The 9/11 Forum

Has this already been discussed?

http://www.youtube.com/watch?v=RqwbBn4bbFs at 2:35 s in.

He doesn't say specifically this is horizontal velocity, but even if it isn't, doesn't it suggest a horizontal force was necessary to get it going?

If it's not going down perfectly vertically (which it isn't of course) then it absolutely has been subjected to forces with horizontl components.

Yes, we've looked at most pieces of ejecta. We've probably tracked the piece back to origin.

That it's moving with a rapid horizontal velocity doesn't ring alarm bells. There were plenty non-nefarious sources of horizontal force kicking about.

Suggest you ask MT if he's tracked to piece to source.

I suspect that the facade's motion was attributable to a combination of forces and mechanisms. One was that as the floors collapsed the facade was left laterally unsupported and its unsupported height grew at the rate of 100' per second or there abouts. It rapidly became too tall for the plan dimension and became increasingly unstable and subject to Euler buckling. When a multi segmented column experiences Euler buckling it will impart horizontal forces.. just as a single piece columns bows at the center when it buckles. The multi part column likely causes some of the parts to be sprung out of column with considerable force... example apply downward force on a thin column (stick of wood) and when it DOES buckle it flies laterally with quite a large velocity.

The second cause of the facade motion is related to the lateral pressure that the aggregating mass of the falling floor materials represents. The facade was attempting to hold the growing floor mass inside... like the walls of a cardboard carton does when sand or gravel is poured into it. The facades bulge and bulging begins to pull the spandrel joints apart... shearing the bolts. It's trying to stretch like a balloon, but it isn't elastic so the weakest link goes first of course... the facade separates neatly at the spandrel joints. Euler forces on the vertical joints - column to column... and lateral on the spandrel joints caused by the outward pressure of the massive debris it is trying to contain or cage. When the forces overwhelm the bolts they likely impart some decent lateral forces to some sections of the facade.

And buckling is not very noisy either I would think.

Just a guess.

I see it flinging from the top of a large peeling perimeter.

Without acknowledging the mechanism of perimeter peeling that is visible from the N, E and W sides during the same moments in the same video, focusing on only one piece seems a bit strange.

Do you think I am missing something?

dadeets wrote:Has this already been discussed?

http://www.youtube.com/watch?v=RqwbBn4bbFs at 2:35 s in.

He doesn't say specifically this is horizontal velocity, but even if it isn't, doesn't it suggest a horizontal force was necessary to get it going?

More specifically, Chandler suggests that the force acting upon multi-ton steel segments and accelerating them to such velocities came from explosives.

This begs the question: How can explosives accelerate large steel segments like that? Surely, no one would attach explosives to the steel with the purpose of flinging them around at high speeds, when the goal is to just sever the steel.

So Dwain, I'd like for you to ponder a few questions:

1. How would you attach explosives to a perimeter panel if you wanted to give it a velocity of 35 m/s, and how what amount of explosives would it take? Please have considerations in mind such as conservation of momentum, and that all the explosive energy that goes into kinetic energy cannot be used to also sever steel.

2. Do actual controlled demolitions throw multi-ton building segments laterally like this? Got examples?

3. In a non-explosive demolition, do you expect any debris parts to move laterally, or none? If yes, is there a limit to the size or velocity of such laterally moving pieces, and how would you derive it?


I think you will find that, to fling such masses with explosives, you'd need extremely large charges which would then have to be extremely loud - as in would unmistakably be heard 10 miles away as an explosion and be recorded on every video. And also that such a use of explosives would have been extremely wasteful and silly. Im short: That explosives don't provide a reasonably explanation.


A different angle to tackle this:
It has been claimed that the towers "fell into their footprints", and that this is a telltale characteristic of "controlled demolitions", which implies that natural collapses would NOT fall into their footprints, which is another way of saying that, in a natural collapse, major lateral ejections would be expected.
Perhaps you are rejecting the footprint argument, but if you think it is valid, then I don't see why you think lateral ejections are a sign of explosive CD?

Oystein wrote:Chandler suggests that the force acting upon multi-ton steel segments and accelerating them to such velocities came from explosives.

But dadeets has not. dadeets is simply asking if we've looked at the element. A good idea imo.

This begs the question(s): How can explosives accelerate large steel segments like that?

Again. Assuming inference and intent is definitely one of those things we shy away from here. Such may be the norm in other places, but certainly not here. And anyway, obviously an explosion of great enough magnitude would be able to fling a chunk of steel in any number of directions.

Surely, no one would attach explosives to the steel with the purpose of flinging them around at high speeds

A very strange thing to say.

when the goal is to just sever the steel

Really ?

So Dwain

Stating dadeets name in other forms is also frowned upon, and that doesn't sound friendly. Suggest you pull your horns in.

I'd like for you to ponder a few questions

I'd like for you to simply answer the simple question in the OP, rather than 'go on the offensive'.

The answer to which is clearly, yes, a horizontal force was applied.

More constructive response would include various sources of such force that you think were present, rather than you focussing on what you think didn't happen.

1. How would you attach explosives to a perimeter panel

Who suggested such a requirement ? You did.

if you wanted to give it a velocity of 35 m/s

Wanted to ? Weird trail of thought Oystein.

and how what amount of explosives would it take?

Again. If you have looked at that element, impart what you DO know.

Please have considerations in mind such as conservation of momentum, and that all the explosive energy that goes into kinetic energy cannot be used to also sever steel.

Come on.

2. Do actual controlled demolitions throw multi-ton building segments laterally like this?

Silly question.

Got examples?

Silly question, and rude.

You are NOT at JREF.

3. In a non-explosive demolition

By that, do you mean "collapse" ? Would you still classify that as demolition ?

do you expect any debris parts to move laterally, or none?

"none" is rather condescending don't you think ?

Speak as equals.

If yes, is there a limit to the size or velocity of such laterally moving pieces, and how would you derive it?

Have you done such ? Providing that information would be more productive.

I think you will find that, to fling such masses with explosives, you'd need extremely large charges

Do you ? Think how you feel... Got examples ? (not pleasant is it.)

Im short

No need to put yourself down

A different angle to tackle this

There's an idea. Constructive and informative information to follow I'm sure...

It has been claimed that the towers "fell into their footprints", and that this is a telltale characteristic of "controlled demolitions", which implies that natural collapses would NOT fall into their footprints, which is another way of saying that, in a natural collapse, major lateral ejections would be expected.

Oh. Not particularly constructive. And twisting yourself into logical knots.

Perhaps you are rejecting the footprint argument

dadeets has simply asked if it's been looked at here

I don't see why you think lateral ejections are a sign of explosive CD?

I suggest you read the OP again.

You are not at JREF. Sort it out.

Chandler obviously appears to not consider the lateral forces generated when a column buckles or the lateral forces that a container such as a silo experiences. While the tower was not a silo...the collapsing floor debris did not disappear and became an increasing volume much like the grain in a silo and would push outward on the facade. Chandler's cartoonlike conception seems to be that explosions sent all the floors and content materials through windows.

It's an interesting conception to say the least since the floor masses were behind the spandels and the ejections are coming from the windows below or above said spandrels. One would think that the explosions would force the spandrels and the panels themselves outward... with the large force to destroy the slabs rendering them to dust. Yet what we see is the facade stands and the ejected debris emerges from the windows. This seems to counter intuitive to exploding slabs. It appears to me that Chandler conflates collapses with only vertical motion.

SanderO wrote:Chandler obviously appears to not consider the lateral forces generated when a column buckles

One item of evidence as I remember it is the columns (by and large) did not buckle. Has this projectile been mapped back to a specific floor? If so, is there reason to believe columns may have buckled on that floor?

dadeets wrote:One item of evidence as I remember it is the columns (by and large) did not buckle.

Correct. Most failed at their inter-column connections.

Has this projectile been mapped back to a specific floor?

Probably, though just by positioning and trajectory it's likely to be near initiation zone.

If so, is there reason to believe columns may have buckled on that floor?

It may not be a buckled piece. It's not a big piece. Even if it's from a bit below initiation zone, there's no reason to think it wouldn't be kicked out by the ongoing ROOSD process.

Watch for the same projectile here.

femr2 wrote: there's no reason to think it wouldn't be kicked out by the ongoing ROOSD process.

This goes one step too many. I would need a more specific explanation consistent with ROOSD. Short of that, it looks like a nefarious force at work.

dadeets, that is absolutely correct.

It probably looks that way to millions of other people also. (Just a reminder that the large majority of the earth's population live outside the "first world", and outside the proper context, the global mass and particulate flow may look quite mysterious.)

It does appear strange to many people. But, hey, f*ck em. Block descriptions are "good enough" for some of us.

Who cares what those losers think, anyway?

DaDeets...

Are you asking how ROOSD could account for an energetic lateral motion of a quite heavy steel section?

ROOSD is a description of the floors in a runaway down to the ground progressive destruction. In the twins this *vertical avalanche* as I describe it... had consequences to the columns which held up the floors and of course themselves.

One function of the floor system was the lateral support of both the facade columns AND the the core columns. The OOS floors spanning between the facade and the core perimeter braced the entire facade *against* the string 3D space frame / lattice of the core.

The core had floors too... and the floor beams braced the core columns. But it had lots of shafts with no floor membrane.

The collapse of the top ALSO destroyed the floors within the core... and most of it bracing. The longest surviving bracing was between rows 500-600 and 900-1000. This was because THAT bracing did not support and floors it was in open express shafts and so no floors came crashing down on that bracing and it held and so we see row 500-600 pairs and the 900-1000 pairs in the so called *spire*. These also happen to include the strongest columns of the core.

When the bracing is stripped from the columns by ROOSD their ration of height to cross section shoots up very quickly and this REDUCES the yield strength of the column and can even cause it to buckle from its own weight - Euler buckling. This basically says that depending on the modulus of elasticity of the material... there is a slenderness ratio which limits the length a column can even self support. You know that taller columns are always thicker.. no?

The unbraced length at the twins was about 11' (less than the 12' foot story height). Destroy one floor and bracing and the slenderness ratio more than doubles! An article about Euler Buckling
http://www.esm.psu.edu/courses/emch13d/ ... cdes1u.pdf

When a multi part columns buckles the downward force makes the column to bow and flex and this is where the so called spring energy which is expressed as lateral ejections of segments likely comes from.

Does this make sense?

SanderO wrote:Does this make sense?

It makes sense to a very small degree. That is, makes sense as an explanation for some horizontal forces. But,...

1. Being responsible for the 35 m/s which supposedly was through direct contact with a free structural element strains credulity.
2. If this horizontal force also broke the structure free of its attachments, that would be an additional requirement.
3. Was this hypothesized core column buckling phenomenon also responsible for the mass field of debris, though with somewhat less than 35 m/s horizontal velocities?
4. While keeping in mind other reasons to suggest nefarious forces in the mix, such as the evidence of persistent heat beneath the debris pile.

I suspect that the piece in question came not from the core but from that facade. Can we be certain that it is in fact a piece of structural steel. The columns segments were 36' long and less than 14" wide except at the starter sections above and below the mech floors which had 12' and 24' length. ALL the aluminum cladding was in 12' lengths.

We DO see cladding flying off the facade... chaotically and energically at the beginning of the top drop. Many 12 sections were sprung off the frame where as the facade buckled or parted and began to descend.

The piece in question may have come from lower down in the collapse and if it is not 36' long it would have had to come from just above or below the mech floors.... Or it is a piece of steel from a longer section which broke... perhaps from buckling? 35m/sec is about 100 miles an hr... so that's quite fast... I can't dispute the value but I think femr2 needs to do some traces and confirm the velocity. Was it slowing down or speeding up?

I have no idea how much horizontal speed a bucking column could impart. I imagine if you press down on a think stick of wood and it bows and then snaps and trace the speed of the pieces that fly off one might get a feel for how fast buckled sprung sections might travel. But there are material and scale issues.

1. Why does it strain credulity? What speed would you expect something steel that snapped and sprung off to move at which wouldn't strain credulity?

2. I am not sure what you are asking here.... the buckling Euler bucking forces would likely separate the column to column connections and the stretching of the facade from the outward pressure of the collapsing debris (gain in the silo kinda thing) would separate the spandrel connections. MOST the the facade was failed at these joints and the steel itself was not "broken".

3. The core buckling had nothing to do with the debris.. crushed floors etc. The initiation WAS a buckling of the core which led to the top's crashing down and the floors destroyed each other... essentially *bypassing* the columns.. ripping themselves from the columns... and the beams which carried those floor slabs... which was also the bracing which stabilized and reduced the unbraced length of the columns. The floors stripping caused the column to quickly buckle... the facade to peel off and so forth.

4. The persistent heat *beneath* the pile indicates that there was an enormous amount of heat present. The pile was a huge heat sink and the heat gradient would be coolest at the outer edges of the heated mass. The pile acted like a huge insulator as well.. huge thermal mass. Why would the hottest zone be at the bottom and not the top? If the heat was generated from mechanical destruction of the concrete does it make sense that the bottom of the floor mass would see a concentration of the heat generated? Isn't the center of the earth hotter there because of the pressure? Could the process and the high heat be a similar artifact?

The persistence was simply because of the size of the heated mass. It takes an awful long time for that amount of mass to radiate the heat to the surroundings. Thermal masses are used in solar heat systems to hold and store heat energy. More mass more energy can be stored. We're talking about the mass of a building weighing in at 400,000 tons largely reduced to a thermal mass.