Merged Applicability of Bazant's model to the real world

[carlitos]

Thanks ozeco41, for the detailed explanation.

Being a bit of a simpleton, let me push my luck with a follow up. I understand that it's likely the columns missed each other as you said, but is what Tony is saying axiomatic in engineering terms?

1 - That is, is there always a jolt when a dynamic load is applied?
1a - Is that jolt always discernable?

1a seems rather unlikely, in a bowling ball / dixie cup type scenario. Or even a human being / soda can one.

If so, it seems like "discernable" is the problem, and all we have to prove / disprove it are a bunch of videos that weren't designed to measure anything at all, but rather to film a big fire. (femr2's analysis notwithstanding)

I'm guessing that some of this is why the "Missing Jolt" paper isn't in the ASCE Journal of Engineering Mechanics?


* disclaimer - I am not comparing any portion of the WTC 1, 2, or 7 to a dixie cup.

 

[pgimeno]

There are other factors of course, but I think it's clear that is one of them.

For reference, *mini-jolts* have, for all intents and purposes, already been identified...

Thanks, I know, but I also think that Tony's question needs an answer (what could cause a jolt after a 3 ft fall, then after a ~7.2 ft fall, then after a ~19 ft fall...)

I'd accept dampening as an answer.

 

[femr2]

Thanks, I know, but I also think that Tony's question needs an answer (what could cause a jolt after a 3 ft fall, then after a ~7.2 ft fall, then after a ~19 ft fall...)

I'd accept dampening as an answer.

Speculation, as they could be caused by any number of different elements impacting, but I'd hazard a guess that, given that it's a NW corner trace rather than antenna or south side feature, and that south side collisions would occur before the same members in the north side collided, that the first one may be the initial south side floorpan collision. Too much deformation of upper block after that to speculate even further at the mo'.

 

[ozeco41]

Thanks ozeco41, for the detailed explanation.

Being a bit of a simpleton, let me push my luck with a follow up. I understand that it's likely the columns missed each other as you said, but is what Tony is saying axiomatic in engineering terms? ...

Most of Tony's claims have a core factor which is a "truism" - that is "a claim that is so obvious or self-evident as to be hardly worth mentioning," (Wikipedia definition) So each claim looks to be true BUT Tony then misapplies the claim either explicitly or implicitly. This is a stock standard bit of truther trickery - you will notice that I challenged Tony on use of truther tricks a few posts back. He denied it but his denial is not worth the bandwidth wasted posting it and I did not bother to respond.

So let's look at your next questions:

1 - That is, is there always a jolt when a dynamic load is applied?
1a - Is that jolt always discernable?...

In brief the answer to "1" is "yes". The answer to 1a is "Theoretically 'Yes'". The practical thing being that, if you have only a little jolt it may be too small to measure.

Let me explain further. First the terminology you use is a little imprecise - some of it inherited from Tony's need to explain a back to front situation. Let me put it in my terms and see if that helps.

To "jolt" something means to "to jar with a quick or hard blow" or "to cause to move with a sudden jerky motion" (Adapted from Merriam Webster online dictionary)

So a jolt is both the applied dynamic load as in "jar with a quick or hard blow" AND it is the result of that blow which is "a sudden jerky motion".

The basic physics is Newton's First Law of Motion" - originally stated as "Every body persists in its state of being at rest or of moving uniformly straight forward, except insofar as it is compelled to change its state by force impressed."

Now with WTC Tony is looking at the situation where the "top block" is falling. The "jolt" he is looking for is the "jar with a quick or hard blow" which should happen when the top block columns hit firmly on the lower tower columns - that is the two separated halves of column meet. The jolt is also the change in velocity - the "sudden jerky motion" which the "quick hard blow" would cause. So far all is correct.

(There is a complicating factor in that Tony is working in terms of accelerations not velocities but the difference is of no consequence for sake of this explanation and any explanation as to why Tony is misapplying the principles. The difference has confused a number of people several times over the threads of this forum but forget it for now)

So the answer to your Q1 is "Yes" and the answer to your Q1a is "it will always be discernible provided you can measure small values."

Look at the excellent work that femr2 and his colleagues do on measurement. They can detect "mini jolts" whist Tony was looking for a very big jolt.

The error in Tony's work is not in the base physics of jolts. Rather it lies in his refusal to recognise that the top block falling on lower tower was not a mechanism that would cause a "very big jolt".

...1a seems rather unlikely, in a bowling ball / dixie cup type scenario. Or even a human being / soda can one...

You are half way to the full explanation. Both those analogies recognise that, with a big mass/weight and a flimsy support, the resistance would be so small compared to the falling weight that the "jolt" could be too small to detect. So you have "half the story right".

The other half is that as the WTC top block falls on the lower tower it does not land in one contact. Unlike both the bowling ball/dixie cup and human/soda can analogies both of which make one single contact of the full falling item on the object beneath.

The first contact WTC top block with lower tower will be one small part - beam or column - not the whole block BUT that first beam or column to contact would have the whole falling weight to land on it. One beam resisting the whole weight produces a very small - possibly unmeasurable jolt.

So look at my "paint brush" analogy:

I cannot think of a perfect analogy..

However. Think of a small paint brush. Cut all the bristles but one leaving the one protruding. Then drop the brush on that one bristle. Alternatively try to push something with that one bristle.

Now the situation is a lot more complicated that I have explained so far. There would be many different contacts following closely in time. Some may coincide most will occur at different times but the time intervals could be milliseconds. Try a paint brush with all bristles cut short except 6 or 8. Those 6 or 8 cut to different lengths. Drop the paint brush bristles down. The longest bristle hits first. Too weak to produce a significant jolt. almost no jolt at all. Then the second longest lands - still no jolt...Then the third...the fourth...the fifth.

That in a very simple and very much simplified model is how the top block of WTC landed on the lower tower.

I will leave that bit of explanation there- I can take it into more detail if needed.

...If so, it seems like "discernable" is the problem, and all we have to prove / disprove it are a bunch of videos that weren't designed to measure anything at all, but rather to film a big fire. (femr2's analysis notwithstanding)..

Yes

...I'm guessing that some of this is why the "Missing Jolt" paper isn't in the ASCE Journal of Engineering Mechanics?...

I would phrase it differently as "I'm guessing that this is some of why the "Missing Jolt" paper isn't in...."

...* disclaimer - I am not comparing any portion of the WTC 1, 2, or 7 to a dixie cup.

..nor am I comparing WTC to a paint brush -- but model and analogies do have their uses.

 

[W.D.Clinger]

In brief the answer to "1" is "yes". The answer to 1a is "Theoretically 'Yes'". The practical thing being that, if you have only a little jolt it may be too small to measure.

For more on the Chandler/MacQueen/Szamboti fallacy, see

http://www.internationalskeptics.com/forums/showpost.php?p=6092716&postcount=62
http://www.internationalskeptics.com/forums/showpost.php?p=6094041&postcount=79

Especially the second of those two.

 

[ergo]

The science ignorance, or is it anti-science? on this forum is shocking.

He relies on the fact that the top block started to fall and therefore was moving. From there he wrongly applies two assumptions of Bazant and Zhou:

1. That the falling columns of the top block would land on their corresponding column parts in the lower tower; AND
2. The resistance presented by those lower parts of columns would cause a "jolt" which would be discernible as deceleration of the top block.

Since there was no jolt he makes a massive leap of faith to "no jolt means unnatural causes".

The more appropriate step is to read "no jolt means column ends missing each other".

Even if column ends are missing each other initially, eventually the collision interface will meet intact building structure and must produce a deceleration, in accordance with the physical phenomenon known as Newton's Third Law. This applies to all materials in our physical universe, whether they are an assemblage of different things, or whether they are more rigid structures.

Since it is obvious that two things are occurring:

• The top block and lower tower are both elastic flexing structures where columns landing on or near columns can flex sufficiently to bypass; AND
• The top block moving proves that the majority of column ends are not "end for end" - column ends failed by buckling simply will not stay in end for end contact the deformed surfaces will automatically cause the falling end of column to slip off the deformed end of the lower column.

Those are the key facts which Tony has to ignore to "prove" that his "Missing jolt" means demolition.

I don't see that it matters if the building components are flexible or not. If you have a theory that states that the upper portion of something is descending through the lower portion of same construction, you have to account for why the lower portion produces virtually no resistance. Even a "falling" block of storeys (which, actually, can't even happen according to the official theory, and to reality) must still meet resistance in a structure it is falling through. Four seconds of resistance, or even 10 seconds of resistance is not plausible. Not even possible, in our physical universe. If you disagree please cite the physical law which supports this "crush-down" notion. I notice none of you have yet done this.

 

[ergo]

Sorry to confuse you, I meant top-part-on-floor impact. The first was 95th floor, and then there'll be about 94 more impacts.

Going bump, bump, bump each time, as they meet resistance. That is if we could even realistically posit that a top block of storeys (that have burned for an hour or more) will remain intact through these "impacts" all the way through 95 floors.

You do realize how ridiculous this theory is?

A "jolt" as in "change of acceleration"? Yes. But a very small one. We actually find that acceleration changed all the time. Just not by as much as Tony would like to see. Which ich because the top assembly is elastic, and doesn't hit the structural elements below all at once.

If the top assembly is "elastic" (and I don't even know what you mean by this) then so is the bottom.

after very few floors (about 2), the velocity of the rubble layer is much closer to that of the top part than to that of the bottom part.

There is no "velocity" after the first impact. All kinetic energy in such a model would be redirected both upward and downward, resulting in destruction of whatever floors are still colliding.

That is precisely what Bazant and Zhou have shown. I know it is counter-intuitive. But imagine yourself standing on a fat slab of concrete, falling down, and crushing through stuff. Imagine your worst enemy on the other side of the slab. You'll understand that you'll be much better off then he is.

I wouldn't feel so great when my fat slab of concrete hits a lower fat slab of concrete (presuming it misses all the columns and other building components) and cracks into several pieces, losing its kinetic energy in that fracturing.

 

[beachnut]

...
You do realize how ridiculous this theory is?
...

There is no "velocity" after the first impact. All kinetic energy in such a model would be redirected both upward and downward, resulting in destruction of whatever floors are still colliding.


I wouldn't feel so great when my fat slab of concrete hits a lower fat slab of concrete (presuming it misses all the columns and other building components) and cracks into several pieces, losing its kinetic energy in that fracturing.

LOL, yes, your theory of CD is nonsense.

No velocity!? Pure moronic physics failure. Good for you, ignore physics and post delusions.

Fat slab? 4 inches of light weight concrete.

 

[W.D.Clinger]

The science ignorance, or is it anti-science? on this forum is shocking.

ergo provides an excellent example of that ignorance:

If the top assembly is "elastic" (and I don't even know what you mean by this) then so is the bottom.

There is no "velocity" after the first impact. All kinetic energy in such a model would be redirected both upward and downward, resulting in destruction of whatever floors are still colliding.

I wouldn't feel so great when my fat slab of concrete hits a lower fat slab of concrete (presuming it misses all the columns and other building components) and cracks into several pieces, losing its kinetic energy in that fracturing.

FYI: Elastic means kinetic energy is conserved. Inelastic means kinetic energy is not conserved. From what you have said above, you are saying the collisions were inelastic. Fine. We can still use conservation of momentum to calcululate the expected loss of velocity in a perfectly inelastic collision.

 

[ozeco41]

...Even if column ends are missing each other initially, eventually the collision interface will meet intact building structure and must produce a deceleration,...

Correct.

... in accordance with the physical phenomenon known as Newton's Third Law. This applies to all materials in our physical universe, whether they are an assemblage of different things, or whether they are more rigid structures....

Yes.

...I don't see that it matters if the building components are flexible or not. If you have a theory that states that the upper portion of something is descending through the lower portion of same construction, you have to account for why the lower portion produces virtually no resistance....

You have lost the context of my statements. That context is the initial downwards movement of the top block up to the point where Tony claims there should be a "big jolt" (my words). Tony insists that there must be column on column axial contact to cause a "big jolt" at the end of the first discrete bit of top block downwards movement. I was addressing that bit of false logic. It matters at that point that the building is flexible because that flexibility allows the column ends to bypass. To be brutally open with the logic for both sides of the "demolition - no demolition" debate there are three reasons why there would be no "big jolt";

1. A bit of column was removed by Aircraft Impact;
2. A bit of column was removed by demolition; OR
3. The two parts, top and bottom, of a buckled column are sliding past each other therefore no big resistance to cause a "big jolt" of ends of the columns

Your post refers to a later stage in the collapse which is not included in my posts so far.

 

[ergo]

Tony insists that there must be column on column axial contact to cause a "big jolt" at the end of the first discrete bit of top block downwards movement.

I believe Tony is saying that there must be a jolt in order to deliver the impact required to initiate failure in this model.

I was addressing that bit of false logic. It matters at that point that the building is flexible because that flexibility allows the column ends to bypass. To be brutally open with the logic for both sides of the "demolition - no demolition" debate there are three reasons why there would be no "big jolt";

1. A bit of column was removed by Aircraft Impact;
2. A bit of column was removed by demolition; OR
3. The two parts, top and bottom, of a buckled column are sliding past each other therefore no big resistance to cause a "big jolt" of ends of the columns

But even if the columns are missing each other, the floors then are impacting each other - crunch - and then there are a whole new set of intact columns on the other sides of both of those floors.

 

[ozeco41]

For more on the Chandler/MacQueen/Szamboti fallacy, see

http://www.internationalskeptics.com/forums/showpost.php?p=6092716&postcount=62
http://www.internationalskeptics.com/forums/showpost.php?p=6094041&postcount=79

Especially the second of those two.

Thanks for the reference. There are at least several ways of analysing WTC collapses.

I put them in three broad categories:

1. Broad upper or lower bounded approaches using massively simplifying assumptions. Bazant and Zhou is a valid example of this - discussed as an aspect of the OP early in this thread. (And more recent discussion , yet again, of how Tony Sz. got the assumptions wrong way round to support his "missing Jolt" );
2. Detailed calculations and or metrication. With finite element analysis being one example from this end of the spectrum. I seriously doubt that a detailed analysis could ever be achieved for the WTC TWin Towers initial collapses. The necessary details are simply not available - broad mechanisms can be postulated, some proved by visual evidence, but no complter member by member analysis; AND
3. The middle ground of noting observable mechanisms, nominating likely unobservable ones then adding the lot up in a ball park quantification having in mind upper and lower bound probabilities.

I prefer "3" for my explanations of WTC Twin Towers Collapses for reasons I have explained several times but can outline if there is any interest. But see my next comment.

ergo ...FYI: Elastic means kinetic energy is conserved. Inelastic means kinetic energy is not conserved. From what you have said above, you are saying the collisions were inelastic. Fine. We can still use conservation of momentum to calcululate the expected loss of velocity in a perfectly inelastic collision.

And if you can tell me how to apply that to the multiple combinations of contacts between column and/or beam and/or floor slab and/or accumulating rubble and/or whatever else which was the transition from the initial collapse to the global collapse phase for the Twin Towers. - Well you are a better engineering forensic analyst than I am.

 

[ergo]

FYI: Elastic means kinetic energy is conserved. Inelastic means kinetic energy is not conserved. From what you have said above, you are saying the collisions were inelastic. Fine. We can still use conservation of momentum to calcululate the expected loss of velocity in a perfectly inelastic collision.

I wasn't sure that this is what Ozeco was meaning, since the argument seems to be that this was an inelastic collision.

 

[Newtons Bit]

If you have a theory that states that the upper portion of something is descending through the lower portion of same construction, you have to account for why the lower portion produces virtually no resistance.

The only thing capable of supporting the weight of the upper block is the fully intact and braced columns of the lower block. When the collapse starts, the connection between the columns of the upper block and lower block has severed. The columns of the upper block fall, mostly, onto the floors of the lower block. The floors can't support it and they collapse.

There's also the common misconception by "truthers" that the columns of the upper block should fall aligned with what's left of the columns of the upper block, never mind that the columns on both ends have been horribly mangled during the collapse initiation event. But even if that were true, the columns would still not be able to support each other if they were just 1" off-center. The perimeter columns at the floors where the collapse started were about 14" x 14" x 5/16" tubes. An offset impact would mean that two 5/16"x5/16" area spots on both the bottom and top column come into contact. This is roughly 1% of the total area of the column. What proceeds from here would be something akin to a hot knife through butter. Sure, there's a block of butter on both sides, but it's not doing anything to resist the knife.

 

[W.D.Clinger]

And if you can tell me how to apply that to the multiple combinations of contacts between column and/or beam and/or floor slab and/or accumulating rubble and/or whatever else which was the transition from the initial collapse to the global collapse phase for the Twin Towers. - Well you are a better engineering forensic analyst than I am.

No, I'm sure you're the better engineering forensic analyst. My "perfectly inelastic" is an example of what you referred to as a "massively simplifying" assumption, but it might improve upon ergo's baseless speculation.

 

[ozeco41]

I believe Tony is saying that there must be a jolt in order to deliver the impact required to initiate failure in this model...

Take care with looseness of terminology and sequence/timing. Tony's jolt comes after the initial collapse has started. He presumes that "unnatural methods" (his term) have removed bits of columns and is ambiguous as to whether that is "initial collapse" or some transition to the later global collapse. BUT he does not claim that a jolt should start the whole show - or that is is "required to initiate failure in this model"

...But even if the columns are missing each other, the floors then are impacting each other - crunch - and then there are a whole new set of intact columns on the other sides of both of those floors.

True but that is later - it is not the "brief moment in time" which is under discussion. I can give the full length comprehensive explanation but that is not the current discussion.

That full length explanation has a number of identifiable stages. The ones surrounding where we are at present are, in sequence:

• Plane hits building. Damage done. Fires start;
• Fires not fought, more damage accumulates;
• (For the pro demolition people) Charges fired (This time/sequence point in the process still exist for those who say "no charges fired")
• Top block starts moving downwards;
• (Tony's jolt fits in here);
• The initial collapse transitions into global collapse;
• Global collapse pancakes floors all way to near ground;
• Remnant of core remains standing then collapses;
• Aftermath events as needed.

My discussion is about D and E. Your comments about "the floors then are impacting each other - crunch - and then there are a whole new set........" fit into F and progress into G

 

[ozeco41]

No, I'm sure you're the better engineering forensic analyst. My "perfectly inelastic" is an example of what you referred to as a "massively simplifying" assumption, but it might improve upon ergo's baseless speculation.

 

[ozeco41]

I wasn't sure that this is what Ozeco was meaning, since the argument seems to be that this was an inelastic collision.

I was not specifically saying either. This is why.

The concepts of elastic and inelastic collisions are most applicable to collisions between single homogeneous bodies. Two steel balls or pool/snooker balls being examples of elastic and two lumps of plasticine/playdoh example of inelastic.

The reason that these ideas do not fir well with the WTC collapses are mainly due to there being many elements of the contacting parts and each element on element contact will have two components. At the micro local level the bounce of the lump of beam on the lump of column or whatever will probably be elastic in the classic sense of local compression of the elements which then rebounds. BUT at a broader level a beam on beam contact would cause each beam to bend - initially elastically - and the bend would rebound. Then, going even broader, each beam would tend to act on the other beams it is joined to causing that part of the structure to act - initially elastically.

Take all the permutations and combinations and you have one unholy unexplainable mess which defies definition as an elastic entity.

So that is what I was not meaning.

When I spoke of "flexibility" I was meaning that, in the overall set-up of top block on lower tower contact, there would easily be enough "give" in the whole structure to allow any column to bend away from axial contact with its mate.

 

[carlitos]

Thanks again. Very helpful.

 

[ozeco41]

Thanks again. Very helpful.