Maybe this has occurred to some of you guys already but it just struck me. WTC2's upper floors leaned appreciably before its vertical collapse,
while WTC1's upper floors pretty much started off falling vertically. WTC2 also had
only the inner part of its core standing afterwards (some
floors below the collapse initiation point), while WTC1
only had a section of the outer part of its core still standing (also some
floors below the collapse initiation point).
Does it seem likely to anyone else that WTC2's upper floors leaned because WTC2's core columns were severed
at the impact floor first, but
since there still had to be core structure beneath it (what we would later see partially standing by itself), the building was prevented from falling
into itself until the floors below also had their core structure compromised?
If that stands, then the implication for WTC1 is that its core was more completely compromised around the initiating floor, and more rapidly. At the
same time, WTC1's initiation floor was somewhere around the 93rd or 94th floor, so the columns were smaller than they were on WTC2's impacted
floors. In both cases, what remains of the cores stand about 20+ floors (off the top of my head) below where the collapses started.
And like I said, only WTC2's inner core remained while only part of WTC1's outer ring of core columns remained. That would seem to mean either
different demolition methods were used on the cores, or else the cores didn't matter below a certain range of floors at a time, and everything else
was cleaned out afterwards in the dust cloud.
Also along those lines, photos from Ground Zero show that WTC1's inner core wasn't severed in the basements, but was still intact above ground at
the base:
Cutting out the cores
completely before the rest of the collapses underground would shift the entire building load onto the outer columns, not
just to a certain floor, but down the entire outside wall all at once.
Wouldn't that run the risk of columns failing sporadically throughout the entire outer wall, and not floor-by-floor, section-by-section of the
building? For example, failing the core at a higher floor would shift less additional weight onto the perimeter wall, and if the lower columns had
higher redundancies,
then it would only encourage structural failures in certain ranges of the buildings at a time.
At least, that's what I'm beginning to think. What do you guys think?