Ok, enough of this. You're probably new enough here to where you haven't seen this brought up over the course of the years, but you need to realize that you're arguing from a false premise and stating an invalid conclusion. First of all, the fact that it's never happened before doesn't mean it is impossible to happen. Second, the one actual controlled experiment - the Cardington tests - did indeed demonstrate what happens to steel when exposed to intense fires. The distortions evident from the Cardington test inform our understanding of the WTC collapses, and demonstrate clearly that the sorts of failure modes either observed in the steel (the main towers) or modeled (WTC 7) can and indeed
will occur. Creep, severe distortion of a structure, expansion, etc.
were observed in the test rig, and when you apply the principles of behavior established in those tests to the specifics of how either the Twin Towers or 7 World Trade were constructed, you can clearly demonstrate that the fires effects could and indeed
did collapse the towers.
There were multiple factors in each towers collapse. For the main towers, the design led to the unfortunate fact that debris impacting the floors sever lateral supports, leading to unstable exterior columns. For 7 World Trade, there's the design that left it vulnerable to thermal expansion of the long-span trusses. Until and unless those are taken into account in analyses, as well as the other unique issues at work that day - not the least of which was the severe damage from the impacts to the main towers, nor the extreme length of time the fire affected 7 World Trade - then blithe write-offs of the notion of steel structures not collapsing under fire are nothing more than demonstrations of ignorance.
All the details apply, not simply the gross comparison of steel framed structures.
Furthermore, remember that while there are zero cases of high-rise buildings that are entirely steel framed collapsing, there are indeed cases of
steel structures doing so. Take the Kader Toy factory as an example: The only part of the building that remained standing was the non-steel part. The steel part of the structure suffered total failure.
There are other examples I cannot recall off the top of my head. But this argument has been tried before, and has failed. See past threads, such as this one:
http://www.internationalskeptics.com/forums/showthread.php?t=133271
The point is that you're attempting to claim that steel structures do not collapse when subjected to fire. All the research that has been done by engineers such as the Arup and University of Edinburgh ones, by the various fire and structural engineering researchers in the US, such as Astaneh-Asl and James Quintiere, and so on all point to the fact that steel can indeed collapse in fires. The fact that no skyscraper has done so yet is a canard: Few suffered the same sorts of fires, none suffered jet impact damage, and among the biggest fires in history, only two or three (Beijing CCTV and Andrus Bank fire in Brazil) were even remotely as large, and I can't think of any off the top of my head where not only no fire retardation systems (i.e. sprinklers, firewalls, etc.) rendered ineffective, but no active firefighting was conducted. The point is, saying that no steel structures have ever collapsed due to fire is like saying no human has ever been killed by supernova or stellar phenomena: The principle is demonstrated very clearly; the fact that it hasn't happened before is not a demonstration that it cannot ever happen.
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And last: Take care in trying to critique Grizzly Bear's choice of citations. Wiki is to be avoided as a sole and ultimate authority, but when it's used simply as a description of details (such as the structural categorizations that GB was showing), the information is verifiable. You risk writing it off and thus demonstrating ignorance at your own peril; the real critique of a Wikipedia source is whether it's
accurate. In too many cases, it's not, but that doesn't extrapolate to all, and you've not demonstrated that it's inaccurate in this specific case to begin with. So don't write it off; address his
point, not his source. Your text following your write off does neither; it merely makes an unsupported assertion that professional surprise at the collapses means that the collapses couldn't have happened. As demonstrated by not just the NIST conclusions, but also the Arup findings, the Purdue ones, and other organizations, it's accepted that it indeed occurred. Regardless of surprise.