How were WTC core columns separated at the weld planes?

[BenBurch]

In fact didn't firefighters report a floor collapse WAY down in the building in Tower 1? I can't find that now, but I recall it.

 

[Disbelief]

That is what I like to call the "Magic Air Theory" where air decides to skip some floors and windows only to eject debris several floors down and through certain windows only well ahead of the collapse zone on multiple sides of the building. Quite amazing isn't it?!

Or maybe just pressure build up? The air pressure should be uniform as it goes through the building?

 

[tsig]

That is what I like to call the "Magic Air Theory" where air decides to skip some floors and windows only to eject debris several floors down and through certain windows only well ahead of the collapse zone on multiple sides of the building. Quite amazing isn't it?!

Only to those who do not understand compressed air.

The magic air theory is that you can breathe without cue cards saying "IN" "OUT"

 

[Major_Tom]

tsig writes:

Only to those who do not understand compressed air.

The first powerful horizontal row of "compressed air" ejections is clearly visible.

The second powerful horizontal row of "compressed air", also clearly visible, appears after and under the first, but 3 or 4 floors below.

The layout of the WTC towers is not a mystery. The blueprints of the North Tower are publicly accessible. So all elevator shafts and vertical air duct passageways are easy to locate.

I assume that you would consider yourself one of "those who understand compressed air".


Could you please explain how these initial ejections bypassed 2 or 3 floors?


Dave, I'll address your concerns in a post later today. Thanks for your measured response.

 

[uruk]

That is what I like to call the "Magic Air Theory" where air decides to skip some floors and windows only to eject debris several floors down and through certain windows only well ahead of the collapse zone on multiple sides of the building. Quite amazing isn't it?!

Each floor was not air tight. There were many ways for air to flow through out the entire building. Ventillation systems, network cable drop conduits, elevator shafts. When you compress air within a volume the air pressure increases everywhere within the volume uniformily. The increasing pressure will cause the air to escape out of the area of least resistance.

Not all windows are built the same. Some are sturdier than others. The air will burst out the windows that break first under the pressure.
Try squeezing a balloon til it bursts. The ballon will not shred into billions of pieces as the air escapes through every point of the balloon at once. You'll see that the air will burst out the weakest point on the balloon first.

 

[Major_Tom]

Dave, you are explaining that the lack of visible ejections from the floors between these 2 powerful horizontal rows of visible ejections is due to possible holes (from the aircraft strike and broken windows) on these floors alleviating the pressure buildup? These are very powerful ejections. Your explanations suggests that the 2 floors from where we see the ejections didn't have nearly the quantity of holes as the 2 or 3 floors in between. It also suggests that we should see very forceful ejections from the floors in between through these very holes which are alleviating the pressure. After all, these holes alleviate pressure by letting the built-up air to escape through them, no? So, according to your explanation, we should see high pressure air ejections through these holes on the floors in between.

Perhaps I am misunderstanding you. Is the above description consistent with what you wrote?

 

[Major_Tom]

uruk wrote:

Not all windows are built the same. Some are sturdier than others. The air will burst out the windows that break first under the pressure.

So you are suggesting that those 2 rows of windows, 3 or 4 floors apart, stretching entirely across one side of the building, were just weaker than all the others? I could understand a few windows in a much more random pattern, but you are saying the entire row of windows where we see the second major horizontal row of ejections were just poorly built? Is this what you are saying?

 

[Dave Rogers]

Dave, you are explaining that the lack of visible ejections from the floors between these 2 powerful horizontal rows of visible ejections is due to possible holes (from the aircraft strike and broken windows) on these floors alleviating the pressure buildup? These are very powerful ejections. Your explanations suggests that the 2 floors from where we see the ejections didn't have nearly the quantity of holes as the 2 or 3 floors in between. It also suggests that we should see very forceful ejections from the floors in between through these very holes which are alleviating the pressure. After all, these holes alleviate pressure by letting the built-up air to escape through them, no? So, according to your explanation, we should see high pressure air ejections through these holes on the floors in between.

Perhaps I am misunderstanding you. Is the above description consistent with what you wrote?

Partly, but not entirely. In fact, thinking about it further, there is an equally valid explanation which is consistent with the observation that the ejections are not laterally uniform across the floors on which they occur. If the two floors that produce no ejecta on your video simply happen to be weaker on the far side of the building, for whatever reason (non-uniform distribution of fires as observed and documented in the NIST report, for example, or specific properties of the impact hole) then there may indeed be ejections from those floors as well, but taking place on the far side of the building, and hence not visible in the video you're viewing. If you could simultaneously view a set of videos taken from viewpoints all around the building, with sufficiently accurate timestamping for synchronisation and good enough resolution for accurate referencing of floor numbers, then you might get a more complete picture.

In fact, the more thought I give this, the more possible causes I can find for ejections at some floors but not others. For example, the hanging slabs observed in various photographs will not only allow an increased amount of communication between floors (so air from a floor where the perimeter structure is slightly stronger could escape through holes in the floor slabs to repressurise a floor where the perimeter has blown out), but will also change the relative capacity of different inter-floor spaces, so the floor below a hanging slab will have a smaller initial volume than the floor above and hence will experience less air compression than the floor above resulting in a smaller overpressure.

In summary, then, your video only shows that certain floors eject debris on the side of the building that is visible and others do not; it's quite possible that this is balanced out by ejections from the intermediate floors that can't be seen because they're on the opposite side. Even if that's not the case, there are observed characteristics of the towers just prior to collapse that could lead to very different overpressures in different floors. Given that there are also observed characteristics of the fires that could lead to very different conditions of the perimeter structure on adjacent floors, and that the ejections are due to the relative strength of these two randomly variable parameters, it would be difficult to construct any possible ejecta behaviour that wasn't easily explained by random variations in the condition of the structure (other than, of course, the ejection of no debris whatsoever, which might be a little difficult to understand in any scenario).

Dave

 

[Major_Tom]

uruk wrote:

Not all windows are built the same. Some are sturdier than others. The air will burst out the windows that break first under the pressure.

So you are suggesting that those 2 rows of windows, 3 or 4 floors apart, stretching entirely across one side of the building, were just weaker than all the others? I could understand a few windows in a much more random pattern, but you are saying the entire row of windows where we see the second major horizontal row of ejections were just poorly built? Is this what you are saying?

 

[Dave Rogers]

So you are suggesting that those 2 rows of windows, 3 or 4 floors apart, stretching entirely across one side of the building, were just weaker than all the others? I could understand a few windows in a much more random pattern, but you are saying the entire row of windows where we see the second major horizontal row of ejections were just poorly built? Is this what you are saying?

Don't forget the airliner impacts and the fires, which will have had a varyingly catastrophic effect on the condition of the perimeter structure as a whole and the windows in particular. The towers weren't in as-built condition, otherwise they wouldn't have collapsed. [1]

Dave

[1] To state the bleedin' obvious.

 

[DGM]

Let's not forget that a change in air pressure (even less than 1 PSI) acting on a surface 4x10'x210' equals an enormous amount of force.

 

[Major_Tom]

Thanks for the comments. I'd like to introduce a second video clip from the same angle, taken at the same time. This second clip is actually a very well edited extreme close-up of the same area, linked below

http://es.youtube.com/watch?v=xtpWu-XZ7kM


And, for easy reference, the first video clip introduced previously is at

http://es.youtube.com/watch?v=fWi1fmxCGAw


In this second video we can actually see point ejections (many of them) instead of simply the horizontal rows mentioned before.

It is interesting to note that it will become increasingly difficult to explain these point ejections by simple pressure build-up because the floors from which they originate already are heavily damaged and are therefore not enclosed systems. Pressure build-up would show itself by air escaping from any hole possible, somewhat evenly distributed across existing holes in any localized area.

Pressure ejections wouldn't "choose" to leave through some point sources while "ignoring" existing escape routes right next to it on the same floor.

Fascinating video.

 

[uruk]

uruk wrote:



So you are suggesting that those 2 rows of windows, 3 or 4 floors apart, stretching entirely across one side of the building, were just weaker than all the others? I could understand a few windows in a much more random pattern, but you are saying the entire row of windows where we see the second major horizontal row of ejections were just poorly built? Is this what you are saying?

I'm saying that a window or windows on the floors that you mentioned broke first. The window could have had a crack in it or it could have been improperly installed or maintained.
Once the window busted and the air started flowing out, it would have releaved pressure and stress on the other windows untill the falling debris pushed past that particular floor.

 

[Gravy]

I'm saying that a window or windows on the floors that you mentioned broke first. The window could have had a crack in it or it could have been improperly installed or maintained.
Once the window busted and the air started flowing out, it would have releaved pressure and stress on the other windows untill the falling debris pushed past that particular floor.

There were, in fact, broken windows below the impact zones. For example, in one case a woman called the PAPD desk from the 83rd floor of the north tower and reported a shattered window. And let's not forget the ventilation louvers on the MER floors.

 

[uruk]

Thanks for the comments. I'd like to introduce a second video clip from the same angle, taken at the same time. This second clip is actually a very well edited extreme close-up of the same area, linked below

http://es.youtube.com/watch?v=xtpWu-XZ7kM

In that video you can see debri busting out relativly uniformly across the floors just below line of collapse. that's pretty much what you'd expect to see.

And, for easy reference, the first vidio clip introduced previously is at

http://es.youtube.com/watch?v=fWi1fmxCGAw


In this second video we can actually see point ejections (many of them) instead of simply the horizontal rows mentioned before.

Are you refering to the flashes? or the small plumes of dust and debri starting in the center rows and working thier way outward?
The flashes are sunlight reflecting into the cameras direction from falling glass. The plumes starting inthe center of the row is what you would expect if the floor had sagged and became detached from the wall spandrels. There would be more deflection or stress in that area of the wall as it lost lateral support from the floor connections. This deflection would put extra stress on the glass and weaken them first.

Not saying that's exactly what happend. Since I can't tell if the floor sagged or became detached in that area. Just that it is a possibility

It is interesting to note that it will become increasingly difficult to explain these point ejections by simple pressure build-up because the floors from which they originate already are heavily damaged and are therefore not enclosed systems. Pressure build-up would show itself by air escaping from any hole possible, somewhat evenly distributed across existing holes in any localized area.
Pressure ejections wouldn't "choose" to leave through some point sources while "ignoring" existing escape routes right next to it on the same floor.

Fascinating video.

Remember the path of least resistance. The bigger the hole the greater the air flow.

 

[uruk]

There were, in fact, broken windows below the impact zones. For example, in one case a woman called the PAPD desk from the 83rd floor of the north tower and reported a shattered window. And let's not forget the ventilation louvers on the MER floors.

Thanks Gravy

There would be your other points of weakness or paths of least resistance to airpressure.

It would be nice to also get rwguinn to input his expertise here also. Fluid mechanics is his thing

I'm really just a dilettant.

 

[DGM]

Major Tom:
Why don't you cut to the chase and present your hypothesis as to what you think is happening? We have seen all of these videos before. Just get on with it.

 

[rwguinn]

Thanks Gravy

There would be your other points of weakness or paths of least resistance to airpressure.

It would be nice to also get rwguinn to input his expertise here also. Fluid mechanics is his thing

I'm really just a dilettant.

er--no.
I'm a structures analyst. I think we're looking for one of the other guys...
I don't like fluids (except beer and Single malt...)

 

[uruk]

er--no.
I'm a structures analyst. I think we're looking for one of the other guys...
I don't like fluids (except beer and Single malt...)

My bad.

Sorry. didn't mean to confuse you with someone else.

I remember posting in a thread about some wagg calling the huge dust cloud a "pyroclastic flow" because the "billowing" effect could only be cause by a temperature differential in the air masses. And this person, who did his doctoral or did some research using fluid mechanics, was trying drill through his CT addled head that the "billowing effect" was cause by the dust being carried by moving air colliding with relatively stationary air.

I wish I could remember his name. I'm sure he could answer a quite few questions

 

[Mr. Skinny]

Thanks Gravy

There would be your other points of weakness or paths of least resistance to airpressure.

It would be nice to also get rwguinn to input his expertise here also. Fluid mechanics is his thing

I'm really just a dilettant.

Well, RMackey is pretty knowledgable on fluid flow, as is Vorticity (I think his custom name is "Fluid Mechanic").

Might be one of those two.