WTC - Building 7

[Berzerker]

It is indeed quite shocking that a well-engineered building with evenly distributed weight collapses in that manner. I would expect it would fall sideways, with a mushroom cloud above.

I'd expect part of the building to collapse - piecemeal, the part damaged by falling debris and set on fire. But not the whole thing all at once...

Just seemed strange how it fell - the other buildings pancaked but WTC 7 dropped like a boxer out on his feet.

[Hauldren Collider]

I'd expect part of the building to collapse - piecemeal, the part damaged by falling debris and set on fire. But not the whole thing all at once...

Just seemed strange how it fell - the other buildings pancaked but WTC 7 dropped like a boxer out on his feet.

They are designed to fall evenly. What about this is surprising?

[BlackCat]

They are designed to fall evenly. What about this is surprising?

[Asher]

He's not joking, if you think he is.

Contained failure is part of the engineering of modern towers. That building was finished in 1987 or so, it was pretty modern.

[BlackCat]

I can see the logic in letting a building fall straight down in worst case, but I have some trouble seeing how it can be implemented handling say partial damage on one side - in that case the damage has to spread to the rest of the building letting it all collapse. Though, I can't recall it mentioned in the NIST report on WTC7, but I admit I just skimmed it (there was some nutcases claiming it was brought down with thermite).

[Asher]

This isn't some far-fetched design scenario. Building 7 collapsed due to uncontained fires, not impacts.

And buildings ARE designed with this in mind. My brother works specifically on this kind of stuff, as a "fire engineer".

[Berzerker]

that sounds quite unsafe, and it still sounds illogical - the whole building comes down if a 3rd or 1/2 is damaged enough to collapse? To be fair I just saw WTC 7 collapse very recently and from one angle, for all I know the outer perimeter hid a partial collapse of the interior.

[BlackCat]

Don't get me wrong, I DON'T think there are some evil conspiracy - wtc7 fell due to structural damage caused by the fire.

I assume that even my three storey building has the same design patterns to protect neighbours in worst case - I just can't remember it mentioned as a reason of why the buildings collapsed as they did - then again, I haven't digged deep, just enough to fence of the worst conspiracy belivers .

[BlackCat]

that sounds quite unsafe, and it still sounds illogical - the whole building comes down if a 3rd or 1/2 is damaged enough to collapse? To be fair I just saw WTC 7 collapse very recently and from one angle, for all I know the outer perimeter hid a partial collapse of the interior.

This is why it's both safe and logical :

[Berzerker]

it failed at the building

[Asher]

that sounds quite unsafe, and it still sounds illogical - the whole building comes down if a 3rd or 1/2 is damaged enough to collapse? To be fair I just saw WTC 7 collapse very recently and from one angle, for all I know the outer perimeter hid a partial collapse of the interior.

If part of a building like that goes down, it's highly likely the rest of the building will go down as well.

They're designed to survive a long amount of time if possible (almost 8 hours in WTC 7) before they collapse completely on itself -- enough time for people to get out. The twin towers were also designed for this, but the incredible heat from the fire was unusual and expedited its collapse. Still, it was up long enough for many, many people to get out.

Not to mention the obvious...if they fall sideways, you could very well get a domino effect.

[Hauldren Collider]

If the planes hadn't had so much fuel still in them I think it's possible the towers wouldn't have come down at all. But I'm not a building engineer, I don't know.

[Asher]

That's the consensus from a couple experts I've read in various post-mortems as well.

[BlackCat]

It wasn't the fuel that was the problem, it was the fullfledged fire across a storey it caused and that the airplane cut off water supply to extinguishers that softened the beams enough to collapse. Actually, the fuel was used up pretty fast, so the main fuel was office "stuff".

[Asher]

It wasn't the fuel that was the problem, it was the fullfledged fire across a storey it caused and that the airplane cut off water supply to extinguishers that softened the beams enough to collapse. Actually, the fuel was used up pretty fast, so the main fuel was office "stuff".

I've read repeatedly that the quantity and type of fuel was precisely what the main problem was -- the fire was ridiculously intense for a very long period of time, which is what softened the beams.

I also recall reading that the WTC was designed to withstand a plane strike, just not a plane carrying so much fuel...