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RE: Questions About the Events of September 11th (off topic)

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A few important clarifications based upon what I know....

> ... the blast from the explosion blew off the
>fireproofing on the floor trusses.

This assumption is being questioned extensively right now. Some experts have
advocated that the reason for differences in the collapse times for the
towers is that the North tower had twice as much spray-on as the South
tower. The only way that could make any difference is if the fireproofing
were still in place.

> The heat from the fire caused weakening of the
>interior columns that had re-distributed loads
>and the lack of fireproofing & caused the
>trusses and their shelf angle supports to
>become over loaded. The shelf
>angle brackets then failed.

We will never know for sure, but I don't think those truss-to-exterior wall
connections failed. I saw them still attached to the structural elements
(perimeter columns and truss chords) in the piles of debris. And from what I
saw, it appeared to me that they would have had to have been torn apart in
the collapse, not at the initiation point, though. Many times, it was the
truss chords that had fractured from the welded gussets (not the two-bolt
erection connections that were widely reported as being the "cause" of the
collapse).

>If the fireproofing could have stayed on the
>trusses, I think this only would have made
>the building stand up maybe an hour longer
>(saving more lives)

As mentioned above, it may be that the fireproofing did remain adhered much
more extensively than at first thought. Where it did come off, I do not
think anybody has anything that would have remained intact. Some advocated
that we should return to wrapping the steel in concrete, but the concrete
cover was obliterated in the Pentagon attack. The 14-in.-square RC columns
became round with exposed rebar in the path of the plane there.

Unfortunately, the popular press is either lost on these and similar aspects
or does not care.

Charlie






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