John Groos NIST engineer admits fire dont melt steel...

Originally posted by thematrix
Even if that were so, only where there was fire the steel would have been weakend to the point of loosing loadbearing capability, it doesn't explain at all how the building collapsed as if there was no steel or even concrete in the building at all.

It came down way to fast for that and the entire structure disintegrated and came down in a time period and at a speed CD specialists would be jealous about.

15-22 seconds? That's fast? It gives around 59mph for the average fall speed, averaged over both towers. For the 1st tower that fell it's like 71mph and for the 2nd it's like 48mph. That difference is important, since it's exactly what we'd expect from a progressive-collapse type UNcontrolled demolition: it's much slower than freefall (~9s) and the tower with the bigger "plunger" piece falling down (more weight on the top, so more able to overcome the resistance of the building below), falls faster.

[edit on 7-1-2009 by mike3]

[edit on 7-1-2009 by mike3]

Originally posted by ANOK
The problem is how did the heat from a few fires, on just a few floors, heat ALL the steel up to 500c?

It's not as simple as you seem to think. The columns would have acted like heat syncs, taking the heat from the part being heated and spreading it along the whole length of the columns, thus cooling it.

So...using this logic, it would be impossible to heat one end of a steel beam to, say 1,000 degrees without the other end of the steel beam, regardless of length, also heating to 1,000 degrees? Is that what you're saying here?

reply to post by adam_zapple


Column failure theory is bogus anyway, even according to NIST. There was definitely not enough heat or time to sufficiently heat so much mass. Thus the truss failure theory, which only requires reasonable amounts of heat, to cause expansion as normally observed in heated steel frames.

Beyond that, when this expansion theoretically causes deflection and then somehow a failure that causes a vertical drop, NIST didn't bother to explain anything or even do any tests to validate their hypothesis. No peer review, either. So really their whole report is unsupported where it matters most.

Originally posted by bsbray11
reply to post by adam_zapple

 

Column failure theory is bogus anyway, even according to NIST. There was definitely not enough heat or time to sufficiently heat so much mass.

As the report showed....it wasn't necessary to heat very much mass (with respect to the total mass of the building). The heat from the fire heated floor trusses, causing them to sag and pull inward on exterior columns (you can actually SEE this inward bowing in videos of the buildings before their collapses). This inward bowing is what ultimately caused the collapse.