World Trade Center 7

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World Trade Center 7
Salomon Brothers Building
World Trade Center 7
The WTC 7 from the former south tower of the World Trade Center
Basic data
Place: 250 Greenwich Street, 10007 Manhattan , New York , United StatesUnited StatesUnited States 
Construction time : 1984-1987
Status : Collapse on September 11, 2001
Architectural style : Modern
Architect : Emery Roth & Sons
Use / legal
Usage : offices
Owner : Silverstein Properties
Technical specifications
Height : 186 m
Floors : 47
Elevators : 32
Usable area : 200,000 m²
Floor area : 4400 m²
Building material : Steel , glass , aluminum
Construction: Tishman Construction

The World Trade Center 7 (also Salomon Brothers Building ; abbreviated WTC 7 or 7 WTC ; German  World Trade Center - building 7 ) was a skyscraper in New York City . It opened in 1987 and collapsed completely on September 11, 2001 at around 5:20 pm.

The collapse was the result of the terrorist attacks that day on the twin towers of the World Trade Center . When WTC 1 collapsed, debris fell on neighboring WTC 7 and triggered fires that burned uncontrollably for up to seven hours on at least six floors. Due to destroyed main water pipes, a failed sprinkler system and inaccessible sources of fire, the fire brigade withdrew all rescue workers from around the already unstable building. In November 2008, the National Institute of Standards and Technology (NIST) identified the thermal expansion of some steel girders as a result of the fires and the subsequent overloading of three adjacent supporting pillars as the main cause of the building collapse and invalidated popular conspiracy theories .

From 2002 to 2006 the new 7 World Trade Center was built on the property .

history

Location of WTC 7 in the WTC complex

The 186-meter-high WTC 7 was built between 1984 and 1987 as part of the World Trade Center complex on property owned by the New York Port Authority in Lower Manhattan and opened in March 1987. The client and owner was the real estate company Silverstein Properties , the design came from the architects' office Emery Roth & Sons , and the construction work was carried out by Tishman Construction , as was the case with the twin towers of the World Trade Center . WTC 7 stood outside the actual World Trade Center square north of Vesey Street , but was connected to the main complex of the World Trade Center by a promenade and a pedestrian bridge at the level of the third floor . The 47-story skyscraper had a total floor space of 200,000 square meters, of which 174,000 square meters were designed as office space. The architects chose an irregular trapezoid as the external shape in accordance with the building plot . On the north side the WTC 7 was about 100 meters long, on the south side it was 75 meters long and on the east and west side it was 44 meters wide. The capped a reddish granite facade WTC 7 was in part over a 1967 built ConEdison - substation built.

In 1989, on behalf of the new main tenant, Salomon Brothers, an extensive $ 200 million conversion was carried out to create a "building-within-a-building" that was unique at the time. During these renovations, an additional 375 tons of steel were used to reinforce the floors for the Salomon Brothers' special equipment. After this redesign, the WTC 7 was also called the Salomon Brothers Building .

On September 11, 2001 at 5:20 p.m., the building collapsed after several hours of fire as a result of the aircraft attacks on the twin towers. Several neighboring buildings were seriously damaged, including the 32-story New York Telephone Building (140 West Street) to the west. It was restored for 1.4 billion US dollars. The Fiterman Hall (30 West Broadway) to the north of the City University of New York had to be completely demolished. In 2012 the new Fiterman Hall was opened on the property.

In June 2002, real estate entrepreneur Larry Silverstein, as the owner of WTC 7, received a sum of 861 million US dollars from Industrial Risk Insurers . Of this, $ 489.4 million had to be paid back to the Blackstone Group and Banc of America Securities for mortgages that still weighed on the collapsed WTC 7 . From November 2002 to May 2006 the 228 meter high 7 World Trade Center was built on the site of WTC 7, which collapsed on September 11, 2001.

Tenant 2001

The WTC 7 Silverstein Properties owning company rented office space to finance, insurance and government agencies.

floor Tenant function
46-47 Citigroup / Salomon Smith Barney (SSB) House technic
26.-45. Investment banking
25th U.S. Department of Defense (DOD) US government agency
25th Central Intelligence Agency (CIA) US federal agency
24.-25. Internal Revenue Service (IRS) U.S. tax authority
23. Office of Emergency Management (OEM) New York City Disaster Response Team
22nd Federal Home Loan Bank mortgage Bank
21st First State Management Group Investment company
19. – 21. ITT Hartford Insurance Group Insurance company
19th National Association of Insurance Commissioners (NAIC) Insurance association
18th Equal Employment Opportunity Commission (EEOC) US federal agency
15-17 Citigroup / Salomon Smith Barney Investment banking
14th Not a tenant unlet
13. Provident Financial Management Financial enterprise
13. American Express Financial enterprise
11-13 United States Securities and Exchange Commission (SEC) US Securities and Exchange Commission
9-10 US Secret Service US federal agency
7th-8th American Express Bank International Banking company
7. (partly) Office of Emergency Management (OEM) 3 generators + tanks for OEM
6th Citigroup / Salomon Smith Barney (SSB) Switchgear, storage rooms
5. Switchgear, 12 generators, transformers
4th Opening to the lobby on the 3rd floor, switchgear
3. Lobby, SSB conference center, management rooms, rental rooms
2. Opening to the entrance lobby, switchgear, transformer room
1. Entrance lobby, loading docks, energy supply, switchgear, fuel storage

collapse

FEMA investigation report

NIST model for buckling in pillars number 79, 80 and 81
NIST simulation of the collapse of the WTC 7

In September 2002 the Federal Emergency Management Agency (FEMA) published a preliminary investigation report into the collapse of WTC 7, which was based on the known building data, video and photo material as well as testimony from eyewitnesses, and which expressly requested a more thorough investigation.

The report found debris damage to floors 24, 25, and 39 to 46 on the outer southwest side of the building and on the facade between the eighth and eighteenth floors. Irregular sources of fire were found on the south side on floors 6, 7, 8, 10, 11 and 19, fires on the east side on floors 11, 12, 13 and 28 and on the west side on the 29th and 30th floors as well as fire and smoke noted from the lower floors. A collapse of load-bearing structural elements in the building was assumed, which preceded the overall collapse that was visible from the outside and began on the lower floors of the eastern part of the building. Shifts in weight would then also have caused the transfer beams and / or support pillars in the middle section to buckle and fail. This process has expanded into the western part of the building. FEMA suspected collapse scenarios that were triggered between the fourth and seventh floors. From which failing support element and on which floor the total collapse was initiated, can only be determined after precise individual studies in the future.

Course of the WTC 7 collapse
17:20:33 pm The WTC 7 begins to collapse.
5:21:03 pm The eastern penthouse collapses.
17:21:08 pm The western penthouse collapses.
17:21:09 pm A kink forms on the roof edge.
5:21:10 pm The rest of the building collapses.

NIST investigation report

The NIST was supposed to clarify the causes of the collapse of the twin towers and WTC 7 and in 2002 published a preliminary investigation report with a small part on WTC 7. In 2004 an interim report followed. In 2006, investigator S. Shyam Sunder stated that the final report would be delayed due to a lack of staff, budget constraints and difficult verification of the initial collapse hypotheses. On August 21, 2008, NIST submitted the 130-page final report. 88 experts from various institutions had evaluated construction plans, witness statements, photos and video recordings as well as computer simulations.

When the north tower (WTC 1) collapsed at 10:28 a.m. on September 11, debris fell on WTC 7, 110 meters away. Significant structural damage occurred on the south-western exterior between the 7th and 17th floors. Fires broke out on at least ten floors on the southwest side of the building, some of which were fed by materials in the building. The fires, which were visible at times on floors 19, 22, 29 and 30 at the south-western corner of the building, did not spread according to NIST and probably dried up, as no more fires were observed there after 1 p.m. From the 21st floor, fires may have been extinguished by the automatic sprinkler system because it was fed from a separate water tank on the roof of the building. The sprinkler system for the 20 lower floors, on the other hand, was connected to the main water line of the city of New York, which had been damaged by the collapse of the neighboring twin towers. At times, uncontrolled fires could develop on floors 7 to 9 and 11 to 13. The initial assumption that diesel fuel from tanks in the basement had contributed to the development of heat and thus to the collapse was not confirmed.

The fires could not be fought effectively due to several circumstances: The house alarm system of WTC 7 had been in an eight-hour test or maintenance mode since 6:47 a.m. on the morning of September 11, 2001, so that it ignored all incoming fire signals or classified them as error messages . The responsible surveillance company registered a fire report at 10:00 a.m., but could not determine the exact location of the fire in the building. Furthermore, the water pressure was too low for attempts to extinguish the fire because of severely damaged water pipes and hydrants. At 11:30 a.m., the firefighters were instructed to stay away from WTC 7 for safety reasons. At 2:30 p.m., the New York Fire Brigade's operations management had all activities of the rescue services in and around WTC 7 preventively suspended and the building and its surroundings evacuated. The emergency services should not be exposed to any mortal danger if WTC 7 were to collapse. Nobody was injured in the collapse of WTC 7.

The ongoing fires caused the vertical and horizontal steel girders to expand. That is why many horizontal ceiling beams jumped off three load-bearing pillars (numbers 79, 80 and 81). Pillar 79 was free to stand between the 5th and 14th floors, pillar 80 between the 5th and 15th floors, and pillar 81 between the 7th and 15th floors. As a result of the overloading, pillar 79 buckled first, and in the following second, pillar 80 and 81 also buckled.

Outwardly visible, the eastern penthouse collapsed on the roof first, about five seconds later the western penthouse sank into the already collapsed interior of the building. This was followed by a kink in the middle edge of the roof and the rapid collapse of the rest of the building. The east side of the building, which had arched first, pulled the west side down evenly. The collapse of the north facade accelerated for 2.25 seconds to a pace of free fall and slowed down again when the upper part of the facade hit the already piled building rubble.

As a result, according to NIST, thermal expansion caused by fire was the main cause of the collapse. Up until September 11, 2001, there had been no comparable case of high-rise fires with a similar steel frame construction and a likewise failed sprinkler system. According to NIST, the building damage caused by the fallen rubble of WTC 1 was not decisive for the collapse of WTC 7. The building would only have collapsed from the fires. Had the sprinkler system been fully functional, the fires could probably have been controlled and the collapse prevented.

conspiracy theories

Since September 11, 2001, conspiracy theses about a controlled demolition of the twin towers and WTC 7 have been spread. They point out that WTC 7 was not hit by airplanes and claim that the building was blown up with explosives secretly previously placed inside it .

The preliminary NIST report in 2004 found that there was no evidence of bombs, missiles or a controlled demolition of the building. The final report outlined this in a separate section and named evidence that excluded an explosion. Various demolition experts have confirmed this. The NIST study result was verified in a peer review and published in an independent specialist journal.

literature

  • Therese McAllister, Omer Erbay, John Gross, Steven Kirkpatrick, Robert MacNeill, Andrew Sarawit, Mehdi Zarghamee: Analysis of Structural Response of WTC 7 to Fire and Sequential Failures Leading to Collapse. Journal of Structural Engineering, Volume 138, Issue 1 (2012), ISSN 0733-9445, doi: 10.1061 / (ASCE) ST.1943-541X.0000398 .
  • Howard J. Hill: Failure Point: How to Determine Burning Building Stability. PennWell, Tulsa 2012, ISBN 978-1-59370-283-0 , pp. 108-113.
  • Arthur Scheuerman: How the Fire Collapsed the World Trade Center Buildings. 2011, ISBN 978-1-60594-766-2 .
  • Geoff Craighead: High-Rise Security and Fire Life Safety. Butterworth-Heinemann, 3rd edition 2009, pp. 46–59.
  • Nadine M. Post: Engineers' Reaction Strong To Seven WTC Collapse Report. Engineering News-Record, September 8, 2008, Volume 261, No. 7, p. 13.
  • Professional Safety: NIST Research Examines Structural Collapse Hazards. November 2007, Volume 52, No. 11, p. 6.
  • Contractor Magazine: High-rises need redundant sprinklers: NIST. September 2005, Volume 52, No. 9, p. 16.

Web links

Commons : World Trade Center 7  - Collection of Pictures, Videos and Audio Files

Individual evidence

  1. ↑ WTC.com: 7 World Trade Center
  2. ↑ Company history of Silverstein Properties
  3. ^ Architectural Guidebook to New York City. Francis Morrone; P. 57 ISBN 1-58685-211-6
  4. ↑ Robert Tishmann, 94, died. New York Times, October 12, 2010
  5. ^ NIST Structural Fire Response and Probable Collapse Sequence of World Trade Center Building 7. 2.1 History of the building; P. 9, 10.
  6. ^ The Salomon Solution: A Building Within a Building, at a Cost of $ 200 Million. New York Times, February 19, 1989
  7. ↑ Herculean Effort to Restore a Landmark Battered on 9/11. New York Times, January 6, 2003
  8. ↑ Verizon Building Restoration for 1.4 billion US-Dollar ( Memento of September 26, 2007 in the Internet Archive )
  9. ^ Ground Zero building to be razed. Badly damaged CUNY building will be replaced. Crains New York, November 13, 2008
  10. ^ The New Fiterman Hall Opens. ( November 9, 2013 memento on the Internet Archive ) Lower Manhattan Info, August 29, 2012
  11. ^ Silverstein May Use Insurance Money to Pay Bondholders. Insurance Journal, June 7, 2002; Even as Foundation Is Set, a New 7 World Trade Center Faces Barriers. New York Times, January 13, 2003
  12. ↑ FEMA: WTC 7 , Table 5.1; Page 2 (PDF)
  13. ↑ FEMA: WTC 7 , Table 5.1; Page 2 (PDF)
  14. ↑ FEMA: WTC 7 , Section 5.5.3: Fires at WTC 7 (PDF; p. 20f)
  15. ↑ FEMA: WTC 7 , 5.5.4 Sequence of WTC 7 Collapse, page 31f (PDF)
  16. ↑ NIST study 2002 (PDF)
  17. ^ The Ground Zero Grassy Knoll. New York Features, March 27, 2006
  18. ↑ NIST Final Report 2.3: Progress Of The Fires In WTC 7. (PDF p. 19 f.)
  19. ^ NIST Progress Report: Active Fire Protection Systems — Fire Alarm Systems, Finding 2.27. (PDF; pp. 28, 68 f.)
  20. ^ Engineers Suspect Diesel Fuel in Collapse of 7 World Trade Center. ( March 25, 2016 memento on the Internet Archive ) New York Times, November 29, 2001
  21. ↑ NIST Federal Building and Fire Safety Investigation of the World Trade Center Disaster 5.9: Emergency Response Operations At World Trade Center 7. (PDF p. 111)
  22. ^ Statement by Daniel Nigro, chief fire officer, on the evacuation order for WTC 7 on September 11, 2001 , New York Times, August 12, 2005
  23. ↑ NIST Final Report 2.4: The Probable Collapse Sequence. (PDF p. 21 f.)
  24. ↑ NIST Global Structural Analysis of the Response of World Trade Center Building 7 to Fires and Debris Impact Damage 4.3.2: Overview of Global Collapse Results (PDF; p. 76)
  25. ↑ David Dunbar, Brad Reagan: Debunking 9/11 Myths. Why Conspiracy Theories can't stand up to the facts. Hearst Books, New York 2006, ISBN 1-58816-635-X , p. 55.
  26. ↑ NIST Final Report 3.6: Timing of Collapse Initation and Progression. (PDF; p. 45f)
  27. ↑ NIST Structural Fire Response and Probable Collapse Sequence of World Trade Center Building 7, May 12, 3: Timing of Collapse Initation and Progression. (PDF; p. 602)
  28. ^ NIST Final Report World Trade Center Building 7, Executive Summary ES.1. (PDF p. Xxxv to xxxvii)
  29. ^ David Dunbar, Brad Reagan: Debunking 9/11 Myths , New York 2006, p. 53; Philip Mole: 9/11 Conspiracy Theories. In: Derek Soles (Ed.): The Essentials of Academic Writing. 2nd edition, Houghton Mifflin, 2009, ISBN 0-547-18133-7 , pp. 386f. ; Michael Shermer: The Believing Brain: From Ghosts and Gods to Politics and Conspiracies - How We Construct Beliefs and Reinforce Them as Truths. St. Martin's Press, 2012, ISBN 978-1-250-00880-0 , pp. 215-219
  30. ↑ David Dunbar, Brad Reagan: Debunking 9/11 Myths. Why Conspiracy Theories can't stand up to the facts. Hearst Books, New York 2006, ISBN 1-58816-635-X , p. 58.
  31. ^ NIST Final Report 3.3: Hypothetical Blast Scenarios. (PDF pp. 26–28)
  32. ^ World Trade Center 7 Report Puts 9/11 Conspiracy Theory to Rest. Popular Mechanics, August 20, 2008; Mike Rudin, Christoph Röckerath : September 11th - The secret of the third tower. ZDF, September 7, 2008; 9/11 - The Truth behind the Third Tower. BBC, June 30, 2011; Brent Blanchard: A critical analysis of the collapse of WTC Towers 1, 2, and 7 from an explosives and conventional demolitions viewpoint. Journal of Debunking 911 Conspiracy Theories, Aug. 8, 2006
  33. ^ Therese McAllister et al .: Analysis of Structural Response of WTC 7 to Fire and Sequential Failures Leading to Collapse. Journal of Structural Engineering, Volume 138, Issue 1, January 2012

Coordinates: 40 ° 42 ′ 48 "  N , 74 ° 0 ′ 43"  W.