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

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>Don't you think that [steel yield strength degradation]
>was caused to a great degree by the now known gross
>inadequacy of the type of spray-on fire retardant
>treatment which was used on the steel?

I strongly disagree with this statement. In fact, it is such an
unsubstantiated mischaracterization of the truth, I'll presume to lecture
you a bit -- forgive me, please.

If you truly consider spray-on to be grossly inadequate based upon the WTC
experience, then you must also accept that concrete cover suffers the same
gross inadequacy based upon the Pentagon experience. The Pentagon's
reinforced concrete structure was fire protected with a layer of cover
concrete that would insulate the reinforcing steel inside it. The World
Trade Center towers steel structure was fire protected with a spray-applied
fire-resistive coating that would similarly insulate the steel inside it. On
September 11, 2001, the cover concrete in the Pentagon was obliterated by
impact and debris just as extensively as the spray-applied fire-resistive
coating in the World Trade Center towers. As a result, the Pentagon was just
as susceptible to its eventual fire-induced collapse, which occurred after
30 minutes, as were the World Trade Center towers, which collapsed in 56 and
103 minutes.

We should also bear in mind that the events of September 11, 2001 are not
normal or by any means anticipated in design or construction. In normal
cases of fire, history shows that steel and reinforced concrete structures
both have excellent records of performance. Other than on September 11,
2001, no fire-protected steel high-rise, and only a limited number of
reinforced concrete high-rises, had ever collapsed in a fire.


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