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Originally Posted by Pacifier
I get the conclusion that steel looses much of it stability at lower temperatures. It doesn't need to melt to collapse.
What are your conclusions?
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Jet fuel burns at 800° to 1500°F, not hot enough to melt steel (2750°F). However, experts agree that for the towers to collapse, their steel frames didn't need to melt, they just had to lose some of their structural strength--and that required exposure to much less heat. "I have never seen melted steel in a building fire," says retired New York deputy fire chief Vincent Dunn, author of The Collapse Of Burning Buildings: A Guide To Fireground Safety. "But I've seen a lot of twisted, warped, bent and sagging steel. What happens is that the steel tries to expand at both ends, but when it can no longer expand, it sags and the surrounding concrete cracks."
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Note: The following is conjecture and science about the North and South towers collapsing as it relates to questions abouyt the Madrid building.
The real question is: Why did the top story cave straight down, followed by the next to the top, followed by the third from the top, leading to the building collapsing at free fall speeds from metal beginning to bend just in the area with the jet fuel?
The jet fuel could have warped the structure in the area it was burning, and I'm sure that it did. But why did the top floor collapse down first without any collpase underneith it? It just seems odd to me. In order for it all to fall straight down into itself, the whole steel frame would have to be compromised almost at once.
What would have happened if the steel warped causeing the building to collapse: The planes hit, they burn very hot for hours and hours, possibly days. Eventually, the middle (middle meaning impact area) of the buildings becomes weak and a strong enough wind or the weight of the top of the buildings causes the middle to give. If it is wind, the top part of the building is blown away from the wind, crushing the back part of the building as it falls. If the weight of the top causes the middle to give, you'll see the top half of the building crunch down on the middle, then you see the building crumble as it all goes to the ground. Neither of those happened.
Also, the American Free Press reported pools of "molten steel" found at the base of the collapsed twin towers weeks after the collapse. That just doesn't fit with the jet fuel theory.
It is important to note that the theory about the melting frame collapse was just a theory put fourth by FEMA after the initial invesigation of the collapse. This theory has never been proven.
One theory is that there were thermite charges installed for some time before this happened in case the building was going to topple on it's side, crushing many buildings and possibly killing tens of thousands. The WTC was bombed before, so this was clearly something that could have beeen considered. The building was hit and it could have possibly collapsed, so they decided to "pull" the buildings (i.e. demolish them straight down, like a controled demolition). This would explain the manner of the falls, as well as the m,olten steel. Thermite burns at approximately 5,400 degrees (F), more than enough to liquify the structure. I've seen a video of thermite instantly liquifying a jeep engine.
Just one theory, I guess. It's up to you to figure out what you want to believe.