[ctdonath2]

Pardon my lack of a comprehensive peer-reviewed treatise on the subject. Others have provided that re: WTC collapse.

Start a HOT fire in such a building, and let it burn a while, and (exact chemistry escapes me, and I don’t know exactly which building materials were used) either the tempered steel loses its tempering (causing collapse), or you literally burn away the material (causing collapse). You’ll notice that whichever chemistry is involved, the consequence is collapse.

My LOX comment was retorting to the “my barbecue doesn’t melt/collapse” comment by observing that if you burn a sufficiently hot fire, your barbecue DOES melt/collapse (or as depending on materials, burn/collapse). It was also an excuse to reference something I found amusing.

And watching that video snippet shows the collapse beginning in exactly the area suffering intense heat, with the rest of the structure promptly following as a gazillion tons of upper building systematically crushes the some-weakened, some-overwhelmed supports.

And rather than insulting someone for not presenting perfect comprehension of a complex subject in a casual comment, how about you show YOUR advanced knowledge and explain to us what happens when a jet-fuel-and-office-materials fire burns for 45 minutes against structural supports for a couple dozen or so stores of very large building there above? Either the hardened/tempered metals involved weaken from prolonged exposure to intense heat, or they literally burn away - right? Do inform me.

[TXnMA]

My FRiend, you are absolutely right in taking offense at my smart-@$$3d #60, to you! I woke up from my siesta thinking, "You cranky old fart, you should have taken your nap instead of spouting off at ctdonath2 like that!!"

Please accept my apologies; it was totally uncalled-for!

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Considering the stoichiometric excess of fuel to air (reducing atmosphere) in those confined spaces, I seriously doubt that there was any excess oxygen available to burn away (rapidly oxidize, as with LOX or an oxy-acetylene torch) anything but a microscopically-shallow surface layer of the steel.

And, I have even stronger doubts that temperatures anywhere inside the WTC structures -- in any location -- reached the fusion temperature required to literally liquify (definition of "melt") any alloy of iron (steel).

OTOH, I have zero doubt that temperature/time conditions were met to seriously (thermally) soften and/or anneal (de-temper and weaken) even bulky steel structural members-- sufficiently to allow buckling of uprights and floor trusses. (See my anecdote about our garage door springs in #71.)

More importantly. I am certain (from photographic evidence in the debris) that catastrophic failures of the floor-truss attachments to both the outer columns and to the central core were the rule, rather than the exception. There are plentiful examples of where the bolts failed and/or ripped right through the softened steel of the support connectors.

img src="http://911research.wtc7.net/mirrors/guardian2/wtc/fig-4-22.jpg">

And, in many cases the bulk (body) of the steel members simply softened and tore like paper as the arithmetically-increasing weight of collapsed floors slammed down on them.

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The first impression of many of us, when we saw those first encircling puffs of smoke and dust, was "Demolition charges!" For me that lasted for about a half dozen floors, and then, I realized I was seeing the "pancake piston effect", where the "piston" of falling floors compresses the air in each successive floorspace -- and it escapes the only way it can -- out the sides of the structure...

It's instructive to study the right side of that little animated GIF I posted to you. You can see the compressing upper-floor-collapse as it progresses from left to right. And, by watching the black (oxygen-deficient) smoke at right, you can see the beginning of the "pancake piston puff"...

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Well, enough of that! Again, please accept my apologies for letting my grouchiness overwhelm common decency, FRiend!