The only unusual thing about World Trade Center Building 7 is that diesel fuel was stored in the building to fuel Rudy Giuliani's emergency command bunker.

However, NIST admitted yesterday that the destruction of Building 7 had nothing to do with diesel fuel.

As of yesterday, NIST's "working collapse hypothesis" is, instead, that:

• An initial local failure occurred at the lower floors (below floor 13) of the building due to fire and/or debris-induced structural damage of a critical column (the initiating event) which supported a large-span floor bay with an area of about 2,000 square feet;

• Vertical progression of the initial local failure occurred up to the east penthouse, and as the large floor bays became unable to redistribute the loads, it brought down the interior structure below the east penthouse; and

• Triggered by damage due to the vertical failure, horizontal progression of the failure across the lower floors (in the region of floors 5 and 7 that were much thicker and more heavily reinforced than the rest of the floors) resulted in a disproportionate collapse of the entire structure.

NIST explains that "The working hypothesis for the initiating event sequence that characterizes the initial local failure is based on fire-induced failures initiating in the tenant floors:

• Floor beams, slabs, and connections heat more quickly and to higher temperatures than the columns.

• Elevated temperatures in the floor elements lead to thermal expansion, sagging, and weakening that result in failure of floor connections and/or buckling of floor beams.

• Sufficient floor component failures (connections and/or beams) result in at least one long unsupported column at the lower floors, which leads to the initiation of global collapse.

Uh . . . then how come office fires in other modern steel skyscrapers -- which have sometimes burned much longer and hotter than WTC 7 -- didn't experience the same conditions of "differential heating" and "local failures"? Or, if they did, why didn't they totally collapse also? See this, this, this and this (and video here).

And remember that experts and member of the assessment team organized by the American Society of Civil Engineers and FEMA stated about World Trade Center building 7:

"A combination of an uncontrolled fire and the structural damage might have been able to bring the building down, some engineers said. But that would not explain steel members in the debris pile that appear to have been partly evaporated in extraordinarily high temperatures"

Structural steel beams have never been partly evaporated in any other modern high-rise fire. How can NIST's working hypothesis explain that?

NIST needs to change its working hypothesis to controlled demolition.

Note: Even if diesel fuel had caused the destruction of Building 7, it would not have led to temperatures high enough to partly evaporate structural steel beams.

http://georgewashington.blogspot.com/2007/12/nist-pretends-modern-steel-...