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RE: Nova program on World Trade Tower Collapse

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>I've only read the executive summary of the draft report but it seems 
>to me that the NOVA program and NIST agreed that the proximate cause of

>the collapse was the lateral loading produced by the floor truss sag:

NOVA asserted through the testimony featured that the bolted truss end
connections failed leaving the exterior tube unsupported, initiating
collapse. This was as false as the notion that the floor framing was

NIST concluded differently that the structural damage and ensuing fire
created a situation where the core framing above the damage levels was
hanging from the hat trusses and the floor framing, which was robust in
catenary action at each level. One of NIST's video segments tracks the
dishing of the exterior wall from initiation all the way to collapse. As
it became more and more pronounced, the global mechanism of collapse was
achieved, followed by the progression of a downward force that could not
be arrested -- it is essentially impossible to stop a 15-story building
(25-story building in the other tower) that starts falling.


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