On 16/09/18 22:45, juan wrote:
On Mon, 17 Sep 2018 06:30:09 +1000 jamesd@echeque.com vomited:
What was actually shown was the controlled demoltion of the twin towers.
Controlled by OBL perhaps. But it didn't need any explosives, hand-positioned thermate, or the like - the burning jet fuel would do that to a building like WTC. I am a Brit and I don't know crap about WTC7, or the Pentagon, except to suggest that if I were the terrorist in charge I'd have attacked the White House, Congress, Senate, suchlike instead - but OBL was well-known for antipathy to the New York financial world and the US military. But I do know a lot about metal (and more than enough about explosives, and demolitions), and let me tell you, the jet fuel fire woulda done it. No need for any explosives. If a lot of men in black suits or keffiyas did somehow carefully plant explosives and/or thermate in WTC (without anyone noticing), their effort was wasted.
it was surprising to me as I watched the second plane hit the second tower that it did no fall immediately.
Actually that would have astonished me - the building weighs maybe 5000 times more than the plane, and is built to take huge wind side loads. Getting knocked over by the plane crashing into it would be like you getting knocked over by a pingpong ball. But after the crash, the thermal protection on the interior steelwork had been shattered, and the fuel started burning. The steel never melted, nor did it come close to melting - but there was a lot of fuel, and the whole of two or so floors was on fire. That's a lot of heat in one place. The word "inferno" comes to mind. The temperature in the center of the floor would have been at least 650C, and more likely somewhere around 700-800C. Even at 650C A36 structural steel has only 38% of its room-temperature yield strength. At 800C it would be less than 17%. How much steel do you think they put into something like WTC? - the answer is, a little more than three times what's needed to stop it collapsing. Ever seen a blacksmith work? He takes the steel out of the furnace and squashes it with a hammer. It starts off at about 900C, when it's glowing yellow and the steel is quite soft, but he will still hammer the steel until it is dull red at about 550C, when it becomes too hard to squash with a hammer blow. Hey, would you even think about the possibility of squashing that lump of steel at room temperature with a hammer? Yet a smith can do it with ease when the metal is at the same temperature as the steel in WTC got to. Then consider that the inside of the outer steel shell would have been a lot hotter than the outside - which would cause the box columns of the shell to bend and buckle. Both the above phenomena, the loss of strength and the bending and buckling are well-known to metallurgists, and are easy to demonstrate. So, no wonder it collapsed. The straight-down nature of the collapse might seem surprising, but it isn't really - take a rod as long as the WTC was high, and tip it over slightly. It takes a long time to get moving - but it only took ten seconds for the WTC to collapse. There wasn't enough time for it to go any way except straight down. The reason it collapsed so fast is interesting though - one or two floors collapsed, then the the top ten floors fell down on the next-highest intact floor - which had no chance of withstanding the impact. That floor failed immediately, and so the cascade continued. If I have given the impression that the first floor to collapse collapsed all at once, it probably didn't - most likely part of it, perhaps a part which had been damaged by the impact as well as weakened by the fire, collapsed first; then the uncollapsed part of the floor had a whole lot of extra weight on it. In time this might have tipped the top ten floors sideways - IIRC the top floors did tip a bit on one tower, but I haven't seen the film recently - but there wasn't enough time for that to develop, the uncollapsed part of the floor also collapsed, and the top ten floors fell as a lump. After that, once the top ten floors get some momentum, they go straight down; and there ain't nothing underneath strong enough to stop that momentum. So, that's how it would have happened if the fire caused the collapse. Seems to me to be pretty much what actually happened. If it was spies, or terrorists, or demolition contractors, I'd expect something different. Peter Fairbrother