7 World Trade Center

Infobox Skyscraper
building_name=7 World Trade Center


The new 7 World Trade Center (view from southeast)
construction_period=2002–2006
use=Office
location=250 Greenwich Street New York City, New York, United States
roof=741 ft (226 m)
floor_count=52
floor_area=1.7 million sq ft 158,000 m²
architect=David Childs (S.O.M.)
engineer=WSP Cantor Seinuk
developer=Silverstein Properties
lighting design=Cline Bettridge Bernstein Lighting Design|

7 World Trade Center is a building in New York City located across from the World Trade Center site in Lower Manhattan. The name "7 World Trade Center" has referred to two buildings: the original structure, completed in 1987, and the current structure. The original building was destroyed on September 11, 2001 and replaced with the new 7 World Trade Center, which opened in 2006. Both buildings were developed by Larry Silverstein, who holds a ground lease for the site from the Port Authority of New York and New Jersey.

The original 7 World Trade Center was 47 stories tall, clad in red exterior masonry, and occupied a trapezoidal footprint. An elevated walkway connected the building to the World Trade Center plaza. The building was situated above a Consolidated Edison (Con Ed) power substation, which imposed unique structural design constraints. When the building opened in 1987, Silverstein had difficulties attracting tenants. In 1988, Salomon Brothers signed a long-term lease, and became the main tenants of the building. On September 11, 2001, 7 WTC was damaged by debris when the nearby North Tower of the WTC collapsed. The debris also ignited fires, which continued to burn throughout the afternoon on lower floors of the building, with a lack of water to fight the fires. The building collapsed completely at 5:20 p.m., when a critical column on the 13th floor buckled and triggered structural failure throughout.

The new 7 World Trade Center construction began in 2002 and was completed in 2006. It is 52 stories tall and still situated above the Con Ed power substation. Built on a smaller footprint than the original to allow Greenwich Street to be restored from TriBeCa through the World Trade Center site and south to Battery Park, the new building is bounded by Greenwich, Vesey, Washington, and Barclay streets. A small park across Greenwich Street occupies space that was part of the original building's footprint. The current 7 World Trade Center's design placed emphasis on safety, with a reinforced concrete core, wider stairways, and thicker fireproofing of steel columns, and incorporates numerous environmentally friendly features.

1983–2001

The original 7 World Trade Center was a 47-story building, designed by Emery Roth & Sons, with a red granite façade. The building was 610 feet (186 m) tall, with a trapezoidal footprint that was 330 ft (101 m) long and 140 ft (43 m) wide.cite book |title=Design, Construction, and Maintenance of Structural and Life Safety Systems (NCSTAR 1-1) |publisher=National Institute of Standards and Technology (NIST) |pages=p. 13 |author=Lew, H.S., Richard W. Bukowski, Nicholas J. Carino |month=September | year=2005] cite web|url=http://www.emporis.com/en/wm/bu/?id=114932 |publisher=Emporis.com |title=Seven World Trade Center (pre-9/11) |accessdate=2006-05-07] Tishman Realty & Construction managed construction of the building, which began in 1983. In March 1987, the building opened, becoming the seventh structure of the World Trade Center.

The building was constructed above a Con Edison substation that had been on the site since 1967.cite web |year = 2004 |url = http://wtc.nist.gov/progress_report_june04/appendixl.pdf | format = pdf | title = Interim Report on WTC 7 | work = Appendix L | publisher = National Institute of Standards and Technology |accessdate = 2007-08-20] The substation had a caisson foundation designed to carry the weight of a future building of 25 stories containing 600,000 sq ft (55,700 m²). The final design for 7 World Trade Center was for a much larger building covering a larger footprint than originally planned when the substation was built. [cite book |url=http://wtc.nist.gov/oct05NCSTAR1-1index.htm |title=Final Reports of the Federal Building and Fire Investigation of the World Trade Center Disaster |chapter=NIST NCSTAR 1-1: Design, Construction, and Maintenance of Structural and Life Safety Systems |author=Lew, H.S., "et al" |publisher=NIST |month=September | year=2005 |pages=p. xxxvii |format=pdf|accessdate=2008-02-17]

The structural design of 7 World Trade Center included features to allow a larger building than originally planned to be constructed. A system of gravity column transfer trusses and girders was located between floors 5 and 7 to transfer loads to the smaller foundation. Existing caissons installed in 1967 were used, along with new ones, to accommodate the building. The fifth floor functioned as a structural diaphragm, providing lateral stability and distribution of loads between the new and old caissons. Above the seventh floor, the building's structure was a typical tube-frame design, with columns in the core and on the perimeter, and lateral loads resisted by perimeter moment frames.

A shipping/receiving ramp, which served the entire World Trade Center complex, occupied the eastern quarter of the 7 World Trade Center footprint. The building was open below the third floor, providing space for truck clearance on the shipping ramp.cite conference |author=Salvarinas, John J. |year=1986 |title=Seven World Trade Center, New York, Fabrication and Construction Aspects |booktitle=Proceedings of the 1986 Canadian Structural Engineering Conference |location=Vancouver |publisher=Canadian Steel Construction Council] The spray-on fireproofing for structural steel elements was gypsum-based Monokote which had a two-hour fire rating for steel beams, girders and truss, and a three-hour rating for columns.

Mechanical equipment was installed on floors four through seven, including 12 transformers on the fifth floor. Several generators in the building were used by the Office of Emergency Management, Salomon Smith Barney and others. Storage tanks contained 24,000 gallons (91,000 L) of diesel fuel to supply the generators. [cite journal |url=http://fpemag.com/archives/article.asp?issue_id=14&i=183&p=1 |title=Study of Building Performance in the WTC Disaster |author=Milke, James |journal=Fire Protection Engineering |date=Spring 2003|accessdate=2008-02-17] Fuel oil distribution components were located at ground level, up to the ninth floor. [cite book |url=http://wtc.nist.gov/NISTNCSTAR1-1J.pdf |format=pdf| title=Final Reports of the Federal Building and Fire Investigation of the World Trade Center Disaster |chapter=NIST NCSTAR 1-1J: Documentation of the Fuel System for Emergency Power in World Trade Center 7 |month=September | year=2005 |author=Grill, Raymond A., Duane A. Johnson |publisher=NIST|accessdate=2008-02-17] After the World Trade Center bombings of February 26, 1993, New York City mayor Rudy Giuliani decided to situate the emergency command center and associated fuel tanks at 7 World Trade Center. Although this decision was criticized in light of the events of 9/11, the fuel in the building is today not believed to have contributed to the collapse of the building. [cite news|url=http://query.nytimes.com/gst/fullpage.html?res=9C02EEDD103EF933A15751C1A9679C8B63|title= A Nation Challenged: The Trade Center; City Had Been Warned of Fuel Tank at 7 World Trade Center| author=Glanz, James and Eric Lipton|publisher=New York Times|date=2001-12-20|accessdate=2007-11-21] ["Rudy Giuliani's 5 Big Lies About 9/11: On the Stump, Rudy Can't Help Spreading Smoke and Ashes About His Dubious Record," "Village Voice" August 8–14, 2007, pp. 22–36.] [cite web | url=http://www.newsmax.com/archives/articles/2004/5/23/204909.shtml | title=Replying to Giuliani | author=Ruddy, Christopher | date=2004-05-24 | publisher=NewsMax | accessdate=2007-06-12] [cite web | url=http://www.foxnews.com/story/0,2933,271917,00.html | title=Transcript: Rudy Giuliani on Fox News Sunday | date=2007-05-14 | accessdate=2007-09-29 | quote=Then why did he say the building — he said it's not — the place in Brooklyn is not as visible a target as buildings in Lower Manhattan |publisher=Fox News] [cite news | title=Onetime Giuliani Insider Is Now a Critic | publisher=New York Times|author=Russ Buettner|url=http://www.nytimes.com/2007/05/22/us/politics/22giuliani.html?_r=1&pagewanted=2&oref=slogin | date =2007-05-22|accessdate=2007-06-12] [cite web | title=Giuliani Blames Aide for Poor Emergency Planning | url=http://nymag.com/daily/intel/2007/05/guiliani_blames_aide_for_poor_emergency_planning.html | publisher=Daily Intelligencer|date=2007-05-15|accessdate=2007-06-12 ] cite web | url=http://wtc.nist.gov/media/NCSTACMeetingMinutes121807.pdf | title=Transcript: Meeting of the National Construction Safety Team Advisory Committee, December 18, 2007 | author=National Construction Safety Team Advisory Committee|format=PDF] The roof of the building included a small west penthouse and a larger east mechanical penthouse.

Each floor had 47,000 sq ft (4,366 m²) of rentable office space which made the building's floor plans considerably larger than most office buildings in the City. [cite news |author=Horsley, Carter B |title=Lower Manhattan Luring Office Developers |publisher=The New York Times |date=1981-10-25|url=http://query.nytimes.com/gst/fullpage.html?res=9A07E5DB1039F936A15753C1A967948260|accessdate=2008-02-17] In all, 7 World Trade Center had 1,868,000 sq ft (174,000 m²) of office space.cite book |author=Gilsanz, Ramon, Edward M. DePaola, Christopher Marrion, and Harold "Bud" Nelson |url=http://www.fema.gov/pdf/library/fema403_ch5.pdf |format=pdf| publisher=FEMA |title=World Trade Center Building Performance Study |chapter=WTC7 (Chapter 5) |month=May | year=2002 |accessdate=2008-02-17] Two pedestrian bridges connected the main World Trade Center complex, across Vesey Street, to the third floor of 7 World Trade Center. The lobby of 7 World Trade Center had three murals by artist Al Held: "The Third Circle", "Pan North XII", and "Vorces VII". [cite web |url=http://www.nga.gov.au/InternationalPrints/Tyler/Default.cfm?MnuID=3&ArtistIRN=11644&List=True |title=Al Held |publisher=National Gallery of Australia |accessdate=2007-05-29] [cite news |title=Is Bigger Necessarily Better? |publisher=Newsweek |date=1989-04-17 |author=Plagens, Peter] A sculpture by Alexander Calder, called "WTC Stabile" (also known by other names, "The Cockeyed Propeller" and "Three Wings") was on a plaza in front of the building. [cite news |url=http://www.ifar.org/911_public2.htm |title=Public Art at the World Trade Center |author=Wenegrat, Saul |publisher=International Foundation for Art Research |date=2002-02-28 |accessdate=2007-07-27]

Tenants

In June 1986, before construction was completed, Silverstein signed Drexel Burnham Lambert as a tenant to lease the entire 7 World Trade Center building for $3 billion over a term of 30 years. [cite news |author=Scardino, Albert |title=A Realty Gambler's Big Coup |publisher=The New York Times |date=1986-07-11] In December 1986, after the Boesky insider-trading scandal, Drexel Burnham Lambert canceled the lease, leaving Silverstein to find other tenants. [cite news |author=Scardino, Albert |title=$3 Billion Office Pact Canceled by Drexel |publisher=The New York Times |date=1986-12-03] Spicer & Oppenheim agreed to lease 14 percent of the space, but for more than a year, as Black Monday and other factors adversely affected the Lower Manhattan real estate market, Silverstein was unable to find tenants for the remaining space. By April 1988, Silverstein had lowered the rent and made other concessions. [cite news |author=Berg, Eric N |title=Talking Deals; Developer Plays A Waiting Game |publisher=The New York Times |date=1988-04-07|url=http://query.nytimes.com/gst/fullpage.html?res=940DE6DE113AF934A35757C0A96E948260|accessdate=2008-02-17]

In November 1988, Salomon Brothers withdrew from plans to build a large new complex at Columbus Circle in Midtown and agreed to a 20-year lease for the top 19 floors of 7 World Trade Center. [cite news |author=Berkowitz, Harry |title=Salomon to Move Downtown |publisher=Newsday |date=1988-11-29] The building was extensively renovated in 1989 to accommodate the needs of Salomon Brothers.cite news |publisher=The New York Times |date=1989-02-19 |title=The Salomon Solution; A Building Within a Building, at a Cost of $200 Million |author=McCain, Mark|url=http://query.nytimes.com/gst/fullpage.html?res=950DEFDD113BF93AA25751C0A96F948260|accessdate=2007-02-17] Most of three existing floors were removed as tenants continued to occupy other floors, and more than 350 tons (U.S.) of steel were added to construct three double-height trading floors. Nine diesel generators were installed on the 5th floor as part of a backup power station. "Essentially, Salomon is constructing a building within a building - and it's an occupied building, which complicates the situation," said a district manager of Silverstein Properties. The unusual task was possible, said Larry Silverstein, because it was designed to allow for "entire portions of floors to be removed without affecting the building's structural integrity, on the assumption that someone might need double-height floors."

At the time of the September 11, 2001 attacks, Salomon Smith Barney was by far the largest tenant in 7 World Trade Center, occupying 1,202,900 sq ft (111,750 m²) (64 percent of the building) which included floors 28–45.cite news |url=http://www.cnn.com/SPECIALS/2001/trade.center/tenants7.html |title=Building: 7 World Trade Center |publisher=CNN | year = 2001 | accessdate=2007-09-12] Other major tenants included ITT Hartford Insurance Group (122,590 sq ft/11,400 m²), American Express Bank International (106,117 sq ft/9,900 m²), Standard Chartered Bank (111,398 sq ft/10,350 m²), and the Securities and Exchange Commission (106,117 sq ft/9,850 m²). Smaller tenants included the Internal Revenue Service Regional Council (90,430 sq ft/8,400 m²) and the United States Secret Service (85,343 sq ft/7,900 m²). The smallest tenants included the New York City Office of Emergency Management, National Association of Insurance Commissioners, Federal Home Loan Bank, First State Management Group Inc., Provident Financial Management, and the Immigration and Naturalization Service. The Department of Defense (DOD) and Central Intelligence Agency (CIA) shared the 25th floor with the IRS. Floors 46–47 were mechanical floors, as were the bottom six floors and part of the seventh floor. [cite web|url=http://www.cbsnews.com/stories/2001/11/05/archive/main316911.shtml |publisher=CBSNews.com / AP |title=CIA Lost Office In WTC: A secret office operated by the CIA was destroyed in the terrorist attacks on the World Trade Center, seriously disrupting intelligence operations' |date=2001-11-05|accessdate=2008-02-17]

Collapse

As the North Tower collapsed on September 11, 2001, debris hit 7 World Trade Center, causing heavy damage to the south face of the building. The bottom portion of the building's south face was heavily damaged by debris, including damage to the southwest corner from the 8th to 18th floors, a large vertical gash on the center-bottom extending at least ten floors, and other damage as high as the 18th floor. The building was equipped with a sprinkler system, but had many single-point vulnerabilities for failure: the sprinkler system required manual initiation of the electrical fire pumps, rather than being a fully automatic system; the floor-level controls had a single connection to the sprinkler water riser; and the sprinkler system required some power for the fire pump to deliver water. Also, water pressure was low, with little or no water to feed sprinklers. [cite web |url=http://wtc.nist.gov/media/P4InvestigationofActiveFireProtection.pdf|format=pdf |title=Active Fire Protection Systems Issues |author=Grosshandler, William |publisher=NIST |accessdate=2007-09-11] [cite web |url=http://wtc.nist.gov/NISTNCSTAR1-4.pdf |format=pdf|title=Active Fire Protection Systems |author=Evans, David D |publisher=NIST |month=September | year=2005 |accessdate=2007-09-11]

After the North Tower collapsed, some firefighters entered 7 World Trade Center to search the building. They attempted to extinguish small pockets of fire, but low water pressure hindered their efforts. [cite web |url=http://graphics8.nytimes.com/packages/pdf/nyregion/20050812_WTC_GRAPHIC/9110313.PDF |format=pdf|title=Oral Histories From Sept. 11 - Interview with Captain Anthony Varriale |publisher=The New York Times |date=2001-12-12 |accessdate=2007-08-22] A massive fire burned into the afternoon on the 11th and 12th floors of 7 World Trade Center, the flames visible on the east side of the building. [cite video | people=Spak, Steve | date=September 11 2001 | url=http://video.google.com/videoplay?docid=6790722824543352916&hl=en | title=WTC 9-11-01 Day of Disaster | medium=Video | location=New York City | publisher=Spak, Steve] [cite paper |author=Scheuerman, Arthur |url=http://wtc.nist.gov/media/ScheuermanStatementDec2006.pdf |format=pdf |title=The Collapse of Building 7 |date=2006-12-08 |publisher=NIST |accessdate=2007-06-29] During the afternoon, fire was also seen on floors 6–10, 13–14, 19–22, and 29–30. In particular, the fires on floors 7 through 9 and 11 through 13 continued to burn out of control during the afternoon.cite web |url=http://www.nist.gov/public_affairs/factsheet/wtc_qa_082108.html |title=Questions and Answers about the NIST WTC 7 Investigation |publisher=NIST |accessdate=2008-08-21] At approximately 2:00 p.m., firefighters noticed a bulge in the southwest corner of 7 World Trade Center between the 10th and 13th floors, a sign that the building was unstable and might collapse.cite web |url=http://www.firehouse.com/terrorist/911/magazine/gz/hayden.html |title=WTC: This Is Their Story, Interview with Chief Peter Hayden |publisher=Firehouse.com |date=2002-09-09 |accessdate=2007-06-28] During the afternoon, firefighters also heard creaking sounds coming from the building. [cite web |url=http://www.firehouse.com/terrorist/911/magazine/gz/boyle.html |title=WTC: This Is Their Story, Interview with Captain Chris Boyle |publisher=Firehouse.com |month=August | year=2002 |accessdate=2007-08-22] Around 3:30 pm FDNY Chief Daniel Nigro decided to halt rescue operations, surface removal, and searches along the surface of the debris near 7 World Trade Center and evacuate the area due to concerns for the safety of personnel. [cite web |url=http://www.nytimes.com/packages/html/nyregion/20050812_WTC_GRAPHIC/Nigro_Daniel.txt |title=Oral Histories From Sept. 11 - Interview with Chief Daniel Nigro |publisher=The New York Times |date=2001-10-24 |accessdate=2007-06-28] At 5:20 p.m. EDT on September 11, 2001, 7 World Trade Center collapsed. There were no casualties associated with the collapse.

In May 2002, the Federal Emergency Management Agency (FEMA) issued a report on the collapse based on a preliminary investigation conducted jointly with the Structural Engineering Institute of the American Society of Civil Engineers under leadership of Dr. W. Gene Corley, P.E. FEMA made preliminary findings that the collapse was not primarily caused by actual impact damage from the collapse of 1 WTC and 2 WTC but by fires on multiple stories ignited by debris from the other two towers that continued unabated due to lack of water for sprinklers or manual firefighting. According to FEMA, structural elements were exposed to high temperatures for a sufficient period of time to reduce their strength to the point of collapse; nevertheless, it has since been determined that the fires burned out in 20 minutes at any given location as they moved from point to point.

The report did not reach final conclusions about the cause of the collapse and called for further investigation:

Loss of structural integrity was likely a result of weakening caused by fires on the 5th to 7th floors. The specifics of the fires in WTC 7 and how they caused the building to collapse remain unknown at this time. Although the total diesel fuel on the premises contained massive potential energy, the best hypothesis has only a low probability of occurrence. Further research, investigation, and analyses are needed to resolve this issue. [Ch. 5, p. 31.]

In response to FEMA's concerns, the National Institute of Standards and Technology (NIST) was authorized to lead an investigation into the structural failure and collapse of the World Trade Center twin towers and 7 World Trade Center. [cite web |url=http://www.nist.gov/public_affairs/factsheet/nist_investigation_911.htm |title=NIST’s World Trade Center Investigation |publisher=NIST |accessdate=2007-08-20] The investigation, led by Dr S. Shyam Sunder, drew not only upon in-house technical expertise, but also upon the knowledge of several outside private institutions, including the Structural Engineering Institute of the American Society of Civil Engineers (SEI/ASCE), the Society of Fire Protection Engineers (SFPE), the National Fire Protection Association (NFPA), the American Institute of Steel Construction (AISC), the Council on Tall Buildings and Urban Habitat (CTBUH), and the Structural Engineers Association of New York (SEAoNY).cite web |url=http://wtc.nist.gov/NISTNCSTAR1CollapseofTowers.pdf |format=pdf|title=Final Report on the Collapse of the World Trade Center |publisher=National Institute of Standards and Technology (NIST) |month=September | year=2005 |accessdate=2008-02-17]

The bulk of the investigation of 7 World Trade Center was delayed until after reports were completed on the collapse of the World Trade Center twin towers. In the meantime, NIST provided a preliminary report about 7 World Trade Center in June 2004, and since then has released occasional updates on the investigation. According to NIST, the investigation of 7 World Trade Center has been delayed for a number of reasons, including that NIST staff who had been working on 7 World Trade Center were assigned full-time from June 2004 to September 2005 to work on the investigation of the collapse of the twin towers.cite web |url=http://wtc.nist.gov/pubs/factsheets/faqs_8_2006.htm |title=Answers to Frequently Asked Questions |publisher=National Institute of Standards and Technology |month=August | year=2006|accessdate=2008-02-17] In June 2007, Shyam Sunder explained, "We are proceeding as quickly as possible while rigorously testing and evaluating a wide range of scenarios to reach the most definitive conclusion possible. The 7 WTC investigation is in some respects just as challenging, if not more so, than the study of the towers. However, the current study does benefit greatly from the significant technological advances achieved and lessons learned from our work on the towers."cite press release |url=http://www.nist.gov/public_affairs/releases/wtc_062907.html|title=NIST Status Update on World Trade Center 7 Investigation|year=2007|last=Newman|first=Michael|date=2007-06-29 |publisher=National Institute of Standards and Technology|accessdate=2008-02-17]

In its progress report, NIST released a video and still-photo analysis of 7 World Trade Center before its collapse that appears to indicate a greater degree of structural damage from falling debris than originally assumed by FEMA. Specifically, NIST's interim report on 7 World Trade Center displays photographs of the southwest façade of the building that show it to have significant damage. The report also highlights a 10-story gash in the center of the south façade, toward the bottom, extending approximately a quarter of the way into the interior. [cite news |url=http://www.popularmechanics.com/technology/military_law/1227842.html?page=5#wtc7 |title=Debunking the 9/11 Myths: Special Report |publisher=Popular Mechanics |date=March 2005|accessdate=2008-01-17] A unique aspect of the design of 7 World Trade Center was that each outer structural column was responsible for supporting 2,000 sq ft (186 m²) of floor space, suggesting that the simultaneous removal of a number of columns severely compromised the structure's integrity. [cite web |url=http://wtc.nist.gov/pubs/WTC%20Part%20IIC%20-%20WTC%207%20Collapse%20Final.pdf |format=pdf|title=NIST Response to the World Trade Center Disaster (Part IIC - WTC 7 Collapse) |date=2005-04-05 |publisher=NIST |accessdate=2007-08-23] Consistent with this theory, news footage shows cracking and bowing of the building's east wall immediately before the collapse, which began at the penthouse floors. In video of the collapse, taken from the north by CBS News and other news media, the first visible sign of collapse is movement in the east penthouse 8.2 seconds before the north wall began to collapse, which took at least another 7 seconds. [cite video |url=http://www.archive.org/details/cbs200109111651-1733 |people=CBS News |date=September 11 2001 |title=CBS Sept. 11, 2001 4:51 pm - 5:33 pm (September 11, 2001) |publisher=WUSA, CBS 9, Washington, D.C |medium=Television - View [http://www.youtube.com/watch?v=4k6GMddY-lQ footage] of the collapse captured by CBS]

The working hypothesis, released in the June 2004 progress report and reiterated in a June 2007 status update, was that an initial failure in a critical column occurred below the 13th floor, caused by damage from fire and/or debris from the collapse of the two main towers. The collapse progressed vertically up to the east mechanical penthouse. The interior structure was unable to handle the redistributed load, resulting in horizontal progression of the failure across lower floors, particularly the 5th to 7th floors. This resulted in "a disproportionate collapse of the entire structure." [cite web | year = 2004 |url = http://www.nist.gov/public_affairs/factsheet/wtc_keyfindings.htm | title = Key Findings of NIST’s June 2004 Progress Report on the Federal Building and Fire Safety Investigation of the World Trade Center Disaster | work = Fact sheets from NIST | publisher = National Institute of Standards and Technology |accessdate = 2006-07-28]

On August 21, 2008, NIST released its draft report on the causes of the collapse of 7 World Trade Center, beginning a period for public comments. In its investigation, NIST utilized ANSYS to model events leading up to collapse initiation and LS-DYNA models to simulate the global response to the initiating events. [cite web |url=http://wtc.nist.gov/media/WTC7_Approach_Summary12Dec06.pdf |format=pdf|title=WTC 7 Technical Approach and Status Summary |author=McAllister, Therese |publisher=NIST |date=2006-12-12|accessdate=2008-02-17] NIST determined that diesel fuel did not play an important role, nor did the structural damage from the collapse of the twin towers. But the lack of water to fight the fire was an important factor. The fires burned out of control during the afternoon, including on floor 13, where a critical interior column buckled. With the buckling of that column, adjacent columns also failed along with the floor structure above. This triggered a vertical progression of floor failures to the roof. The collapse then progressed east-to-west across the structure, and ultimately the entire structure collapsed. The fires, fueled by office contents, along with the lack of water, were the key reasons for the collapse. [cite web |url=http://wtc.nist.gov/media/NIST_NCSTAR_1A_for_public_comment.pdf |title=Final Report on the Collapse of World Trade Center Building 7 - Draft for Public Comment |publisher=NIST |pages=xxxii |month=August | year=2008 |format=PDF]

When 7 World Trade Center collapsed, debris caused substantial damage and contamination to the Borough of Manhattan Community College's Fiterman Hall building, located adjacent at 30 West Broadway, to the extent that the building is not salvageable. As of August 2007, Fiterman Hall is undergoing deconstruction. [cite web |url=http://www.lowermanhattan.info/construction/project_updates/fiterman_hall_39764.aspx |title=Fiterman Hall — Project Updates |publisher=Lower Manhattan Construction Command Center/LMDC |accessdate=2007-08-23] The adjacent Verizon Building, an art deco building constructed in 1926, had extensive damage to its east façade from the collapse of 7 World Trade Center, though was able to be restored at a cost of US$1.4 billion.cite web |url=http://newyork.construction.com/projects/TopProjects04/Verizon.asp |title=Verizon Building Restoration |publisher=New York Construction (McGraw Hill) |accessdate=2007-06-28]

World Trade Center 7 housed SEC files relating to numerous Wall Street investigations, as well as other federal investigative files. All the files for approximately 3,000 to 4,000 SEC cases were destroyed. While some were backed up in other places, others were not, especially those classified as confidential.cite news | first= | last= | coauthors= | title= SEC & EEOC: Attack Delays Investigations | date=2001-09-17 | publisher= | url =http://www.wanttoknow.info/010917natllawjournal.WTC7SECfiles | work =New York Lawyer | pages = | accessdate = 2008-07-09 | language = ] Files relating Citigroup to the WorldCom scandal were lost.cite news | first= | last= | coauthors= | title=Citigroup Facing Subpoena in IPO Probe | date= | publisher= | url =http://www.thestreet.com/markets/matthewgoldstein/10036925.html | work =The Street | pages = | accessdate = 2008-07-09 | language = ] The Equal Employment Opportunity Commission estimates over 10,000 cases will be affected.cite news | first= | last= | coauthors= | title=Federal Agencies: Re-Creating Lost Files | date=2001-09-14 | publisher= | url =http://www.nylawyer.com/login.php?source=/news/01/09/091401b | work =New York Lawyer | pages = | accessdate = 2008-07-09 | language = ] The Secret Service had its largest field office, with more than 200 employees, in WTC 7 and also lost investigative files. Says one agent: “All the evidence that we stored at 7 World Trade, in all our cases, went down with the building.”cite news | first= | last= | coauthors= | title=Ground Zero for the Secret Service | date=2002-07-23 | publisher= | url =http://www.g4tv.com/techtvvault/features/27904/Ground_Zero_for_the_Secret_Service.html | work = | pages = | accessdate = 2008-07-09 | language = ]

The collapse of 7 World Trade Center is remarkable because it was the first known instance of a tall building collapsing primarily by uncontrolled fires. [cite news |url=http://www.nist.gov/public_affairs/factsheet/wtc_qa_082108.html |title=Questions and answers about the NIST WTC 7 Investigation |publisher=NIST]

Conspiracy theorists believe the building collapses on September 11, including that of building seven, were the result of controlled demolition. [cite news |url=http://www.usnews.com/usnews/news/articles/060903/11conspiracy.htm |title=Viewing 9/11 From a Grassy Knoll |author=Sullivan, Will |date=2006-09-03|publisher=U.S. News & World Report|accessdate=2008-02-17] [cite news |title= The evolution of a conspiracy theory |url=http://news.bbc.co.uk/1/hi/magazine/7488159.stm |publisher=BBC News |date=2008-07-04 |accessdate=2008-07-04 ] [cite journal |last=Asquith |first=Christina |year=2006 |month=Sept |title=Conspiracies continue to abound surrounding 9/11: on the eve of the fifth anniversary, a group of professors say the attacks were an "inside job.". |journal=Diverse Issues in Higher Education |pages=12 |url=http://findarticles.com/p/articles/mi_m0WMX/is_15_23/ai_n27000635 |accessdate=2008-07-04 ] [cite web |url=http://www.popularmechanics.com/technology/military_law/1227842.html?page=5#wtc7 |title=WTC 7 Collapse |accessdate=2008-07-09 |work=Debunking the 9/11 Myths: Special Report |publisher=Popular Mechanics |month=March | year=2005 ] The draft NIST report rejected this hypothesis, as the window breakages and blast sound that would have occurred if explosives were used were not observed. [cite web |url=http://wtc.nist.gov/media/NIST_NCSTAR_1A_for_public_comment.pdf |title=Final Report on the Collapse of World Trade Center Building 7 - Draft for Public Comment |publisher=NIST |pages=22-3|month=August | year=2008 |format=PDF]

Rebuilding 7 World Trade Center

Design

The new 7 World Trade Center has 52 stories and is 741 ft (226 m) tall. [cite web |url=http://www.rics.org/Networks/Regions/Americas/7_world_trade_center_tour.html |title=7 World Trade Center tour makes huge impression |accessdate=2008-05-20 |date=2006-05-24 |publisher=Royal Institution of Chartered Surveyors] [cite news |first=Anthony |last=Ramirez |title=Construction Worker Dies in Fall at Trade Center Site |url=http://www.nytimes.com/2004/09/30/nyregion/30accident.html |publisher="The New York Times" |date=2004-09-30 |accessdate=2008-05-20 ] The building has 42 floors of leasable space, starting at the 11th floor, and a total of 1,700,000 sq ft (158,000 m²) of office space.cite web|url=http://www.emporis.com/en/wm/bu/?id=170407 |publisher=Emporis.com |title=Seven World Trade Center (post-9/11) |accessdate=2007-11-22] The first ten floors house an electrical substation, which provides power to much of Lower Manhattan. The office tower has a narrower footprint at ground level than its predecessor so the course of Greenwich Street could be restored in an effort to reunite TriBeCa and the Financial District.

David Childs worked in conjunction with glass artist and designer James Carpenter to create a design that uses ultra-clear, low-iron glass to provide reflectivity and light, with stainless-steel spandrels behind the glass to help reflect sunlight. Stainless steel used in the building façade is molybdenum-containing Type 316, which provides improved resistance to corrosion. [cite journal |title=New 7 World Trade Center Uses Type 316 Stainless Steel |author=Houska, Catherine |journal=International Molybdenum Association News Letter |pages=pp. 4–6 |month=January | year=2004] To enclose the power substation and improve its aesthetics, the base of the building has a curtain wall with stainless steel louvers that provide ventilation for the machinery. [cite news |title=A World of Light and Glass |url=http://www.businessweek.com/innovate/content/mar2006/id20060328_770161.htm?chan=innovation_architecture_product+spotlight |author=Blum, Andrew |date=2006-03-28 |publisher=BusinessWeek|accessdate=2008-02-17] During the day, the curtain wall reflects light, while at night it illuminates with blue LED lights. [cite book |author=Marpillero, Sandro, Kenneth Frampton, Jorg Schlaich |title=James Carpenter: Environmental Refractions |publisher=Princeton Architectural Press |year=2006 |pages=pp. 55–70 |isbn=1568986084] The curtain wall around the lobby uses heavily laminated, heat-strengthened glass that meets high standards for blast resistance. [cite news |url=http://web.archive.org/web/20050225083353/http://www.theslatinreport.com/top_story.jsp?StoryName=1116curtains.txt|title=Curtain (Wall) Time |author=Garmhausen, Steve |publisher=Slatin Report |date=2004-11-16|accessdate=2005-02-25] At night, a large cube of light above the lobby also emanates blue light, while during the day it provides white light to the lobby, and at dusk it transitions to violet and back to blue. [cite news |url=http://www.architectmagazine.com/industry-news.asp?sectionID=1325&articleID=554018 |title=7 World Trade Center — Outstanding Achievement, Exterior Lighting |publisher=Architectural Lighting Magazine |date=2007-07-01|accessdate=2008-02-17] Inside the main lobby, artist Jenny Holzer created a large light installation with glowing text moving across wide plastic panels. The entire wall, which is 65 ft (20 m) wide and 14 ft (4 m) tall, changes color according to the time of day. Holzer worked with Klara Silverstein, the wife of Larry Silverstein, to select poetry for the art installation. The wall is structurally fortified as a security measure. [cite news |title=At Ground Zero, Art Pact Results In Wall of Words |publisher=The New York Times |date=2006-03-06 |author=Collins, Glenn]

The building is being promoted as the safest skyscraper in the U.S.cite web|url=http://www.lowermanhattan.info/construction/project_updates/7_world_trade_center_75464.asp#activities|publisher=Lower Manhattan Construction Command Center|title=Downtown Construction and Building Information|accessdate=2006-05-22] According to Silverstein Properties, the owner of the building, it "will incorporate a host of life-safety enhancements that will become the prototype for new high-rise construction". [cite press release |title=Silverstein Properties Names CB Richard Ellis to Serve as Exclusive Leasing Agent for 7 World Trade Center |publisher=Silverstein Properties |date=2004-09-28] The building has 2 ft (60 cm) thick reinforced-concrete and fireproofed elevator and stairway access shafts. The original building used only drywall to line these shafts.cite news |url=http://www.skyscrapersafety.org/html/article_20040309.html |title=Shortcuts to Safety |author=Reiss, Matthew |publisher=Metropolis Magazine / Skyscraper Safety Campaign |date=March 2003|accessdate=2008-02-17] The stairways are wider than in the original building to permit faster egress. Steel columns are encased in much thicker fire protection, which consists of a medium-density, portland cement-based product that adheres well to the steel columns, among other advantages over alternate types of spray-applied fire-resistive material. [cite journal |url=http://www.na.graceconstruction.com/custom/toplevel_pages/featured_articles/pdf/Fire-resistive_materials.pdf |format=pdf|title=Post Impact: The Focus on Durability of Fire-Resistive Materials in Structures |author=Zanghi, Philip A. |journal=National Fire Protection Association Journal |date=September/October 2005|accessdate=2008-02-17]

7 World Trade Center is equipped with Otis destination elevators. [cite news |title=No-button elevators take orders in lobby |publisher=Charleston Gazette (West Virginia) |date=2006-11-19 |author=Angwin, Julia] After pressing a destination floor number on a lobby keypad, passengers are grouped and directed to specific elevators that will stop at the selected floor (there are no buttons to press inside the elevators). This system is designed to reduce elevator waiting and travel times. The elevator system is integrated with the lobby turnstile and card reader system that identifies the floor on which a person works as he/she enters and can automatically call the elevator for that floor. [cite news |url=http://www.architechmag.com/articles/detail.aspx?contentID=3608 |author=Kretkowski, Paul |title=First Up |publisher=ARCHI-TECH |date=March 2007|accessdate=2008-02-17]

In conjunction with Scott Chrisner of Chrisner Group, Tishman supported the LEED gold status for 7 World Trade Center in the U.S. Green Building Council's Leadership in Energy and Environmental Design (LEED) program. The certification will name 7 World Trade Center New York City's First ‘Green’ Office Tower.cite press release|url=http://www.tishmanconstruction.com/pdfs/7wtcgreen.pdf|format=pdf|publisher=Silverstein Properties|title=7 World Trade Center officially certified as New York City's first 'green' office tower|date=2006-03-08 |accessdate=2006-05-26] Nearly 30 percent of structural steel used in the building consists of recycled steel. [cite news |title=How Green Is My Tower? |publisher=The New York Times |date=2006-04-16 |author=Pogrebin, Robin] Rainwater is collected and used for irrigation of the park and to cool the building. Along with other sustainable design features, the building is designed to allow in plenty of natural light, power is metered to tenants to encourage them to conserve energy, the heating steam is reused to generate some power for the building, and recycled materials are used for insulation and interior materials. [cite news |author=DePalma, Anthony |title=At Ground Zero, Rebuilding With Nature in Mind |publisher=The New York Times |date=2004-01-20|url=http://query.nytimes.com/gst/fullpage.html?res=9D03E6D91539F933A15752C0A9629C8B63|accessdate=2008-02-17] [cite web |url=http://www.nyas.org/snc/gallery.asp?exhibitID=25&page=2 |title=The Academy's New 'Green' Home |publisher=New York Academy of Science |accessdate=2007-07-01]

Construction

Tishman Construction Corporation of New York began work at the new 7 World Trade Center in 2002, soon after the site was cleared of debris. Restoring the Con Ed electrical substation was an urgent priority to meet power demands of Lower Manhattan.cite news |author=Dunlap, David W |title=21st-Century Plans, but Along 18th-Century Paths |publisher=The New York Times |date=2002-04-11|url=http://query.nytimes.com/gst/fullpage.html?res=9405E4D91F3DF932A25757C0A9649C8B63|accessdate=2008-02-17] Because 7 World Trade Center is separate from the main 16 acre (6.5 ha) World Trade Center site, Larry Silverstein required approval only from the Port Authority and rebuilding was able to proceed quickly. [cite news |title=Developer's Pace at 7 World Trade Center Upsets Some |publisher=The New York Times |date=2002-01-31 |author=Bagli, Charles V|url=http://query.nytimes.com/gst/fullpage.html?res=9C01E4DD1F3AF932A05752C0A9649C8B63|accessdate=2008-02-17] Building Seven was not included in the original World Trade Center master plan by Daniel Libeskind, but was designed by Skidmore, Owings & Merrill under the leadership of David Childs, who largely redesigned the Freedom Tower.

Once construction of the power substation was complete in October 2003, work proceeded on building the office tower. An unusual approach was used in constructing the building; erecting the steel frame before adding the concrete core. This approach allowed the construction schedule to be shortened by a few months. [cite news |title=Strategy for Seven World Trade Center Exceeds Expectations|author=Post, Nadine M |publisher=Engineering News Record |date=2005-09-12|url=http://archrecord.construction.com/news/wtc/archives/050912seven.asp|accessdate=2008-02-17] Construction was completed in 2006 at a cost of $700 million.cite news |title=Major Step at Ground Zero: 7 World Trade Center Opening
publisher=Architectural Record |date=2006-05-17|url=http://www.archrecord.construction.com/news/wtc/archives/060517opening.asp|accessdate=2008-02-17] Though Silverstein received $861 million from insurance on the old building, he had $400 million remaining in mortgage to pay off. [cite news |author=Herman, Eric |title=No Tenants for New 7 WTC, Construction to Begin with Financing in Doubt |publisher=Daily News (New York) |date=2002-05-31] Costs to rebuild were covered by $475 million in Liberty Bonds, which provide tax-exempt financing to help stimulate rebuilding in Lower Manhattan and insurance money that remained after other expenses. [cite news |url=http://www.nytimes.com/2006/07/12/realestate/12liberty.html?ex=1310356800&en=cf5291a4979664b2&ei=5090&partner=rssuserland&emc=rss |title=A Pot of Tax-Free Bonds for Post-9/11 Projects Is Empty |publisher=The New York Times |date=2006-07-12|author=Pristin, Terry|accessdate=2008-02-17]

A 15,000 sq ft (1,400 m²) triangular park was created between the extended Greenwich Street and West Broadway by David Childs with Ken Smith and his colleague, Annie Weinmayr, of Ken Smith Landscape Architect. The park comprises an open central plaza with a fountain and flanking groves of sweetgum trees and boxwood shrubs. [cite news|url=http://www.nyas.org/publications/updateUnbound.asp?updateID=66 |title=A Prism with Prose — Seven World Trade Center |author=Collins, Glenn |date=July/August 2006 |work=Update Unbound |publisher=New York Academy of Science|accessdate=2008-02-17] As the seasons change, so will the colors in the park, providing a natural complement to the tower. At the center of the fountain, sculptor Jeff Koons created "Balloon Flower (Red)", whose mirror-polished stainless steel represents a twisted balloon in the shape of a flower. [cite news |title=Luster of 7 World Trade Center Has Tattered Reminder of 9/11 |publisher=The New York Times |date=2006-05-24|author=Dunlap, David W]

Building opened

The building was officially opened at noon on May 23, 2006, with a free concert featuring Suzanne Vega, Citizen Cope, Bill Ware Vibes, Brazilian Girls, Ollabelle, Pharaoh's Daughter, Ronan Tynan (of the Irish Tenors), and special guest Lou Reed. [cite web |url=http://www.lowermanhattan.info/news/7_world_trade_center_50451.aspx |title= 7 World Trade Center Opens with Musical Fanfare |publisher=Lower Manhattan Development Corporation (LMDC) |date=2006-05-22 |accessdate=2007-07-27] Prior to opening, in March 2006, the new 7 World Trade Center frontage and lobby were used in scenes for the movie "Perfect Stranger" with Halle Berry and Bruce Willis. [cite news|url=http://www.downtownexpress.com/de_149/undercover.html |title=Under Cover, Tower 7 is no ‘Stranger’ to fame |date=March 17–23 2006 |publisher=Downtown Express|accessdate=2008-02-17]

Since the building opened, several unleased upper floors have been used for events such as charity lunches, fashion shows, and black-tie galas. Silverstein Properties allowed space in the new building to be used for these events as a means to draw people to see the building. [cite news |url=http://www.nysun.com/article/54369?page_no=2 |title=The City's Hottest Event Space? Try 7 World Trade Center |author=Birkner, Gabrielle |publisher=New York Sun |date=2007-05-14|accessdate=2008-02-17] From September 8 to October 7, 2006, the work of photographer Jonathan Hyman was displayed in "An American Landscape", a free exhibit hosted by the World Trade Center Memorial Foundation at 7 World Trade Center. The photographs captured the response of people in New York City and across the United States after the September 11, 2001, attacks. The exhibit took place on the 45th floor while the space remained available for lease. [cite press release |url=http://www.buildthememorial.org/site/DocServer/5th_Anniversary_Exhibitions.pdf?docID=1881 |format=pdf|title=WTC Memorial Foundation Announces Photography Exhibitions to Mark 5th Anniversary of 9/11 |publisher=World Trade Center Memorial Foundation |date=2006-08-07|accessdate=2008-02-17]

As of March 2007,update after|2008|01|01 60 percent of the building had been leased. [cite news |url=http://www.ny1.com/ny1/content/index.jsp?stid=203&aid=62235 |title=9/11: Five Years Later: 7 World Trade Open For Business, Lacking Tenants |publisher=NY1 News |date=2006-08-31 |author=Spitz, Rebecca|accessdate=2008-02-17] In September 2006, Moody's signed a 20-year lease to rent 15 floors of 7 World Trade Center. [cite news |url=http://findarticles.com/p/articles/mi_m3601/is_6_53/ai_n16776901|title=Moody's signs on dotted line at 7WTC|publisher=Real Estate Weekly|date=2006-09-20 Retrieved from findarticles.com on 2008-02-17.] [cite news |url=http://gothamist.com/2006/06/20/pricey_midtown.php |title=Pricey Midtown Rents Mean Big Tenant for 7 WTC |date=2006-06-20 |publisher=Gothamist|accessdate=2008-02-17] Other tenants that had signed leases in 7 World Trade Center, as of May 2007, include ABN Amro, [cite news |title=Lower Manhattan: A Relative Bargain but Filling Up Fast |publisher=The New York Times |date=2007-02-28|author=Pristin, Terry] Ameriprise Financial Inc., [cite press release |url=http://www.ameriprise.com/amp/global/press-center/press-release-45.asp |title=Ameriprise Financial to lease 20,000 SF at 7 WTC |publisher=AmeriPrise Financial|date=2006-01-04|accessdate=2008-02-17] Darby & Darby P.C., [cite press release |url=http://web.archive.org/web/20061106174551/http://www.darbylaw.com/news/news_detail.asp?id=1932|title=Darby & Darby P.C. to move headquarters to 7 WTC |publisher=Darby & Darby |date=2006-08-24 Retrieved from 2006-11-06 internet archive. ] Mansueto Ventures LLC, business publisher of Fast Company and Inc., [cite press release |url=http://goliath.ecnext.com/coms2/gi_0199-5604926/Mansueto-Ventures-Signs-Lease-at.html#abstract |title=Mansueto Ventures signs lease at 7 World Trade Center to become the first corporate tenant to locate its national headquarters in the building |publisher=Goliath |date=2006-07-26|accessdate=2008-02-17] and the New York Academy of Sciences. [cite news |url=http://www.nyas.org/about/newsDetails.asp?newsID=210 |title=New York Academy of Sciences Signs Lease at 7 WTC |publisher=New York Academy of Sciences |date=2005-12-16|accessdate=2008-02-17]

The space occupied by Mansueto Ventures has been designed to use the maximum amount of natural light and has an open floor plan. [cite news |title=An Open, Sunlit Space At 7 World Trade Center |url=http://www.nytimes.com/2007/05/13/realestate/commercial/13sqft.html?ex=1336708800&en=ceda67d8a2e597df&ei=5088&partner=rssnyt&emc=rss |author=Wilson, Claire |date=2007-05-13|accessdate=2008-02-17 |publisher=The New York Times] The space used by the New York Academy of Sciences on the 40th floor, designed by H³ Hardy Collaboration Architecture, works with the parallelogram shape of the building. Keeping with the green design of the building, the NYAS uses recycled materials in many of the office furnishings, has zoned heating and cooling, and lights that detect motion, coming on automatically only when people are present, and adjust according to incoming sunlight. [cite book |title=The New York Academy of Sciences (brochure) |publisher=H³ Hardy Collaboration Architecture |author=H³ Hardy Collaboration Architecture |year=2007]

Silverstein Properties also has offices in 7 World Trade Center, along with office space used by the architectural and engineering firms working on the Freedom Tower, 150 Greenwich Street, 175 Greenwich Street, and 200 Greenwich Street. [cite news |url=http://www.nytimes.com/2007/01/25/nyregion/25blocks.html?ex=157680000&en=53cdb254a428dd39&ei=5124&partner=permalink&exprod=permalink |title=What a View to Behold, And It's Really Something |publisher=The New York Times |date=2007-01-25 |author=Dunlap, David W] [cite news |title=Behind the Scenes, Three Towers Take Shape |publisher=The New York Times |date=2007-01-18 |author=Dunlap, David W |url=http://www.nytimes.com/2007/01/18/nyregion/18blocks.html?ex=157680000&en=9ee0bb381409176f&ei=5124&partner=permalink&exprod=permalink] As of September 2008, space remains available on the ten uppermost floors and floors 33(Portion) and 36 of 7 World Trade Center. [cite web |url=http://www.silversteinproperties.com/inner_page.aspx?id=5 |title=7 World Trade Center — Current Space Availabilities |publisher=Silverstein Properties |accessdate=2007-07-27]

ee also

*List of tallest buildings in New York City
*World Trade Center in popular culture

References

External links

* [http://www.wtc.com/ World Trade Center]
* [http://www.silversteinproperties.com/ Silverstein Properties]