The 9/11 Forum

OneWhiteEye wrote:Hello Stundie (or do you prefer stundie?), welcome.

Hi OneWhiteEye and thanks for the welcome. I'm very easy to please, so Stundie or stundie is fine

OneWhiteEye wrote:I'm inclined to believe your question was directed at the theoreticians, hope you don't mind me commenting.

Not at all OWE, it was aimed at anyone and everyone, so I do not mind you commenting or answering it.

OneWhiteEye wrote:

Seeing as we still do not know exactly how WTC 1, 2 & even 7 collapsed and all these fire induced collapse theories seem to have serious faults which do not match the evidence (As in the photos & videos) or are physically impossible.

First, I should disclaim myself:

1) I know very little
2) I'm slightly inclined towards the notion that the towers fell too slowly, at least based on theory and the alleged (something I haven't checked myself, in other words) measured total times

There are some significant discrepancies between theory and observation.

You know more than me about the subject, I've looked at the computer models you have made and they are excellent and very detailed. So I don't undervalue your skills as you are able to have created them. Personally, I wouldn't know where to start...lol

There are indeed many discrepancies between theories and observation and this is why I ask the question.

There are obvious discrepancies between the theories of lets say NIST and observations, this is not taking away anything from NIST as such, but it shows us that NIST got some theories wrong. If the theory doesn't match the observations and evidence, then it is not a viable theory.

OneWhiteEye wrote: You may see I'm lobbying for advancement of the theory so as to achieve a better qualitative description, at the very least.

And I agree with you totally OneWhiteEye.

Lets say we have a fire induced initiation collapse theories 1 to (insert figure here) and evidence/observations A, B, C, D, E, Fetc. So we look at theory 1, great it matches evidence/observations A & B, but none of the others. So we look at theory 2, it matches A,C and D but not B & E and you keep going until theory you have ran out of possible theories (insert figure here)

What happens when we have exhausted all possible theories? Do we take theory 2 and ignore/handwave B & E to make the theory fit with what happened?

There are flaws with such theories and there must be a point when we have to say "Right, I'm giving this up..." or even "putting it on pause..." "...for the moment and will look at alternative theories that may explain some or possibly all the evidence."

OneWhiteEye wrote:You might also see I have great respect for the theory*** to date for, while I've not checked every jot and tittle personally, it elegantly expresses so much of what one needs to know to even begin to approach an understanding of this problem. I'm not there yet, and it will be some time.

I can believe that. The more you learn about anything, the more you understanding you have.

OneWhiteEye wrote:Could you elaborate on 'physically impossible'?

I think it was a poor choice of wording, maybe I should have used the words "not possible" instead because theoretically, nothing is impossible.

I find the Crush Down theory of the WTC as something I would ascribe to as being physically impossible, as in not possible. The problem is that is that the upper portion block A would have to remain intact while pounding the lower portion block B, when the reality is that forces generate by the fall of the upper portion block A (x floors) would have collided with the lower portion block B (x floors) the forces generated would have to be distributed equally, as they are the same objects but in 2 separate pieces.

If the failure point was lower down, then this would be physically possible....

OneWhiteEye wrote:

How long is it before you give up hypothesising a fire induced collapse theory if all avenues of your investigation and research so far suggests that it did not happened?

Not entirely sure but, from my perspective, the words 'you' and 'your' above do not refer to the same parties, at least on this board. Do you get what I mean?

***as if there were only one!

I get what you mean, but I mean individually, I honestly wasn't talking collectively as in a group or groups of people.

I agree with what you and Major Tom are suggesting, that maybe it's time to think of advancing another theory, however to discuss this further would be off topic and might be better off on another thread.

One dimensional homogenous structure crush down is indeed what Newton's laws require. This was first briefly explained in Bazant & Verdure and elaborated more fully in Bazant's 'reply to comments' in a more recent issue of J. Engg. Mechanics.

Of course, the collapse of WTC 1 only begins to approach the assumption of homogeneity after about three floors are crushed. After that, the layer of crushed materials does the damage to the portion below and protects the part above (ideally) from further damage. In the actual event, we know that the spire punched through the top portion; after that the top portion began to fall apart. It seems that it fell completely off before the crush down was complete, but not much before.

If this detail is of sufficient importance, find the video showing the antenna tower flying away at about a 70 degree angle. Do the timing analyss to determine how long after initiation this was and, if possible, how high up the antenna tower was at that time.

My claim of not much before the end of crush down is based on the excellent timing fit of BLGB. Some adjustment, of course, can be made, but not having the top portion fall off the crushed zone at, say, 4 seconds into the collapse.

In the actual event, we know that the spire punched through the top portion; after that the top portion began to fall apart. It seems that it fell completely off before the crush down was complete, but not much before.

Thanks for your comment, as always. How do you know these things?

I've found zero photographic evidence that these events took place.

It is also very hard for me to accept that the individual columns of which the spire consisted were capable of punching through the proposed hard top.

Major_Tom wrote:I've found zero photographic evidence that these events took place.

It is also very hard for me to accept that the individual columns of which the spire consisted were capable of punching through the proposed hard top.

Well, there are the videos of the standing spire.

It clearly is not just the columns, but also the core beams connecting the columns. The top portion, being tilted, meant that the one column line only had to punch through trussed office floors and then finally though the beamed floors of the top mechanical floor; the roof is a triviality but the hat truss is not.

I am supposing that all this began rather earlier with the core columns and beams failing after doing some of the damage. The importnt part is that the top portion's exterior walls remained (more or less) intact containing most of the materials for the ride towards the bottom. This clearly did not happen during the collapse of WTC 2.

stundie:

Thanks for the details and the kind words. This thread is a very specific topic so I won't go into length, just some quick thoughts since we're right here. (By nature, there's a fuzzy boundary around some of these topics, anyway, and a great deal of tie-in. For instance, the topic 'How fast did WTC1 collapse?', by all rights, needs to be settled before this one can get off the ground.)

What happens when we have exhausted all possible theories? Do we take theory 2 and ignore/handwave B & E to make the theory fit with what happened?

There are flaws with such theories and there must be a point when we have to say "Right, I'm giving this up..." or even "putting it on pause..." "...for the moment and will look at alternative theories that may explain some or possibly all the evidence."

In itself, who could disagree that? I wrote and erased a lot of officious nonsense before settling on this: A thousand arguments are going on right now about mechanics of collapse, how many of the participants could be certain of their position based on their own understanding? Without such understanding, bluntly, the cut is across the ideological line of smell-a-rat or not. A whole lot of nothing being said. This is one of the few places where theory meets pavement. I think it will be a good ride.

I find the Crush Down theory of the WTC as something I would ascribe to as being physically impossible, as in not possible. The problem is that is that the upper portion block A would have to remain intact while pounding the lower portion block B, when the reality is that forces generate by the fall of the upper portion block A (x floors) would have collided with the lower portion block B (x floors) the forces generated would have to be distributed equally, as they are the same objects but in 2 separate pieces.

Does not David B. Benson break bread, so to speak, with Professor Bazant? He's said here that he doesn't believe the upper block made it all the way down fully intact, either. For me:

I come before you
to stand behind you
And tell you something
I know nothing about

OneWhiteEye wrote:stundie:

Thanks for the details and the kind words. This thread is a very specific topic so I won't go into length, just some quick thoughts since we're right here. (By nature, there's a fuzzy boundary around some of these topics, anyway, and a great deal of tie-in. For instance, the topic 'How fast did WTC1 collapse?', by all rights, needs to be settled before this one can get off the ground.)

I agree with what you are saying in order for any model to be correct. But does the speed it collapses actually support a theory one way or the other?

For the sake of argument lets say we all agree that it took 20 sec for WTC1 to collapse, how does that support either theory? As I'm sure that proponents of both theories will claim that this supports their theories.

OneWhiteEye wrote:In itself, who could disagree that? I wrote and erased a lot of officious nonsense before settling on this: A thousand arguments are going on right now about mechanics of collapse, how many of the participants could be certain of their position based on their own understanding? Without such understanding, bluntly, the cut is across the ideological line of smell-a-rat or not. A whole lot of nothing being said. This is one of the few places where theory meets pavement. I think it will be a good ride.

I totally agree. I can't be certain of my position as my understanding of the collapses is based on my limited knowledge of physics.

So I will sit back and enjoyed the ride.

OneWhiteEye wrote:Does not David B. Benson break bread, so to speak, with Professor Bazant?

Not really, I'm not going to pretend I understand the technical details of their model but from a laymans point of view, I am being asked to believe that a crush down happened by the upper portions pulverising (I hope that is an acceptable word for it!) the lower portions.

However, it doesn't match the video/photographic evidence and based on my limited knowledge, I also struggle with how this is actually possible.

WTC 1 was hit between floors 93 and 99, so even if we use the lowest floor as our failure point, is there enough energy in those upper portions (Floors 94-110) to pulverise the lower portions? (floors 92-0) There are other problems, like the floors in the lower portions were progressively stronger lower down and the thickness of the steel in the columns tapered with height. So in effect, shouldn't that have provided more resistance the lower it got?

I can't think of a real world example of a collision between 2 objects that are comprised from the same materials, where the smaller object had enough energy to over come or pulverise the larger object.

That is not to say this is not possible, it just my understanding based on my limited knowledge of the subject.

OneWhiteEye wrote:He's said here that he doesn't believe the upper block made it all the way down fully intact, either.

I believe they propose a build up of rubble which creates some kind of shield that protects the upper portions, but I struggle with the concept too. Both of the objects colliding are made of the same materials, therefore if there was any build up of rubble that created this barrier, it would soon meet its demised as it collides with other materials in the lower portions and there is no photographic/video evidence to support this idea.

I'm not saying it is impossible but even from my basic point of view, it seems highly unlikely.

OneWhiteEye wrote:For me:

I come before you
to stand behind you
And tell you something
I know nothing about

The last 2 sentences kind of sum up my position, I'm indeed telling people something I know nothing (or very little) about. However, I think it is good that there have been critical skeptics who do not accept arguments from authority when there are sound critical arguments to be made.

If the towers collapse could be explained and match the evidence, then we certainly wouldn't here debating the issues. So again it brings about the question.

How many revisions or at what point does a theory become unworkable and worth giving up. As in it is not possible or a highly unlikely theory?

stundie --- Consider the Lego bricks and playing card model I proposed on another thread. There is some space between the playing cards. Once the top portion's Lego brick walls wedge inside the lower portion's, it is the Lego bricks impacting the playing cards and ripping those off their cardboard connections to the Le3go brick walls. So the 'crushed' playing cards accumulate just below the top portion's Lego brick walls; these then take out playing cards further down, but the playing cards of the upper portion are never disturbed.

Using a one dimensional model is a means to estimate the resisting force as the collapse progressed; these estimates are in good accordance with the actual physics of moving air out of the building, concrete comminution, etc. Indeed, BLGB takes into account the greater mass of columns further down (although this actually makes little difference). BLGB determines the initial resistive force from Dr. G's data; the resistive force grows as the square of the speed due to air movement and comminution, with previously known constants; the result is a crush down collapse time which agree well with the seismological record. I don't see how one cfan ask for a better demonstration that the (unassisted) crush down hypothesis is (approximately) correct.

David B. Benson wrote:If this detail is of sufficient importance, find the video showing the antenna tower flying away at about a 70 degree angle. Do the timing analyss to determine how long after initiation this was and, if possible, how high up the antenna tower was at that time.

It's on the list, which is quite long and is chipped away slowly. It may be difficult to prove the mast is still attached, though I believe it is.

My claim of not much before the end of crush down is based on the excellent timing fit of BLGB. Some adjustment, of course, can be made, but not having the top portion fall off the crushed zone at, say, 4 seconds into the collapse.

What if it's only the very top that falls off? What if much of the upper block debris remains interior to the perimeter? Whether or not the full upper block participates, there is already a deviation between the model and actual conditions, since the perimeter peeled away and did not participate in crush; it was not buckled nor did it add its mass to the front. Yet the model gives excellent timing. Why does it fit so well despite this discrepancy?

Going a little further, has anyone done an analysis on simple pancaking? Is there already a reason to believe that the collapse time would be significantly different if it involved only the floors (and perhaps a load of debris from the top)?

I would also like to get your opinion on whether it is reasonable to expect structural failure in a corner well below the advance of the crush front. If there were a load cell to measure 3-axis force at a column down at the base, what would the load profile look like as the block tipped then descended? Would there also be significant lateral forces introduced on the lower structure by the asymmetric collapse?

stundie:

But does the speed it collapses actually support a theory one way or the other?

I don't think so, not in the range of possible times. Collapse within a few percent of freefall rates would be difficult to explain conventionally, but that doesn't seem to have happened.

For the sake of argument lets say we all agree that it took 20 sec for WTC1 to collapse, how does that support either theory?

As I understand, it would put the collapse close to arrest. This is a graph from Seffen's paper showing collapse time as a function of residual capacity:

Seffen wrote:Figure 7: Comparison of the time period for collapse, [tau] , for both WTC towers (solid, WTC1; dashed, WTC2). The thicker lines refer to solutions derived from Lagrange's equation using Eqn 12 whereas the thinner lines relate to the Newtonian method via Eqn 27.

The lines stop where they do because greater values of residual capacity (p*, x-axis) prevents collapse from progressing to completion, so it's meaningless to talk about a total collapse time. In this model, the towers can't take more than a given time to collapse. If the observed time were 35 seconds, then this model would be inapplicable without refinement. The total time is relatively insensitive to residual capacity until approaching arrest.

I can't draw conclusions or make distinctions from collapse times, not yet. Maybe someone else can.

WTC 1 was hit between floors 93 and 99, so even if we use the lowest floor as our failure point, is there enough energy in those upper portions (Floors 94-110) to pulverise the lower portions?

Yes. That is, if one accepts the premise that the mass already destroyed is still available to crush structure below; that is, it accrues instead of being shed. Once initiated, the only point to argue is what portion of the available energy was actually expended in work done destroying the structure.

There are other problems, like the floors in the lower portions were progressively stronger lower down and the thickness of the steel in the columns tapered with height. So in effect, shouldn't that have provided more resistance the lower it got?

Yes. DBB mentions BLGB accounts for increase in mass, I don't know if strength increase is accounted for also. Bear in mind the model accounts for energy expended in hinge buckling columns but doesn't require it. For the most part, columns were not severely buckled, that energy was not spent. If the failure mode really is debris in a chute, the floor supports provided the resistance and they didn't vary in strength with height.

I can't think of a real world example of a collision between 2 objects that are comprised from the same materials, where the smaller object had enough energy to over come or pulverise the larger object.

It is important that the collision be along a vertical axis and any debris from the collision remain coherent. Then the smaller object snowballs into a larger object, absorbing debris from the larger object and using it against it. Sounds insane, doesn't it? That's because of the way I chose to describe it. The potential energy of the upper block does not need to be sufficient in itself. Once a portion below the block is destroyed, it becomes part of the destroying mass falling from above. So every part of the tower contributes its portion of potential energy to destroy what is below it and, in essence, the entire building's PE is used, not just the small upper block.

True, a compact car will not crush a bus in a collision (although if the car were doing 60,000mph I suspect it would vaporize it). Neither will it crush a bus if they were stood on end and it was dropped 3.7m onto the bus. However, if both were made of glass, it's not too difficult to imagine the both shattering completely. Is that a fair comparison, structural steel to glass? Not really, glass is brittle, but it is a real world example.

I'm taking the position of defending theories I don't fully understand, so if I'm giving a less than adequate defense, don't be surprised. Here's a decidedly unscientific thought experiment, but it works for me:

You are on the 100th floor of a tower. Workmen with torches begin severing perimeter and core columns randomly at the 80th floor. How many columns are severed before you personally lose confidence in the integrity of the building and leave? Would you consider it safe to take the elevator down to the 40th floor and wait there, or would you want to get out of the building altogether and get clear of the area?

I say this because I don't have a good intuitive feel about when such a structure should break, or what it looks like when it does.

OneWhiteEye wrote:What if it's only the very top that falls off? What if much of the upper block debris remains interior to the perimeter?

It is only a matter of having enough mass.

Whether or not the full upper block participates, there is already a deviation between the model and actual conditions, since the perimeter peeled away and did not participate in crush; it was not buckled nor did it add its mass to the front. Yet the model gives excellent timing. Why does it fit so well despite this discrepancy?

Because the analysis in BLGB takes continuous mass loss into account, although this does not matter so much because most of the mass was floors, cores and contents.

Is there already a reason to believe that the collapse time would be significantly different if it involved only the floors (and perhaps a load of debris from the top)?

The cores were large and heavy. I'd expect some noticable difference if these are left out.

I would also like to get your opinion on whether it is reasonable to expect structural failure in a corner well below the advance of the crush front. If there were a load cell to measure 3-axis force at a column down at the base, what would the load profile look like as the block tipped then descended? Would there also be significant lateral forces introduced on the lower structure by the asymmetric collapse?

No, unlikely. The load profile at the base would remain essentially constant until the crushing front reached that level.

OneWhiteEye wrote:stundie:
I don't think so, not in the range of possible times. Collapse within a few percent of freefall rates would be difficult to explain conventionally, but that doesn't seem to have happened.
As I understand, it would put the collapse close to arrest. This is a graph from Seffen's paper showing collapse time as a function of residual capacity:
http://i37.tinypic.com/8vwz9f.png

Seffen wrote:Figure 7: Comparison of the time period for collapse, [tau] , for both WTC towers (solid, WTC1; dashed, WTC2). The thicker lines refer to solutions derived from Lagrange's equation using Eqn 12 whereas the thinner lines relate to the Newtonian method via Eqn 27.

The lines stop where they do because greater values of residual capacity (p*, x-axis) prevents collapse from progressing to completion, so it's meaningless to talk about a total collapse time. In this model, the towers can't take more than a given time to collapse. If the observed time were 35 seconds, then this model would be inapplicable without refinement. The total time is relatively insensitive to residual capacity until approaching arrest.

I can't draw conclusions or make distinctions from collapse times, not yet. Maybe someone else can.

Hi again OneWhiteEye,

Thanks for the information and very interesting. The time of collapse is very important as it can be used to support a theory whether fire induced or demolition but I don't think it will be enough to swing an argument either way.

On a side note, I am wondering if the collapse times would ever be able to disprove a demolition theory?

Hambone stated earlier...

"Considering that the fall times do not favor the CD explanation we have to look at other evidence"

When people think demolition, they usually think of the typical controlled demolition like this one. http://www.youtube.com/watch?v=mOIaOs0Fmdo&feature=related ...Or even WTC7!

I'm not an explosives expert by a long shot, but I am aware that by placing charges in various parts and the timing of the detonation would affect many different aspects of how the building collapses.

So could it be argued that the speed of a collapse doesn't disprove the demolition theory because invariably by demolition, you can control the speed of a collapse?

I agree wholeheartedly with Hambone when he says "that we should look at the other evidence" as well. However, I do not see how the timing of the collapse will swing an argument on it's own unless it is somehow proven the collapse should have arrested.

Stundie

David B. Benson wrote:stundie --- Consider the Lego bricks and playing card model I proposed on another thread. There is some space between the playing cards. Once the top portion's Lego brick walls wedge inside the lower portion's, it is the Lego bricks impacting the playing cards and ripping those off their cardboard connections to the Le3go brick walls. So the 'crushed' playing cards accumulate just below the top portion's Lego brick walls; these then take out playing cards further down, but the playing cards of the upper portion are never disturbed.

Hi David B Benson,

Thanks for commenting.

I am a layman in the typical sense of the word, I've studied basic physic many years ago but never needed it in my line of work, so please excuse me if I do not understand exactly what you are suggesting here.

In this model, the top portions lego brick walls get wedge inside the lower portions, then how can there be no damage when to get it wedged, there as to be a collision?

So what about the upper portions lego bricks walls and it's cardboard connections? Is there any reason why they do not get disturbed? If the upper portion's lego brick or card collide to bring down the lower portions lego bricks and card, then surely it should be disturbed?

David B. Benson wrote:Using a one dimensional model is a means to estimate the resisting force as the collapse progressed; these estimates are in good accordance with the actual physics of moving air out of the building, concrete comminution, etc. Indeed, BLGB takes into account the greater mass of columns further down (although this actually makes little difference). BLGB determines the initial resistive force from Dr. G's data; the resistive force grows as the square of the speed due to air movement and comminution, with previously known constants; the result is a crush down collapse time which agree well with the seismological record. I don't see how one cfan ask for a better demonstration that the (unassisted) crush down hypothesis is (approximately) correct.

Trust me when I say, I can't argue with your data, methods and physics of how you have formulate your theories. I wouldn't know where to start....lol

In the case of WTC1, the upper portion pretty much dissolves before the lower portions starts to move.

If you are suggesting that the upper portions in your model are wedged inside and pushing against the lower portions, then what about the forces from the collision from the lower portions pushing against the upper portions?

I hope I have explained myself in way which will help you understand why I have problems with the unassisted hypothesis and why I disagree with it being approximately correct. That is not to say your theory is wrong or that the upper portions survived and manage to collapse the undamaged structure underneath it unassisted.

Thanks

Stundie

stundie wrote:In the case of WTC1, the upper portion pretty much dissolves before the lower portions starts to move.

It disappears from view, not dissolves. The lower portion is being crushed behind the exterior walls. Everything is shrouded with smoke, dust, aned larger particles forced out with the air

If you are suggesting that the upper portions in your model are wedged inside and pushing against the lower portions, then what about the forces from the collision from the lower portions pushing against the upper portions?

The upper portion exterior walls break trust seats in the lower portion;hardly an equal contest. Once two or three floors are crushed, the crushed materials insulate the upper portion from much further damge; the bottom of the crushed materials is the crushing front which crushes floors yet further down.

DBB:

I am looking at a WTC 1 & 2 collapse model that attempts to account for ALL possible natural collapse "assistance" vs. collapse "resistance" effects.

At least two parameters are needed to follow collapse initiation or what I call the "assistance" term, and a minimum of one additional parameter is needed to follow the collapse "resistance".

The "assistance" parameters are used to express (i) How hard the lower structure was pushed on to start the collapse, so it's the initial acceleration, and (ii) How fast it was pushed, so it's an initial velocity. I am setting the initial acceleration somewhere between zero and g; the inital velocity is allowed to vary between zero and 8.5 m/s - the free fall velocity at the end of a drop of 1 floor.

The "resistance" parameter is more difficult to quantify but I have been using a Hooke's Law "spring constant", calculated from column cross-section data. i.e. a vertical reaction force that increases linearly as you move down the tower.

I have also added a viscous flow term that's proportional to the collapse velocity to allow for friction.

The results so far show that these parameters need only be changed by small increments to go from a collapse that takes 12 seconds to one that takes 5 minutes, i.e. to go from "near free fall" to borderline collapse arrest!

I think an effective "friction" force could prove to be important to collapse models, since I suspect it is a much neglected energy sink.

The WTC collapse debris had a wide range of "particle" sizes including core and perimeter column sections, floor truss assemblies, chunks of concrete flooring, wall board sections, floor pans, stair-well sections, electrical wiring, plastic and metal plumbing, duct work, tables, desks, counters, office partitions, suspended ceilings, book shelves, chairs, computers, filing cabinets, carpets, glass doors, etc, etc, .....

When all of this material is compacted, friction forces come into play ........