Tags:
  1. psikeyhackr

    psikeyhackr Member

    I am somewhat curious about the interest in modeling since it has been FIVE YEARS since I posted mine



    and it has been more than TWO YEARS

    http://breakfornews.com/forum/viewtopic.php?p=81614#81614

    since I suggested doing it with a 3D printer.

    Why should amateurs be doing this when engineering schools should have been doing it far better in 2002, though even they did not have 3D printers back then.

    I was never claiming that my washers represented floors. They are simply masses supported by the weakest supports I could come up with but still hold the static load. I have not seen Cole specify the weight of each of his masses or anything about the strength of the loops, just paper and match sticks.

    So is Mick now saying that our engineering schools should do some really good models because now he can hardly say the models are worthless? Of course his separate and independent floors on the opposite sides of his "core" are nonsense. :rolleyes:

    psik
     
    • Agree Agree x 1
    • Disagree Disagree x 1
  2. Mick West

    Mick West Administrator Staff Member

    I'm not saying anything about what engineering schools should do, I'm just trying to build a model that illustrates the likely mode of collapse.

    Could you expand a bit on the "nonsense" aspect of the separate left/right floors? I'd agree it's a problem with the model being largely 2D - however expanding it to 3D would be an order of magnitude harder to model in a way that accurately reflected the way floors would break and fail. My "floors" are essentially infinitely strong. The main thing I'm modeling is the breaking of the connections, not the floors themselves. So if I modeled a "square donut" shaped floor out of single piece of wood, then it going to behave radically differently to a 3" lightweight concrete slab over the multiple floor trusses. You would need to create a complex floor slab that satisfied the supporting of 6x sudden loading, but failed in a reasonably realistic manner. There are many scale problems here.

    I'd argue though that for this simple demonstration it's unnecessary, and the fact that you point it out really seems to indicate that you accept the basic principle that top down collapse of a tall structure is possible, but you are just arguing some specific details about what you think would have happened in the WTC.
     
  3. aka

    aka Member

    I beg to differ. They are an interesting study in "inevitability", completeness of collapse, rate of fall, symmetry and lateral distribution and invite to gedankenexperiment [thought experiment] what happens when you stack >30 of those one-level (3-floor) assemblies upon each other.

    Try to keep up, psik! Bazantian crushing is soooo 13. September 2001. ROOSD (RubeGoldberg Open Office Self Destruction) is all the rage these days.

    Someone will correct me when I try to relay how I understood it: there is an ideal pancake where the top somehow densified and fell on the lower floor slabs [where all momentum is conserved in a perfectly inelastic collision (Dirac function, anyone?) to lose no millimeter nor microsecond, and reach the bottom in time]. It looks like magnets are already too slow, but that's due to Cube-Square Law [Size Matters Law].

    Then, because the core is unbraced, it also comes down -- maybe. Sometimes. Video evidence of a portion of the the swaying, battered cores disappearing in a cloud of dust/smoke/sand proves that's how it happened.
     
    Last edited: Apr 3, 2016
  4. tinkertailor

    tinkertailor Senior Member

    In those two years, 3D printing technology has gotten more and more inexpensive and accessible. Have you been actively designing and planning this 3D printed model in two years? Do you know anyone with one? I'm sure there's someone with a 3D printer in the 9/11 Truth movement that you could talk to. It would be interesting to see what that design looked like and how it worked...
     
  5. aka

    aka Member

    I told you. No reasonable skeptic would deny that progressive collapse à la Ronan Point is a thing. Nobody claims "impossibility". It was a poor strawman from the very beginning.
    What, of a tower that likely arrests collapse or one where collapse progression is guaranteed?
     
  6. Mick West

    Mick West Administrator Staff Member

    It's not a strawman, AE911 claim that progressive TOTAL collapse of a structure into itself is impossible. It's a cornerstone of Richard Gage's (and hence AE911's) case. I'm specifically debunking this.


    I don't think the core came down simply because it was unbraced by the office floors, it suffered an incredible amount of damage as well, with large sections of the core falling essentially inside the core. However that's another thing that's rather difficult to model here.

    I don't think your description on an "ideal" pancake relates to anything. The collapse of the real towers was extraordinarily chaotic, and my model reflects only a simple aspect to that.
     
  7. psikeyhackr

    psikeyhackr Member

    The nitwits at AE911truth either have one or access to one. But they are selling little models to look at for ridiculous prices.

    The model would still have to have the correct distribution of mass as the original building and I still don't see that data anywhere. My idea of a decent model would be each level 2 ft by 2 ft 1.5 inches high for a 100:1 scale model. 3D printers that can do that still aren't cheap and the model would be almost 14 ft tall. That should be doable for an engineering school.

    psik
     
    • Agree Agree x 1
    • Disagree Disagree x 1
  8. aka

    aka Member

    I think it does relate, namely to the comparison between @Oystein's computational model and the real thing. It shows you need 95 perfectly inelastic collisions between the individual floor slabs hovering midair and the dynamically densified debris donut of 15 floors coming from above as a perfectly accreting mass to reach the ground in time, otherwise, you lose tempo. You crack a joint, you lose tempo. You do any damage to the core or perimeter, you lose tempo. The collision between the debris donut and the next floor is a bit elastic, you lose tempo.
    Of course it is difficult to model a complete symmetrical total progressive top-down collapse. Why, then, is there so much opposition when "truthers" say the very same thing to prove that such a collapse is not inevitable, and thus, the fall of the Twins deserves some honest, agnostic, objective scientific inquiry?
     
    • Disagree Disagree x 2
  9. Mick West

    Mick West Administrator Staff Member

    We seem to be drifting off topic here, and revisiting old ground. This thread is for discussing this model and what it does or does not represent.

    Please keep on topic.
     
    • Agree Agree x 2
  10. Oystein

    Oystein Active Member

    No, my spreadsheet model doesn't show what "you need". I merely described my model to explain a bit what it does.

    In the context of this thread and Mick's effort to scale certain properties right, my model shows me that it's ok to have floor heights considerably less than 12 feet, as the average acceleration, resulting from the competing effects of gravity vs. momentum transfer / KE dissipated in inelastic collision, turns out to not be a function of floor height but of floor count.
    I still haven't sat down to grasp this insight analytically - it just falls out of my spreadsheet as a result from fiddling with the input parameter "floor height".

    It is obvious that if and WHEN the initial drop has too little KE to overcome the connection strength of the first floor BECAUSE mass was under 6 floors and drop height so low that not enough PE existed to start with, then the small drop height is a problem, for a drop of the full 12 feet would surely give even a single floor enough KE.
    From this, it seems obvious that IF the KE of the falling mass is not much larger than the energy needed to break the connections, insufficient story height affects significantly.

    I believe that in the real world, the falling tops of the towers had more than 20 times the KE needed to shear the first set of truss seats by the time the first complete floor got in the way (but maybe less than 100x that KE). Therefore, if the model has floor heights of 1 ft or more (factor ~10) (and connection strength scales properly), it's on the safe side. Psyk's suggested story height of just 1.5 inches (factor 100) on the other hand may be too little.



    tl;dr: Mick, carry on with drop heights between floors of 1 foot or more - my simple spreadsheet model suggests that that's probably not a serious scaling error:; but don't go far below 1 ft.
     
    • Agree Agree x 1
  11. Jeffrey Orling

    Jeffrey Orling Active Member

    What do you think the connection yield strength actually is?

    Which is material performs "better" .... a concentrated dynamic load on a slab or the same load applied to the connection?

    With all the talk about connection failures it appears that the slabs survive the dynamic load but the connection fails.... are we talking pancakery?
     
  12. Oystein

    Oystein Active Member

    Jeffrey,
    we know from the forensic record that a large number of truss seats did IN FACT fail in shear from downward loads. So this failure mode is real, and Mick is right to model it.
    IF floor slabs failed somewhere between seats, before the seats failed, then that makes the assemblies weaker, I'd say - less fit for survival. Is that a problem in the context of this model?

    You can drive your objection to its logical conclusion by pointing out that the floor slabs were shattered into millions of pieces. So please make a suggestion to improve Mick's model such that the slabs shatter into many pieces! How would you make them re-assembable? The connection strength between any two pieces of concrete was far far less than the strength of the truss seats - how would you scale this properly - perhaps use spit as glue? Into how many pieces should they shatter? Will 1,000 do? :) And what about the trusses themselves?
     
  13. Jeffrey Orling

    Jeffrey Orling Active Member


    As far as a model goes if the same magnets are used to connect sections of slabs together AND the assembly to the column... the threshold load falling will break the connection whether its mid span of adjacent to a column. If the floor assembly magnets are weaker than the slab to column ones than a uniform drop MAY cause the slab at the columns to lag or re remain cantilevered from the column The the connection to the column is weaker the floors may hold together until more collisions and the mass has increased.

    Admitted this is subtle and difficult to model.

    The connection failures I saw mostly were bent over flanges and bolt withdrawals. If the the angle or the stand offs remained connected then the welds were strong enough to withstand the shear. And this seems the case in most failures. Of course the connection is the welds, bolts, seats, stand offs and the angle.

    In order for the connection to be bent or ripped apart or sheared the floor where it is occurred....has to be stronger than the connection which it failed. No?

    As the floor drop likely was not entire slabs (pancakes) there had to be some way for the slabs to break apart and for the connection to fail. Perhaps the slabs and damaged trusses would create two cantilevers as opposed to simply supports and introduce a moment at the connection???
     
  14. psikeyhackr

    psikeyhackr Member

    There were no sections of slab. The floor outside the core was a single poured concrete slab with a steel mesh inside. The upper "knuckles" of the trusses were imbedded in the concrete. Separate pieces on opposide sides of the core supposedly simulating a single floor are nonsense.

    The magnets are interesting but nothing physically bends or breaks in that model.

    psik
     
  15. Oystein

    Oystein Active Member

    I think that in a very real sense, the breaking of a magnetic bond is a good model of the breaking of the bonds between the iron atoms within the steel.
    In practice, what matters is that the static bond strength scales reasonably and that the force to break that magnetic bond goes along some distance that is short compared to floor height.

    Which induces me to brain-storm... Mick makes sure that the static force is scaled properly - magnets holding under 6 floors that are applies suddenly, but more than 3. What about the energy required to separate the magnets? Does that scale properly? To figure this out, I think we'd need to know what the magnetic force between the magnets is as a function of distance along the path that the magnets slide off each other as the floor fails.
    Is that relevant enough to warrant measuring and crunching some numbers?
     
  16. econ41

    econ41 Active Member

    I need to place these comments on record.

    My concern remains - what is the purpose?

    Have fun making a physical model? - no problem.

    BUT the base realities remain unchanged from when I first identified them many months back.

    The model is one class of the two classes of possible models.

    EITHER:
    A) A demonstration of a mechanism - which it does well within limits. BUT who benefits from it? As a demonstration. Mick, you Oystein, I and many others already understood the mechanism. Otherwise we couldn't model it. Or judge whether is is valid or not. We already know what it demonstrates. And the finesse of details is pursuing a better approximation. To what end?

    OR
    B) Scientifically rigorous modelling to allow quantified measured testing of some aspects. Useful if we do not have access to the real prototype event. But the real mechanism and relevant data is available and can be used directly for any legitimate quantified engineering assessment. And this model no matter how refined will not ever rival direct application of physics to the real, full scale prototype data.

    The objective has always been ambiguous and has drifted. Hence my withdrawal from discussion in these recent stages.

    The genesis was as means of explaining to persons similar to Cube Radio and aka. Those who do not comprehend - or claim they do not comprehend - the actual mechanism.

    I ranked Mick's original Jenga Block model as the best I had seen. This later work extends the scope in terms of more floors and other details. It is a great effort. I would support it for the same sort of reasons as I supported Chris Mohr's work on thermXte - viz it may help a few persons who do not understand. But only those who genuinely do not understand and genuinely want to understand. And they are a small target group.

    But those of us doing it already understand and there are only two groups of persons we see on forums who may benefit - who don't understand or pretend to not understand.

    The first legitimate group includes Cube Radio, aka and those like psikeyhackr who have either no understanding of mechanism OR a false understanding. And all three of those have shown repeatedly a reluctance to understand the reality whether explained in pictures, word or physical models.

    The other group - rampant on another forum - includes those who are dedicated to remaining unclear for reasons of personality disagreement. No point modelling for them - deal with the real issues of group psychology and cop the occasional flack as I do.

    So my concerns once again placed on the record.

    And it is still a great modelling effort.
     
    Last edited: Apr 6, 2016
  17. econ41

    econ41 Active Member

    This is where I usually part company with several of my respected friends. Notably OWE/"Kat Dorman" with whom I have "tag teamed" on some serious technical issues over the years. He from dedicated pure science research perspective and me - the pragmatic focus on reality. Similarly with yourself Oystein. And you together with OWE/KD are in that central small group of colleagues who are top of my list for respect.

    So "Why do you want to measure or crunch numbers?"

    The parting of the ways usually because my focus remains on explaining the actual WTC collapses of 9/11 - I am interested in pursuit of engineering science aspects which are necessary to the goal of explain WTC 9/11 collapses. For the purposes of extending my own understanding of the events so that I can explain them to other persons.

    I have limited interest in the pursuit of loosely related or unrelated science. Especially when that pursuit derails, obscures or confuses discussion focussed on explanation of WTC real event mechanisms.
     
    Last edited: Apr 6, 2016
  18. aka

    aka Member

    Ha! That's why I believe in morphogenetic fields:

    just today I had the idea (yesterday I played with Algodoo all day long) that Mick could fine-tune the energy by adjusting the magnets accordingly - either by seperating them with varying thicknesses of paper, or by pre-adjusting (as much as possible) the area where the magnet is in contact with the metal, if ever the rate of fall is an issue. Would be a lot of additional fiddling, but doable.

    You know, like

    |
    |
    |)
    |)
    |)[]
    | [](|°°°°°°°°°°°° °
    | . (|____________ __ _
    |
    |
    |



    But the rate of fall shouldn't be an issue yet.
     
    Last edited: Apr 6, 2016
  19. Mick West

    Mick West Administrator Staff Member

    The magnetic force isn't really the force holding up the floors, it's the static friction between the magnets and the steel plates. This friction is a function of the magnetic force. The magnet provides the "normal force" - i.e. the force normal to (at right angles to) the surfaces. This is also the tension force keeping the wall stable, and essentially the moment resisting forces.
     
    • Like Like x 1
    • Agree Agree x 1
  20. Oystein

    Oystein Active Member

    oz,
    even for a demonstration model, we need to make sure that the model is a valid representation of the original, and proper scale is key to making it valid.
    No its not possible, or at least not practical, to scale every aspect of the model correctly to validly demonstrate any behaviour. We need to draw a line.
    What does Mick try to demonstrate?
    -> The cascading failure of the floor-to-vertical-elements connecions
    -> Perhaps more

    Several truther models exist - psikey's, Jon Cole's, ...
    These models fail.
    One reason is that they try to model the wrong mechanism.
    Another reason is that their models do not scale properly - not even to validly demonstrate the wrong mechanism.
    And there are probably more reasons, but those are the big ones.
    As so often with the more elaborate truther efforts ("nano-thermite"; "NoC witnesses"; "freefall"; "molten metal"), these models are cascading failures. They don't merely fail out of the box by racing in the wrong direction on a non-existing track, they continue to fail as they move along their fantasy track.
    Back to the big ones:
    Mick is off in the right direction.
    If we can answer the question if his model scales properly, or which aspects he scales properly, we pre-empt quid-pro-quo objections about scale - and at the same time demonstrate how to think about scale.

    I think this is for the benefit of those non-truthers who are confused by truther models and arguments about the failures: Demonstration is good, but valid demonstration even better.
    If the occasional genuine truther who mit drop in from time to time benefits, then that's a bonus.

    But mostly it's for our own benefit.
    I, for example became aware of / understood two things recently by discussing this model, and the debate over Cole's model over at ISF:
    1. When the first impacted floor fails before downward motion is arrested (and mass shed per floor is not more than mass added by taking stationary floor for the ride), then collapse progression must accelerate all the way down. This is kinda obvious when you think about it, but I wasn't sufficiently aware of this to avoid getting foooled by faulty intuition
    2. Any such model must not have the inital drop significantly larger than subsequent drops, or else there is a possibility for arrest after some number of floors
     
    • Like Like x 1
  21. Jeffrey Orling

    Jeffrey Orling Active Member

    Oystein,

    With all due respect... why are you addressing Ozzie in the previous response?

    Mick has made a model which demonstrates that with a threshold mass... equal to the likely number of dropping floors in the twin towers... the collapse does not arrest and the resistance is not apparent to the naked eye.

    He has simulated the real world in an experiment in his garage. He has scaled as much as he could given the fact that mechanical interactions cannot be scaled. His model demonstrates what he wanted.

    The model CAN be refined to demonstrate other aspects of the cascading collapse. For example if the floors of similar mass can be made from multiple joined pieces (simulated the concrete bonds for example) the collapse should reveal a collapse does not require pancakes and that it is not ONLY the connection to the axial structure that has failed.

    Frankly your comment was a waste of time. This is not about Cole's or anyone else's models and why they failed. THAT was inherent in how Mick designed his experiment.

    If you want to have a discussion econ41 send him a PM or an email.
     
    Last edited: Apr 7, 2016
  22. aka

    aka Member

    Not yet, the core is still standing up.
     
  23. econ41

    econ41 Active Member

    Edited
     
    Last edited: Apr 7, 2016
  24. Mick West

    Mick West Administrator Staff Member

    I think other issues of scale are quite reasonable topics of discussion regarding my model. A huge part of the problem with AE911's argument from incredulity is a misunderstanding of scale factors. So anything that helps us either understand or explain scale is useful.

    But I fear the few posts above are veering off into some philosophical/epistemological discussion, and I'd like to try to keep things practical.
     
  25. Mick West

    Mick West Administrator Staff Member

    I'm going to make a less monolithic core later today which will collapse, but it's not really going to model damage to the interior connections of the core.
     
    • Like Like x 1
  26. aka

    aka Member

    Please include a lateral stability test as in some of the previous videos (small nudge).
     
  27. Oystein

    Oystein Active Member

    Jeffrey,
    "He has simulated the real world in an experiment in his garage. He has scaled as much as he could given the fact that mechanical interactions cannot be scaled. His model demonstrates what he wanted."
    You claim this, and insinuate that all scaling issues are sufficiently accounted for to make this a valid demonstration, but remember that truthers believe their models are valid demonstrations, too, with scaling properly taken care of - which, in Cole's case, means that Cole believes scale is actually not an issue he needs to account for; look what Cole writes:
    Amazing, huh?
    I think we ought not make the same mistake of proclaiming that we need not consider (more) scaling issues. I argue that we should give all scaling issues due consideration, so we know why we don't scale what we don't scale.

    Hence I suggested thinking about the energy dissipation caused by overcoming the magnetic connections: I am not saying this is relevant for Mick's purposes and must be scaled right, and I suspect that it probably does already scale okay, but think about we should.
    The energy dissipated is the area under a stress-strain diagram (?). A steel truss seat that bends and then has the bold torn out behaves different from a magnet that is pulled along a steel plate before it comes undone. Do these differences amount to more than, say, an order of magnitude? Then perhaps Mick's floors dissipate way too little (or too much?) energy to be a fair demonstration of "collapse accelerates".
    (Plus, there's the problem that the real floor slabs shatter and dissipate energy in inelastic collision, and I still feel somewhat uneasy about the relatively more elastic wood floors of the model)

    I am lacking the theoretical and technical skills to tell you how do these considerations (this would require getting some empirical numbers and then doing some math), and others apparently lack the interest.


    Mick,
    since you won't be modelling the core in its 3D complexity, I don't think it's wise to fudge with it just to get something similar looking. That smacks of "faking" it.
    Or you ought to preface any presentation of the demonstration with the disclaimer that the core is not a model of the real thing and merely an illustration (rather than a demonstration) of the real mechanisms. Focus remains on floor failures.
     
  28. Jeffrey Orling

    Jeffrey Orling Active Member

    The issue with scaling physical models of mechanism interactions... is that the performance of materials... chemical bonds is not scalable.

    You do not have to model what happens to a beam which is bolted with a knife connection to a column... this is settled science... just as it is how much force it takes to shatter various types and thickness of concrete.

    So the mechanics of the collapse are in a sense trivial and settled science.

    Each floor, beam, connection is designed to perform under certain load conditions in a building. And this INCLUDES a reasonable and afforbable margin or error call it reserve strength of safety factor. When the real world conditions exceed the design specs INCLUDING the actual strength of the material in shear, compression, bending and on... the material fails.

    The WTC collapses were MECHANICAL failures when parts of the structure each experienced conditions/loads outside their "ratings". So a twin tower floor may have had a 52#/SF design spec but it could obviously carry more but up to a limit... it would sag and something would give... the lower truss chord, the concrete, the end condition and so forth. If this failure was a super imposed load... all similar/identical floors and assemblies would fail as well. Trivial. No proof necessary.

    If you want to test the mechanical properties of the systems.... you do it full size..

    If you want to demonstrate that in a floor fails from a superimposed load and the ones below it will.... Mick's model does this/. It doesn't matter if he simulates the connection with magnets or silly putty. He's got a model which visually relates to the real world.

    Newton's laws apply and this does not have to be demonstrated or invoked. It's a waste of time. Engineering IS APPLIED PHYSICS... using the properties of the materials.
     
  29. Svartbjørn

    Svartbjørn Senior Member

    Wasnt this basically what happened to the Sampoong Department building in Seoul, Jeff? The weight per floor well exceeded their design specs, among other things like shoddy workmanship, which then resulted in the collapse of the South Tower in a similar "pancaking" event as 9/11?
     
  30. Mick West

    Mick West Administrator Staff Member

    I partially agree, however what I'm ultimately demonstrating here is that a tall stable structure can fully collapse (at a rapid rate) from a partial failure near the top. Basically a refutation of Gage's cardboard boxes demonstration. Hence it's a better demonstration if it actually does collapse, rather than just strip the sides off.

    I'll perform a stability test first to demonstrate it can withstand occupants walking about, winds, earthquakes, and planes hitting it (to scale).

    In fact, I'll go do that right now.
     
    • Like Like x 1
  31. Mick West

    Mick West Administrator Staff Member

    A different approach to collapse. No drop involved, just columns on the top part failing in a way that they become non-aligned.

    [​IMG]
     
    • Like Like x 2
  32. Mick West

    Mick West Administrator Staff Member

    Collapse was only slightly slower than free-fall

    20160407-145236-ozjkt.

    See attached .mov file. I'll upload a longer clip to YouTube later with stability tests. Might be tomorrow.
     
    • Like Like x 1
  33. Mick West

    Mick West Administrator Staff Member

    Clip:
     

    Attached Files:

  34. Jeffrey Orling

    Jeffrey Orling Active Member

    So the misaligned dropping columns from X floors will kick off the floor collapse as well!
     
  35. Mick West

    Mick West Administrator Staff Member

    And in this example they only drop half a floor.
    20160407-151908-nn5dm.
     
  36. Oystein

    Oystein Active Member

    Excellent!
    You'd not need any drop height at all to start the collapse with walls impacting floor, as the static weight on the wall exceeds the floor connection capacity (provided you have a few stories above)
     
  37. Mick West

    Mick West Administrator Staff Member

    More details, showing strength and stability tests and the final stages of construction.

     
    • Like Like x 3
    • Useful Useful x 1
  38. Nada Truther

    Nada Truther Active Member

    The model (especially in slo-mo) also replicates the "boom-boom-boom" that people heard that some think were explosions from explosives. I didn't see any in your model; so I can only assume that you didn't use any. Well done.
     
    • Funny Funny x 1
  39. Spectrar Ghost

    Spectrar Ghost Senior Member

    While this last collapse is impressive, I'm concerned by the offset initiation. It concentrates all the force on the base of the columns, very near the magnets, and all across the width of the floor. This effectively slices the floors away from the uprights instead of pancaking them. While we can assume that columns would have pierced the lower floors in the towers, it would not have been able to simply slice them from their seats across an entire edge like that. The earlier pancaking action more closely approximates the actual event, IMO.
     
    • Agree Agree x 1
  40. econ41

    econ41 Active Member

    1 Yes - as "illustrating-the-progressive-collapse" - AKA a demonstration of the progression stage once it became a stable and continuing process.

    2 There are two issues arising which underpin your other comments.
    (a) The focus has shifted from "progression" stage to "initiation" stage and the transition from "initiation" to "progression". The shift of scope raises some significant issues about comprehension of the mechanism of those sub-stages. Your issues of concern also go to "transition"; AND
    (b) The actual technical issues of offset and the several other details you raise - which have to be explained within the appropriate part of the sequence where they arise. Which for most is NOT the "progression stage" that the model originally set out to model.

    To explain where those several issues "fit" in the real event sequence we need to recognise the stages which occurred - at least sufficient for current needs for clear discussion. There "sub-stages" should suffice:
    (A) The stage of progressing cascade failures which led to tilting of the Top Block(s);
    (B) The START of "bodily descent of the Top Block at which point all columns were failed and the ends either bypassing or irreversibly committed to bypassing. At that point the main portions of the Top Block(s) were still structurally integral - damage and failure being in the impact, fire and cascade failure zone;
    (C) As the Top Block "fell" it started concurrent shear down and shear up with the result that for both towers both the Top Block and the corresponding top portion of the Lower Tower went into mutual destruction.
    (D) THEN a stage of stable progression for most of the distance down to near ground level.

    From the start of this exercise I certainly took the scenario being modelled as being D the established progression mechanism. NOT the much more complicated initiation and transition mechanisms which are now being considered.

    So - against that sequenced scenario some explanations of your points. For simplicity I'll continue presenting as "bare assertions":

    2 and 3
    -- First recognise that we are talking about sub-stage "C".

    -- "Pancaking" and floor on floor or debris loading were not the primary mechanisms at that time - they became the mechanisms at sub-stage D - concentrated "knife edge loading" from the falling Top Block perimeter impacting the floors below and the converse effect of "rising" perimeter of Lower Tower impacting the underside of the floors above started the floor shear of process. BEFORE there was sufficient debris for debris to be the major factor.
    -- Yes Mick's model has that effect. Reality was that (IMO most) of the perimeters did impact close to the columns BUT it was closer to mid span for the WTC2 collapse - the two sides affected by tilt and for WTC 1 some undefined distance for the two sides affected by tilt but to a lesser extent that WTC2
    -- If the intention is to model both the in initiation AND transition mechanisms then we need to think a lot more about the issues you raise.

    -- For what I understood to be the original objective it matters not how it is started - the demonstration is good enough for purpose from the second impacted floor down. Subject to all the previously expressed concerns about "how close to reality" is the model intended to achieve.

    4 -- That is what happened in the real event - ends of perimeter column sheets impacted - effectively across the width of the floor. So - is the model now intended to cover this stage?

    5 -- "Pancaking" was not the dominant mechanism at this stage. Slicing of the connections was. And it would occur even though for 2 (WTC2
    "tilt affected sides") or 4 (Both WTC1 and WTC2 "tilt affected sides") of the eight sides were further from the columns

    6 -- "piecing" is doubtful under any circumstance - and only relevant to sub-stages B and C - by sub-stage D which is what the model so far demonstrates well the Top Block is disintegrated and column piecing becomes moot.

    7 -- Take it as "not so" - there is a more subtle aspect of partial truth we can explore in an appropriate thread if there is any interest.

    8 -- Not so - for reasons already outlined. "Pancaking" is secondary at best at the stage being considered.