Posted by Andrzej Gliwinski on September 22, 2002 at 09:16:30:
1. Why the south tower has collapsed as first, since it became hit as second, an hour after that north and that - as members of investigative committee found - without larger damages for constructional trunk of building, without larger than the north, of course? Some hints (contained in the English documentary film of BBC, which I looked in on French TV channel PLANETE in such also edition under title "Les Dernieres Heures de World Trade Center") that main reason was a sloping hitting of airplane into lower storeys, what caused smaller direct mechanical damages (for structural core) but for larger quantity of storeys; larger also quantity of storeys were found above gap done through hitting of airplane (larger charge of opening + boosted fire caused the accelerated fall of ceilings laid above gap on the lower, and in effect faster collapse of the south tower) seem quite right to me.
2. Different observations contained in this film connecting with fire protection.
To protect the steel members it was used new materials then (and now used on the whole world, i.a. in Poland), viz. a foam ( a type of Flame Control? ) for protection of floor flat trusses and light plates ( a type of PROMATEC?) to protect of load-bearing poles. From film it resulted that lift shafts and evacuation staircases had such a light casing only, resistant onto an activity of fire and high temperature, but no onto side mechanical damages! In context of terroristic assassination and formed results, it seems this evident error, sequent to a literal understanding of builders' and fire protection rules; but I would like to see such project on the world, in which such possibility would become consider! It does not take itself them into account now, let alone 30 years ago! Light casing of lift shafts permitted, besides, to enable 2 or 6 persons to be saved from death - they knocked out a hole in it and went out on lower storey when lift stopped between storeys. It's worse matter with such casing of evacuation staircases; under influence of hitting of airplane, which be stuck into the constructional trunk of the North tower, at once it peeled off from pillars, which it was to protect and it barred the way on the evacuation stairs, but I understand that in States ( as in Poland) every project received to realization demands a co-ordination with an expert of fire protection. Project of WTC also was co-ordinated 30 years ago with this regard, moreover, it has proved correct by 30 last years. It has met requirements of fire protection and it became handed over to users without reservation on the part of fire guard! In course of use it did not raise any reservation?
3. Mentally crushed author of its structure design (L.Robertson) has found, what is a sensation in plus for me, that in this project considered yet a possibility of hitting of airplane (the accidental, and not the purposeful and terroristic, restrictive in its flight, and not on full speed), but - of course - such what flew then, and the largest Boenig 707 was, surely considerably smaller from those, which were rammed in the both towers, and with smaller quantity of fuel in reservoirs. Self-critically yet he conceded it was not thought about a possibility of fuel spilling oneself inside from airplane tanks; mechanical damages were considered only; whence i.a. a carriage of part of load-bearing pillars onto circumference of the building (and their comparatively compact spacing).
4. Although the fire came from outside, none of towers did not burst into flames. Only whiffs of smoke rose from interiors of the both; fire digested interiors of sky-scrapers, what even created delusive hope for a time that it will go out and both towers will be stand, as they stood. It argues that external casing was non-flammable and in spite of mechanical damages it endured 1-2 h of open fire. As far as I know, internal partitions are desined onto internal sources of fire by standards, and the external on the external + distances among buildings, which guarantee a fire-safety. It takes itself into account also flying source of fire, as a lightning, but an usual system of lightning-rods serves to offtake it to the ground.
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