Do you think the 9/11 hijackers knew that the WTC buildings would collapse?

[u/JMRooDukes808]

I really don’t know where else to ask this. There is obviously an overload of information about the event itself online, but one thing I can’t find out is if the hijackers intended to, or knew that the WTC buildings would collapse. Do you think they just planned on the impact and fires to be the extent of the damage caused? As far as I know, no steel structure buildings in history had collapsed from fire at that point, so it makes me wonder if they actually “succeeded” in their plan more than they intended.

Edit: no conspiracies please, that was not the point of my post

[u/MoreGaghPlease]

So we actually have a told answer to this both from tapes of Bin Laden found in Afghanistan early in the war and from evidence given by KSM when he was being tortured by the CIA.

Bin Laden did not expect the towers to collapse, and they were secondary targets. The main targets were the White House and the Pentagon, and he believed that both would be destroyed if the planes hit their target (obviously the Pentagon was only damaged, probably they did not appreciate how big it is). But they did not expect the towers to collapse. They had no knowledge or understanding of the engineering of the towers, they believed that it was likely to cause a fire and maybe kill the people above the impact. But they also didn’t care very much or really think about this aspect of it, it was more like something that they just mused about.

[u/millerlit → u/MoreGaghPlease]

On 60 minutes they did a story with the NYFD.  They believed the towers would not fall due to their never was a case of a skyscraper coming down from fire up until that time.

[u/Backwoods_Barbie → u/millerlit]

But there wasn't just a fire, planes also crashed into them. Which is a huge lateral impact load and my understanding is the exterior steel columns were designed to handle some of the loads, so cutting some of them in half compromises the whole building. Maybe a building with all interior supports and a non-bearing curtain wall facade would fare better. 

I think people just have a hard time imagining such significant buildings failing so catastrophically, leading to overconfidence in their integrity. I wonder how they differently they would have handled things if they considered collapse a serious threat. 

[u/Bacong → u/Backwoods_Barbie]

the main reason they collapsed was the fires weakening the perimeter columns, causing the floors to buckle which caused the buildings to collapse on themselves.

jet impact certainly did not help however.

[u/UglyInThMorning → u/Bacong]

On top of the structural damage, the impact also blew off a tremendous amount of the fireproofing. There was a worse fire damaging material that had already been compromised, it was a lot of impact related stuff compounding.

[u/AngriestManinWestTX → u/UglyInThMorning]

I think a lot of people also underestimate just how flammable the average building is even with fireproofing measures. Paper, electronics, carpet, and everything else. Now imagine all of the water mains for sprinklers have been severed.

[u/LightRobb → u/Bacong]

The core columns also relied on the exterior for a lot of bracing for wind and general movement. With those gone it was only a matter of time before the forces took down the core. I recall images where the core was "delayed" in collapse behind the exterior.

[u/notaredditer13 → u/Bacong]

Kinda, but backwards: the floors sagged due to their weakening, which pulled the columns inwards, causing them to buckle.

[u/Bacong → u/notaredditer13]

correct, just like you said.