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NIST Releases Report On WTC 7 Collapse
photonic writes "After three years of study, the National Institute of Standards and Technology (NIST) finally released its report on the collapse of World Trade Center building 7. The main conclusion is that the building came down due to fire, not due to debris damage or some conspiracy demolition team. The fire started pretty small after the collapse of WTC 1, but was left to burn several floors out completely. The important finding is that the collapse was triggered by thermal expansion of beams, which could detach asymmetrically loaded girders from the main columns. Some limited pancaking of floors then caused a lack of lateral support and buckling of a single column. This triggered the failure of the entire core of the building, which finally fell down as a single piece. Crackpot theories can be discussed elsewhere; please limit the discussion to the science here. All documents can be found at NIST's WTC page, which read like a porn magazine for finite element junkies. Simulation movies are also available. And yes, they used Beowulf clusters to do the simulations, some of which lasted for several months."
I guess 2 minutes.
Crackpot theories can be discussed elsewhere; please limit the discussion to the science here.
Hah! What an optimist.
Wrongo, old chap!
Again, this is all from a UK graduate thesis that's being hosted locally at a 9/11 research site...
"...While admitting that fire test's such as ASTM E119 are conservative, they do not emphasize that such tests are very conservative. Here is a quote from [1].
Steel beams in standard fire tests reach a state of deflections and runaway well below temperatures achieved in real fires. In a composite steel frame structure these beams are designed to support the composite deck slab. It is therefore quite understandable that they are fire protected to avoid runaway failures. The fire at Broadgate showed that this (runaway failure) didn't actually happen in a real structure. Subsequently, six full-scale fire tests on a real composite frame structure at Cardington showed that despite large deflections of structural members affected by fire, runaway type failures did not occur in real frame structures when subjected to realistic fires in a variety of compartments.
So beams and columns that fail when tested according to ASTM E119 or (BS 476) do not fail when they are part of a larger (composite steel frame) structure, when subjected to the same conditions. In fact, experiments done in Britain to test this exact hypothesis, experienced no runaway failure at all. Here is a quote from [2].
The Broadgate Phase 8 fire is probably the most notable. This accidental fire happened during the Construction phase when the steel frame was only partially fire protected. Despite very high temperatures during the fully developed phase of the fire and considerable deflections in the composite slab there was no collapse. This initiated construction of an 8-storey composite steel frame at Building Research Establishment's (BRE's) large scale test facility in Cardington. Six fire tests were conducted, of varying size and configuration, to observe and ultimately explain why composite steel-framed structures adopt very large deflections during a fire but do not collapse.
and a quote from [3].
The Cardington frame fire tests and subsequent numerical modelling has shown that multi-storey steel-frame structures survive compartment fires when all the steel beams are unprotected, despite temperatures in the steel of > 1000ÃfC...."
http://911research.wtc7.net/mirrors/guardian2/wtc/WTC_apndxA.htm [wtc7.net]
http://911research.wtc7.net/mirrors/guardian2/fire/SLamont.htm [wtc7.net]
You have to make your conclusions based on the actual facts at hand.
The facts are... ...no amount of jet fuel can burn down a steel framed skyscraper. It burns at too low a temperature to have any significant effect on the structural integrity of steel beams. Period.
I don't care if Manhattan Island is completely submerged in jet fuel, ignited, and the fire is allowed to burn for years... ... when the fires do go out, the steel frames of the skyscrapers will emerge mostly intact.
If jet fuel could not burn down the WTC buildings, and it couldn't, then there had to be another cause. The evidence from every single sample of WTC ash tested by independent labs shows thermite residue in every one of those samples.
http://www.journalof911studies.com/articles/WTCHighTemp2.pdf [journalof911studies.com]
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Again, this is all from a UK graduate thesis that's being hosted locally at a 9/11 research site...
"...While admitting that fire test's such as ASTM E119 are conservative, they do not emphasize that such tests are very conservative. Here is a quote from [1].
Steel beams in standard fire tests reach a state of deflections and runaway well below temperatures achieved in real fires. In a composite steel frame structure these beams are designed to support the composite deck slab. It is therefore quite understandable that they are fire protected to avoid runaway failures. The fire at Broadgate showed that this (runaway failure) didn't actually happen in a real structure. Subsequently, six full-scale fire tests on a real composite frame structure at Cardington showed that despite large deflections of structural members affected by fire, runaway type failures did not occur in real frame structures when subjected to realistic fires in a variety of compartments.
So beams and columns that fail when tested according to ASTM E119 or (BS 476) do not fail when they are part of a larger (composite steel frame) structure, when subjected to the same conditions. In fact, experiments done in Britain to test this exact hypothesis, experienced no runaway failure at all. Here is a quote from [2].
The Broadgate Phase 8 fire is probably the most notable. This accidental fire happened during the Construction phase when the steel frame was only partially fire protected. Despite very high temperatures during the fully developed phase of the fire and considerable deflections in the composite slab there was no collapse. This initiated construction of an 8-storey composite steel frame at Building Research Establishment's (BRE's) large scale test facility in Cardington. Six fire tests were conducted, of varying size and configuration, to observe and ultimately explain why composite steel-framed structures adopt very large deflections during a fire but do not collapse.
and a quote from [3].
The Cardington frame fire tests and subsequent numerical modelling has shown that multi-storey steel-frame structures survive compartment fires when all the steel beams are unprotected, despite temperatures in the steel of > 1000ÃffC...."
http://911research.wtc7.net/mirrors/guardian2/wtc/WTC_apndxA.htm [wtc7.net]
http://911research.wtc7.net/mirrors/guardian2/fire/SLamont.htm