9/11

Site Issues 2006 Archive Room
#41

Yep, there are loads of possibilities.

Go on, ye doubters. The obvious explanation - that I watched on TV, having switched on just in time to see the second impact - is obviously insufficient. Engineering teaches me that in general the obvious explanation is the right one, so why is it that having seen a jet liner carsh into a building I should think of mossad bombs not an Al Qaeda plot taking advantage of deficiencies in the US domestic airline security set up?

I’m not sure what to believe but the way the towers fell is just wrong, why would they go strait down, in particular the building that got hit in the corner, would it not have fallen towards the corner? That’s what my knowledge of engineering tells me.

#42

The strength of the Towers was in the middle though with everything else hanging off that inner core!

#43

But surely just that smaller weakness in the corner would have caused it to fall that way?

#44

I taped a documentary programe on the 9-11 and the desighn and building of the Twin Towers and the towers were designed excelant. Like Firefly said the strenth of the towers were in the centre of the buildings and were it not for this they would have went downearlier and it saved a lot of lives.

They were great buildings and it is a shame that they were destroyed and so many lives lost. The whole thing were so that the American public would feel scared in their own country and that it would make the country unstable, but actualy it brought the Americans together.

I think the US should actualy build the Towers over again to show them that it would not get them down.

Henk

#45

You sure about that? I was under the impression that they were effectively a steel tube, with the concrete floors suspended from the the side walls and the lift tube being non-structural. A structural core would probably have to take up too much room at the base of the building.

As for the collapse method, the buildings were basically a stack of weights with light spacers. Given the way the spacers weakened (damage to two opposite sides followed by fire - and steel gets radically weaker in fire) it is no surprise that they collapsed at roughly the same time, and the inertia of the upper floors was enough to cause them to collapse straight down. I did have a lecture a few years ago from a rather well known materials type called Mike Ashby (co-author of Ashby & Jones, which several of the UK engineers on here may well recognise) on ways of stopping the collapse. He was of the opinion that it was probably possible to stop the collapse once it had started but would involve dedicating a lot of building volume to metal foams. Preventing it from happening in the first place is probably prohibitively expensive.

#46

http://www.pbs.org/wgbh/nova/wtc/collapse.html

http://www.pbs.org/wgbh/nova/wtc/collapse2.html

“Why the Towers Fell: An Engineer’s Perspective.”

#47

Nice links nickdfresh… Thanks

#48

Doesn’t actually give any details of what the structure actually was, just reiterates some fairly obvious stuff about how steel weakens when heated and a few other odds and ends.
Oh, and I’m 90% certain he’s talking bull***t about the loss of HMS Sheffield too…

#49

Doesn’t actually give any details of what the structure actually was, just reiterates some fairly obvious stuff about how steel weakens when heated and a few other odds and ends.
Oh, and I’m 90% certain he’s talking bull***t about the loss of HMS Sheffield too…[/quote]

I believe they mention structural steel… And I disagree, since the Iraqis did much the same to the USS Stark with an Exocet…

I’ve also hear US Vietnam vets talk about how the aluminum hull of an M-113 APC would melt if an RPG set off secondary explosions and lit up the engine… In fact, I recall seeing a picture in a book on Vietnam where circular holes were melted in the top of M-113s after the aluminum burned…