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Structural Safety Of Freedom Tower

  1. Sep 10, 2008 #1
    I haven't heard much about this in detail, but does anyone know what changes they made in the structural design of the Freedom Tower to prevent the collapse of the tower in the case of it being attacked via jetliners? I know it can't be 100% certain, but I would think they would have done something to the design to increase the likelihood of the structure standing in case of another attack.
  2. jcsd
  3. Sep 10, 2008 #2


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    Details are somewhat fuzzy from what I've found. Nontheless, searching Google will turn up lots of results.

  4. Sep 10, 2008 #3
    So if I'm reading that second paragraph correctly, if one side of the structure gets overloaded in the case of an attack, this structure will have a more robust design to handle that than the old WTC towers?
  5. Sep 17, 2008 #4
    yes. Post 9/11 structures are now designed to consider robustness. The scenarios being undertaken could either be one or few columns removed in the perimeter frames (either by bomb attack or any other terrorist action) and check the structure for a range of combinations of removed columns if the structure satisfies & meets the performance objective set by the building owner, either life-safety or collapse prevention.
  6. Sep 17, 2008 #5


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    It's difficult to find among all the conspiracy rubbish - but my understanding was that the original world trade centre design was a bit marginal even by the building standards of the 70s.

    There is also a shift to using elevators to evacuate in a fire, with modern buildings the elavator shaft is actually one of the strongest and most fire proof parts - it's just that people have been conditioned for so many years not to use the elavator.
  7. Sep 17, 2008 #6
    So if in the case of 9/11 repeating (North Tower like hit), would the Freedom Tower just burn, but never collapse?
  8. Sep 17, 2008 #7
    http://www.civil.usyd.edu.au/latest/aibs_2002_wtc.pdf" [Broken]

    On page 2 it said the original towers core carried vertical loading only. Is it possible for newer structures to have both vertical and horizontal loading?
    Last edited by a moderator: May 3, 2017
  9. Sep 17, 2008 #8
    Are you thinking of the asbestos that was replaced in the mid-1990s?
  10. Sep 17, 2008 #9


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    I think it was one of the first very large core+curtain wall / cantilever floor buildings and there was a concern that if one floor failed it would take out the floor below in a domino effect.

    A similair accident happened in a residential tower block in the UK soon after, a corner floor section failed and took out every corner beneath it, fortunately they all snapped neatly and didn't destroy the main floor slabs.
  11. Sep 18, 2008 #10
    supposedly, yes as this is the case for any structure that has been designed on performance-based philosophy which is gaining acceptance on the design of tall buildings.
  12. Sep 18, 2008 #11
    That's why post 9/11, a lot of research/studies has been undertaken to mitigate the effects of progressive collapse (i.e. domino effect) on structures there have been a lot of ammendments in the structural and building design codes to address this issue.

    I'm not sure of any recent event. Perhaps you were talking about the not-so recent event such as the Ronan Point incident?

  13. Sep 18, 2008 #12
    I'm really curious about this subject matter so pardon all of the inquiry, but how will the loads be more robust in the newer skyscrapers to reduce the likelihood of a collapse?
  14. Sep 18, 2008 #13


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    Thats the one, I meant soon after the WTC was built, I remembered it as rowan point so I couldn't find any detals.
  15. Sep 18, 2008 #14
    http://www.nypost.com/seven/06302008/news/regionalnews/report__wtc_faces_up_to_3_year_delay_117912.htm" [Broken]

    It appears there will be a three year delay to the opening of the Freedom Tower due to "over budget and unrealistic estimates."
    Last edited by a moderator: May 3, 2017
  16. Sep 19, 2008 #15
    the thing is, it's not the load that is robust but the structural elements and structural system become more robust to mitigate progressive collapse. The structural elements become more robust by achieving a ductile detailing and careful attention of the load path when critical elements (such as columns) are taken out of the system (for any reason including terror attacks and fire).
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