This construction photograph of the North Tower
shows that the core structures consisted of bundles of columns
cross-linked by horizontal and diagonal members.
Construction photographs of the Twin Towers reveal a possible
reason FEMA went to such great lengths to hide the existence
of the structural cores.
Each tower's core contained 47 continuous box columns which
ran from the bedrock foundations seven stories below street level
to near the tops of the Towers,
where they transitioned to I-beams.
These box-columns measured 36 inches by 16 inches and were
fabricated of steel four inches thick near the Towers' bases.
FEMA's report hides and minimizes the core structures whose
their existence made the symmetric total collapses of the
Towers due to gravity impossible.
Even if the collision and fire damage could have induced
they would have caused the Towers to topple like trees,
pivoting about the cores at the impact zones.
Destroying the core columns is key to achieving
total building collapse, yet FEMA's long report has only one short
passage explaining how the cores self-destructed.
As the floors collapsed, this left tall freestanding portions
of the exterior wall and possibly central core columns.
As the unsupported height of these freestanding exterior wall elements
increased, they buckled at the bolted column splice connections,
and also collapsed.
Note the legalistic language of
possibly central core columns
The authors knew the core columns were not free-standing
and would not instantly self-destruct if the floors fell away.
Nor were the perimeter columns,
stitched together by horizontal spandrell plates,
free-standing as the passage implies.
By qualifying this key assertion,
FEMA's team might have been protecting themselves
from possible future prosecution
for obstruction of justice.