On Sat, 03 Nov 2007 09:28:22 -0700, wrote:


1) There was little or no jet fuel in the building.

Aparet from the 70,000kg carried on the plane...
2) The carpets and furniture were fire resistant.
Doesn't matter. Firslty fire resistance is generlly to limit flame spread -
it will still burn. I woudl also be surprised if the furnitreu and carpets
were especially fire resistant, unless it was required by the building
code. Given the sprinkler system, there isn't much point from a fire
engineering perspective.
There is PLENTY of other fuel (beside the jet fuel) in an office - paper,
desks, wooden fittings, panelling, softboard ceiling tiles, etc.
3) Even if there was an adequate supply of readily combustible fuel
present, 56 minutes is not enough time to develop a fire intense
enough or large enough in extent to weaken the steel enough, given the
thermal mass of steel and concrete present (every floor had hundreds
of thousands of kg of steel and over one million kg of concrete).
Sure it is. The floors were supported on relatively lightweight trusses,
whcih have a lot of expeosed area (high surface to cross section ratio)-
this means it will heat up fast.
a 610UB will reach 500 deg C in around 9 minutes in a "standard" fire, at
which point it has around 20% of the original strecnght. Steel starts to
weaken around 300 deg C. If you want the exact figures, it will have to
wait until Monday when I am back at work.
More importanly for the WTC collapse was the connections of the trusses at
each end - to the central core and the vertical columns at the preimeter.
These failed (rather than the trusses) so theends failed in sear, so the
collapesed straight down - hence the pancake.

Geoff M (B.E(mech), ME (Fire)).