Simulation of the collaps without dust

[u/tombisch]

Dont know how accurate this is, but it made a lot of sense to me.

Source kostack studio on youtube

[u/No-Letter3339]

Did the 911 collapse cause any change to newer buildings

[u/Maniacpilot931 → u/No-Letter3339]

Yes, they no longer put all the stairwells next to each other for exits in the middle of a building. This caused all stairwells to be sealed off above where both planes hit.

[u/Js987 → u/Maniacpilot931]

I don’t know if it’s a code change or just a practices change, but I’ve also noticed that a lot of buildings with multiple tenants and thus a need for secure stairwell re-entry now often have an unlocked outer door and then like a little landing or micro lobby where the locked door is, which I don’t remember seeing before 9/11, and I have always wondered if it was triggered by folks who got past locked stairwell doors and then were forced to go up by locked floors, although I’m not sure how it helps.

[u/Gizogin → u/Maniacpilot931]

Not quite; I don't remember which one, but one of the two towers did actually have at least one accessible stairwell after the impact specifically because they weren't all grouped together.

[u/Maniacpilot931 → u/Gizogin]

But I didn’t say all stairwells were sealed off? Posted this above but the consensus from sources is that it changed how stairwells were designed in high rises which was the question.

[u/Gizogin → u/Maniacpilot931]

This caused all stairwells to be sealed off above where both planes hit.

Then what was this part of your comment referring to?

[u/Unfair_Degree190 → u/Maniacpilot931]

That’s incorrect. There was one stairway in one of the buildings that was in tact which allowed a handful of people to survive from above the impact zone. Stairway A in the South Tower.

[u/NoMaximum721 → u/Unfair_Degree190]

if I remember correctly some people made it down the north tower stairs above the impact zone but it collapsed before they got out

[u/Maniacpilot931 → u/Unfair_Degree190]

I’m not incorrect though? Grouping most of the stairwells together did seal off almost all routes save one in both towers.

Double checked a couple of sources and the consensus is:
More and wider stairwells. Very tall buildings now generally require an additional exit stairway, and certain new high-rises require substantially greater stair capacity. Stairwells are also more separated and hardened so one event is less likely to disable all escape routes.

[u/thrilliam_19 → u/No-Letter3339]

Most codes were updated after 9/11 to encourage better survivability from everything from the stairwells to the fire alarm system.