The World Trade Center towers did not have a conventional steel space frame construction. The exterior walls and floors were the structural elements that held the building up. The gaping holes from the impacts severely weakened theit structural integrity. The fires were not consuming only the contents of building, but were fueled mostly by the jet fuel. Once the floors above the impact zone softened due to the heat of the fire, the buildings could not hold the weight of the floors above.
Thanks for the explanation,
and I stand corrected in lieu
of different construction practices,
with the added presence of diesel
fuel as accelerant.
The question I asked about fire
safety (directed at the engineer)
was asked long before the sad
events of 9/11.