NIST Petition Demands Corrections

[Belz...]

Has MM forsaken us ?

This was just getting good !

 

[R.Mackey]

The question of material strength of impactors is a complicated one.

There's competing effects at play. Stronger impactors lead to greater chances of elastic collisions. An elastic collision has a slightly higher pressure than an inelastic one, but delivers less impulse, because it bounces off and remains in contact for a shorter period of time. For this reason, an infinitely strong impactor ("aircraft engine core") may actually do less damage than an infinitely weak one (say an equivalent mass blob of fuel). Or it may do more. It depends on the exact speed, geometry, hardness of the surface hit, etc.

This is academic in the WTC cases. The trajectory of materials exiting shows it all traveled in more or less a straight line, so the collisions are basically inelastic.

In the inelastic case, a harder impactor will do less damage, because the impactor can now dissipate more energy as it is destroyed. It takes no energy to break up a fluid, but it takes quite a bit to mangle an engine core. This is the principle behind fenders on cars.

And nobody should doubt the destructive potential of the cloud of debris. This cloud weighs over 100 tons and is moving at around 250 meters per second, all funneled into just a couple of floors. Bad stuff.

 

[Miragememories]

I'm sorry to have to guess that Miragememories won't be returning, seeing as he has posted five times since last week, but still hasn't replied in this thread, leaving my questions still unanswered.

Well, It's nice to know someone is monitoring my posting behaviour.

That's fine. To Miragememories, in case you merely forgot about thsi thread, you are welcome to rejoin the conversation at any time.

No I hadn't forgotten. Boredom is a terrible thing and the responses here..

I'd like to press on, however, since this thread gathered more interest and went quite a bit longer than I expected it to. I think it needs some closure. Let me then revisit my last question:

Originally Posted by R.Mackey
Now let me restate my question, thus: The landing gear started in the body of the aircraft at left; this is "Point A." The landing gear exited at or very near the red rectangle at right; this is "Point B." You have claimed that the landing gear got from "Point A" to "Point B" without damaging the core. How do you think this happened?

Quote=Miragememories in reply to Mancman
The nose gear possibly could behave similarly, as possibly could main landing gear if 'sheared' by a core column during passage.

Obviously we have no examples of intact landing gear outside the towers so clearly the landing gear sections that were found were likely damaged by contact inside the tower. The most likely subjects for causing this damage would be the core and the opposite perimeter wall. Keep in mind the landing gear was inside the wing during impact so that profile would have been a factor in how, and how much it made contact after breaking through the first perimeter wall which could very well have sheared or partially fractured a landing gear strut.

So I don't claim there was no core damage, I'm only claiming core damage by the landing gear, engines and portions of, that were stopped by the core.

To answer this question, I propose the answer is that it is impossible.

And as indicated above I agree as well. I just don't agree with how much!

My reasoning is as follows: Consider my figure in the post quoted above. We have a pretty solid estimate of where the landing gear entered the building and where it exited. So what happened in between?

Keeping in mind there is no proof that this landing was 'intact' or what it's 'orientation' was when it entered the core region.

We know the landing gear came in contact with structural elements at some point. There is just no way for it to get from one side to the other without doing so. The core is a mesh of cross members and columns spaced about 15 feet side to side, and 12 feet high. If the aircraft had hit it flat and level, lucky objects as big as perhaps ten feet square could have made it through, if they were perfectly aligned -- but the incoming aircraft is looking at this at a ten degree angle. This means that anything that enters the core will exit on a different floor than it arrived, as seen in the diagram.

Using these estimates, the widest "slot" of daylight that any piece will see is a mere 2.6 feet high from its perspective. Or at least it would, if there wasn't a substantial floor present in the core. But the floors make no difference for purposes of this argument, since the landing gear, entering sideways, is almost four feet across. It simply won't fit.

That is an assumption based on an intact landing gear and an assumed profile. It also doesn't considered the different dimensions and orientation of the nose gear.

Ever play one of those carnival games, where you try to throw a baseball through a just-barely-bigger-than-a-baseball hole? Ever win anything?

I figured out the trick before wasting my money.

Me either. This situation is far worse.

Since we know the landing gear contacted the core, we also know that it damaged the core. The landing gear passed essentially straight through the structure, indicating little elasticity in its collisions. Furthermore, it has sufficient momentum to exceed the column P-I limits as expressed in NIST NCSTAR 1-2B, chapter 10. It is likely that the landing gear was itself heavily damaged after the initial contact with the core, so perhaps it inflicted only minor damage later in its path -- but at some point it had to hit the core, and hit it hard.

We know it passed through 2 perimeter walls and likely made contact with core columns. We don't know how much contact or what portions made contact. We know that after passing through the core region it had significant remaining momentum as it was able to burst through the opposite perimeter wall.

There are two other clues. The pieces that exited all showed extreme damage. We do not expect main gear, buried deeply in the back of the aircraft, to be destroyed by the perimeter columns, since the nose and fuselage of the plane should have cleared that out.

The nose and the fuselage were not a 'block' in front of the 2 sets of landing gear.

We also do not expect the building interior to have had much effect, since its trajectory was hardly deviated by anything, including the much stronger structural elements. However, if the landing gear had inflicted no damage on the core, we would expect it to hit the far perimeter more or less intact. It did not. Only one wheel and part of the carriage made it through, not even a quarter of the landing gear's original structure. Also, we would have expected the landing gear to exit with much more speed, had it not experienced major impacts inside the structure. Its exit speed was estimated at about a quarter of its entry speed.

That is hardly surprising after encountering the velocity reducing effects of 2 perimeter walls.

If you crash a thousand planes into a thousand WTC towers, you probably would see a landing gear set make it through the core more or less intact a few times.

So here you admit the impossible is possible..albeit unlikely?

High-speed collisions are complicated and difficult to predict. So are simulations. Done right, they accurately capture the "deterministic chaos" effect where minute changes to the initial conditions have significant downstream effects to a particular trajectory. Weird things can happen. This is why any model will have some inaccuracies, and we need to accept that. A point I've made here before is that we cannot accurately simulate what a single thrown die will do, and likely never will. The large scale behavior is much more important than fussing over every individual piece of debris.

In a nutshell, what we don't see we have to make an educated guess about. In this case we have the NIST model to act as a tool to assist in the educated guess.

Nonetheless, had this event been one of those lucky trials, we would have been able to tell by the condition of the exiting debris. It didn't happen on these flights. We know the landing gear was badly damaged, and we know the core did some if not all of it, and suffered in the process.

We don't know how much the core did and we don't know how much suffering the core went through.

----

This argument shows that landing gear debris passing through the core means damage was inflicted on the core. This is the first step in a logical chain, that goes as follows:

1. The exit of landing gear opposite the impact, through the core, signifies damage inflicted on the core.

Or that the landing gear was damaged and it's profile re-oriented by the first perimeter wall impact and that in it's deformed state made superficial contact with the core.

2. This is true for all debris, not just landing gear.

Rationale: Material strength and discrete impacts are minor effects in computing impact damage. Collisions inside the building are largely inelastic, as evinced by the near straight-line trajectory of the debris path, thus energy transfer is governed by momentum and not by hardness or ultimate strength of materials in the aircraft or in the tower.​

I don't accept this as valid since material strength and mass significantly determine the damage to key building structural components. Aside from the landing gear and the engines, most of the debris was of soft low strength materials which would have had little serious effect on the core columns.

​

3. More debris exiting the other side of the core means more damage inflicted on the core, in the real-world scenario.

Rationale: Since any individual piece exiting opposite the core is understood to have inflicted some damage according to 2. above, we can reason inductively to prove 3. rigorously -- for any impact scenario, adding a new piece of debris exiting means adding more damage, therefore the amount of damage in the new scenario is higher than that in the old scenario, for any arbitrary amount of debris pass-through.​

More debris simply means more debris. Not all debris is equal as I indicated above. Since you've established the gaps between the core columns, debris arrival on the other side need not indicate any, or significant, core contact. I would argue that less debris if anything would suggest the possibility of greater core damage since it would imply the core stopped (more damaging) rather than deflected (less damaging) the debris.

​

4. More debris exiting the other side of the core means more damage inflicted on the core, in the simulation.

Rationale: This is empirically observable, repeatable and testable. The NIST report shows that severity of impact is correlated with the amount of debris pass-through. There can be no doubt on this point, though this is actually the crucial observation.​

I will agree that the more severe the impact, the greater will be the core damage. I must note that NIST did a lot of re-thinking regarding the aircraft speed they chose in the extreme case scenarios.

​

5. Combining 3. and 4., an observation of more debris pass-through in the real world is best fit by a simulation of more severe impact.

Rationale: Both real-world and simulation show a increase in core damage when debris pass-through is increased. Therefore, an increase in observed debris pass-through is never better fit by a simulation with lesser impact severity.​

Assumption. There is no real world evidence to quantify this core damage estimate. The simulation naturally shows more debris pass-through in the extreme case scenario as it would in any extreme plus scenarios.
​

6. The best fit to the real-world observations in WTC 1 and WTC 2, out of the three cases NIST studied for each, is the most severe case.

Rationale: The baseline and less severe cases show virtually no debris pass-through. There are no cases with less pass-through than zero. Since both WTC 1 and 2, real-world, experiences some pass-through, 5. above guarantees that the baseline case underestimates the impact. Since the simulation shows the correct correlation between core damage and debris pass-through, we infer that the baseline case (and thus the less severe case as well) underestimate core damage.
​

WTC 2 simulated a 230 mph chunk accepted by you and NIST as landing gear which was not observed in the less severe and baseline scenarios. The WTC 2 extreme case scenario failed, strangely, to show the exit of a largely intact engine that was observed in reality. This in spite of the fact that the engine had a clear trajectory to the opposite perimeter wall and only unanchored office furniture blocking it's path. WTC 1 showed no landing gear or engine aircraft debris exit for any of the 3 scenarios.
​

QED.

On the basis of this logical chain, the petition "demanding corrections" is therefore proven to be in error. Steven Jones and his friends are either willfully attempting to confuse readers, or unable to comprehend the contents of the NIST report. Their motive is not central to this discussion -- we reject their conclusions regardless of the source of their error.

Thank you again for your participation. I'll return again to clean up a few remaining details, as I promised to do last week.

As stated, I feel your case is flawed as is the NIST Model and all the assumptions used to support it.

MM

 

[Mancman]

The nose and the fuselage were not a 'block' in front of the 2 sets of landing gear.
[qimg]http://www.internationalskeptics.com/forums/imagehosting/10252462f22171f3fe.jpg[/qimg]

This is true when the gears are down.

But when they are up, you can be pretty certain a path was cleared for them:

More debris simply means more debris. Not all debris is equal as I indicated above. Since you've established the gaps between the core columns, debris arrival on the other side need not indicate any, or significant, core contact. I would argue that less debris if anything would suggest the possibility of greater core damage since it would imply the core stopped (more damaging) rather than deflected (less damaging) the debris.

Strange comment. If this were true, the less severe cases would have the greatest core damage.

WTC 2 simulated a 230 mph chunk accepted by you and NIST as landing gear which was not observed in the less severe and baseline scenarios. The WTC 2 extreme case scenario failed, strangely, to show the exit of a largely intact engine that was observed in reality. This in spite of the fact that the engine had a clear trajectory to the opposite perimeter wall and only unanchored office furniture blocking it's path. WTC 1 showed no landing gear or engine aircraft debris exit for any of the 3 scenarios.

There is nothing strange about the 'failure' of the engine exit. As has been stated several times, a minor change in plane height would have the engine avoid a floorslab and retain 80% of it's original energy after penetrating the perimeter, rather than the 42% it retained in the actual severe simulation as a direct result of hitting the floorslab. Even with this impact, the engine was within a few feet of the trajectory needed to exit at the corner.

 

[beachnut]

MM has proved to me the petition is flawed and insignificant. Why is he unable to see his own energy work, and make the correct conclusion as he pointed out in his karate energy study?

 

[R.Mackey]

Well, It's nice to know someone is monitoring my posting behaviour.

Welcome back.

I merely wanted to see if, perhaps, you hadn't answered my questions because you had been away from the JREF Forum. Sadly, that appears to be false.

Keep in mind the landing gear was inside the wing during impact so that profile would have been a factor in how, and how much it made contact after breaking through the first perimeter wall which could very well have sheared or partially fractured a landing gear strut.

Poster Mancman has eloquently explained your error here. The landing gear was in fact inside the fuselage at the time of impact. This should have been obvious from NIST NCSTAR1-2, which you told me you had read.

And as indicated above I agree as well. I just don't agree with how much!

You haven't answered my questions, so I don't know what you believe. Certainly you haven't expained "how much," i.e. quantification of your opinions is impossible. You might want to try answering my questions sometime...

Keeping in mind there is no proof that this landing was 'intact' or what it's 'orientation' was when it entered the core region.

Makes no difference. The four-foot width of the landing gear is its minimum dimension. Any change in orientation will make it still more difficult to fit through the core.

That is an assumption based on an intact landing gear and an assumed profile. It also doesn't considered the different dimensions and orientation of the nose gear.

I believe my assumption that the perimeter columns were cleared out before the main gear entered the building is pretty safe. They were behind the main spar, for crying out loud.

The nose and the fuselage were not a 'block' in front of the 2 sets of landing gear.

As before, yes it was. Please re-read the NIST NCSTAR1-2, or refamiliarize yourself with the layout of the Boeing 767 aircraft.

So here you admit the impossible is possible..albeit unlikely?

You've misinterpreted me, but the confusion is understandable. My mistake. I will be glad to clarify.

If you crash 1000 planes into 1000 towers, I believe it is possible but highly unlikely for landing gear to shoot straight through without damaging the core, in one of two ways:

1. The landing gear is deflected while still attached to the aircraft, in such a way that it encounters the core flat and level. Stress of impact twists the aircraft such that the landing gear just happens to shoot through the core without passing from one floor to another. In this orientation, assuming it's also aligned with a clear "hallway," it barely fits.

However, this is impossible in WTC 1 or 2, because we have the exit point of the landing gear. We know it exited a floor below where it entered, and therefore must have encountered the core.

2. The forward parts of the plane damaged the core so heavily that a hole was made for the landing gear to pass through relatively unscathed.

This case isn't inconsistent with the observation that more debris == more damage... and clearly the WTC cases didn't experience this much trauma at impact.

So to summarize, it "is possible" in general, but it is not possible in terms of WTC 1 and 2. The entry and exit points alone are enough to guarantee that the landing gear didn't make it through the core without hitting it somewhere along the way.

In a nutshell, what we don't see we have to make an educated guess about. In this case we have the NIST model to act as a tool to assist in the educated guess.

Exactly.

We don't know how much the core did and we don't know how much suffering the core went through.

... but we have an educated guess. Not sure what you're trying to say.


Now, as far as my proof that the petition complaint is wrong:

[Responding to point 1.]
Or that the landing gear was damaged and it's profile re-oriented by the first perimeter wall impact and that in it's deformed state made superficial contact with the core.

Impossible. See above. There is no reason to expect the landing gear is heavily damaged prior to reaching the core, and there is no orientation that will get it through with only "superficial contact." You're grasping at straws.

[Responding to point 2.]
I don't accept this as valid since material strength and mass significantly determine the damage to key building structural components. Aside from the landing gear and the engines, most of the debris was of soft low strength materials which would have had little serious effect on the core columns.

I don't really care if you accept it. You've made this assertion several times, and I've corrected you several times. I've given you theoretical and empirical evidence why the material strength and mass of individual pieces are not the dominant factors. You've stated it again, and again you refuse to support it. This has become tiresome.

I don't think you know what you're talking about. Either support your statement and let me see what you think you know, or I will treat this as yet another argument from personal belief, and ignore it.

[Responding to point 3.]
More debris simply means more debris. Not all debris is equal as I indicated above. Since you've established the gaps between the core columns, debris arrival on the other side need not indicate any, or significant, core contact. I would argue that less debris if anything would suggest the possibility of greater core damage since it would imply the core stopped (more damaging) rather than deflected (less damaging) the debris.

I'm amazed you tried to argue this one, because this is mathematically proveable.

I'm even more amazed that you still claim more debris pass-through == less damage. The core is not some sparse network that Cessnas could comfortably buzz through, particularly when you hit it ten degrees nose down. I'm going to ignore this outrageous position of yours as well, out of pity.

[Responding to point 4.]
I will agree that the more severe the impact, the greater will be the core damage. I must note that NIST did a lot of re-thinking regarding the aircraft speed they chose in the extreme case scenarios.

Nope!

Here's NIST:

A speed estimate was then calculated from the individual videos. A mean value was calculated using the weighted average of the mean values. The measurement precision (the reciprocal of the variance) was used as a weight factor on the mean values. If measurements were independent, the uncertainty in the mean could be calculated by summing the individual measurement precisions, giving 443 ± 21 mph for AA 11 and 542 ± 14 mph for UAL 175. However, some uncertainties were systematic and the actual bound on the uncertainty was larger as a result. Therefore, the uncertainty range was increased to ± 30 mph and ± 24 mph for AA 11 and UAL 175, respectively. A summary of the impact conditions derived from video analysis (both complex and simplified motion analyses) is presented in Table 6–3.

[Discussing the WTC 1 "more severe" case]
The parameters for the more severe WTC 1 impact scenario are compared to the corresponding parameters in the base case analysis in Table 7–3. For the flight parameters, the impact speed was 472 mph in the more severe impact scenarios, which was the upper bound obtained from the analysis of aircraft impact conditions described in Chapter 6.

[Discussing the WTC 2 "more severe" case]
For WTC 2, the variations in the parameters from the base case were similar to those for WTC 1 (see Table 7–3), with two exceptions. The first exception was the introduction of the strength of the building contents as a parameter. There was less information available about the layout of building contents in the WTC 2 impact zone and therefore a larger uncertainty associated with the contents was assumed (the workstation layout from WTC 1 was used for WTC 2). Thus, in the more severe case, the contents strength was reduced to 80 percent of the baseline value.

The second exception was the failure strains for the aircraft and tower materials. For the more severe WTC 1 analysis, 125 percent and 80 percent of the baseline values were used for the aircraft and tower failure strains, respectively. For the more severe WTC 2 analysis, 115 percent and 90 percent of the baseline values were used. The more severe WTC 2 analysis was the final global impact analysis performed. Based on the previous analyses, the variation in damage levels indicated that the WTC 2 more severe impact analysis would produce impact damage state that was not viable (e.g., the amount of debris exiting the north wall). To ensure that a viable damage state was obtained, the aircraft and tower materials were adjusted to the values presented in Table 7–8.

In other words, the "more severe" case speeds were determined as the "one sigma" bounds of observational error from videos, and there was no "rethinking" as you claimed.

Are you SURE you read it? This makes two more errors about the report in your last post alone...

From now on, whenever you claim something NIST says, I want to see you cite a page number, or else I'm just going to ignore it. You've been pretty good about it so far, but you're still making huge mistakes, assuming they are mistakes and not outright fabrication.

[Responding to my point 5.]
Assumption. There is no real world evidence to quantify this core damage estimate. The simulation naturally shows more debris pass-through in the extreme case scenario as it would in any extreme plus scenarios.

All I see here is a complaint that we have no direct observation of the core. Big surprise, that's why the model is necessary. What matters is that it behaves as it is supposed to. It does.

[Responding to my point 6.]
WTC 2 simulated a 230 mph chunk accepted by you and NIST as landing gear which was not observed in the less severe and baseline scenarios. The WTC 2 extreme case scenario failed, strangely, to show the exit of a largely intact engine that was observed in reality. This in spite of the fact that the engine had a clear trajectory to the opposite perimeter wall and only unanchored office furniture blocking it's path. WTC 1 showed no landing gear or engine aircraft debris exit for any of the 3 scenarios.

The engine exit issue has been beat to death. It's not relevant because it didn't contact the core, and its trajectory is highly sensitive to minor initial condition errors that are well within the limits of observation.

And, for the tenth time, this only suggests that even the most severe cases weren't severe enough. You're supporting my argument, whether or not you realize it.

As stated, I feel your case is flawed as is the NIST Model and all the assumptions used to support it.

I'm well aware of your feelings, but they just don't make that much difference. You cannot support them, you continue to err about the contents of the NIST report, and you refuse to answer the most basic questions about your own theory. I'm no longer interested in your feelings.

If you want me to help you, you need to start explaining why you believe these things, where you got the ideas, and how you've supported them with real experts, real sources, or real experiments. You have an opportunity here to learn and to become a better researcher. Impress me.

 

[Corsair 115]

Poster Mancman has eloquently explained your error here. The landing gear was in fact inside the fuselage at the time of impact. This should have been obvious from NIST NCSTAR1-2, which you told me you had read.

It's also obvious from watching any of the numerous videos of the impacts that the landing gear were not extended. At the speeds the aircraft were estimated to be travelling, I don't believe it would have been possible to extend the gear in any case.

 

[Belz...]

Poster Mancman has eloquently explained your error here. The landing gear was in fact inside the fuselage at the time of impact. This should have been obvious from NIST NCSTAR1-2, which you told me you had read.

In fact, had he used the Truthers' vaunted "common sense", he would've figured out that the gear was retracted at the time of impact.

 

[Miragememories]

I think we've reached a point where we know each other's point of view quite well.

Further case presentation is going to be more rehash.

The NIST Model is a software construction tool that is understandably built on a series of logical assumptions based on known mathematical, physics, and engineering relationships combined with reference data and laboratory test results.

My engineering background is sufficient for me to appreciate the complexity and the uniqueness of the challenge faced by NIST in attempting to reproduce computer simulations of the impact-to-collapse timeline of WTC 1 and WTC 2.

The problem with a model of this type, is that it only has to agree with one event. As you admit, it's extremely complex. The more complex the greater the uncertainty factor.

Fundamentally, we have two very large incendiary projectiles fired into two very large structures.

We don't know the exact weight, speed or trajectory of the projectiles.

We are missing data on the effected unanchored components within the structure.

We only have visual data on the entry and exit points.

We have no confirmed data regarding the damage to the inside of the structure other than amateur eyewitness accounts of collapsed drywall in the stairwells.

We do have 2 pieces of projectile debris for each structure.

We know exactly how long the structures will stood from the time of impact to the point of collapse.

The task was to create an accurate model that will react in close approximation of the real event.

A Model was created by NIST based on the most accurately possible determination of the event parameters. This is the foundation for the baseline scenario simulation. The simulation fails on both models. No projectile debris exits from either Model in the baseline scenario and the simulated structures fail to collapse in accordance with the real events time frames.

The Model is 'pushed' to an extreme but supposedly still realistic scenario.
The aircraft is made heavier, stronger and faster and the structures are made weaker. The simulations succeed and collapses are initiated although the real time exit debris event is again not matched.

It is determined that this 'lack of a match' with the known observables is not significant to the simulated outcome and that because the observed simulated collapse reasonably matches the real time observed collapse, this simulation is adopted as an accurate representation of what occurred.

Aside from the initial damage profile simulated by the extreme case scenario, the rest of the simulation result is based on the effect of various fires on the simulated damage to the structures. While the impact timeline was a few seconds at most, the fires timelines were approximately 3600 and 4200 seconds. A number of assumptions were employed. It was assumed that most of the fireproofing was removed and it was assumed that sufficiently high temperatures were reached to weaken and deform the steel to the extent that the perimeter walls failed.

I have read reports that dispute aircraft speed, likely aircraft damage, amount of fireproofing material likely to be removed and the maximum temperatures normally achievable in an office fire. I've also observed the nature of WTC 1 & 2 sudden, rapid and complete collapses.

EVEN if all the NIST assumptions were met, there are 2 major points that my incredulity cannot accept.

I don't believe it makes sense for WTC 1, the North Tower, to 'drop' 10 feet under the proposed circumstances. To my mind, logically, if the perimeter wall lost it's integrity to the point that it could no longer support the load from above, the gradually weakening vertical support steel would gradually bend (rather than 'snap') under the weight of the floor above. The floor above at that point would sink rather than drop down. Other parts of the perimeter wall might become overwhelmed but I can't believe they would fail in instant unison and that they would 'snap' to allow the 'drop' necessary to argue an irresistible downward force. Yet somehow we are to believe that the perimeter walls and internal core gave up virtually simultaneously, allowing the huge structure above 'drop' 10 feet to overwhelm the intact and steadily stronger floors below.

In WTC2 prior to it's complete collapse, we clearly see the huge section above the impact zone lean and apparently about to topple free. Strangely this is 'arrested' and like the rug being pulled out from under it, it's topple is abruptly halted and it appears to 'ride' downwards on the previously intact structure that implodes below it.

I'm well aware than in your eyes this reply amounts to no more than unsourced speculation and incredulity. For me wasting further long hours in a fruitless attempt to argue against an entrenched belief would be about as useful as beating my head against the proverbial brick wall.

Regardless, the NIST model is still only a model and the NIST explanation for the collapses of WTC 1 and 2 is only a theory. A theory that conveniently sits well with the Official Story.

MM

 

[Pardalis]

To my mind, logically, if the perimeter wall lost it's integrity to the point that it could no longer support the load from above, the gradually weakening vertical support steel would gradually bend (rather than 'snap') under the weight of the floor above.

How so?

The floor above at that point would sink rather than drop down.

What's the difference? Something that sinks usually drops down.

Other parts of the perimeter wall might become overwhelmed but I can't believe they would fail in instant unison and that they would 'snap' to allow the 'drop' necessary to argue an irresistible downward force.

Yet somehow we are to believe that the perimeter walls and internal core gave up virtually simultaneously, allowing the huge structure above 'drop' 10 feet to overwhelm the intact and steadily stronger floors below.

What is your definition of "overwhelm"?

In WTC2 prior to it's complete collapse, we clearly see the huge section above the impact zone lean and apparently about to topple free. Strangely this is 'arrested' and like the rug being pulled out from under it, it's topple is abruptly halted and it appears to 'ride' downwards on the previously intact structure that implodes below it.

What force was used to halt this progression?

How can you ascertain that the topple was "halted" when it disappears in a cloud of smoke and dust?

 

[pomeroo]

I think we've reached a point where we know each other's point of view quite well.

Further case presentation is going to be more rehash.

The NIST Model is a software construction tool that is understandably built on a series of logical assumptions based on known mathematical, physics, and engineering relationships combined with reference data and laboratory test results.

My engineering background is sufficient for me to appreciate the complexity and the uniqueness of the challenge faced by NIST in attempting to reproduce computer simulations of the impact-to-collapse timeline of WTC 1 and WTC 2.

The problem with a model of this type, is that it only has to agree with one event. As you admit, it's extremely complex. The more complex the greater the uncertainty factor.

Fundamentally, we have two very large incendiary projectiles fired into two very large structures.

We don't know the exact weight, speed or trajectory of the projectiles.

We are missing data on the effected unanchored components within the structure.

We only have visual data on the entry and exit points.

We have no confirmed data regarding the damage to the inside of the structure other than amateur eyewitness accounts of collapsed drywall in the stairwells.

We do have 2 pieces of projectile debris for each structure.

We know exactly how long the structures will stood from the time of impact to the point of collapse.

The task was to create an accurate model that will react in close approximation of the real event.

A Model was created by NIST based on the most accurately possible determination of the event parameters. This is the foundation for the baseline scenario simulation. The simulation fails on both models. No projectile debris exits from either Model in the baseline scenario and the simulated structures fail to collapse in accordance with the real events time frames.

The Model is 'pushed' to an extreme but supposedly still realistic scenario.
The aircraft is made heavier, stronger and faster and the structures are made weaker. The simulations succeed and collapses are initiated although the real time exit debris event is again not matched.

It is determined that this 'lack of a match' with the known observables is not significant to the simulated outcome and that because the observed simulated collapse reasonably matches the real time observed collapse, this simulation is adopted as an accurate representation of what occurred.

Aside from the initial damage profile simulated by the extreme case scenario, the rest of the simulation result is based on the effect of various fires on the simulated damage to the structures. While the impact timeline was a few seconds at most, the fires timelines were approximately 3600 and 4200 seconds. A number of assumptions were employed. It was assumed that most of the fireproofing was removed and it was assumed that sufficiently high temperatures were reached to weaken and deform the steel to the extent that the perimeter walls failed.

I have read reports that dispute aircraft speed, likely aircraft damage, amount of fireproofing material likely to be removed and the maximum temperatures normally achievable in an office fire. I've also observed the nature of WTC 1 & 2 sudden, rapid and complete collapses.

EVEN if all the NIST assumptions were met, there are 2 major points that my incredulity cannot accept.

I don't believe it makes sense for WTC 1, the North Tower, to 'drop' 10 feet under the proposed circumstances. To my mind, logically, if the perimeter wall lost it's integrity to the point that it could no longer support the load from above, the gradually weakening vertical support steel would gradually bend (rather than 'snap') under the weight of the floor above. The floor above at that point would sink rather than drop down. Other parts of the perimeter wall might become overwhelmed but I can't believe they would fail in instant unison and that they would 'snap' to allow the 'drop' necessary to argue an irresistible downward force. Yet somehow we are to believe that the perimeter walls and internal core gave up virtually simultaneously, allowing the huge structure above 'drop' 10 feet to overwhelm the intact and steadily stronger floors below.

In WTC2 prior to it's complete collapse, we clearly see the huge section above the impact zone lean and apparently about to topple free. Strangely this is 'arrested' and like the rug being pulled out from under it, it's topple is abruptly halted and it appears to 'ride' downwards on the previously intact structure that implodes below it.

I'm well aware than in your eyes this reply amounts to no more than unsourced speculation and incredulity. For me wasting further long hours in a fruitless attempt to argue against an entrenched belief would be about as useful as beating my head against the proverbial brick wall.

Regardless, the NIST model is still only a model and the NIST explanation for the collapses of WTC 1 and 2 is only a theory. A theory that conveniently sits well with the Official Story.

MM

So, you remain impervious to all of Mackey's corrections? You are incapable of actually responding to anything he's explained to you, but he's the proverbial brick wall? Isn't this thread, once quite interesting and informative, in danger of ending up an Ace-Baker farce? Admittedly, you strive to appear sane, but the significance of the arguments of the rationalist side don't ever register with you.

 

[aggle-rithm]

I don't believe it makes sense for WTC 1, the North Tower, to 'drop' 10 feet under the proposed circumstances. To my mind, logically, if the perimeter wall lost it's integrity to the point that it could no longer support the load from above, the gradually weakening vertical support steel would gradually bend (rather than 'snap') under the weight of the floor above. The floor above at that point would sink rather than drop down. Other parts of the perimeter wall might become overwhelmed but I can't believe they would fail in instant unison and that they would 'snap' to allow the 'drop' necessary to argue an irresistible downward force. Yet somehow we are to believe that the perimeter walls and internal core gave up virtually simultaneously, allowing the huge structure above 'drop' 10 feet to overwhelm the intact and steadily stronger floors below.

Here's how it works:

When one support fails, the weight it was carrying is immediately transferred to the other supports.

Not after a few minutes. Not after a few hours. IMMEDIATELY.

What do you think will happen when you have the minimum number of supports in place, and one fails?

The weight is transferred IMMEDIATELY to the remaining supports, and since they are insufficient to support it, they fail IMMEDIATELY. All at the same time.

I defy you to create a model for a high-rise building that works otherwise.

In WTC2 prior to it's complete collapse, we clearly see the huge section above the impact zone lean and apparently about to topple free. Strangely this is 'arrested' and like the rug being pulled out from under it, it's topple is abruptly halted and it appears to 'ride' downwards on the previously intact structure that implodes below it.

And yet no real engineers are surprised by this behavior. A correction of this sort is PREDICTED in a high-rise collapse, since the falling portion is not able to retain its form when tilted more than a certain angle, and so tends to fall straight down.

I'm well aware than in your eyes this reply amounts to no more than unsourced speculation and incredulity. For me wasting further long hours in a fruitless attempt to argue against an entrenched belief would be about as useful as beating my head against the proverbial brick wall.

Trying to learn something new, especially about something that is obviously so important to you, is not fruitless at all. It's a pity you refuse to do so.

Regardless, the NIST model is still only a model and the NIST explanation for the collapses of WTC 1 and 2 is only a theory. A theory that conveniently sits well with the Official Story.

MM

Gravity is "only" a theory, too.

 

[Pardalis]

I'm sorry if I missed it in this thread, but what does MM suggest would have happened, in his world, once the collapse started?

MM, please fill in the blank:

The top section starts to collapse onto the impact zone, then _______

 

[R.Mackey]

My engineering background is sufficient for me to appreciate the complexity and the uniqueness of the challenge faced by NIST in attempting to reproduce computer simulations of the impact-to-collapse timeline of WTC 1 and WTC 2.

Evidence?

The problem with a model of this type, is that it only has to agree with one event.

Another lie. NIST used numerous criteria for evaluation, not just one. Unless you're rolling all of them into "one event," which is similarly dishonest.

Cite where NIST says this, support your statement, or retract it. Those are your options.

I have read reports that dispute aircraft speed, likely aircraft damage, amount of fireproofing material likely to be removed and the maximum temperatures normally achievable in an office fire.

No you haven't, unless you can cite them. And the works of Steven Jones do not count, as his abuse of the term "peer review" disqualifies him.

EVEN if all the NIST assumptions were met, there are 2 major points that my incredulity cannot accept.

Personal incredulity is ignored. You just don't have the training to be a good judge of expected behavior. This entire thread has proven that point over and over again.

Here's yet another example:

I don't believe it makes sense for WTC 1, the North Tower, to 'drop' 10 feet under the proposed circumstances. To my mind, logically, if the perimeter wall lost it's integrity to the point that it could no longer support the load from above, the gradually weakening vertical support steel would gradually bend (rather than 'snap') under the weight of the floor above. The floor above at that point would sink rather than drop down.

No. Steel reaches its elastic limit at about 3% strain, and plastic limit somewhere around 5%. That means, if it's a load bearing structure supporting tens of thousands of tons, it will stretch and flow a little bit -- about 5% -- and then, something will fracture. It is not like a sponge.

This is extremely basic strength of materials knowledge. Any first-year could tell you this is completely ordinary.

This is why I now reject any and all unsupported speculations you make. If you read something that backs you up, fine, let's see it. If not, you're out of your field, and you should be asking questions rather than posting assertions.

I'm well aware than in your eyes this reply amounts to no more than unsourced speculation and incredulity. For me wasting further long hours in a fruitless attempt to argue against an entrenched belief would be about as useful as beating my head against the proverbial brick wall.

Quite correct. Go get better sources, or else you cannot possibly make any progress.

Regardless, the NIST model is still only a model and the NIST explanation for the collapses of WTC 1 and 2 is only a theory. A theory that conveniently sits well with the Official Story.

Only a model and a theory, perhaps, but one that you have yet to find any legitimate criticism of, not for want of trying. As for its conclusions matching the observed evidence, and not requiring some mysterious physics, that is a feature, not a bug. Sorry it doesn't match your preconceived world view, but that's the way science goes sometimes.

 

[lozenge124]

Here's how it works:

When one support fails, the weight it was carrying is immediately transferred to the other supports.

Not after a few minutes. Not after a few hours. IMMEDIATELY.

What do you think will happen when you have the minimum number of supports in place, and one fails?

The weight is transferred IMMEDIATELY to the remaining supports, and since they are insufficient to support it, they fail IMMEDIATELY. All at the same time.

But why do the columns fail at or around the levels where the planes crashed? The perimeter and core columns after all are basically vertical structures that span the building height.
To use an analogy, if you push down vertically on a straw, you cannot tell beforehand where it will "fail" or bend. This may be at anypoint along the straw. Why does the overloading of the WTC structure not result in any visible structural failure or damage lower down in the tower also (at "initiation")? Why does the collapse happen "floor by floor" when the support columns are vertical structures that will react as a whole to any overloading?

 

[beachnut]

We don't know the exact weight, speed or trajectory of the projectiles.

We do have 2 pieces of projectile debris for each structure.

MM

We know the speed, the weight, and the trajectory of each plane.

Flying, a pilot has to know his aircraft weight. There is no mistake on the weights of the aircraft. If you want to find the exact weight you can find if for each plane, it is a matter of record. Wrong on this.

Using the different videos you can get the speed of each aircraft, and if you are a scientist you can get the speeds using other methods.

The trajectory is fixed with 175 very precisely if you want it. Two different video sources will give you enough information to make a very accurate trajectory.

This is the kind of research that Dr Jones does too, he just says it to cast doubt on what we saw on 9/11. There is no thermite/thermate in the WTC, and Dr Jones is making himself look foolish to engineers and scientist. Millions of engineers vs one nut case who still hold the modern flat earth 9/11 truther mentality of lies.

You still ignore you own physics work proving the petition insignificant.

 

[R.Mackey]

But why do the columns fail at or around the levels where the planes crashed? The perimeter and core columns after all are basically vertical structures that span the building height.
To use an analogy, if you push down vertically on a straw, you cannot tell beforehand where it will "fail" or bend. This may be at anypoint along the straw. Why does the overloading of the WTC structure not result in any visible structural failure or damage lower down in the tower also (at "initiation")? Why does the collapse happen "floor by floor" when the support columns are vertical structures that will react as a whole to any overloading?

Welcome to the JREF forum. These are good questions, but easy to answer.

First of all, if you look closely at the video, there is actually some damage evident several floors below the initial collapse, as some of the shock is transmitted downward and fails a few places in advance of the descending mass.

However, in general, the columns are not going to react as a whole to overloading:

• They are not solid pieces of steel, but rather sections, joined together by splices
• We're dealing with impact rather than a gentle, quasi-static loading
• Even if the columns were purely vertical and homogeneous, the vertical stress wave would propagate at a fixed speed, not instantly load the entire column. This speed is about 5100 m/s -- fast, but not infinitely fast.
• Most importantly, look at the specific failure mechanism. The columns buckle rather than being compressed to fracture. At the point of initiation, this involves an inward twisting, and this doesn't get transmitted downward efficiently.

What you're expecting is the damage progression to take the form of longitudinal waves, whereas a better model would be a Rayleigh wave. Also, the columns preferentially buckle at the top due to coincident damage to the horizontal bracing, whereas deep in the structure the bracing is intact, and the columns resist buckling by this mode until additional force and damage are applied.

Way down in the structure this no longer holds, though. This is why we saw a piece of core columns remain standing briefly after the main collapse. In that case, some columns survived, but all bracing was failed. The surviving columns then collapsed under their own weight.

No mysteries here, just deeper concepts of structural mechanics.

 

[lozenge124]

Welcome to the JREF forum. These are good questions, but easy to answer.

First of all, if you look closely at the video, there is actually some damage evident several floors below the initial collapse, as some of the shock is transmitted downward and fails a few places in advance of the descending mass.

Thanks for the reply.

However, in general, the columns are not going to react as a whole to overloading:

• They are not solid pieces of steel, but rather sections, joined together by splices

• 
  True, but the splices are AFAIK horizontal so a vertical gravitational force pushing down from above should transfer through easily.
  
  

  [*]We're dealing with impact rather than a gentle, quasi-static loading

  After initiation, I agree, but at initiation itself I think it is fair to call it quasi-static. For WTC1, the NIST has the south tower columns bowing which increases the load in the rest of the structure, but I do not think they make the case that "instability progressed horizontally" very convincingly, because the columns are being loaded in a quasi-static situation - I think the straw example still applies, the failure could occur lower down.
  
  

  [*]Even if the columns were purely vertical and homogeneous, the vertical stress wave would propagate at a fixed speed, not instantly load the entire column. This speed is about 5100 m/s -- fast, but not infinitely fast.

  True, but I still have trouble understanding how the 5100m/s wave damage is so localized. (how the waves apparently focus their energy on the next set of splices with the next splice below being unaffected for the most part)
  
  

  [*]Most importantly, look at the specific failure mechanism. The columns buckle rather than being compressed to fracture. At the point of initiation, this involves an inward twisting, and this doesn't get transmitted downward efficiently.

  I am not convinced by the NIST inward bowing theory. In any case that still leaves the sides (East & West for WTC1) which were compressed.
  
  

  What you're expecting is the damage progression to take the form of longitudinal waves, whereas a better model would be a Rayleigh wave. Also, the columns preferentially buckle at the top due to coincident damage to the horizontal bracing, whereas deep in the structure the bracing is intact, and the columns resist buckling by this mode until additional force and damage are applied.
  
  Way down in the structure this no longer holds, though. This is why we saw a piece of core columns remain standing briefly after the main collapse. In that case, some columns survived, but all bracing was failed. The surviving columns then collapsed under their own weight.
  
  No mysteries here, just deeper concepts of structural mechanics.

  I think it would have been interesting if the NIST had done some computer visualizations of the collapse, or built some scale models to see if these concepts are applicable in the manner you describe, or at least to validate their theory.
  
  But thanks for the reply, usually (at the physorg forum) the answer is "it is obvious, see Greening, Bazant Zhou/Verdure E1 energy considerations". To me it is quite complex and not obvious at all.
  
  (had to delete the wikipedia links to get the post through)

 

[Belz...]

Regardless, the NIST model is still only a model and the NIST explanation for the collapses of WTC 1 and 2 is only a theory. A theory that conveniently sits well with the Official Story.

So, in order for that theory to be acceptable to you it must NOT support the official story ?

Isn't that a tad biased ?

 

[gumboot]

Hi, welcome to the forums.

I just thought I'd provide my ignorant addition to your post, since the enormous amount of knowledge R.Mackey possesses just isn't quite enough...

But why do the columns fail at or around the levels where the planes crashed? The perimeter and core columns after all are basically vertical structures that span the building height.
To use an analogy, if you push down vertically on a straw, you cannot tell beforehand where it will "fail" or bend.

The overloading on the columns wasn't vertical, it was horizontal. Remember, the exterior columns didn't bow inwards because of weight pressing down on them. They were pulled inwards by the sagging floor trusses.

Consider... take an empty can and jump on it. In this scenario, you're quite right - the can could buckle anywhere. However, take another identical can, and put a dent in one side of the can, then jump on it. The can will, of course, buckle at the spot you put the dent.

This may be at any point along the straw. Why does the overloading of the WTC structure not result in any visible structural failure or damage lower down in the tower also (at "initiation")? Why does the collapse happen "floor by floor" when the support columns are vertical structures that will react as a whole to any overloading?

One thing to remember about the WTC is it comprised of three distinct components. These components were all constructed differently, and their behaviour during collapse was also very distinctly different.

The exterior columns were in fact constructed as panel assemblies, three sections of column side by side, connected by cross beams. These panels were staggered across the face, much as you would stagger bricks on a wall.

The core columns, in contrast, were comprised of long single pieces of steel, bolted one atop the other.

As far as I can tell the attachment points for each section of core column were at the same heights for each column, but they may have been staggered too, I don't know.

Finally, the light weight floor trusses, which kept the building rigid, were bolted between the core columns and exterior panel columns.

During collapse, the exterior column panels peeled away from the building in large sections - sometimes as much as a dozen floors at once. Theres were the parts of the building that almost exclusively caused damage to surrounding buildings.

These column panels had quite a clear outward movement, which implies the collapse force was applied partially laterally as well as vertically. I postulate that this is because the upper section fell inside the exterior panels, and as the mass of disintegrating building fell, it pushed the panels outwards.

At the same time, the floors were contained within the exterior column panels, thus they fell straight down. The downward force against them easily exceeded the bolts holding them to the core columns and exterior column panels, thus they fell downwards. Their is ample eyewitness testimony from survivors beneath the collapsing buildings to suggest that the floors collapsed ahead of the visible exterior collapse, forcing a massive volume of air and building contents with them, like a giant piston.

This failure of the floor trusses would have aided in the exterior column panel failure I described above, as it would strip the exterior panels of their rigidity.

This leaves the core columns.

IMHO the core columns are the most likely to respond as you described. The force acting on the core columns was indeed compression - the very force they were designed to resist.

This is why the cores of the buildings did not fail with the rest of the structure. It is more clear in the collapse of WTC1, but significant sections of the building cores were still standing after the remainder of the structure had collapsed.

I propose that the upper sections fell, and as they hit the lower core columns, they were ripped apart. Imagine a cluster of hard sticks jutting out of the ground. Imagine falling from a height, face-first, into the cluster.

Quite.

That's what I think happened. The core columns ripped the upper section to pieces.

After the exterior column panels had peeled away and the floor contents had piled, all we are left with are the core columns. these remained standing for a short while - a testament to their strength - however they were never intended to stand alone, and they had never been designed to have half a skyscraper smash against them. The connections of these core columns - bolts and welds - then failed. This is why the core columns broke into neat lengths on top of the pile.

The photographs from ground zero show debris lying in a pattern that precisely reflects the collapse sequence I proposed above. We have exterior column panels scattered far and wide, hanging from other buildings, and so forth. We have the actual floor contents, piled tightly near the base of where the towers stood. And we have the massive core columns, in equal length sections, scattered across the top of the pile.

-Gumboot