This chap has done some research and found a few cases of progressive
collapse in steel-frame high-rise buildings.
http://911myths.com/html/progressive_collapse.html
While none of these perfectly replicate the conditions at the WTC,
they do show that once the load exceeds the structural integrity,
progressive collapse is initiated.
So we've established that the fire was hot enough to initiate the
phase change in the steel (any heat over 600C), we've established
that there have been other cases of progressive collapse.
As for the Thermite: thermite is aluminium and iron oxide. If any of
the beams were exposed, which they would have been after a plane flew
through the central core, there may well have been rust about. We
know there was aluminium flowing through the buliding, as the planes
were made of it. It's entirely plausible that thermite reactions
occurred at places, and these may have caused additional weakening.
However, I think we've established that the heating of the steel
beams to over 600C was probably sufficient to initiate collapse.
Have a wander round that 911myths site, it's not bad as he provides
pretty substantial references.
Charlie
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