Hardfire: Physics of 9/11

[ozeco41]

(b) If the building mass didn't move downwards, it's still there. You might want to go to New York and take a quick look. If you can see the Twin Towers, then the above paragraph makes sense. If you can't...

Dave

One of my favourite responses to those claims which lead to the absurd conclusion.

You beat me to it - I yield to your seniority on this forum

Eric

 

[Heiwa]

...well if we don't all agree on that bit there is no point discussing - some of us are in cloud cuckoo land. YES the top bit fell and YES there was a global collapse.

...and if that is your hypothesis it conflicts with the drawings series. I'll stick with "it fell" rather than "it was blown apart and didn't fall on the lower bit - which BTW is the implicit position you take most of the time. Nothing like being consistent is there?
... you are respoinding to my post and I am neither for or against NIST and I care not whether NIST is right or wrong.

HOWEVER: ....as I have said the "collapse which actually happened" was not A "solid mass" which was "contacting [A single] spring". I explain what "actually happened" I am not interested in rebutting your derail into a fantasy event unrelated to the WTC Collapse.

if you take wrong steps to arrive at false conclusions why should I follow. "Arrest would soon follow" BUT it didn't - the global collapse continued inevitably.

...actually I can see that is true BUT the contact was not between "weak above" striking "strong below". It was "heavy and moving above" striking the weakest links below - the floor joist connections to the columns. Once again you switch horses in mid stream. You switch from discussing the point I make which you purport to address and focus on your own fantasy which is not analogous to the WTC 9/11 collapse.

AND for double measure note it was "heavy and moving" from above WHETHER OR NOT it was still one piece strong OR already broken into components - which incidentally is why MOST of the "crush up crush down" stuff is nonsense resembling the faeces of the male bovine.

... and, once again, my objective is to explain the collapse not to support OR rebut NIST. And that applies whether NIST is right or wrong.

Please, visit the Heiwa Challenge thread and produce a structure that can perform your fantasies.

 

[Heiwa]

Two questions:
(a) If you can't see the buckled columns, how do you know which is the part of the building mass above the buckled columns? This is a new variant on the classic Heiwa fallacy of claiming that the collapse didn't initiate in the collapse initiation zone.
(b) If the building mass didn't move downwards, it's still there. You might want to go to New York and take a quick look. If you can see the Twin Towers, then the above paragraph makes sense. If you can't...

Dave

(a) mass above (section C) is blown to pieces and there are no buckled columns.
(b) mass below (section A) was soon after blown to pieces.

Pls, section C, assisted by gravity, cannot one-way crush down section A ... in any scale. But section A can stop section C. It happens in any scale/size.

 

[nicepants]

Good. Now you can address the 3rd point. A progressive, one-way crush down is NOT possible (and not likely). Upper part M is too weak and small. I wonder why Mackey (and NIST and Bazant) suggest something else?

Pls, section C, assisted by gravity, cannot one-way crush down section A ... in any scale. But section A can stop section C. It happens in any scale/size.

How much of section A could be crushed by section C?

 

[ozeco41]

Please, visit the Heiwa Challenge thread ...

I have seen your thread - It does not interest me because I am only interested in discussing WTC and 9/11

....and produce a structure that can perform your fantasies.

Whatever you mean by that.

I have no need to invent any structure when the actual WTC structures are there to discuss and those structures actually collapsed. My explanations may assist other readers. I note you are not interested in discussing what really happened.

 

[Niclas]

The core, though mostly not visible, must have missed some columns, bent others out of the way and probably buckled some others. BUT NONE were "crushed" and the balance or proportions missed<>pushed aside<>buckled is not critical.

Could you clarify this please?
What is doing the bending, the buckeling etc?
What is being bent, buckled etc?

 

[bill smith]

How much of section A could be crushed by section C?

If you reversed the view in your mind and dropped the 97 floors of part A the 3.7 metres onto the 13 floors of part C then C would be crushed flat almost at freefall speed.

Interestingly if you dropped the 13 floors of part C the 3.7 metres onto the 97 floors of part A then part A would also be crushed flat almost at freefall speed.

Only on 9/11.lol

 

[Newtons Bit]

Could you clarify this please?
What is doing the bending, the buckeling etc?
What is being bent, buckled etc?

Durr, the mass from all the floors above perhaps? The columns becomming unbraced and buckling elastically under self-weight?

 

[stateofgrace]

If you reversed the view in your mind and dropped the 97 floors of part A the 3.7 metres onto the 13 floors of part C then C would be crushed flat almost at freefall speed.

Interestingly if you dropped the 13 floors of part C the 3.7 metres onto the 97 floors of part A then part A would also be crushed flat almost at freefall speed.

Only on 9/11.lol

But this didn't happen on 9/11,did it Bill ?

 

[bardamu]

I have no need to invent any structure when the actual WTC structures are there to discuss and those structures actually collapsed. My explanations may assist other readers. I note you are not interested in discussing what really happened.

If you want to know what really happened, you need to watch the videos and think about why part of the upper block appears to disintegrate before the 'collapse front' begins to move down.

 

[TheRedWorm]

roight, because videos and intuition, regardless of how flawed, always reveal the truth.

 

[Heiwa]

How much of section A could be crushed by section C?

Exactly as much that section C is crushed by section A assuming elements are still attached to other elements in A and C.

External elements of C may be completely detached and will then drop down outside A.

Internal elements of C cannot be completely detached, i.e. they remain parts of C (forget any idea of loose debris from A or C crushing down A).

As C<1/10 A, C cannot one-way crush down A.

All this in accordance with the Björkman Axiom re structures and structural damage analysis:

You cannot one-way crush an isotropic or composite 3-D structure part A by a part C of itself (C = 1/10 A) by dropping part C on part A using gravity. Part C either bounces on part A or gets damaged in contact with part A and is stopped by part A that is also damaged a little. It is quite basic and all due to gravity. Materials, size and particulars of the elements of the structure part A doesn't matter the least. Part C of part A cannot destroy part A.

 

[ozeco41]

Could you clarify this please?
What is doing the bending, the buckeling etc?
What is being bent, buckled etc?

Sure can. May take a few words although it would only take 30 seconds with a whiteboard.

First let me set the context.

In the time sequence of the collapse we have some readily definable stages:

• Aircraft hits, cuts right through a number of columns and disrupts structure in the "impact zone", starts fires, BUT building remains standing;
• fires cause noticeable damage, outer wall columns bend inwards etc
• The total damage reaches a stage where the "Top Block" cannot be supported and it starts to drop
• As it falls it wedges inside the outer tube
• Global collapse follows rapidly clearly involving the pancaking of floors downwards in sequence;
• Outer Tube Wall columns peel of, break at their assembly joints and fall in various sized sheets.

Now, whilst that sequence is readily seen from available evidence, there are two key points I have not addressed:

• Demolition. At this stage of this post I have not "proven" no demolition; AND
• "What happens to the Core?" whilst the outer columns are simple peeling off and falling freely.

That is where your question comes in. Remember we are at the stage where the "Top Block" is falling AND I am only addressing your request for clarification of what happens to the core.

So refer to this piece of classic art work....

So my comments refer to the mix of vertical columns and horizontal beams of the core which will crash into each other in the area marked by the green ellipse I am not referring at this stage to the impacts between outer wall columns marked by blue ellipses OR the impacts between the outer office space floors marked by red ellipses.

The core was a three dimension matrix of vertical columns and horizontal beams but with a lot of space between the columns. I show it as a two dimension caricature but clear enough to make explanations from.

And as the collapse progressed generally the core disapeared - it was not (with one exception) left standing as a spike, on its own, after the rest collapsed.

So "What happened" - and that is what I described by bent buckled or missed etc.

Look first to sketch "A" - a column is intended to take axial compression forces and, provided the column stays straight, it can take a large force. Marked A_A in the sketch. However if it is pulled out of line see "J" in sketch "B" the axial load it can carry is seriously reduced - a decimal order of magnitude less is reasonable. So the Axial force carried by an out of line strut or column is far less than for a straight one. A_B <<< A_A

Now if we massively increase the load on a column it will fail by "buckling" - not necessarily a simple single "V" like "B" but that is one possibility. It could go into an "S" shape or any other mess.

And I used "buckling" to refer to either the failure of a column such as at "B" when it is pulled out of line and fails at low loading OR to refer to the failure of a straight column which under massive overload will buckle as the mode of failure.

I used bending to refer to the bending of horizontal beams and "C" shows a descending beam which will fall across another beam and the result both beams will be bent - one down, one up. As shown in "D".

Now it will rapidly get very complicated because (one example only) as our two beams at "C" become bent at "D" they will each tend to pull sideways on the columns that are attached to thereby weakening the columns which may then fail under axial load.

So a "domino effect" as one failure leads to another and obviously the whole situation rapidly becomes a confused mess. So can we say anything positive and quantified?

Fortunately yes. Because buckled or bent columns are far weaker than straight ones and thus the whole strength of the core would rapidly be weakened in the collision between the top block and the lower structure. And the weakening will be more than enough to allow the overall collapse of the core (bold assertion which I can engineeringly qualify if needed)

And "missed" should be self evident. The chance of any column which has been cut falling on its matching half and carrying full load is near zero. Most descending bits of Top Block columns will simply miss the lower portion.

Others will glance off and bend/buckle themselves out of line as they continue to fall. etc etc

Now my rushed simplified explanation may have clarified some things for you OR it may have made it worse. Let me know please. Hopefully the outline will give you enough to see what would and must have happened.

And if you have been reading much on WTC 9/11 you will realise that what we are discussing makes nonsense of most of the "explanations" which presume that the top bit and the bottom bit impacted and interacted as if both or either were solid single entities. (Several poster on these threads; Chandler, Szamboti, Seffen and a lot of Bazant stuff) It is not so and therefore you can throw out their "explanations" - false premise>>>false conclusions.

Let me know if this helps.

eco

 

[ozeco41]

....You cannot one-way crush an isotropic or composite 3-D structure part A by a part C of itself (C = 1/10 A) by dropping part C on part A using gravity. Part C either bounces on part A or gets damaged in contact with part A and is stopped by part A that is also damaged a little. It is quite basic and all due to gravity. Materials, size and particulars of the elements of the structure part A doesn't matter the least. Part C of part A cannot destroy part A.

******** .... The quoted bit is like unto the faeces of a male bovine.



Gawd this is an interesting forum - you can call each other all the names BUt not use a simple everyday word like B-U-L-L-S-H**

I am (was) a sewage engineer and how do I say **** turd crap poop

 

[Hokulele]

If you want to know what really happened, you need to watch the videos and think about why part of the upper block appears to disintegrate before the 'collapse front' begins to move down.

And a better way to understand what really happened is to earn a degree in structural engineering.

 

[bardamu]

roight, because videos and intuition, regardless of how flawed, always reveal the truth.

Mackey's model is not constistent with the photographic and video evidence. If Mackey is right, the photographs and videos must be wrong.

Not sure how 'intuition' managed to sneak into the discussion.

I used bending to refer to the bending of horizontal beams and "C" shows a descending beam which will fall across another beam and the result both beams will be bent - one down, one up. As shown in "D".

Would the joints between the vertical columns and horizontal beams be stronger than the horizontal beams themselves?

 

[twinstead]

Mackey's model is not constistent with the photographic and video evidence.

I disagree. I'm not the only one. To those who actually understand Mackey's model the building is doing exactly what one would expect it to do.

 

[TheRedWorm]

Mackey's model is not constistent with the photographic and video evidence. If Mackey is right, the photographs and videos must be wrong.

...

Do you have a better model, then?

 

[ElMondoHummus]

Mackey's model is not constistent with the photographic and video evidence. If Mackey is right, the photographs and videos must be wrong.

This completely and utterly misses the point Mackey explicitly stated. He's not trying to do anything other than model a single issue regarding the collapse. Overall, he's trying to demonstrate to others how to think about the collapse. His model is not consistent because it's simplified in order to teach people how to consider the individual element being discussed.

I can't believe that Ryan came out and very clearly and explicitly stated this, and people still complain about the model anyway. I just can't believe it. People: Understand his point! It was to teach an approach, not fully describe the event!

 

[T.A.M.]

Mackey's model is not constistent with the photographic and video evidence. If Mackey is right, the photographs and videos must be wrong.

Not sure how 'intuition' managed to sneak into the discussion.

Please point out where Mackey has said his model is suppose to replicate the scenario, and then within those areas, how his model differentiates from the photographic and video evidence, with reference to the areas in his model and the corresponding incongruities in the videos/photos.

Thanks

TAM