54 Comments

  1. Tim S

    The back span of the cantilevered joist (into the building) must be at least twice the cantilevered distance, but a 3:1 ratio is preferred.

  2. meeeee

    If you think about it –

    These are structures that are very solid and hard, usually stone. That's powerful.

    Also, they're supporting some of the heaviest parts of buildings and structures, which is powerful. I hope this helps.

  3. Miranda M

    You can find a lot of construction detail on sites associated with the "9/11 Truth Movement." You see the 9/11 Commission report stated that there was no internal steel support columns, but if you check the truther's site, you will see pictures of the twin tower construction with 38 steel support columns. If the truther's are right, then the 9/11 Commission progressive collapse theory is all wet. They've agreed that progressive collapse is impossible, but they don't have a plausible second explanation.

    The PBS special is not reliable. It ignores the fact that the steel support in the center would have protruded. The steel support structure appears to have been undermined and cut. In other words, the construction of the towers suggests that the destruction was a planned demolition.

    The core was not hollow, despite what the previous administration wants you to believe.

  4. Ramona C

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