A CD thought experiment

Originally posted by 2PacSade

Originally posted by ANOK

Originally posted by HomeBrew
The thing people seem to forget here is the WTC twin towers were of a unique design, heavily relying on the outer 'skeletal' structure for support, not the steel framework.

You is wrong. The central core carried the majority of the vertical load, the outer steel mesh carried the lateral loads. You only have to look at the design and common sense should tell you this. You should go look it up...

Exactly-

That's why many perimeter columns could be breached, all at once, and the buildings didn't fall from it.

If what you say is true then why didn't they collapse upon impact?

Just a thought. . .

2PacSade-

Not exactly, this skeletal structure held the colums in a position to carry the load and provided stabitily, not just purely laterally but to a large degree. It was damaged largly on impact but much more so after subsiquent burning and floors collapsing. This stressed the colums that damaged the skeletal structure and this all branched downward via gravity. In result created a downward collapse.

[edit on 25-4-2007 by HomeBrew]

Let me simplify the question, since contributors have naturally tended to get drawn into the 9/11 scenario. Forget that for a minute; I want to either establish a point of principle or else reject one.

If the upper section of WTC1, say 25 floors, were to be dropped from a height of one storey, without resistance, onto the lower 75 floors, would it result in a global, straight-down, near-freefall speed collapse?

If not one storey, what about from a height of two stories?

If not, what height would such a mass need to be dropped from in order to initiate such a collapse?

Or, would such a collapse be impossible under such circumstances?

Originally posted by HomeBrew
Not exactly, this skeletal structure held the columns in a position to carry the load and provided stabitily, not just purely laterally but to a large degree. It was damaged largly on impact but much more so after subsiquent burning and floors collapsing. This stressed the colums that damaged the skeletal structure and this all branched downward via gravity. In result created a downward collapse.

What? You're not making sense. The fire did not do anything to the outer mesh, you can clearly see that in the video's. And the whole building collapsed at the same time, the floors didn't go first at all.

The idea of floors collapsing (pancaking) is not even excepted by NIST anymore.

The outer mesh was designed so if it was damaged it would spread the load to undamaged sections. That's how a mesh works, that's why they use that design. That's why the planes impact had no effect on the building.

Also I didn't say the outer mesh didn't hold some of the vertical load. Of course it would, but that's not what it was specifically designed to do.

So gravity has the power to overcome resistance? You need to re-think about that...

People say the design was unique, really it wasn't. It was unique for a tall skyscraper, but the mesh design is well known and used a lot in other applications. The build might be unique, but the concept is as old as the hills, and engineers know it works.

Originally posted by coughymachine
If the upper section of WTC1, say 25 floors, were to be dropped from a height of one storey, without resistance, onto the lower 75 floors, would it result in a global, straight-down, near-freefall speed collapse?

If not, what height would such a mass need to be dropped from in order to initiate such a collapse?

No, how many times does this have to be explained? Thousands of tons of bolted and welded steel is not going to just fall apart at near free-fall speed from a quarter of it's weight falling on it, when the building was designed to hold at least 2.5 times it weight.

But it's a mute point anyway cause the building was not just falling on itself, it was being ejected laterally (up to 600 ft.), and the concrete was turning into dust. So there was no mass falling on lower floors to begin with.
You can clearly see that in videos. Trust your eyes not what someone is telling you.

Even if you dropped a gazillion tons on it you would still have massive resistance from the tons of welded and bolted steel, which would slow the collapse. But what we see is a collapse that accelerates, which is impossible unless all the columns and thousands of welds and fasteners failed in perfectly timed way.

You can test this yourself, if you have access to a machine shop. Just weld some steel rods together, similar to the towers central core, and then see if you can get it to collapse onto itself by dropping weights on it.
It ain't gonna happen, no way, no how. Go ahead and prove me wrong.



No building EVER in the history of building has ever , or will ever, collapse straight down on itself from anything but a controlled mechanism.

[edit on 25/4/2007 by ANOK]

Originally posted by ANOKNo, how many times does this have to be explained? Thousands of tons of bolted and welded steel is not going to just fall apart at near free-fall speed from a quarter of it's weight falling on it, when the building was designed to hold at least 2.5 times it weight.

Easy tiger - you and I are on the same page.

I am trying to use this 'thought experiment' as a way of demonstrating that those buildings could not possibly have undergone a straight down, near-freefall speed global collapse as a result solely of local impact and fire damage.

Originally posted by coughymachine
...Easy tiger - you and I are on the same page...

OK I hear ya, sry it's hard to tell peoples motivation sometimes...

The de-bunkers whole argument is based on a lack of knowledge of basic physics. Once the physics is explained their arguments tend to fall flat.
I hope your post does what you intended...

Originally posted by ANOK
No building EVER in the history of building has ever , or will ever, collapse straight down on itself from anything but a controlled mechanism.
[edit on 25/4/2007 by ANOK]

Quoted for truth. This is PURE, SIMPLE and to the point.

Any structural engineers around... ?

I'm not offering any definitive answers here but just two quick points just to focus the thought process.

Originally posted by coughymachine
Would it be possible?

I think you're asking the wrong question in a fairly subtle way. The implication of your wording is to ask if you would design a process in this way to bring the building down, to which the answer is, I think, a pretty unequivocal "No". A more interesting, (and relevant), question is could you initiate such a collapse in this way, (taking into account, of course, all the fires and collateral damage that would ensue). Now, the answer to that is much more tricky and if any of us knew that answer for certain then there would be no debate either here or in any more august circles about what happened. But we don't, and there is.

Secondly, Pootie, (I think), asked "does cutting a chunk out of a tree 25% of the way down cause the rest of the tree to collapse or does the top part fall off?".

Well, once again I think we all know the answer to that one, however, the WTC towers were large, burning steel and concrete buildings, not trees, and their construction was not even remotely comparable. It's a tempting analogy but only on a strictly superficial level.

Originally posted by timeless test
Secondly, Pootie, (I think), asked "does cutting a chunk out of a tree 25% of the way down cause the rest of the tree to collapse or does the top part fall off?".

Well, once again I think we all know the answer to that one, however, the WTC towers were large, burning steel and concrete buildings, not trees, and their construction was not even remotely comparable. It's a tempting analogy but only on a strictly superficial level.

Hollow out the tree and light it on fire...

WILL IT COLLAPSE STRAIGHT DOWN ONTO ITSELF in a symmetrical fashion crushing the entire trunk?

Originally posted by timeless testI think you're asking the wrong question in a fairly subtle way. The implication of your wording is to ask if you would design a process in this way to bring the building down, to which the answer is, I think, a pretty unequivocal "No". A more interesting, (and relevant), question is could you initiate such a collapse in this way, (taking into account, of course, all the fires and collateral damage that would ensue). Now, the answer to that is much more tricky and if any of us knew that answer for certain then there would be no debate either here or in any more august circles about what happened. But we don't, and there is.

I accept this, with the exception of the highlighted piece; there would be no ensuing fires if you knocked out the core columns between floors 75 and 80 in the CD scenario I'm suggesting.

What's interesting about the rest of your reply is that the answer is, as you say, we don't know. But surely, if the 'official' collapse theory is solid, then the answer should have been "yes, it would initiate a collapse similar to the one observed, because that mechanism has already been proven."

Originally posted by Pootie
Hollow out the tree and light it on fire...

OK, so now it's a hollowed out burning tree and that's still not the same as a steel and concrete building or remotely similar.

It's faintly amusing how NIST and the like get regularly castigated for what are perceived as unrepresentative tests and modelling techniques but it is OK to quote this kind of superficial analogy as being somehow meaningful.

[edit on 26-4-2007 by timeless test]

Originally posted by timeless test
It's faintly amusing how NIST and the like get regularly castigated for what are perceived as unrepresentative tests and modelling techniques but it is OK to quote this kind of superficial analogy as being somehow meaningful.

Trying to make a VERY SIMPLE law of physics easy to understand for those who know jack about it.

Objects do not fall through the path of greatest resistance, almost perfectly symmetrically, with acceleration or constant speed naturally. Nothing, never.

Never.

Originally posted by coughymachine
if the 'official' collapse theory is solid, then the answer should have been "yes, it would initiate a collapse similar to the one observed, because that mechanism has already been proven."

Not necessarily, the answer should be "it COULD initiate the collapse". That is to say that the scenario is conceivable if not necessarily repeatable or even probable.

Plenty of unlikely things happen every day. The fact that they are improbable does not make them impossible.

edit to clarify my (poorly expressed) last line.

[edit on 26-4-2007 by timeless test]

Originally posted by Pootie
Trying to make a VERY SIMPLE law of physics easy to understand for those who know jack about it.

Thank you, I'll try to look on it as some kind of public service.

No problem. I do what I can.

The outer mesh was designed so if it was damaged it would spread the load to undamaged sections. That's how a mesh works, that's why they use that design. That's why the planes impact had no effect on the building.

I saw the video where they compared a pencil piercing a window screen to the planes hitting the towers in relation to the strength of the mesh. The scale they used was rubbish. A better scale would be to use a mesh window screen, and throw a lite boomerang through it, and then test its strength. The plane blew a hole all the way through the building at several hundred miles per hour..To assume "the planes impact had no effect on the building" is factually wrong. Honestly, this is the worst opinion I have ever heard on this thread.... Did you not see the hole blown in the building? No effect? Damn......

Originally posted by timeless testNot necessarily, the answer should be "it COULD initiate the collapse". That is to say that the scenario is conceivable if not necessarily repeatable or even probable.

Plenty of unlikely things happen every day. The fact that they are improbable does not make them impossible.

Again, I accept this, however, since it's now a 'COULD', with all its implied sense of improbability, what happens when we're faced with it happening twice in quick succession, from impacts that were demonstrably different?

Originally posted by DeeMackTo assume "the planes impact had no effect on the building" is factually wrong. Honestly, this is the worst opinion I have ever heard on this thread.... Did you not see the hole blown in the building? No effect? Damn......

Please try not to get side-tracked into a discussion about the events of the day themselves; we already have plenty of that.

Instead I'd like your view on this: if you believe that the removal/weakening of the core columns by a plane and resulting fires at floors 75-80 led to a global collapse, do you believe you could achieve the same global collapse (i.e. straight down and near-freefall) by blowing the same columns in a CD?

Originally posted by DeeMack
The plane blew a hole all the way through the building at several hundred miles per hour..To assume "the planes impact had no effect on the building" is factually wrong.

Right. Factually, the impacts took out less than 15% of the structure on the impacted floors, whereas they'd have to take out over 50% to start a collapse if you assume a piss-poor safety factor of 2. If that factor was 3, then you'd have to take out 66%. If it was 4, 75%.

NIST won't release the safety factor information but here's a clue: one of the engineers that designed the towers said that at least some of the perimeter columns had a FoS of 20. This is the engineer's word from the late 1960's, not mine. I'm not saying all of the columns had this much redundancy, but even a global equivalent to a factor of 3 or 4 leaves an impossible amount of work to the fires.

In other words, those buildings were built robust as hell, and totally over-engineered for safety. Older skyscrapers typically were, because they're recent technology, and failure to due unforeseen reasons would be utterly catastrophic. The Empire State Building is probably even more robust, as it was built much earlier, when there was even less knowledge of skyscraper behaviors.

Good engineers always assume worst-case scenarios when designing something, and design intentionally to head-off even problems that they can't foresee. The engineers that designed the towers at least had enough foresight to predict airliner impact and make sure the buildings could withstand it. I don't think they designed specifically FOR an aircraft impact, but only because the buildings were more than robust enough to take them anyway. And they did take them -- and only lost >15% of the columns on the impacted floors. Like I said, even with a piss-poor safety factor, that's not major damage.

[edit on 26-4-2007 by bsbray11]