Quote from Bitstream:
there are many documents describing the concrete walls surrounding the core, i already gave u one link earlier and that's just one doc.
also oxford uni describe it.
here's one:
http://algoxy.com/conc/core.html
and another:
http://www.ussartf.org/world_trade_center_disaster.htm
and again, scroll down 'till u get to the design and description:
http://www.discover.com/issue/oct-02/feature/featbuildings
there are many many more links in the internet.
and these are quotes from wtc engineers:
frank a. demartini, on-site construction manager for the world trade center, spoke of the resilence of the towers in an interview recorded on jan 25, 2001.
"the building was designed to have a fully loaded 707 crash into it. that was the largest plane of the time. i believe that the building could sustain multiple impacts of jetliners because this structure is like a the mosquito netting on your screen door --this intense grid-- and the jet plane is just a pencil puncturing that screen netting. it really does nothing to the screen netting."
john skilling who was one of the two structure engineers responsible for designing the wtc.
skilling recounts his people having carried out an analysis, which found the twin towers could withstand the impact of a boeing 707. he says, "our analysis indicated the biggest problem would be the fact that all the fuel [from the airplane] would dump into the building. there would be horrendous fire. a lot people would be killed, but he says." the building structure would still be there.". "the buildings have been investigated and found to be safe in an assumed collision with a large jet airliner [boeing 707], traveling at 600miles per hour. analysis indicates that such collision would result in only LOCAL DAMAGE WHICH COULD NOT CAUSE COLLAPSE OR SUBSTANTIAL DAMAGE TO THE BUILDING AND WOULD NOT ENDANGER THE LIVES AND SAFETY OF THE OCCUPANTS NOT IN THE IMMEDIATE AREA OF IMPACT."
Where to begin -
Ok, algoxy.com makes a rather poor case for the concrete, honestly. The best evidence seems to be sunlight shining through the building, showing the hallways.
But even funnier is the second link you give. It starts right off in the second para under The Structural System heading with the statement that it was the first super tall building designed without any masonry. FYI - masonry = cement or brick...... It has several more references to wallboard providing the fireproofing to the core steel, with no mention at all of concrete...
It DOES however, have 2 mentions of concrete cladding from some British engineers, BUT it was dated Dec 2001, so maybe they were ill informed. Funny thing, the first link you gave was to a British run site..... I see a pattern here.
The 3rd link was dead, but I searched around a little and found this passage:
Reinforced concrete is much tougher than gypsum, but it is not fireproof. The heat of a fire dehydrates the concrete, and it eventually crumbles.
http://www.discover.com/issues/oct-02/features/featbuildings/
This is the same link. I see absolutely no reference here to the core being concrete in the core, other than for the floors.
So overall, I'd say your evidence for concrete covering the core was VERY weak and definitely contains some conflicts and inconsistencies. I'm sure there's some actual construction plans out there somewhere - Library of Congress, NY city Library, something... Go find it if you want to convince others...
WTC engineers -
DeMartini was a construction manager - so I don't know that he was an engineer or not, do you ? And the netting comment seems a little odd too, since a mosquito net is under tension and the exterior panels would be under tension OR compression , depending on which side of the tower they were on and on load factors such as wind direction, etc. And anyways he states that the towers were designed to withstand the impact of --- A ---- jet plane. The use of A generally means - ONE !!! He states as his OPINION that the towers could withstand multiple impacts. If you want to claim THAT, then it would be an accurate statement.....
As far as Skilling goes - who knows how good a study they did. Remember, this building was designed in the 60's so no computer modeling was available to them. Who knows if they figured the insulation being removed. Do you have a link saying he did?