Why don't you answer for him? Dave doesn't seem to want to touch the question of how the lower structure could have been weakened to the point where it couldn't support the load above it.
Start the analysis here
exhibit A
WTC1 tower collapse as viewed from the North-East
Red lines are placed on the North and East roof lines (top)
and at the North and East walls at the 97th floor (bottom)
Note that the roof-line on both the N and E fall exactly parallel
to the 97 th floor N and E floor lines with no horizontal distortion
indicating the East West roof-lines also fell parallel to the 97th
East and South floor-lines equally. Note that the antenna structure
likewise falls in a linear vertical path at the exact same instant.
At the 97th floor level all of the external columns were the uniform
sized* modular spandrel sectors. The interior core columns were a mix
of box columns and "I" shaped vertical columns of different sizes.
exhibit B- Exterior vertical column and Interior vertical core column placements.\
Each of the four faces of the twin towers had 59 exterior
box columns and the core contained 47 structural steel vertical columns .
exhibit C Hat Truss
The hat truss was a structural steel grid of steel beams that sat on top of the WTC Core and
connected to the exterior column structure with eight
outriggers beams . Four outriggers ran E-W and four were oriented N-S.
The antenna that collapses with the roof-line in exhibit A was married to the Hat truss
with an antenna base structure was integrated into the hat truss
exhibit D -antenna base that forms the top of the hat-truss
The location of the antenna base in the braced frame hat truss
structure is shown in exhibit C as the black dot. The yellow dot
in the center is the actual antenna.
In order for the entire roof structure, the Antenna, and the 98th floor all
to fall in unison ...
- as one event as shown in exhibit A,
every single exterior column,
ALL 59 box columns in all four sides,
a total of 236 would have to neutralized at the exact instant.
Additionally every single one of the
47 core columns would also have to be
neutralized
at the
exact same instant in time.