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World Trade Center Buildings

  1. Jan 23, 2004 #1
    World Trade Center Buildings

    Why did they collapse downward as if they were being demolished through the use of explosives strategically placed and detonated by demolition professionals?
     
  2. jcsd
  3. Jan 23, 2004 #2

    Njorl

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    Professionals know to use the weight of a building itself to aid in demolition. Parts of a building falling will cause those parts beneath to collapse. The terrorist attack duplicated this process. The jet fuel melted supports in the higher floors. As soon as those supports gave way, the floors above collapsed. The impact shattered the supports below, and the collapse cascaded all of the way down.

    Had the impacts of the jets been lower down, it would have been even more disastrous. Not only would more people have been trapped, the buildings might have toppled, rather than collapsed.

    Njorl
     
  4. Jan 23, 2004 #3

    enigma

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    Because the heat from the burning jet fuel melted the internal support ring causing it to fail from the inside out.

    If it were done by professionals, it may have looked the same at the beginning, but towards the end of the collapse, it wouldn't have fallen outward like it did, and it wouldn't have taken a year to clean up.
     
  5. Jan 23, 2004 #4

    NateTG

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    The WTC towers were essentially composed of three structural elements:

    A central tower which was built like typical skyscrapers
    A load-bearing steel exterior
    and
    Floors that tie the two together.

    The mechanism of collapse was that one section or floor would give out, and collapse onto another. Much like knocking blocks out of a stack, the result is that the tower stays mostly upright.

    It also helps that the floors are essentially only tied in at the endges and at the middle, so when the 'sandwiching' occurs, the floors can break off relatively cleanly.

    Enigma - one tower fell inside out, the other fell outside in.

    Although the WTC towers collapsed admirably well, there are two obvious shortcomings that they had:

    One is that the fire retardant and fire response capabilities were inadequate.

    The other is that all of the stairwells were concetrated at the center of the building, so it was possible for the plane to knock them all out at once.
     
  6. Feb 29, 2004 #5
    "One is that the fire retardant and fire response capabilities were inadequate"

    the fire proofing was adequate, the towers fell for two reasons, the first is lazy workmen not covering all the trustes with it.

    the 2nd is that its well known that even if 1 part of a trustes is not protected from fire, the entire floor will fall, knocking the rest.

    what i find intresting is how that one looked like it inploded, half way down everything just started to get sucked into the middle as it fell.

    ________________________
    \/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/


    this is what one floor looks like, the thing about this fast and easy to lay floor is that it relys on its self to keep its self up. removing 1 part makes the entire floor fail.

    ________________________
    \/\/\/\/\/\/\/\/\/\/ /\/\/\/\/\/

    .......................................^
    ....................................ohnos!
     
  7. Feb 29, 2004 #6

    NateTG

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    According to the things I've seen there were two problems with the fire retardant in the WTC, one was that the foam covering the trusses was knocked off by the colision with the jet. The other was that the sheet rock which was supposed to protect the stairwells during a fire was too flimsy.

    There have been no claims that the building was built out of spec.
     
  8. Mar 1, 2004 #7
    yah when it was first built, it was hunky dory.

    but just with anything, it comes down to maintenance. or lack of.
     
  9. Mar 2, 2004 #8

    enigma

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    I'm sure that the impact of the gigantic jet aircraft had nothing to do with it...
     
  10. Mar 2, 2004 #9
    Gravity.
     
  11. Mar 2, 2004 #10

    russ_watters

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    To elaborate, stability is extremely important to structural integrity of tall buildings. If they get just a little bit offcenter (falling slightly crooked), they'll break apart.

    If you remember, the top of one of the buildings (the second , I think) did begin its fall a little offcenter, but a building like that just isn't strong enough to absorb the energy of its own collapse and re-direct it sideways.
     
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