Moderated Continuation - Why a one-way Crush down is not possible

[MIKILLINI]

Personally I find that I am reluctant to argue the upper block-lower block scenario these days. It is a complete waste of time considering that we know that the upper part C was no longer intact. It was more or less a collection of rubble by the time it contacted the lower part of the building.
So this is the standpoint we should be arguing from.

So does that mean you are also reluctant to argue the effect of gravity?

 

[tfk]

Bill,

I don't believe the upper block could have done it either.

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Given your track record of 100% wrong, someone who was uncertain about the issue would actually be comforted by this statement.
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Heiwa has done sterling work of embarrassing you guys ...

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Embarrassment. You ought to be the local expert on that topic.
But apparently you are "embarrassment challenged".
More likely, just calloused over.
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... by proving that you can neither design a model that will perform as Bazant predicts

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Who says. I told Heiwa 6 weeks ago that I have a design that'll do exactly that. I asked only that he honesty answer a few questions & I'd tell him how to do it.

He proceeded to show his REAL interest in this entire issue by not replying.
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nor can you provide a single example of a small fraction of a building crushing the rest of that building down level with the ground.

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Wrong. People have shown you at least 3 examples. You are simply unable to understand.
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This is not surprising considering that it has never before happened in the entire world history of construction on this planet.

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And you know as little about construction as you do about any other engineering topic.
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Models ?...zero.

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Bazant et al.
NIST WTC7 models.

There's two.
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Precedent ?....zero.

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L'Ambiance Plaza (1987) http://www.djc.com/news/co/11155170.html

Ronan Point http://scitation.aip.org/getabs/ser...00019000002000172000001&idtype=cvips&gifs=yes

Windsor Towers http://www.mace.manchester.ac.uk/pr...Study/HistoricFires/BuildingFires/default.htm
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Common sense ?...zero.

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Would that be the common sense it takes to listen to the professional conclusion of experts?

Or the common sense to listen to abject amateurs?


tom

 

[Tony Szamboti]

Explosiveless Hydraulic-Demolished French Building's Part C, Unaware Of Heiwa's Axiom, One-Way Crushes Down Part A. Heiwa Refuses To Admit Axiom Wrong Reality Right, Indignantly Replies - Are You Going To Believe Me Or Your Lying Eyes. Szamboti Applauds Heiwa's Obstinance, Sacrifices Truth For Misguided Loyalty.

http://www.dailymotion.com/video/x17lks_demolition-tour-abc-balzac-vitry_news​

Hardly. You can't use the Balzac-Vitry demolition to prove a one-way crush down of a tall building by a small part of it's upper floors could occur for two reasons. It was actually a simultaneous crush down/crush up, and the reason the upper block lasted long enough as a structure to get the job done was that it was nearly the size of the lower block.

 

[Tony Szamboti]

I've edited the above to correct the typo you identified.

The problem I have with this is that the structure you're starting with has virtually no resemblance to the structure you're using it to represent. You've started from the argument that a solid column and a square tube have roughly the same buckling strength, yet when you actually do the calculation you find that they differ by more than a factor of ten. You're now asserting, without calculations to back it up, that a structure still vastly stronger and heavier than the actual core, with all the structural material concentrated at its edges where it can provide the most resistance to buckling, is again similar in strength against buckling ratio. In effect, you're handwaving away a correction factor that, as you've already shown, can amount to more than an order of magnitude.

I'll be the first to hold my hand up and say that I have absolutely no idea how to calculate the stiffness of the WTC cores. However, your bare assertion that they must behave similarly to two different structures whose buckling strength differs by more than an order of magnitude is simply not credible. Given the extreme differences, you can't claim you've proven anything unless you've analysed at least a reasonable approximation to the actual structure.

Dave

The hollow section calculation is a good estimate of what the actual lattice structure MOI would have been. Some here think using a 12 inch wall wasn't correct, but that is what the plan view of the core stucture would have been similar to, and it is the plan which is what determines MOI as long as there is no local buckling. I explained that one could have cut lots of holes in it to simulate beams and columns instead of a full wall. It would not make much difference.

You can't extrapolate the 10 to 1 difference from a solid to what the hollow would give relative to the lattice. I only used a solid on the 911 free forum to show a column of that plan could easily be self-supporting over the height of the towers. I didn't think I needed to show any more than that at the time.

The central core was self-supporting and what I showed you with the hollow section shows that.

 

[Tony Szamboti]

You missed one. As I've already pointed out more times than I care to remember, the paper also assumes a radically different collapse progression than what was actually observed, in that it assumes no rotation of the upper block; and I've shown that, for a particular set of assumptions, the jolt intensity is critically dependent on the angle of rotation, and decreases very strongly at very small angles. Therefore, the whole analysis is geometrically flawed.

Dave

Where is the spread sheet showing what loads you applied to the columns? You never said what they were and your analysis on this was far from complete.

 

[Grizzly Bear]

Hardly. You can't use the Balzac-Vitry demolition to prove a one-way crush down of a tall building by a small part of it's upper floors could occur for two reasons. It was actually a simultaneous crush down/crush up, and the reason the upper block lasted long enough as a structure to get the job done was that it was nearly the size of the lower block.

I'm sorry but I gotta ask... Where do I learn about this principal about a collapse being directly related to proportional sizes? You know, about how they have to be roughly 50% of the mass as the starting size to inflict fatal damage to a built structure (AKA in the lingo "total crush down")? Or is this something you pick up in the profession?

EDIT: I'd ask Heiwa but it's rather hard to get a straight answer from him... or anyway an answer that's not a word salad...

In your opinion does this mean that all concerns regarding progressive collapse have been over inflated in cases such as the Ronin point plaza?

 

[Tony Szamboti]

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Tony,

I'm doing this for illustration & understanding. You can help. I promise that, throughout this, no insults.

Let's start simple.

A lattice cube, 12' on a side, made up of 12 steel beams (about the size of the tower's peripheral columns near the top, i.e., 14" x 14" x .5" thick box beams) on an edge, with some sort of BOLTING connector at each corner. Weight per beam: (4 x 13" x .5" x 144" x 0.3 lb/in^3 = 1100 lbs/beam. Total weight = 6.7 US Tons.

First time, we're gonna drop it onto an intact floor of the WTC. Say, we were to neatly slice off the tower at the 70th floor, where there was no damage, and set the top aside.

Next, we're gonna drop it onto the massively damaged damaged 97th floor of the Towers. You know, the floor that was missing about 1/6th of its columns due to the airplane crash, about 1/3 of its concrete floor, had all the rest of the columns twisted out of shape by fire, plastic creep and (oh yeah) the passage thru the floor of a 120 ton, 500 mph jetliner.

Tell us. What is the difference in load imparted onto the "floor" if the cube were dropped from the same height (say, 12 feet) if the cube was:

1) bolted together with "unobtanium" (infinite strength) bolts.
2) dropped with all the components in the same orientation, but glued together with crazy glue (i.e., no connection strength).
3) bolted together with small, real bolts
4) crushed first into a giant, intermeshed glob and then dropped.

Assume that, when it hits, one corner hits first.

Please be specific as to the stresses and reactions of both the floor & the cube:
1. at point of contact.
2. global response of the floor.

Here's a matrix to help you answer these. Very brief responses are all that is necessary here. I am trying to illustrate the difference between the impact forces on the floor between an assembled, intact piece and the same piece that has been disassembled in a couple of different ways.

FLOOR intact:
1. Unobtanium bolts:
... Response of floor: ____
--- Response of cube: ____

2. Glued components in a cube: ____
... Response of floor: ____
--- Response of cube: ____

3. Steel bolts: ____
... Response of floor: ____
--- Response of cube: ____

4. All components in a crushed mass: ___
... Response of floor: ____
--- Response of cube: ____


FLOOR Damaged:
1. Unobtanium bolts:
... Response of floor: ____
--- Response of cube: ____

2. Glued components in a cube: ____
... Response of floor: ____
--- Response of cube: ____

3. Steel bolts: ____
... Response of floor: ____
--- Response of cube: ____

4. All components in a crushed mass: ___
... Response of floor: ____
--- Response of cube: ____

There's a couple of important points to this that I want to illustrate. We'll build up the model, piece by piece, so that in about 3 steps, we'll be at the WTC upper block.

Tom

Tom, I think you should provide the answers and write a paper on it.

I promise I'll read it.

 

[FineWine]

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No.

He clearly, intentionally will not discuss ANY particulars with anyone that he perceives sees his massive flaws.

He's not even a GOOD fraud.

A good fraud would address any & all questions. And go into his mumbo-jumbo while pretending to not understand the issues that the other person was raising. When this person is caught, they can pretend that they were just mistaken.

A BAD fraud gives away the fact that he KNOWS that he is wrong by virtue of the very questions that he chooses to NOT answer. He knows that he can not walk down that path, or his mistake will be revealed too easily.

Heiwa sees this coming, refuses to answer specific questions, and resorts to his Rainman "read my paper" speech.

We know he's wrong. He knows he's wrong. We know that he knows he's wrong. And yet, lacking professional dignity, he continues the charade.

Go figure...

tom

I have nothing to teach people like you, Ryan Mackey, Newton's Bit, Dave Rogers, and others with a background in engineering. Gravy says he knows nothing about engineering, but I'd wager he knows more than I do. Yet, I know that I've put my finger on a gaping hole in Heiwa's misconception. I know it because he refuses to address the simple point I continually raise. The part that's falling is bigger than the single floor it hits. That Heiwa can try to dance around this huge boulder in the road is a wonder. Bill just might be obtuse enough to be genuinely oblivious to the collapse mechanism he can plainly see in action on every video. Heiwa, however, knows--at any rate, he knows by now--that he has been exposed. What on earth possesses him to plod on?

 

[Tony Szamboti]

I'm sorry but I gotta ask... Where do I learn about this principal about a collapse being directly related to proportional sizes? You know, about how they have to be roughly 50% of the mass as the starting size to inflict fatal damage to a built structure (AKA in the lingo "total crush down")? Or is this something you pick up in the profession?

EDIT: I'd ask Heiwa but it's rather hard to get a straight answer from him... or anyway an answer that's not a word salad...

In your opinion does this mean that all concerns regarding progressive collapse have been over inflated in cases such as the Ronin point plaza?

The Ronan Point collapses did not involve a superstructure of steel. It was essentially a cantilvered corner of the building which collapsed due to continuous dynamic loads from one story down onto each successive story. In that case one story was enough to do in the one below it.

By the way, there would have been measureable decelerations involved in the Ronan Point collapses.

 

[FineWine]

Tom, I think you should provide the answers and write a paper on it.

I promise I'll read it.

If Gravy acknowledges that he isn't an engineer and you're afraid to debate him, why do you expect Mackey to be an easier opponent for you?

 

[Tony Szamboti]

Tony,

Regarding calculating the "flexibility of the core alone"...

Calculating whether or not the dang thing would stand on it's own is pretty damn hard. The conclusions got nothing to do with the known dimensions. It is determined by things like tolerences of connections, resulting in accumulated "tilt", straightness of beams, strength & stiffness of cross trusses & interconnections. etc.

Very messy FEA problem. (Actually, a pretty neat FEA problem, once you make these factors variable parameters. )

But you can do a couple of things very easy, very quick, with very good (OK pretty good) accuracy.

You can:

Accurately calculate the moment of inertial of the core using I for box beams and the parallel axis theorem. This would get rid of some very BAD assumptions on your part.

Specifically, "I" is, in fact "additive" for materials equal distance from the centroid. And a solid tube at the outer dimensions of the rectangle of the core has got a couple orders of magnitude more material at that location than a continuous thin-walled tube.

Second, you are asking about the stiffness of the core itself. A solid wall of material, even a thin wall, is WAY better connection, and therefore WAY stiffer, than individual hollow box columns with cross bracing. You model is very poor.
___

But the second thing that you can do easily is to compare the Moment of inertial of the whole building to the Moment of Inertia for just the core.

Use the parallel axis theorem, calculating I for the Core, the outer wall using some intermediate, constant wall thickness. (Close enough) Add in "I" for the concrete floors. Then you've gotta add in some equivalent intermediate stiffness for the cross bracing, taken from "free standing column stiffness" nomographs.

My SWAG says the concrete will be responsible for >50% of the stiffness. My SWAG says that the stiffness of the whole building is about 20x the stiffness of the core alone.

I'd do the calc, but I don't really care. It looks like about 15 minutes worth. Less time than writing up a post.

Tom

Tom, all the concrete does is keep the outer shell from buckling. I fully understand how MOI is calculated using the parallel axis theorem. I = sum x^2 x A.

It is more than 15 minutes of hand calculations to determine the MOI of a lattice structure like the core and it can be approximated the way I did it as it is the plan area which counts as long as the beams between the walls restrict local buckling.

It is an easy FEA problem, after one builds the model.

 

[Grizzly Bear]

The Ronan Point collapses did not involve a superstructure of steel. It was essentially a cantilvered corner of the building which collapsed due to continuous dynamic loads from one story down onto each successive story. In that case one story was enough to do in the one below it.

By the way, there would have been measureable decelerations involved in the Ronan Point collapses.

But that doesn't really answer my question... you, bill, heiwa, et al contend that if a section is under a certain proportion of size then global collapse will not take place because [sic] the mutual destruction will assure of this. Where do I read up on this? What academic literature do I reference to learn about this? I was never introduced to this rule in either of my structures courses, nor any of my architecture studio classes, nor any of my methods and materials lectures. Not a single text book I've bought for any of these courses states this rule?

And the second question that concerned me is if indeed this is a true principal in the profession I'm working in, do you think this means that all concerns regarding progressive collapse have been over inflated?

Ronin point was an example, but you're more than free to use something more fitting if you have something better.

 

[Tony Szamboti]

If Gravy acknowledges that he isn't an engineer and you're afraid to debate him, why do you expect Mackey to be an easier opponent for you?

I don't think Ryan Mackey would be an easier debate opponent. On the contrary, he is an engineer and has a technical grasp of the subject matter, which would make him more formidable.

In my opinion, a rational technical debate with Mark Roberts would not be possible.

 

[Tony Szamboti]

But that doesn't really answer my question... you, bill, heiwa, et al contend that if a section is under a certain proportion of size then global collapse will not take place because [sic] the mutual destruction will assure of this. Where do I read up on this? What academic literature do I reference to learn about this? I was never introduced to this rule in either of my structures courses, nor any of my architecture studio classes, nor any of my methods and materials lectures. Not a single text book I've bought for any of these courses states this rule?

And the second question that concerned me is if indeed this is a true principal in the profession I'm working in, do you think this means that all concerns regarding progressive collapse have been over inflated?

Ronin point was an example, but you're more than free to use something more fitting if you have something better.

Building collapses are not exactly something science has concentrated on until recent times in case you haven't noticed. However, the mechanics aren't new and are applicable to any situation. I suggest you write things down and develop a simple model as TFK seems to be starting to do.

 

[FineWine]

I don't think Ryan Mackey would be an easier debate opponent. On the contrary, he is an engineer and has a technical grasp of the subject matter, which would make him more formidable.

In my opinion, a rational technical debate with Mark Roberts would not be possible.

If you are doing more than name-calling, you should explain why someone who has painstakingly assembled a small library of resources for debunkers would be incapable of rational debate. Roberts certainly demolished Gage, Fetzer, Bermas, and Avery.

 

[Grizzly Bear]

Building collapses are not exactly something science has concentrated on until recent times in case you haven't noticed. However, the mechanics aren't new and are applicable to any situation. I suggest you write things down and develop a simple model as TFK seems to be starting to do.

As structural systems go however, there's not really any universally applicable concept, something I've learned rather well in the last few years. I can draw any model I want, but in the end they would all be a bunk if I didn't step into that territory without that understanding.

 

[Tony Szamboti]

This is incorrect on a number of grounds.

1. The compressive strength equation that you provided is only accurate for elastic materials (KL/r > 4.71 * SQRT(E/Fy)). It does not apply less slender members. This was a concept that was discovered several hundred years ago. Please keep up with the times.

2. This general formulation of determining compression strength only applies to elements with compact or non-compact sections. Slender sections (not to be confused with slender elements) use a different formulation that includes local buckling.

The cut-off to use your approach is for elements with a flange to thickness ratio of 1.40 * SQRT(E/Fy), or 33.7. All common structural shapes meet this criteria. Your shape has a b/t ratio of 137. Any analysis of the strength of such a section must include local failures of the walls.

A method to analyze a shape such as this can be found in AISC Manual of Steel Construction Spec: E7. One could also analyze the shape using a plate fixed at it's base and pinned at the sides.

I seriously doubt it could support it's own self-weight, but I really don't care enough to analyze such a silly problem. The core lacked lateral stiffness. The individual elements were not braced. I doubt the bases were even rigid enough to be considered fixed. The individual elements would collapse under their own self-weight (which is what happened, we even have it on film).

The core remnant that buckled and collapsed due to it's own weight was only composed of inner core columns with very possibly a great deal of damage done to the horizontal beams between the columns. It was also a much smaller plan area and much more susceptible to buckling.

I am not saying this to continue the argument as it needs to be looked at rigorously to fully prove. I don't think it is a silly problem and I am interested in it and I will do a rigorous approach when I have time.

 

[Tony Szamboti]

If you are doing more than name-calling, you should explain why someone who has painstakingly assembled a small library of resources for debunkers would be incapable of rational debate. Roberts certainly demolished Gage, Fetzer, Bermas, and Avery.

I obviously don't have the same view of Mark Roberts' collection of so-called facts, the results of his debates, or his tactics as you do. Leave it at that.

 

[boloboffin]

Szamboti's got Gravy on ignore.

 

[tfk]

Are you willing to admit that the 'rigid upper block'- part C was in an advanced state of disintegration by the time it impacted the lower pert A of the building ?

I don't really want to argue that case just to find that you have reverted to the rigid block if the going got tough.

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What the heck are you blabbering about "... advanced state of disintegration"??

The 98th floor buckled. Approximately 1 second later, the 99th floor passed thru the plane that the 98th used to occupy on the way to the 97th. Approximately .7 seconds later, the 99th floor passed thru the location of the (80% destroyed) 97th floor.

At this time, there was little damage at all to the upper block.

Now, finally, your opening for your tale of unremitting stupid regarding the destruction of the upper block.

The one that, in your vivid imagination, puts Zdenek Bazant in his place.

I can't wait...

tk