Saw a video today of a simulated collapse that suggests a possible failure mode given the likely parking garage collapse that occurred before primary collapse:
The other question that obviously follows from this is, were those columns to fail, why did the failure of the columns on one edge of the building cause the entire section of building to collapse catastrophically? At 1:08 of the simulation, you can see the rest of the columns are still standing under the building.
The rebar would have different load bearing capacities in different directions, particularly if it was rusting (i.e. most likely the corrosion was principally on the top face).
A bit counter intuitive.
But that’s building by the sea. Salt can be deposited by mist and chloride ions are the nemesis of reinforced concrete.
Looks almost like punch-through of all floors simultaneously due to shock, almost as if it was a planned demolition where stuctural supports are compromised with precision to assure orderly collapse.
Only this part of the building fell precisely without any carefuly placed dynamite.
But when buildings are stronger, sometimes intentional demolition projects do not complete the job so thoroughly on the first attempt.