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RE: Questions About the Events of September 11th (off topic)

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>What I am interested in is how the building collapsed structually.

Approximately 40 percent of the columns at the impact level were removed in
the perimeter and core in each tower. Simultaneously a gargantuan fire was
begun in each tower over approximately 10 acres of each building. The
remaining structure in each tower was initially capable of resisting the
loads. As the temperature of the fire heated the structure, it lost
strength. The collapses occured at the onset of global instability in each
tower. Then, the exterior tube funneled all debris, containing it and
creating an unstoppable and accelerating mass. Perimeter columns fell away
like a banana peel when their vertical cantilever exceeded the ability to
restrain against self weight (this cantilever was approminately 20 to 30
stories tall). The pancaking/peeling effect replicated all the way down the
building, ending with the 30-story-tall free-standing wall sections that
became famous in shots of the pile.

A similar scenario is true of the Pentagon as well. Damage, simultaneous
large fire, heated structure with structural weakening, onset of global
instability, structural collapse.


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