Total Progressive Collapse
Progressive collapse
describes a collapse in which an initiating event leads
to a disproportionate collapse.
This phenomenon is rare, especially in steel-framed buildings.
The phenomenon of total progressive collapse is even more rare.
In fact, there appears to be no example of total progressive collapse
of a steel-framed building outside of the alleged examples
of the Twin Towers and Building 7.
The example of progressive collapse most often cited is the
collapse of a series of cantilever floor sections on the corner of
a 23-story apartment building in Newham in East London,
on May 16, 1968.
This event was far from a total collapse.
In fact, it did not cause failures of any of the support columns
of this building, and is thus not remotely applicable
as an example of total progressive collapse.
Global Collapse
Despite the absence of a single example of total progressive
collapse of a steel-framed building before or after 9/11/01,
the alleged phenomenon is the lynchpin of the official explanation
for the collapse of the Twin Towers and Building 7.
As if to obscure this fact,
NIST's report
on the Twin Towers employs a new term for the phenomenon:
global collapse,
which it uses multiple times without clarifying its relationship
to total progressive collapse,
although it also uses the term "progressive collapse" 16 times.
The procedures and practices used in the fire resistance design
of structures should be enhanced by requiring an objective that
uncontrolled fires result in burnout without local or global collapse.
Removal of thermal expansion from the spandrels and equivalent slabs
in the tenant area to avoid local buckling that affected convergence
but had little influence on global collapse initiation
This further increased the gravity loads on the core columns.
Once the upper building section began to move downwards,
the weakened structure in the impact and fire zone was not able to absorb
the tremendous energy of the falling building section
and global collapse ensued.
As with WTC 1, once the upper building section began to move downwards,
the weakened structure in the impact and fire zone was not able to absorb
the tremendous energy of the falling building section
and global collapse ensued.
The downward movement of this structural block was more than
the damaged structure could resist, and global collapse began.
The downward movement of this structural block was more than
the damaged structure could resist, and the global collapse began.
Recommendation 8. NIST recommends that the fire resistance of structures
should be enhanced by requiring a performance objective that uncontrolled
building fires result in burnout without local or global collapse.
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page last modified: 2005-10-25
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