FEMA originally hypothesized that the collapse initiation was dependent upon floor failures within the impact region resulting in a significant loss of lateral support for the columns on the impact floors. NIST discarded it as an initiation mechanism, this in no way relates to the collapse progression which very clearly involved the floors pancaking all the way to ground level. I honestly don't know how Bill, how can you expect to have any discussion when you have not read a single piece of the report you're criticizing? If you weren't basing your claim on ignorance then you would more than qualify as a liar.
Parroting Bjorkman without the slightest idea of what you're discussing. Typical... Not a single engineering publication I've read from the ASCE to the steel designer's manual places any significance in this idiocy. Nobody cares what yours or Heiwa's uninformed opinions are because collapse studies aren't based on how big a section has to be in order to result in the collapse of another section. They are based entirely on load paths, load capacity, and other matters relating directly to how the building is realistically able to perform.
The steel designer's manual refers to the circumstances observed in the WTC as accidental loading. Conditions in which the loads exerted on a structure are not expected the be a concern during the building's expected life time. Most designs try to take some incidents into account to ensure that the minimum damage is done, but the towers were never -- EVER designed for the prospect that an entire floor would lose it's integrity leaving all of the structure above that point subject to falling.
