Collapse of the World Trade Center - Some Engineering Aspects

The University of Sydney - Department of Civil Engineering ^ | The University of Sydney - Department of Civil Engineering

[imberedux]

I have NYPD friends -- they tell me that none of the FDNY folks would have left in your scenario. They are the bravest men in the world.

[_Jim]

Like I said - "Volunteers only". Many would stay in a situation like that ...

[imberedux]

In fact, all would. All did. They are truly the first heroes of this war.

[_Jim]

Have you found the fuel capacity of a 767 using google yet?

[AGAviator]

Fires in high-rises often create a "blowtorch" effect, where they make a vacuum which sucks additional air in. If this happened because the fires started in confined spaces, this could have super-heated the combustion.

[yarddog]

I just did a Google search and you are right. I am also shocked. That is as much as four gasoline tanker trucks carry. Actually three if they are large ones.

[patricia]

THANK YOU for posting this data. So pleasant to get expert reflection rather than armchair conjecture.

My conclusion, reached because there doesn't SEEM to be enough debris for all the materials used in the structures, was that large upper portions of the buildings vaporized due to the heat.

Another factor, IF TRUE, is that the terrorist on the flight that downed in Pa. stated they had a bomb. I wondered if all the flights might also have had bombs aboard ... but then, bombs, or their components could not have cleared security.

[_Jim]

I originally looked up the specs on the 757/767 to verify figures that the snooze media were thowing around - that's some kinda 'fuel load isn't it!?

I think the actual max capacity is around 23,980 gallons for a 767 and 11,000 something for a 757 ...

[Slyfox]

Why did the World Trade Center collapse like a telescope? At the very top of both the towers were huge concrete anti-sway stabilizers which were computer-controlled and kept the towers from swaying and causing people to feel nauseous. Those concrete blocks had to be much heavier than just a few floors of concrete in order to do the job. The towers imploded from the top, a first time ever event, because it could not handle the weight of a 757 plus 24,000 gallons of burning jet fuel and a disconected anti-sway stablizer. Those concrete blocks on top acted as huge pile drivers.

SWIRSKY: I imagine, when I saw the pictures of the implosion of the building, it looks like the fuel must have leaked to the core of the building, and from there it was the massive explosion that caused the building to collapse. So it was something completely unforseen, as far as the design was (concerned).

So, even one of the designers of the WTC has no idea why it impolded the way it did. A melting core would not have caused an implosion. Something very heavy at the top would've caused a telescoping implosion. A 'melting core' would've caused the structure to fall over rather than implode.

It was as if the top of the building was acting like a huge pile driver crashing down on the floors underneath." said structural engineer Chris Wise.

The question is, will anyone take note of this fact? How will they rebuild the towers?

[imberedux]

My pleasure. Facts are not always a comfort, but they are always facts.

[yarddog]

Like I said, I am shocked.

I recall the Airlines complaining about the price of fuel and how it would affect ticket prices.

I now realize that fuel costs must be astronomical for them.

[_Jim]

Why did the World Trade Center collapse like a telescope?

Have you read much of what's been posted in this thread yet?

[Slyfox]

Yes, I took the time to read the whole thing. Why?

[po'boy]

I wonder how many people have been around when concrete explodes from too much heat.

In addition to all else if those floors were poured concrete then that to was an element of the collapse.

[laconas]

Great points.

I'm sure someone will note these and many other factors.

How will they rebuild these towers?

Getting away from engineering, the concept in the cultural sense, of the great tower as a symbol of 20th century business might be coming to an end. Or, at least until technology will allow towers as these to be built in a manner that allows safe evacuation, even in extreme cases as these.

Albeit a rare case, but one that has just set precedent that will be followed by future terrorists. Big jet liners can fly accross oceans. All the internal security cannot assure anything. (with less fuel to be sure)

Maybe these towers are done for, in the same way castles were done for when gunpowder and cannons came about.

[Denver Ditdat]

_Jim, I have bashed you in the past, but I'm very grateful for this thread. Good job, and thank you.

[po'boy]

The planes would have had enough fuel to get them to their desination plus a little more for a safety factor.

[Kevin Curry]

Something I would be interested in knowing is how the explosive force of a fully-fueled jet of this size slamming into a building at about 400 knots and igniting compares to the explosive/destructive force of some of our military's conventional armaments. That would be a function of kinetic and chemical (explosive) forces combined. Something tells me that even our big laser-guinded bombs might not have this much punch.

[_Jim]

... also be sure to thank imberedux - whom some call my my not-so-alter-ego ...

[_Jim]

... the explosive force of a fully-fueled jet of this size slamming into a building at about 400 knots and igniting compare[d] to the explosive/destructive force of some of our military's conventional armaments.

That would be a function of kinetic and chemical (explosive) forces combined.

We'll have to contact ex-Gen. Partin for that kind of work, because, as you know he's an expert on that sort of thing (wink wink) ...