggest Foundation |author=Iglauer, Edith |date=November 4 1972 |publisher=The New Yorker}}</ref>  In order to construct the World Trade Center, it was necessary to build the "bathtub," with the [[slurry wall]] along the [[West Street]] side of the site, which serves the purpose of keeping water from the Hudson River out. The slurry method involves digging a [[trench]], and as [[excavation]] proceeds, filling the space with a "slurry" mixture, comprised of [[bentonite]] which plugs holes and keeps water out. When the trench was dug out, a steel cage was inserted, with concrete poured in, forcing the "slurry" out. The "slurry" method was devised by Port Authority chief engineer, John M. Kyle, Jr.
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Thus, the forces were not transferred through the floor membrane to the core, as in most curtain-wall structures. The core supported the weight of the entire building and the outer shell containing 240 vertical steel columns, called  Vierendeel trusses, around the outside of the building, which were bound to each other using ordinary steel trusses. In addition, 10,000 dampers were included in the structure. With a strong shell and core such as this, the exterior walls could be simply light steel and concrete. With the massive core and lightweight shell for structural integrity, Robertson created a tower that was extremely light for its size. This method of construction also meant that the twin towers had high load-bearing walls.
  
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===Construction===
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The buildings were also the second [[supertall]] buildings to use [[sky lobby|sky lobbies]], after the [[John Hancock Center]] in [[Chicago]]. Skylobbies are floors where commuters can switch from an express [[elevator]] that goes only to the sky lobbies to a local elevator that goes to each floor in a section. The local elevators were stacked on top of each other, 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 taking up a minimum of valuable office space. Altogether, the World Trade Center had 95 express and local elevators. This system was inspired by the [[New York City Subway]] system, whose lines include local stations where local trains stop and express stations where all trains stop.
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[[Image:World trade center new york city construction flickr.png|right|thumb|225px|1 World Trade Center and 2 World Trade Center under construction in 1970.]]
 
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Groundbreaking for the construction of the World Trade Center was on August 5, 1966.<ref>{{cite book |author=Federal Emergency Management Agency |date=May 2002 |title=World Trade Center Building Performance Study |chapter=Chapter 1 |url=http://www.fema.gov/rebuild/mat/mat_fema403.shtm}}</ref>  The construction was under the auspices of the semi-autonomous [[Port Authority of New York and New Jersey]].  Thirteen square blocks of low rise buildings in [[Radio Row]], some of which pre-dated the [[American Civil War]], were razed to clear the site for construction.  
 
  
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The excavation of the foundations of the WTC complex, known as [[the Bathtub]], was particularly complicated since there were two [[New York City Subway|subway]] tubes close by needing protection without service interruption. A six-level basement was built in the foundations. The excavation of about 1 million [[cubic yard]]s (760,000 [[cubic meter|m³]]) of earth and rock created a $90 million real estate asset for the project owner, the [[Port Authority of New York and New Jersey]], which helped offset the enormous loss in revenues which came from the tax breaks given to the Trade Center itself. The soil was used to create 23 acres (93,000 m²) of landfill in the [[Hudson River]] next to the World Trade Center site, which became the site of [[Battery Park City]] (still under development).
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The site of the World Trade Center was located on landfill, with the bedrock located 65 feet below. In order to construct the World Trade Center, it was necessary to build the "bathtub," with the [[slurry wall]] along the [[West Street]] side of the site, which serves the purpose of keeping water from the Hudson River out. The slurry method involves digging a [[trench]], and as [[excavation]] proceeds, filling the space with a "slurry" mixture, comprised of [[bentonite]] which plugs holes and keeps water out. When the trench was dug out, a steel cage was inserted, with concrete poured in, forcing the "slurry" out. The "slurry" method was devised by Port Authority chief engineer, John M. Kyle, Jr.
  
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In 1970, construction was completed on One World Trade Center, with its first tenants moving into the building in December, 1970. Tenants first moved into Two World Trade Center in January 1972.<ref>{{cite web|url=http://wtc.nist.gov/pubs/NISTNCSTAR1-1.pdf |author=Lew, H. S., Richard W. Bukowski, and Nicholas J. Carino |publisher=National Institute of Standards and Technology (NIST) |title= Design, Construction, and Maintenance of Structural and Life Safety Systems (pdf)}}</ref>  When the World Trade Center twin towers were completed, the total costs to the Port Authority had reached $900 million.<ref name="Cudahy">{{cite book |author=Cudahy, Brian J. |year=2002 |title=Rails Under the Mighty Hudson: The Story of the Hudson Tubes, the Pennsy Tunnels, and Manhattan Transfer |chapter=Chapter 3 |publisher=Fordham University Press}}</ref>  The ribbon-cutting ceremony was on April 4, 1973.<ref>{{cite web|url=http://www.greatbuildings.com/buildings/World_Trade_Center.html |publisher=Greatbuildings.com |title=World Trade Center - Minoru Yamasaki |accessdate=2006-04-06}}</ref>
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===Construction===
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[[File:WTC-1971-under-construction.jpg|right|thumb|300px|World Trade Center during construction - May 1970]]
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Groundbreaking for the construction of the World Trade Center was on August 5, 1966. The construction was under the auspices of the semi-autonomous [[Port Authority of New York and New Jersey]]. Thirteen square blocks of low rise buildings in Radio Row, some of which pre-dated the [[American Civil War]], were razed to clear the site for construction.  
  
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===Engineers and contractors Involved===
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The excavation of the foundations of the WTC complex, known as [[the Bathtub]], was particularly complicated since there were two [[New York City Subway|subway]] tubes nearby needing protection without service interruption. A six-level basement was built in the foundations. The excavation of about 1 million [[cubic yard]]s of earth and rock created a $90-million, real-estate asset for the project owner, the [[Port Authority of New York and New Jersey]], which helped offset the enormous loss in revenues which came from the tax breaks given to the Trade Center itself. The soil was used to create 23 acres of landfill in the [[Hudson River]] next to the World Trade Center site, which became the site of [[Battery Park City]], which is still under development.
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Guy F. Tozzoli,
 
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Director, World Trade Department, Port Authority of New York and New Jersey
 
  
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Rino M. Monti, Chief Engineer
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In 1970, construction was completed on One World Trade Center, with its first tenants moving into the building in December, 1970. Tenants first moved into Two World Trade Center in January 1972. The ribbon-cutting ceremony was on April 4, 1973. When the World Trade Center twin towers were completed, the total costs to the Port Authority had reached $900 million.
  
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'''Architects''': [[Minoru Yamasaki & Associates]], [[Troy, Michigan]]; [[Emery Roth & Sons]], New York
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==The complex==
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===The Twin Towers===
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[[Image:WTC Building Arrangement and Site Plan.svg|right|thumb|300px|The WTC site building arrangement.]]
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Ultimately the complex came to consist of seven buildings, but its most notable features were the main twin towers. Each of the WTC towers had 110 stories. 1 WTC (the North Tower, which featured a massive 360-foot-high, TV antenna added in 1978) stood 1,368 [[Foot (unit of length)|feet]] high, and 2 WTC (the South Tower, which contained the observation deck) was 1,362 feet  high. The length and breadth of the towers were 208 feet by 208 feet. Although only Tower 1 featured an antenna, the structure of each building was designed to carry a broadcast mast, and in the basement of the complex, The Mall at the World Trade Center was Manhattan's largest mall until September 11th, 2001.
  
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'''Structural Engineers''': Skilling, Helle, Christiansen, Robertson, New York
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When completed in 1972, 1 WTC became the tallest building on Earth, unseating the [[Empire State Building]] after a 40-year reign. 2 WTC became the second tallest building in the world when completed in 1973. As the building neared completion, work had already begun on [[Chicago]]'s [[Sears Tower]], which ultimately reached 1,450 feet.
  
−
'''Foundation Engineers''': [[Port Authority of New York and New Jersey]]-Engineering Department
+
Of the 110 stories, eight were set aside for technical services. All the remaining floors were free for open-plan offices. Each floor of the towers had 40,000 square feet of space for occupancy. Each tower had 3.8 million [[square feet]] of office space. Altogether the entire complex of seven buildings had 11.2-million square feet of space.
  
−
'''Electrical Engineers''': Joseph R. Loring & Associates, New York
+
During the 1990s, approximately 500 companies had offices in the complex, including major financial companies such as [[Morgan Stanley]], [[Aon Corporation]], [[Salomon Brothers]], as well as the Port Authority itself. Electrical service to the towers was supplied by Consolidated Edison (ConEd) at 13,800 volts. This service passed through the World Trade Center Primary Distribution Center (PDC) and sent up through the core of the building to electrical substations located on the mechanical floors. The substations "stepped" the 13,800 primary voltage down to 480/277 volt secondary power and further to 120/208 volt general power and lighting service. The complex also was served by emergency generators located in the sublevels of the towers and on the roof of 5 WTC.
  
−
'''Mechanical Engineers''': Jaros, Baum & Bolles, New York
+
The 110th Floor of 1 WTC (North Tower) housed commercial and public service radio & television transmission equipment. The roof of 1 WTC contained a vast array of transmission antennas including the center antenna mast rebuilt in 1999 by Dielectric Inc. to accommodate DTV. The mast contained the television signals for almost all NYC television broadcasters. Access to the roof was controlled from the WTC Operations Control Center (OCC) located in the B1 level of 2 WTC.
  
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'''General Contractor''': [[Tishman Reality & Construction|Tishman Realty & Construction Company]], New York
+
The World Trade Center complex was protected by an extensive fire detection and voice evacuation paging system upgraded after the 1993 bombing. Fire Command Stations, staffed by Fire Safety Directors were located in the lobbies of each building and the Operations Control Center (OCC) monitored these systems.
  
−
===Architectural criticism===
+
===Observation deck and Windows on the World===
−
Although the towers became an undeniable icon of New York City, they were not without flaws and were handicapped in many ways. Initially conceived, (as the name suggests) as a complex dedicated to companies and organizations directly taking part in "world trade," they at first failed to attract the expected clientele.  During the early years, various governmental organizations became key tenants of the World Trade Center, including the [[Government of New York|State of New York]]. It was not until the 1980s that the city's perilous financial state eased, after which an increasing number of private companies &mdash; mostly financial firms tied to [[Wall Street]] &mdash; became tenants.
+
[[Image:World Trade Center From Queens.jpg|400px|thumb|The World Trade Center as viewed from the borough of Queens]]
 +
Although the majority of space in the World Trade Center complex was off-limits to the general public, 2 WTC (South Tower) featured a public observation area aptly named "Top Of The World." When visiting the observation deck, visitors would first pass through security checks added after the 1993 [[World Trade Center bombing]]. Next, visitors were whisked to the 107th floor indoor [[observatory]] and greeted with a 360-degree view of the [[New York City]] skyline, and exhibitions including a three-dimensional scale model of Manhattan and a simulated helicopter ride around the city. Weather permitting, visitors could take two short escalator rides up from the 107th floor and visit what was the world's highest outdoor viewing platform. At a height of 1,377 feet, visitors were able to take in a view of the North Tower and New York City unlike any other. On a clear day, it was claimed that visitors could see up to 45 miles in any given direction. An anti-[[suicide]] fence was placed on the roof itself, with the viewing platform set back and elevated above it, requiring only an ordinary railing and leaving the view unobstructed.
  
−
Moreover, the trade center's "[[city block#superblock|superblock]]," which replaced a more traditional, dense neighborhood, was regarded by some critics as an inhospitable environment that disrupted the complicated traffic network  typical of Manhattan. For example, in his book ''The Pentagon of Power'', the technical historian [[Lewis Mumford]] denounced the center as an "example of the purposeless [[giantism]] and technological exhibitionism that are now eviscerating the living tissue of every great city." On the other hand, Mr. Yamasaki saw the expanse as a focal point of serenity amidst the chaos of the city.  The twin tower's narrow office windows, only 18 inches wide, were also disliked by many for impairing the view from the buildings.<ref name="pekala">{{cite news |title=Profile of a lost landmark; World Trade Center |publisher=Journal of Property Management |date=November 1, 2001 |author=Pekala, Nancy}}</ref>  This design element reflected on Yamasaki's [[Acrophobia|fear of heights]] and desire to make building occupants secure with narrow windows.<ref name="pekala"/>
+
The North Tower (1 WTC) had a restaurant on the 107th floor called [[Windows on the World]], which was an elegant eatery known as a place for big celebrations, such as weddings. In its last full year of operation, Windows on the World reported revenues of $37.5 million, making it the highest-grossing restaurant in the [[United States]].
  
−
For many years, the immense Austin J. Tobin Plaza was unpopular, but in later years it became a center for outdoor concerts and other activities.  In 1999, the outdoor plaza re-opened after undergoing $12 million renovations, which involved replacing [[marble]] pavers with gray and pink [[granite]] stones, adding new benches, planters, new restaurants and food kiosks, and outdoor dining areas.<ref>{{cite web |url=http://www.panynj.gov/pr/71-99.html |title=World Trade Center Plaza Reopens with Summer-long Performing Arts Festival |publisher=PANYNJ |date=June 9, 1999}}</ref>
+
===The other buildings===
−
 
+
Five smaller buildings stood around the 16-acre block. One was the 22-floor Vista Hotel (3 WTC), later a [[Marriot International|Marriott Hotel]], at the southwest corner of the site. It was crushed between the two towers when they collapsed. Three low-rise buildings (4 WTC, 5 WTC, and 6 WTC) in the same basic design as the main towers also stood around the plaza. 6 World Trade Center, at the northwest corner, housed the [[U.S. Customs and Border Protection|United States Customs Service]] and the [[Commodities exchange|U.S. Commodities Exchange]]. 5 World Trade Center was located at the northeast corner, above the PATH train station, and 4 World Trade Center was at the southeast corner. In 1987, a 46-floor office building called 7 WTC was built north of the block. Beneath the World Trade Center complex was an underground shopping mall, which in turn had connections to various mass transit facilities, including the New York City subway system and the Port Authority's own trains connecting Manhattan to Jersey City.
−
==The complex==
 
−
[[Image:WTC Building Arrangement and Site Plan.svg|right|thumb|250px|The WTC site building arrangement.]]
 
−
===The Twin Towers===
 
−
Ultimately the complex came to consist of seven buildings, but its most notable features were the main twin towers. Each of the WTC towers had 110 stories. 1 WTC (the North Tower, which featured a massive 360 foot high TV antenna added in 1978) stood 1,368 [[Foot (unit of length)|feet]] (417 [[meter|m]]) high,<ref name="height">{{cite web|url=http://www.emporis.com/en/wm/cx/?id=100329 |publisher=Emporis |title=World Trade Center, New York City |accessdate=2006-04-13}}</ref> and 2 WTC (the South Tower, which contained the observation deck) was 1,362 feet (415 m) high.<ref name="height"/> The length and breadth of the towers were 208 feet (63.4 m) x 208 feet (63.4 m). Although only Tower 1 featured an antenna, the structure of each building was designed to carry a broadcast mast, and in the basement of the complex, The Mall at the World Trade Center Manhattan's largest mall until 9-11. 
 
−
 
 
−
When completed in 1972, 1 WTC became the tallest building on Earth, unseating the Empire State Building after a 40 year reign. 2 WTC became the second tallest building in the world when completed in 1973. The difference in height between the two towers was because of a Port Authority request to have two floors, the 43rd and the 67th, in 1 WTC raised, the lower of the taller floors being a cafeteria for PANY workers. 2 WTC did not need these facilities, so it remained 1,362 feet. Regardless, the WTC towers held the height record only briefly. As the building neared completion in 1973, work had already begun on [[Chicago]]'s [[Sears Tower]], which ultimately reached 1,450 feet (442 m).<ref>{{cite web | title = Sears Tower Building Information | url = http://www.thesearstower.com/buildinginfo.axis?type=n&name=Property%20Profile | accessdate = 2006-09-11 }}</ref>  With the World Trade Center's destruction, the Empire State Building again became the tallest building in New York, after spending almost 30 years as the third-tallest in the city.
 
−
[[Image:World Trade Center From Queens.jpg|left|225px|thumb|The World Trade Center as viewed from Queens]]
 
−
The towers' sheer size was the subject of a joke during a press conference unveiling the landmarks. [[Minoru Yamasaki]] was asked: "Why two 110-story buildings? Why not one 220-story building?" His response was: "I didn't want to lose the human scale."  Another popular joke among New York urbanites that died out late in the 1970s from overtelling was that the towers looked like the boxes the [[Chrysler Building]] and Empire State Building came in.
 
−
 
 
−
Of the 110 stories, eight were set aside for technical services ([[mechanical floor]]s) Level B6/B5, Floors 7/8, 41/42, 75/76 and 108/109, in four two-floor areas evenly spread up the building. All the remaining floors were free for open-plan offices.  Each floor of the towers had 40,000 square feet of space for [[occupancy]].<ref name="ruchelman-p11"/>  Each tower had 3.8 million [[square feet]] (350,000 [[square meter|m²]]) of office space, which provided ample room for companies to set up shop. Altogether the entire complex of seven buildings had 11.2 million square feet (1.04&nbsp;km²) of space.
 
−
[[Image:WTC_lobby_19-8-00.png|right|thumb|250px|The lobby of the World Trade Center.]]
 
−
During the 1990s, approximately 500 companies had offices in the complex, including many financial companies such as [[Morgan Stanley]], [[Aon Corporation]], [[Salomon Brothers]], as well as the Port Authority itself.  Electrical service to the towers was supplied by Consolidated Edison (ConEd) at 13,800 volts. This service passed through the World Trade Center Primary Distribution Center (PDC) and sent up through the core of the building to electrical substations located on the mechanical floors. The substations "stepped" the 13,800 primary voltage down to 480/277 volt secondary power and further to 120/208 volt general power and lighting service. The complex also was served by emergency generators located in the sublevels of the towers and on the roof of 5 WTC. <ref>{{cite web|publisher=[[FEMA]]|url=http://www.fema.gov/pdf/library/fema403_ch2.pdf|accessdate=2007-03-08|title=World Trade Center Building Performance Study|quote=Six 1,200-kilowatt(kW) emergency power generators located in the sixth basement (B-6) level provided a secondary power supply.}}</ref><ref>{{cite web|quote=E-J Electric set four generators on the roof of Tower 5, which was nine stories, as opposed to the 110-story Towers 1 and 2. E-J then ran high-voltage feeder cable to Towers 1, 2, 4 and 5, installed three substations and distributed power to the tenants.|publisher=CEE News|date=Jan 1, 2001|accessdate=2007-03-08|url=http://september11.ceenews.com/ar/electric_towering_security_2/index.htm|author=Amy Florence Fischbach|title=Towering security}}</ref>
 
−
 
 
−
The 110th Floor of 1 WTC (North Tower) housed commercial and public service radio & television transmission equipment. The roof of 1 WTC contained a vast array of transmission antennas including the center antenna mast rebuilt in 1999 by Dielectric Inc. to accommodate DTV. The mast contained the television signals for almost all NYC television broadcasters:  [[WCBS-TV]] 2, [[WNBC-TV]] 4, [[WNYW]] 5, [[WABC-TV]] 7, [[WWOR-TV]] 9 [[Secaucus, New Jersey|Secaucus]], [[WPIX-TV]] 11, [[WNET]] 13 [[Newark, New Jersey|Newark]], [[WPXN-TV]] 31, and [[WNJU]] 68. It also had four NYC FM broadcasters on it as well:  [[WPAT-FM]] 93.1, [[WNYC]] 93.9, [[WKCR]] 89.9, and [[WKTU]] 103.5.<ref>http://www.fcc.gov/</ref> Access to the roof was controlled from the WTC Operations Control Center (OCC) located in the B1 level of 2 WTC.
 
−
 
 
−
The World Trade Center complex was protected by an extensive fire detection and voice evacuation paging system upgraded after the 1993 bombing. Fire Command Stations, staffed by Fire Safety Directors were located in the lobbies of each building and the Operations Control Center (OCC) monitored these systems. An extensive study of the performance of World Trade Center Fire Protection Systems was conducted by the National Institute of Standards and Technology (NIST) following 9/11/2001.<ref>http://wtc.nist.gov/NISTNCSTAR1-4C.pdf</ref>
 
  
−
===Observation deck and Windows on the World===
+
One of the world's largest [[gold]] depositories was stored underneath the World Trade Center, owned by a group of commercial banks. The 1993 bomb detonated close to the vault, but it withstood the explosion, as did the towers. Seven weeks after the September 11th attacks, $230 million in precious metals were removed from basement vaults of 4 WTC, which included 3,800, 100-Troy-ounce registered gold bars and 30,000 1,000-ounce [[silver]] bars.
−
[[Image:World Trade Center Observation Deck New York City 1999_corrected.jpg|right|250px|thumb|On the [[observation deck]].]]
 
−
[[Image:Windows on the world window seats.jpg|right|250px|thumb|Windows on the World.]]
 
−
Although the majority of space in the WTC complex was off-limits to the general public, 2 WTC (South Tower) featured a public observation area aptly named "Top Of The World." When visiting the observation deck, visitors would first pass through security checks added after the 1993 [[World Trade Center bombing]].  Next, visitors were whisked to the 107th floor indoor [[observatory]] and greeted with a 360 degree view of the New York City skyline, and exhibitions including a three-dimensional scale model of Manhattan, and a simulated helicopter ride around the city. Weather-permitting, visitors could take two short escalator rides up from the 107th floor and visit what was the world's highest outdoor viewing platform.  At a height of 1,377 feet (420 m), visitors were able to take in a view of the North Tower and [[New York City]] unlike any other.  On a clear day, it was claimed that visitors could see up to 45 [[mile]]s (72 [[kilometre|km]]) in any given direction. An anti-[[suicide]] fence was placed on the roof itself, with the viewing platform set back and elevated above it, requiring only an ordinary railing and leaving the view unobstructed.
 
  
−
The North Tower (1 WTC) had a restaurant on the 107th floor called [[Windows on the World]], which was an elegant restaurant known as a place for big celebrations, such as weddings. In its last full year of operation, 2000, Windows on the World reported revenues of $37.5 million, making it the highest-grossing restaurant in the United States.
+
==Architectural criticism==
 +
Although the towers became an undeniable icon of [[New York City]], they were not without flaws and were handicapped in many ways. Initially conceived, (as the name suggests) as a complex dedicated to companies and organizations directly taking part in "world trade," they at first failed to attract the expected clientèle. During the early years, various governmental organizations became key tenants of the World Trade Center, including the [[Government of New York|State of New York]]. It was not until the 1980s that the city's perilous financial state eased, after which an increasing number of private companies—mostly financial firms tied to [[Wall Street]]—became tenants.
  
−
===The other buildings===
+
Moreover, the trade center's "superblock," which replaced a more traditional, dense neighborhood, was regarded by some critics as an inhospitable environment that disrupted the complicated traffic network typical of Manhattan. For example, in his book ''The Pentagon of Power,'' the technical historian Lewis Mumford denounced the center as an "example of the purposeless giantism and technological exhibitionism that are now eviscerating the living tissue of every great city."<ref>Lewis Mumford, ''The Pentagon of Power'' (Harcourt, Brace and Jovanovich, Inc., 1974).</ref> On the other hand, Mr. Yamasaki saw the expanse as a focal point of serenity amidst the chaos of the city. The twin tower's narrow office windows, only 18 inches wide, were also disliked by many for impairing the view from the buildings. This design element reflected on Yamasaki's [[Acrophobia|fear of heights]] and desire to make building occupants secure with narrow windows.
−
Five smaller buildings stood around the 16 [[acre]] (65,000 m²) block. One was the 22-floor Vista Hotel (3 WTC), later a [[Marriot International|Marriott Hotel]], at the southwest corner of the site, that was crushed between the two towers. Three low-rise buildings (4 WTC, 5 WTC, and 6 WTC) in the same hollow tube design as the towers also stood around the plaza. [[6 World Trade Center]], at the north west corner, housed the [[U.S. Customs and Border Protection|United States Customs Service]] and the [[Commodities exchange|U.S. Commodities Exchange]]. [[5 World Trade Center]] was located at the northeast corner, above the [[World Trade Center (PATH station)|PATH station]], and [[4 World Trade Center]] was at the southeast corner.  In 1987, a 46-floor office building called [[7 World Trade Center|7 WTC]] was built north of the block. Beneath the World Trade Center complex was an [[The Mall at the World Trade Center|underground shopping mall]], which in turn had connections to various mass transit facilities, including the [[New York City subway]] system and the Port Authority's own [[Port Authority Trans-Hudson|PATH]] trains connecting Manhattan to [[Jersey City, New Jersey|Jersey City]].
 
  
−
One of the world's largest [[gold]] depositories was stored underneath the World Trade Center, owned by a group of commercial banks. The 1993 bomb detonated close to the vault, but it withstood the explosion, as did the towers. Seven weeks after the September 11th attacks, $230 million in precious metals were removed from basement vaults of 4 WTC, which included 3,800 100-Troy-ounce registered gold bars and 30,000 1,000-ounce [[silver]] bars.<ref>[http://www.rediff.com/money/2001/nov/17wtc.htm Rediff.com] &ndash; Buried WTC gold returns to futures trade</ref>
+
For many years, the outdoor five-acre Austin J. Tobin Plaza, also known as the World Trade Center Plaza, was unpopular because its appearance was considered barren and unwelcoming. However, in later years it became a popular center for outdoor concerts and other activities. In 1999, the plaza re-opened after undergoing $12 million renovations, which involved replacing [[marble]] pavers with gray and pink [[granite]] stones, adding new benches, planters, new restaurants and food kiosks, and outdoor dining areas.
  
 
==Life of the World Trade Center==
 
==Life of the World Trade Center==
−
On any given day, approximately 50,000 people worked in the towers,<ref name="ruchelman-p11"/> with another 200,000 passing through as visitors. The complex was so large that it had its own [[ZIP Code|zip code]], 10048. The towers offered spectacular views from the observation deck (located on top of the South Tower) and the [[Windows on the World]] restaurant (located on top of the North Tower). The trade center had its many admirers, particularly visitors. For those who deemed it cold and sterile, there were just as many who appreciated its sheer grandeur; some even took advantage of it. French high wire acrobatic performer [[Philippe Petit]] walked between the towers on a tightrope in 1974, and Brooklyn toymaker [[George Willig]] scaled the south tower in 1977. The Twin Towers became known worldwide, appearing in movies, TV shows, postcards, merchandise, magazines and much more. The twin towers became a New York icon, such as the [[Empire State Building]], or [[Statue of Liberty]].  
+
[[Image:WTC_lobby_19-8-00.png|right|thumb|400px|The lobby of the World Trade Center.]]
 +
On any given day, approximately 50,000 people worked in the towers, with another 200,000 passing through as visitors. The complex was so large that it had its own [[ZIP Code|zip code]], 10048. The towers offered spectacular views from the observation deck and the [[Windows on the World]] restaurant (located on top of the North Tower). The trade center had its many admirers, particularly visitors. For those who deemed it cold and sterile, there were just as many who appreciated its sheer grandeur; some even took advantage of it. French high-wire, acrobatic performer [[Philippe Petit]] walked between the towers on a tightrope in 1974, and Brooklyn toymaker [[George Willig]] scaled the south tower in 1977. The Twin Towers became known worldwide, appearing in movies, TV shows, postcards, merchandise, magazines, and much more. The twin towers became a New York icon, not unlike the [[Empire State Building]], or [[Statue of Liberty]].  
  
 
===February 13, 1975 fire===
 
===February 13, 1975 fire===
−
On February 13, 1975, the WTC North Tower was beset by a fire which spread over nearly half of the 11th floor. The fire spread to other floors through openings in the floor slabs which were used to carry phone wires. The fires on other floors were extinguished almost immediately, and the main fire was put out in a few hours. Fireproofing protected the steel from melting and there was no structural damage to the tower (this is in contrast to the fires of September 11th, where much of the structural steel and core of the building was immediately destroyed by the explosions caused by the airplanes, and most of the remaining steel had lost its fireproofing due to the strong impact of the airplanes).  This event led to the instalation of a sprinkler system in both towers. Firefighters claim that had the sprinklers been installed when the tower was built, the fire probably would not had spread as much as it did.  Other than the damage caused by the fire, a few floors below suffered water damage from the extinguishing of the fires above.
+
On February 13, 1975, the WTC North Tower was beset by a fire which spread over nearly half of the eleventh floor. The fire spread to other floors through openings in the floor slabs which were used to carry phone wires. The fires on other floors were extinguished almost immediately, and the main fire was put out in a few hours. This event led to the installation of a sprinkler system in both towers. Other than the damage caused by the fire, a few floors below suffered water damage from the extinguishing of the fires above.
  
 
===Bombing of February 26, 1993===
 
===Bombing of February 26, 1993===
−
{{main|World Trade Center bombing}}
+
[[Image:WTC 1993 ATF.jpg|thumb|400px|Damage from the 1993 bombing.]]
−
On February 26, 1993 at 12:17 PM, a [[Ryder]] truck filled with 1,500 [[Pound (mass)|pounds]] (680 kg) of explosives was planted by [[Ramzi Yousef]] and detonated in the underground garage of the North Tower, opening a 100&nbsp;foot (30&nbsp;m) hole through 5 sublevels of [[concrete]] leaving 50,000 workers and visitors gasping for [[air]] in the shafts of the 110 story towers.
+
On February 26, 1993 at 12:17 PM, a [[Ryder]] truck filled with 1,500 pounds of explosives was planted by [[Islam]]ic terrorist [[Ramzi Yousef]] and detonated in the underground garage of the North Tower, opening a 100-foot hole through five sublevels of [[concrete]] leaving 50,000 workers and visitors gasping for [[air]] in the shafts of the 110-story towers.
−
 
 
−
Many people inside the North Tower were forced to walk down darkened stairwells which contained no emergency lighting, some taking two hours or more to reach safety.  As the Port Authority was a bi-state agency, the towers were exempt from New York City [[building code]]s.  Subsequent to the bombing The Port Authority installed emergency lighting in the stairwells.  It is believed that this lighting saved many lives during the events of September 11, 2001.
 
  
−
In 1997 and 1998, six [[Islamism|Islamist]] extremists were convicted and sentenced to life in prison for their roles in the bombing. According to a presiding judge, the conspirators' chief aim at the time of the attack was to de-stabilize the north tower and send it crashing into the south tower, toppling both landmarks.
+
Many people inside the North Tower were forced to walk down darkened stairwells which contained no emergency lighting, some taking two hours or more to reach safety. As the Port Authority was a bi-state agency, the towers were exempt from New York City [[building code]]s. Subsequent to the bombing, The Port Authority installed emergency lighting in the stairwells. It is believed that this lighting saved many lives during the events of September 11, 2001.
  
−
As a memorial to the victims of the bombing of the tower, a [[reflecting pool]] was installed with the names of those who had been killed in the blast. Following the September 11, 2001 attacks, relief workers found a single fractured piece of this fountain; to date it is the only remaining part of the 1993 memorial that survived the collapse of the towers.
+
In 1997 and 1998, six [[Islam|Islamic]] extremists were convicted and sentenced to life in prison for their roles in the bombing. According to a presiding judge, the conspirators' chief aim at the time of the attack was to de-stabilize the north tower and send it crashing into the south tower, toppling both landmarks.
  
−
===Lease===
+
A granite memorial fountain honoring the six people killed in the bombing was designed by Elyn Zimmerman and dedicated in 1995 on Austin J. Tobin Plaza, directly above the site of the explosion. It contained the names of the six people who perished in the attack as well as an inscription that read:
−
In 1998, plans were approved by the Port Authority to privatize the World Trade Center.<ref>{{cite news |title=PA to ease WTC tax load, rent would be cut to offset hike by city |publisher=New York Daily News |date=February 6, 2001 |author=Herman, Eric}}</ref>  In 2001, the Port Authority sought to lease the World Trade Center to a private entity.  Bids for the lease came from [[Vornado Realty Trust]], a joint bid between [[Brookfield Properties]] and [[Boston Properties]],<ref>{{cite news |title=Bidding for Twin Towers |publisher=The New York TImes |date=January 31, 2001 |author=Bagli, Charles V.}}</ref> and a joint bid by [[Silverstein Properties]] and [[The Westfield Group]].<ref name="cuozzo">{{cite news |title=Larry Lusts for Twin Towers; Silverstein has an Eye on WTC's; Untapped Retail Potential |publisher=New York Post |date=January 30, 2001 |author=Cuozzo, Steve}}</ref>  By privatizing the World Trade Center, it would be added to the city's tax rolls.<ref name="cuozzo"/>  The lease was also intended to raise funds for other Port Authority projects.<ref>{{cite news |title=Port Authority Gets Final Bids on WTC |publisher=New York Daily News |date=January 31, 2001 |author=Herman, Eric}}</ref>  On February 15, 2001, the Port Authority announced that Vornado Trust Realty had won the lease for the World Trade Center, paying $3.25 billion for the 99-year lease.<ref>{{cite news |title=Brookfield Loses Lease Bid |publisher=Toronto Star |date=February 23, 2001}}</ref>  Silverstein was outbid by $50 million by Vornado Realty.  However, Vornado later withdrew and Silverstein's bid for the lease to the World Trade Center was accepted on July 24 2001. The land was then privately owned.
 
  
−
===September 11, 2001===
+
<blockquote>On February 26, 1993, a bomb set by terrorists exploded below this site. This horrible act of violence killed innocent people, injured thousands, and made victims of us all.</blockquote>
−
{{main|September 11, 2001 attacks|Collapse of the World Trade Center}}
 
−
[[Image:National Park Service 9-11 Statue of Liberty and WTC fire.jpg|thumb|250px|right|The World Trade Center on fire.]]
 
−
On September 11 2001 at 8:46 [[a.m.]], [[Al Qaeda]] suicide hijackers crashed [[American Airlines Flight 11]] into the northern facade of the North Tower. <ref>{{cite web |url=http://registry.faa.gov/aircraftinquiry/NNumSQL.asp?NNumbertxt=334AA&cmndfind.x=11&cmndfind.y=24 |title=N-Number Inquiry Results |publisher=Federal Aviation Administration}}</ref><ref name="911commisssion">{{cite web|url=http://www.9-11commission.gov/report/index.htm |title=9/11 Commission Report |publisher=The National Commission on Terrorist Attacks Upon the United States}}</ref> Seventeen minutes later, 9:03 a.m., a second team of hijackers crashed [[United Airlines Flight 175]] into the South Tower,<ref name="911commisssion"/><ref>{{cite web| url=http://registry.faa.gov/aircraftinquiry/NNumSQL.asp?NNumbertxt=612UA&cmndfind.x=0&cmndfind.y=0 |title=N-Number Inquiry Results |publisher=Federal Aviation Administration}}</ref> which collapsed at 9:59 a.m. At 10:28 a.m., the North Tower collapsed. At 5:20 p.m., [[7 World Trade Center]] collapsed. The four remaining buildings in the WTC plaza sustained heavy damage from debris, and were ultimately demolished.
 
−
[[Image:Story.crash.sequence.jpg|125px|thumb|right|A sequential look at United Flight 175 crashing into the south tower of the World Trade Center while the story about the first crash was being covered.]]
 
−
At the time of the incident, media reports suggested that tens of thousands might have been killed in the massacre, as on any given day upwards of 100,000 people could be inside the towers. Ultimately, 2,749 death certificates were filed relating to the 9/11 attacks, as of February 2005.  Of these, 1,588 (58%) were forensically identified from recovered physical remains.
 
  
−
[[Morgan Stanley]] was the largest tenant in the World Trade Center, with approximately 2,500 employees in the South Tower and 1,000 in the North Tower.<ref>{{cite news |title=Jet Crash Victims' Stories Start To Emerge; Loved Ones Describe Lives, Last Contacts |publisher=The Washington Post |date=September 12, 2001 |author=Goldstein, Amy, Cheryl W. Thompson |url=http://www.washingtonpost.com/wp-dyn/content/article/2001/09/12/AR2005033108307.html}}</ref>
+
The fountain was destroyed during the September 11, 2001 attacks. A recovered fragment from the 1993 bombing memorial with the word "John" is being used as the centerpiece of a new memorial honoring the victims of the 2001 attack.
  
−
For the following 8½ months, the [[World Trade Center site]] cleanup and recovery continued 24 hours a day and involved thousands of workers. The massive pile of debris smoked and smoldered for 99 days.
+
===Privatization===
 +
In 1998, plans were approved by the Port Authority to privatize the World Trade Center. In 2001, the Port Authority sought to lease the World Trade Center to a private entity. Bids for the lease came from Vornado Realty Trust, a joint bid between Brookfield Properties and Boston Properties, and a joint bid by Silverstein Properties and The Westfield Group. By privatizing the World Trade Center, it would be added to the city's tax rolls. The lease was also intended to raise funds for other Port Authority projects.
  
−
==Rebuilding the World Trade Center==
+
On February 15, 2001, the Port Authority announced that Vornado Trust Realty had won the lease for the World Trade Center, paying $3.25 billion for the 99-year lease. Silverstein was outbid by $50 million by Vornado Realty. However, Vornado later withdrew and Silverstein's bid for the lease to the World Trade Center was accepted on July 24, 2001. The land was then privately owned.
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{{Future building|World Trade Center}}
 
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{{main|World Trade Center site}}
 
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[[Image:Wtcsite 2006-0911.jpg|thumb|right|250px|World Trade Center site on 9/11/2006.  On the right, early stages of construction and foundation work for the [[Freedom Tower]], which were paused in observance of the fifth anniversary.]]
 
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{{New World Trade Center}}
 
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[[Image:New wtc.jpg|right|thumb|250px|The completed new World Trade Center as expected to look in 2012.]]
 
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The [[Lower Manhattan Development Corporation]], the agency charged with coordinating the reconstruction of the [[World Trade Center site]], selected the master plan, [[Memory Foundations]] by [[Daniel Libeskind]],<ref> {{cite web|url=http://www.renewnyc.com/plan_des_dev/wtc_site/new_design_plans/selected_design.asp |author=Lower Manhattan Development Corp. |title=Selected Design for the WTC Site as of February 2003}}</ref> which includes the 1,776 ft (541 m) [[Freedom Tower]]. The height of 1,776 feet (541 m) was chosen as a reference to the year of [[Declaration of Independence (United States)|American independence]].  A new  [[7 World Trade Center]]  office building, which was not part of the site master plan, officially opened on May 23, 2006.
 
  
−
The Lower Manhattan Development Corporation sponsored the [[World Trade Center Site Memorial Competition]], an international design competition for the [[World Trade Center Memorial]] in spring 2003. The winning design, [[Michael Arad]] and Peter Walker's ''Reflecting Absence'', was chosen in January 2004.
+
===September 11, 2001===
 +
[[Image:National Park Service 9-11 Statue of Liberty and WTC fire.jpg|thumb|400px|right|The World Trade Center on fire after being hit by airplanes.]]
 +
 +
On [[September 11 attacks|September 11, 2001]], at 8:46 a.m., [[Al Qaeda]] [[Suicide attack|suicide]] [[hijack]]ers crashed American Airlines Flight 11 into the northern facade of the North Tower. Seventeen minutes later, at 9:03 a.m., a second team of hijackers crashed United Airlines Flight 175 into the South Tower, which collapsed at 9:59 a.m. At 10:28 a.m., the North Tower collapsed. At 5:20 p.m., 7 World Trade Center collapsed. The four remaining buildings in the WTC plaza sustained heavy damage from debris, and were ultimately demolished.  
  
−
The World Trade Center name will continue to be used as name of the site, as will the [[New York City Subway]] and [[Port Authority Trans-Hudson|PATH]] train stations that serve the complex. A temporary [[World Trade Center (PATH station)|PATH station]], largely following the layout of the original, is the first part of the complex to have re-opened.
+
At the time of the incident, media reports suggested that tens of thousands might have been killed in the massacre, as on any given day upwards of 100,000 people could be inside the towers. Ultimately, 2,749 death certificates were filed relating to the 9/11 attacks, as of February 2005. Of these, 1,588 (58 percent) were forensically identified from recovered physical remains.  
  
−
As of late 2006, work at the World Trade Center site continued. Foundation work has started on the Freedom Tower, Calatrava Hub, and the memorials.  By the end of 2006, the site was expected to look like the massive construction project that built the previous WTC.
+
For the following eight and a half months, the [[World Trade Center site]] cleanup and recovery continued 24 hours a day and involved thousands of workers. The massive pile of debris smoked and smoldered for 99 days.
−
 
 
−
==Film and media==
 
−
The World Trade Center has been featured in numerous [[films]], as well as appearing in many television shows, cartoons, comic books, computer/video games and music videos. The towers were amongst the most famous skyscrapers of the late [[20th Century]]. An episode of ''[[The Simpsons]]'' featured Homer in NYC needing a bathroom, finding the only bathroom available was at the top of the WTC. He climbed one tower to discover that the bathroom was closed and had to climb the other. The pilot episode of ''[[The Lone Gunmen]]'', aired in March 2001, featured a thwarted attempt to crash an airplane into the World Trade Center.  A dance scene in [[Godspell]] takes place on top of one tower, portrayed on the original record album cover. The Twin Towers were partially featured in the 1983 movie [[Trading Places]] where [[Eddie Murphy]] and [[Dan Akroyd]] go into 4 World Trade center. The Twin Towers were seen in the 1981 movie [[Escape from New York]] where [[Kurt Russell]] is on top of one of the towers. In the 1976 remake of [[King_Kong_%281976_film%29|King Kong]], King Kong climbs one of the towers of the World Trade Center. After being attacked by men with flame throwers whilst standing on the roof of the South Tower, Kong flees by leaping across to the North Tower. A photograph of this sequence appears on the original movie album cover. The twin towers are also seen in the [[Steven Spielberg]] film [[A.I. Artificial Intelligence]]. Although the towers were destroyed less than 3 months after the film's release, they were not digitally removed for the [[DVD]] versions. The original preview [[trailer (film)|trailer]] for the 2002 film ''[[Spider-Man (film)|Spider-Man]]'' featured the [[Spider-Man|title character]] capturing a group of bank robbers fleeing in a helicopter by creating a large web between the Twin Towers; this trailer, along with posters featuring the towers reflected in the eyepiece of Spider-Man's mask, was pulled from distribution following the 9/11 attacks, and the scene did not appear in the finished film. The World Trade Center also has several scenes in the Emmy-Award [[Inside 9/11]] in 2005. The [[Beastie Boys]] 2004 album, [[To The 5 Borough's]] front cover and fold out pages features an artists skyline portrait of [[New york]], including [[The Twin Towers]]. The song [[Open letter To NYC]] also includes [[Mike D]] referencing to The Twin Towers and pays homage to [[New York]] City. [[Limp Bizkit]]'s video for ''Rollin'' features the band performing at the top of one of the towers, and there is a zoom-out at the end of the video. The towers have also appeared in many filler-shots in [[Friends]], which have since been edited-out. The Twin Towers were also featured in various music videos and album artworks, including [[Oasis (band)|Oasis]]' ''[[Standing on the Shoulder of Giants]]'', and [[Supertramp]]'s ''[[Breakfast in America]]''.
 
−
 
 
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The events surrounding September 11 are portrayed in the 2002 collective project [[11'9"01 September 11]], in the [[Discovery Channel]]'s 2005 film, ''[[The Flight that Fought Back]]'', and in the [[History Channel]]'s ''[[I Missed Flight 93]]'', [[A&E Network]]'s ''[[Flight 93 (TV film)|Flight 93]]'', [[Oliver Stone]]'s ''[[World Trade Center (film)|World Trade Center]]'', [[Paul Greengrass]]' ''[[United 93 (film)|United 93]]'', which were released in 2006.  Images of the clean-up process at [[Ground Zero]] were taken over nine months by photographer [[Joel Meyerowitz]] following 9/11, and have been compiled in ''[[Aftermath: World Trade Center Archive]]'', published by [[Phaidon Press]] in 2006.
 
  
 +
[[Morgan Stanley]] was the largest tenant in the World Trade Center, with approximately 2,500 employees in the South Tower and 1,000 in the North Tower.
  
 +
==Rebuilding the World Trade Center==
 +
Over the following years, plans were created for the reconstruction of the World Trade Center. The [[Lower Manhattan Development Corporation]] (LMDC), established in November 2001 to oversee the rebuilding process,<ref>Richard Pérez-Peña, [https://www.nytimes.com/2001/11/03/nyregion/nation-challenged-downtown-state-plans-rebuilding-agency-perhaps-led-giuliani.html A Nation Challenged: Downtown; State Plans Rebuilding Agency, Perhaps Led by Giuliani] ''The New York Times'', November 3, 2001. Retrieved September 30, 2022.</ref> organized competitions to select a [[site plan]] and memorial design. [[Memory Foundations]], designed by [[Daniel Libeskind]], was selected as the master plan.<ref>Lower Manhattan Development Corporation, [http://www.renewnyc.com/plandesdev/ The Plan for Lower Manhattan] Retrieved September 30, 2022. </ref> However, substantial changes were made to the design. One World Trade Center (previously coined the "Freedom Tower" by Governor Pataki) is the centerpiece of Libeskind's design.
 +
[[File:WTC Hub September 2016 vc.png|thumb|400px|WTC Hub September 2016]]
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The first new building to be completed was 7&nbsp;WTC, which opened in May 2006. The memorial section of the [[National September 11 Memorial & Museum]] opened on September 11, 2011 and the museum opened in May 2014. The September 11 Museum opened to victims' families on April 15, 2014, and to the general public six days later. One WTC opened on November 3, 2014. One World Trade Center opened for business on November 3, 2014, with its observatory opening on May 29, 2015. The Oculus, the World Trade Center Transportation Hub was completed in 2016. 3 World Trade Center was completed in 2018, leaving 2 and 5 World Trade Center as the last two remaining unbuilt towers in the WTC complex; the construction of St. Nicholas Greek Orthodox Church also remains uncompleted.<ref>[https://www.nycurbanism.com/wtc Sixteen Acres, Eighteen Years: The Status of the WTC Complex] ''NYC Urbanism''. Retrieved September 30, 2022.</ref>
  
 
==Notes==
 
==Notes==
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{{Reflist}}
+
<references/>
−
 
 
  
 
==References==
 
==References==
−
*Gillespie, Angus K. ''Twin Towers: The Life of New York City's World Trade Center'', Rutgers University Press, 1999. ISBN 978-0813527420
+
*Gillespie, Angus K. ''Twin Towers: The Life of New York City's World Trade Center.'' Rutgers University Press, 1999. ISBN 978-0813527420
−
*Harris, Bill. ''The World Trade Center: A Tribute'', Courage Books, 2001. ISBN 978-0762413157
+
*Harris, Bill. ''The World Trade Center: A Tribute.'' Courage Books, 2001. ISBN 978-0762413157
−
*Koch III, Karl. ''Men of Steel: The Story of the Family that Built the World Trade Center'', Three Rivers Press, 2003. ISBN 978-1400049509
+
*Koch III, Karl. ''Men of Steel: The Story of the Family that Built the World Trade Center.'' Three Rivers Press, 2003. ISBN 978-1400049509
−
*Smith, Dennis. ''Report from Ground Zero: The Story of the Rescue Efforts at World Trade Center'', Viking Adult, 2002. ISBN 978-0670031160
+
*Mumford, Lewis. ''The Pentagon of Power.'' Harcourt, Brace and Jovanovich, Inc., 1974. {{ASIN|0156716100}}
 +
*Smith, Dennis. ''Report from Ground Zero: The Story of the Rescue Efforts at World Trade Center.'' Viking Adult, 2002. ISBN 978-0670031160
  
 
==External links==
 
==External links==
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{{commonscat|World Trade Center (New York)}}
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All links retrieved May 19, 2023.
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*[http://www.wtc.com/ World Trade Center official site]
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*[https://www.wtc.com/ World Trade Center official site]  
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*[http://web.archive.org/web/20010813164302/http://www.wtc-top.com/index.html Archived version of Top Of The World Trade Center Observatories website]
+
*[https://www.earthcam.com/usa/newyork/worldtradecenter/?cam=skyline_g World Trade Center Webcams]  
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*[http://www.ericdarton.net]
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*[https://www.oneworldobservatory.com/ One World Observatory]
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*[http://www.buildthememorial.org/ World Trade Center Memorial Foundation]
+
*[https://www.911memorial.org/ 9/11 Memorial & Museum]
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*[http://www.skyscraper.org/WHAT%27S_UP/WTC_DOSSIER/wtc.htm Skyscraper Museum WTC Dossier]
 
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*[http://www.emporis.com/en/bu/sk/wt/ Emporis — Special Coverage of the World Trade Center in New York City]
 
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*[http://www.renewnyc.com/ Lower Manhattan Development Corporation]
 
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*[http://www.lowermanhattan.info/ LowerManhattan.Info] Official site for Lower Manhattan Construction Command Center.
 
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*[http://www.skyscrapercity.com/showthread.php?t=56090 The Mega WTC Picture Thread at Skyscraper City]
 
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*[http://www.wikimapia.org/#y=40711736&x=-74012425&z=16&l=0&m=s Satellite view of World Trade Center site at WikiMapia]
 
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*[http://video.google.com/videoplay?docid=-4334991174539603857&q=World+Trade+Center%2C&hl=en''Building the World Trade Center'', a 1983 documentary about the construction of the WTC by the Port Authority of New York and New Jersey-from Google Video]
 
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*[http://www.wcbstv.com/911 September 11th Remembered]
 
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*[http://www.nyc.gov/html/om/html/2004b/pc070404-freedomtower300k.asx Video of cornerstone laying ceremony for the Freedom Tower on July 4, 2004]
 
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*[http://dmoz.org/Regional/North_America/United_States/New_York/Localities/N/New_York_City/Manhattan/Arts_and_Entertainment/Architecture/World_Trade_Center/ DMOZ directory]
 
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*[http://euge.smugmug.com/gallery/2356647/1/123402359 Construction works in January 2007]
 
  
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===Webcams===
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{{credit|120270941}}
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*[http://www.projectrebirth.org/ Project Rebirth]
 
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*[http://www.earthcam.com/cams/newyork/groundzero/camera2.php World Trade Center Site / Ground Zero Webcams]
 
  
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{{start box}}
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[[Category:Geography]]
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{{succession box |  before=[[Empire State Building]] |  title=[[List of tallest buildings in New York City|Tallest Building in New York City]] |  years=1973&mdash;2001 |  after=Empire State Building}}
 
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{{end box}}
 
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{{Supertall skyscrapers}}
 
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[[Category:nations and places]]
 
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{{credit|120270941}}
 

Latest revision as of 11:15, 19 May 2023


World Trade Center
World Trade Center Ground View 1999.jpg
World Trade Center was the world's tallest building from 1972 to 1973.*
Preceded by Empire State Building
Surpassed by Sears Tower
Information
Location New York City, New York, USA (Lower Manhattan)
Status Destroyed
Constructed 1966-1973
Destroyed September 11, 2001
Height
Antenna/Spire 1,727 feet [1]
Roof 1,368 feet
Top floor 1,355 feet
Technical details
Floor count 110
Floor area 8.6 million square feet (1 & 2)
Elevator count 198 (1 & 2)
Companies
Architect Minoru Yamasaki, Emery Roth & Sons
Contractor Tishman Realty & Construction Company
Owner Port Authority of New York and New Jersey
*Fully habitable, self-supported, from main entrance to highest structural or architectural top.

The World Trade Center in New York City (sometimes informally referred to as the WTC or the Twin Towers) was a complex of seven buildings, mostly designed by American architect Minoru Yamasaki and developed by the Port Authority of New York and New Jersey. It was destroyed on September 11, 2001, in an infamous terrorist attack.

The center was initiated in 1960 by a Lower Manhattan Association created and chaired by David Rockefeller, who had the original idea of building the Center, with strong backing from then New York governor, his brother, Nelson Rockefeller. The complex, located in the heart of New York City's downtown financial district, contained 13.4 million square feet of office space, almost four percent of Manhattan's entire office inventory.

Best known for its iconic, 110-story twin towers, the World Trade Center was beset by a fire on February 13, 1975, and a bombing on February 26, 1993. All of the original buildings in the complex were destroyed in the September 11, 2001 attacks, including the famous North and South Towers and 7 WTC, which collapsed; 3 WTC (the Marriott Hotel) which was crushed by the collapse of the main towers; and 4 WTC, 5 WTC, and 6 WTC were damaged beyond repair and later demolished. In addition, nearby St. Nicholas Greek Orthodox Church (not part of the complex) was destroyed by the collapse of 2 WTC.

The World Trade Center complex was rebuilt over a span of more than a decade. The site is being rebuilt with six new skyscrapers, while a memorial to those killed in the attacks and a new rapid transit hub have both opened. One World Trade Center, the tallest building in the United States, is the lead building for the new complex, reaching more than 100 stories upon its completion in November 2014.

Planning and construction

During the post-World War II period, the United States thrived economically, with increasing international trade. At the time, economic growth in New York City was concentrated in Midtown Manhattan, with Lower Manhattan left out. To help stimulate urban renewal, David Rockefeller, with support from his brother, New York Governor Nelson Rockefeller, suggested that the Port Authority should build a "world trade center" in Lower Manhattan.

Initial plans, made public in 1961, identified a site along the East River for the World Trade Center. Meanwhile, New Jersey's Hudson and Manhattan Railroad (H&M) was facing bankruptcy. Port Authority executive director, Austin J. Tobin agreed to take over control of the H&M Railroad, in exchange for support from New Jersey for the World Trade Center project. With this acquisition, the Port Authority would obtain the Hudson Terminal, and decrepit buildings located above the terminal in Lower Manhattan. The Port Authority decided to demolish these buildings, and use the site along the Hudson River for the World Trade Center.

Aerial view of the WTC.

The complex towers were designed by architect Minoru Yamasaki with Antonio Brittiochi and Emery Roth & Sons as associate architects. The World Trade Center was one of the most striking American implementations of the architectural ethic of Le Corbusier, as well as the seminal expression of Yamasaki's Gothic modernist tendencies.

Structural design

The World Trade Center included many structural engineering innovations in skyscraper design and construction. The towers were designed as framed tube structures, with columns grouped around the perimeter and within the core. The perimeter columns supported virtually all lateral loads, such as wind loads, and shared the gravity loads with the core columns. All columns were founded on bedrock, which unlike Midtown Manhattan, where the bedrock is shallow, is at 65 feet below the surface.

Perimeter columns

Above the seventh floor there were 59 perimeter columns along each face of the building. The perimeter columns had a square cross section, 14 inches on a side, and were constructed of welded steel plate. The thickness of the plates and grade of steel were varied over the height of the tower, ranging from 36 kilogram per square inch (ksi) to 100 ksi, with the steel strength and plate thickness decreasing with height. The perimeter columns supported virtually all lateral loads such as wind loads and shared the gravity loads with the core columns. The perimeter structure was constructed with extensive use of prefabricated modular pieces, which consisted of three columns, three stories tall, connected together by spandrel plates.

The spandrel plates were welded to the columns at the fabrication shop. The modular pieces were typically 52 inches deep, 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, and served to transmit shear flow between columns, thus allowing them to work together in resisting lateral loads. 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 in 1 WTC was oriented with the long axis east to west, while that of 2 WTC was oriented north to south. The core of each tower was a rectangular area 87 by 135 feet and contained 47 steel columns running from the bedrock to the top of the tower. The columns tapered with height, and consisted of welded box-sections at lower floors and rolled wide-flange sections at upper floors. All of the elevators and stairwells were located in the core.

Floor system

The large, column-free space between the perimeter and core was bridged by pre-fabricated, 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 4-inch-thick, lightweight concrete slabs laid on a fluted-steel deck. A grid of lightweight bridging trusses and main trusses supported the floors. The trusses had a span of 60 feet in the long-span areas and 35 feet in the short span area. The trusses connected to the perimeter at alternate columns, and were therefore on six-foot, eight-inch 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 spandel plates with viscoelastic dampers, which reduced building structural vibration and were first utilized in the Twin World Trade Center Towers in New York in 1969, for wind induced vibrations. VE damping system in the Twin Towers is a double-layer shear damper using a 3M material, which is a rubber derivative, glued to steel plate and angle irons.[2] This helped reduce the amount of sway felt by building occupants. The trusses supported a 4-inch-thick, lightweight-concrete floor slab, with shear connections for composite action.

Hat trusses

Hat trusses (or "outrigger truss") located from the 107th floor to the top of the buildings were designed to support a tall communications antenna on top of each building. However, only WTC1 (north tower) actually had an antenna. The truss system consisted of six trusses along the long axis of 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.

Design innovations

A typical floor layout and elevator arrangement of the WTC towers.

To solve the problem of wind sway or vibration in the construction of the towers, chief engineer Leslie Robertson took a then unusual approach—instead of bracing the buildings corner-to-corner or using internal walls, the towers were essentially hollow steel tubes surrounding a strong central core. The 208-foot-wide facade was, in effect, a prefabricated steel lattice, with columns on 39-inch centers acting as wind bracing to resist all overturning forces; the central core took the majority of the gravity loads of the building. A very light, economical structure was built by keeping the wind bracing in the most efficient area, the outside surface of the building.

Thus, the forces were not transferred through the floor membrane to the core, as in most curtain-wall structures. The core supported the weight of the entire building and the outer shell containing 240 vertical steel columns, called Vierendeel trusses, around the outside of the building, which were bound to each other using ordinary steel trusses. In addition, 10,000 dampers were included in the structure. With a strong shell and core such as this, the exterior walls could be simply light steel and concrete. With the massive core and lightweight shell for structural integrity, Robertson created a tower that was extremely light for its size. This method of construction also meant that the twin towers had high load-bearing walls.

The buildings were also the second supertall buildings to use sky lobbies, after the John Hancock Center in Chicago. Skylobbies are floors where commuters can switch from an express elevator that goes only to the sky lobbies to a local elevator that goes to each floor in a section. The local elevators were stacked on top of each other, 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 taking up a minimum of valuable office space. Altogether, the World Trade Center had 95 express and local elevators. This system was inspired by the New York City Subway system, whose lines include local stations where local trains stop and express stations where all trains stop.

The site of the World Trade Center was located on landfill, with the bedrock located 65 feet below. In order to construct the World Trade Center, it was necessary to build the "bathtub," with the slurry wall along the West Street side of the site, which serves the purpose of keeping water from the Hudson River out. The slurry method involves digging a trench, and as excavation proceeds, filling the space with a "slurry" mixture, comprised of bentonite which plugs holes and keeps water out. When the trench was dug out, a steel cage was inserted, with concrete poured in, forcing the "slurry" out. The "slurry" method was devised by Port Authority chief engineer, John M. Kyle, Jr.

Construction

World Trade Center during construction - May 1970

Groundbreaking for the construction of the World Trade Center was on August 5, 1966. The construction was under the auspices of the semi-autonomous Port Authority of New York and New Jersey. Thirteen square blocks of low rise buildings in Radio Row, some of which pre-dated the American Civil War, were razed to clear the site for construction.

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

In 1970, construction was completed on One World Trade Center, with its first tenants moving into the building in December, 1970. Tenants first moved into Two World Trade Center in January 1972. The ribbon-cutting ceremony was on April 4, 1973. When the World Trade Center twin towers were completed, the total costs to the Port Authority had reached $900 million.

The complex

The Twin Towers

The WTC site building arrangement.

Ultimately the complex came to consist of seven buildings, but its most notable features were the main twin towers. Each of the WTC towers had 110 stories. 1 WTC (the North Tower, which featured a massive 360-foot-high, TV antenna added in 1978) stood 1,368 feet high, and 2 WTC (the South Tower, which contained the observation deck) was 1,362 feet high. The length and breadth of the towers were 208 feet by 208 feet. Although only Tower 1 featured an antenna, the structure of each building was designed to carry a broadcast mast, and in the basement of the complex, The Mall at the World Trade Center was Manhattan's largest mall until September 11th, 2001.

When completed in 1972, 1 WTC became the tallest building on Earth, unseating the Empire State Building after a 40-year reign. 2 WTC became the second tallest building in the world when completed in 1973. As the building neared completion, work had already begun on Chicago's Sears Tower, which ultimately reached 1,450 feet.

Of the 110 stories, eight were set aside for technical services. All the remaining floors were free for open-plan offices. Each floor of the towers had 40,000 square feet of space for occupancy. Each tower had 3.8 million square feet of office space. Altogether the entire complex of seven buildings had 11.2-million square feet of space.

During the 1990s, approximately 500 companies had offices in the complex, including major financial companies such as Morgan Stanley, Aon Corporation, Salomon Brothers, as well as the Port Authority itself. Electrical service to the towers was supplied by Consolidated Edison (ConEd) at 13,800 volts. This service passed through the World Trade Center Primary Distribution Center (PDC) and sent up through the core of the building to electrical substations located on the mechanical floors. The substations "stepped" the 13,800 primary voltage down to 480/277 volt secondary power and further to 120/208 volt general power and lighting service. The complex also was served by emergency generators located in the sublevels of the towers and on the roof of 5 WTC.

The 110th Floor of 1 WTC (North Tower) housed commercial and public service radio & television transmission equipment. The roof of 1 WTC contained a vast array of transmission antennas including the center antenna mast rebuilt in 1999 by Dielectric Inc. to accommodate DTV. The mast contained the television signals for almost all NYC television broadcasters. Access to the roof was controlled from the WTC Operations Control Center (OCC) located in the B1 level of 2 WTC.

The World Trade Center complex was protected by an extensive fire detection and voice evacuation paging system upgraded after the 1993 bombing. Fire Command Stations, staffed by Fire Safety Directors were located in the lobbies of each building and the Operations Control Center (OCC) monitored these systems.

Observation deck and Windows on the World

The World Trade Center as viewed from the borough of Queens

Although the majority of space in the World Trade Center complex was off-limits to the general public, 2 WTC (South Tower) featured a public observation area aptly named "Top Of The World." When visiting the observation deck, visitors would first pass through security checks added after the 1993 World Trade Center bombing. Next, visitors were whisked to the 107th floor indoor observatory and greeted with a 360-degree view of the New York City skyline, and exhibitions including a three-dimensional scale model of Manhattan and a simulated helicopter ride around the city. Weather permitting, visitors could take two short escalator rides up from the 107th floor and visit what was the world's highest outdoor viewing platform. At a height of 1,377 feet, visitors were able to take in a view of the North Tower and New York City unlike any other. On a clear day, it was claimed that visitors could see up to 45 miles in any given direction. An anti-suicide fence was placed on the roof itself, with the viewing platform set back and elevated above it, requiring only an ordinary railing and leaving the view unobstructed.

The North Tower (1 WTC) had a restaurant on the 107th floor called Windows on the World, which was an elegant eatery known as a place for big celebrations, such as weddings. In its last full year of operation, Windows on the World reported revenues of $37.5 million, making it the highest-grossing restaurant in the United States.

The other buildings

Five smaller buildings stood around the 16-acre block. One was the 22-floor Vista Hotel (3 WTC), later a Marriott Hotel, at the southwest corner of the site. It was crushed between the two towers when they collapsed. Three low-rise buildings (4 WTC, 5 WTC, and 6 WTC) in the same basic design as the main towers also stood around the plaza. 6 World Trade Center, at the northwest corner, housed the United States Customs Service and the U.S. Commodities Exchange. 5 World Trade Center was located at the northeast corner, above the PATH train station, and 4 World Trade Center was at the southeast corner. In 1987, a 46-floor office building called 7 WTC was built north of the block. Beneath the World Trade Center complex was an underground shopping mall, which in turn had connections to various mass transit facilities, including the New York City subway system and the Port Authority's own trains connecting Manhattan to Jersey City.

One of the world's largest gold depositories was stored underneath the World Trade Center, owned by a group of commercial banks. The 1993 bomb detonated close to the vault, but it withstood the explosion, as did the towers. Seven weeks after the September 11th attacks, $230 million in precious metals were removed from basement vaults of 4 WTC, which included 3,800, 100-Troy-ounce registered gold bars and 30,000 1,000-ounce silver bars.

Architectural criticism

Although the towers became an undeniable icon of New York City, they were not without flaws and were handicapped in many ways. Initially conceived, (as the name suggests) as a complex dedicated to companies and organizations directly taking part in "world trade," they at first failed to attract the expected clientèle. During the early years, various governmental organizations became key tenants of the World Trade Center, including the State of New York. It was not until the 1980s that the city's perilous financial state eased, after which an increasing number of private companies—mostly financial firms tied to Wall Street—became tenants.

Moreover, the trade center's "superblock," which replaced a more traditional, dense neighborhood, was regarded by some critics as an inhospitable environment that disrupted the complicated traffic network typical of Manhattan. For example, in his book The Pentagon of Power, the technical historian Lewis Mumford denounced the center as an "example of the purposeless giantism and technological exhibitionism that are now eviscerating the living tissue of every great city."[3] On the other hand, Mr. Yamasaki saw the expanse as a focal point of serenity amidst the chaos of the city. The twin tower's narrow office windows, only 18 inches wide, were also disliked by many for impairing the view from the buildings. This design element reflected on Yamasaki's fear of heights and desire to make building occupants secure with narrow windows.

For many years, the outdoor five-acre Austin J. Tobin Plaza, also known as the World Trade Center Plaza, was unpopular because its appearance was considered barren and unwelcoming. However, in later years it became a popular center for outdoor concerts and other activities. In 1999, the plaza re-opened after undergoing $12 million renovations, which involved replacing marble pavers with gray and pink granite stones, adding new benches, planters, new restaurants and food kiosks, and outdoor dining areas.

Life of the World Trade Center

The lobby of the World Trade Center.

On any given day, approximately 50,000 people worked in the towers, with another 200,000 passing through as visitors. The complex was so large that it had its own zip code, 10048. The towers offered spectacular views from the observation deck and the Windows on the World restaurant (located on top of the North Tower). The trade center had its many admirers, particularly visitors. For those who deemed it cold and sterile, there were just as many who appreciated its sheer grandeur; some even took advantage of it. French high-wire, acrobatic performer Philippe Petit walked between the towers on a tightrope in 1974, and Brooklyn toymaker George Willig scaled the south tower in 1977. The Twin Towers became known worldwide, appearing in movies, TV shows, postcards, merchandise, magazines, and much more. The twin towers became a New York icon, not unlike the Empire State Building, or Statue of Liberty.

February 13, 1975 fire

On February 13, 1975, the WTC North Tower was beset by a fire which spread over nearly half of the eleventh floor. The fire spread to other floors through openings in the floor slabs which were used to carry phone wires. The fires on other floors were extinguished almost immediately, and the main fire was put out in a few hours. This event led to the installation of a sprinkler system in both towers. Other than the damage caused by the fire, a few floors below suffered water damage from the extinguishing of the fires above.

Bombing of February 26, 1993

Damage from the 1993 bombing.

On February 26, 1993 at 12:17 PM, a Ryder truck filled with 1,500 pounds of explosives was planted by Islamic terrorist Ramzi Yousef and detonated in the underground garage of the North Tower, opening a 100-foot hole through five sublevels of concrete leaving 50,000 workers and visitors gasping for air in the shafts of the 110-story towers.

Many people inside the North Tower were forced to walk down darkened stairwells which contained no emergency lighting, some taking two hours or more to reach safety. As the Port Authority was a bi-state agency, the towers were exempt from New York City building codes. Subsequent to the bombing, The Port Authority installed emergency lighting in the stairwells. It is believed that this lighting saved many lives during the events of September 11, 2001.

In 1997 and 1998, six Islamic extremists were convicted and sentenced to life in prison for their roles in the bombing. According to a presiding judge, the conspirators' chief aim at the time of the attack was to de-stabilize the north tower and send it crashing into the south tower, toppling both landmarks.

A granite memorial fountain honoring the six people killed in the bombing was designed by Elyn Zimmerman and dedicated in 1995 on Austin J. Tobin Plaza, directly above the site of the explosion. It contained the names of the six people who perished in the attack as well as an inscription that read:

On February 26, 1993, a bomb set by terrorists exploded below this site. This horrible act of violence killed innocent people, injured thousands, and made victims of us all.

The fountain was destroyed during the September 11, 2001 attacks. A recovered fragment from the 1993 bombing memorial with the word "John" is being used as the centerpiece of a new memorial honoring the victims of the 2001 attack.

Privatization

In 1998, plans were approved by the Port Authority to privatize the World Trade Center. In 2001, the Port Authority sought to lease the World Trade Center to a private entity. Bids for the lease came from Vornado Realty Trust, a joint bid between Brookfield Properties and Boston Properties, and a joint bid by Silverstein Properties and The Westfield Group. By privatizing the World Trade Center, it would be added to the city's tax rolls. The lease was also intended to raise funds for other Port Authority projects.

On February 15, 2001, the Port Authority announced that Vornado Trust Realty had won the lease for the World Trade Center, paying $3.25 billion for the 99-year lease. Silverstein was outbid by $50 million by Vornado Realty. However, Vornado later withdrew and Silverstein's bid for the lease to the World Trade Center was accepted on July 24, 2001. The land was then privately owned.

September 11, 2001

The World Trade Center on fire after being hit by airplanes.

On September 11, 2001, at 8:46 a.m., Al Qaeda suicide hijackers crashed American Airlines Flight 11 into the northern facade of the North Tower. Seventeen minutes later, at 9:03 a.m., a second team of hijackers crashed United Airlines Flight 175 into the South Tower, which collapsed at 9:59 a.m. At 10:28 a.m., the North Tower collapsed. At 5:20 p.m., 7 World Trade Center collapsed. The four remaining buildings in the WTC plaza sustained heavy damage from debris, and were ultimately demolished.

At the time of the incident, media reports suggested that tens of thousands might have been killed in the massacre, as on any given day upwards of 100,000 people could be inside the towers. Ultimately, 2,749 death certificates were filed relating to the 9/11 attacks, as of February 2005. Of these, 1,588 (58 percent) were forensically identified from recovered physical remains.

For the following eight and a half months, the World Trade Center site cleanup and recovery continued 24 hours a day and involved thousands of workers. The massive pile of debris smoked and smoldered for 99 days.

Morgan Stanley was the largest tenant in the World Trade Center, with approximately 2,500 employees in the South Tower and 1,000 in the North Tower.

Rebuilding the World Trade Center

Over the following years, plans were created for the reconstruction of the World Trade Center. The Lower Manhattan Development Corporation (LMDC), established in November 2001 to oversee the rebuilding process,[4] organized competitions to select a site plan and memorial design. Memory Foundations, designed by Daniel Libeskind, was selected as the master plan.[5] However, substantial changes were made to the design. One World Trade Center (previously coined the "Freedom Tower" by Governor Pataki) is the centerpiece of Libeskind's design.

WTC Hub September 2016

The first new building to be completed was 7 WTC, which opened in May 2006. The memorial section of the National September 11 Memorial & Museum opened on September 11, 2011 and the museum opened in May 2014. The September 11 Museum opened to victims' families on April 15, 2014, and to the general public six days later. One WTC opened on November 3, 2014. One World Trade Center opened for business on November 3, 2014, with its observatory opening on May 29, 2015. The Oculus, the World Trade Center Transportation Hub was completed in 2016. 3 World Trade Center was completed in 2018, leaving 2 and 5 World Trade Center as the last two remaining unbuilt towers in the WTC complex; the construction of St. Nicholas Greek Orthodox Church also remains uncompleted.[6]

Notes

  1. ↑ Skyscraper Page, One World Trade Center. Retrieved September 30, 2022.
  2. ↑ Design Community, Viscoelastic dampers. Retrieved September 30, 2022.
  3. ↑ Lewis Mumford, The Pentagon of Power (Harcourt, Brace and Jovanovich, Inc., 1974).
  4. ↑ Richard Pérez-Peña, A Nation Challenged: Downtown; State Plans Rebuilding Agency, Perhaps Led by Giuliani The New York Times, November 3, 2001. Retrieved September 30, 2022.
  5. ↑ Lower Manhattan Development Corporation, The Plan for Lower Manhattan Retrieved September 30, 2022.
  6. ↑ Sixteen Acres, Eighteen Years: The Status of the WTC Complex NYC Urbanism. Retrieved September 30, 2022.

References
ISBN links support NWE through referral fees

  • Gillespie, Angus K. Twin Towers: The Life of New York City's World Trade Center. Rutgers University Press, 1999. ISBN 978-0813527420
  • Harris, Bill. The World Trade Center: A Tribute. Courage Books, 2001. ISBN 978-0762413157
  • Koch III, Karl. Men of Steel: The Story of the Family that Built the World Trade Center. Three Rivers Press, 2003. ISBN 978-1400049509
  • Mumford, Lewis. The Pentagon of Power. Harcourt, Brace and Jovanovich, Inc., 1974. ASIN 0156716100
  • Smith, Dennis. Report from Ground Zero: The Story of the Rescue Efforts at World Trade Center. Viking Adult, 2002. ISBN 978-0670031160

External links

All links retrieved May 19, 2023.

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