Moderated Steel structures cannot globally collapse due to gravity alone

[Heiwa]

Heiwa,

"Crush down" is different than "collapse"...?

Ahhh, you might have defined your terms sooner. Why don't you give your definition now.

If it "collapses", floor by floor by floor, from the contact interface between the lower & upper segment to the ground, just like the WTC towers did, you do not consider this a collapse?? Seems to me to be a pretty arbitrary definition.

You say the lower segment will NEVER collapse. I disagree. Suppose that you have a weak point on the ground floor. This weak point was strong enough to support the structure above statically. But, due to the combination of the static load and dynamic load, this point may well have a very high STRESS (the factor that determines failure, not force) level that exceeds its strength.

Then, by what I am presuming to be your definition of "collapse", this structure could indeed collapse from this weak point, even if a progressive crush down does not start from the top most floor. There is no mechanical theory that says that a smaller segment can never cause a collapse in a larger lower structure.

It all comes down to local stresses.

tk

Yes, crush down is completely different from collapse. That's obvious!

In a crush down you apply a load from top and crush what is below.

Collapse? I assume you remove a support somewhere below and things above drops down.

NIST/Bazant use the words as equivalent and mix them to suit the circumstances.

It happens! Mother-in-law put her bottom on a chair and the chair collapsed (!). Actually it was mother-in-laws bottom that crushed the chair. Or, mother-in-law sits in a chair and son-in-law removes a leg on the chair: Mother in law collapses? The chair does not collapse! It just tilts on the side.

Thus it is very important in structural damage analysis to identify the failures step by step and find the cause for each failure.

Bazant started out 2001 with a top part C impacting a lower part A that was shaken in pieces. Then it was multiple impacts by C. The latest version 2008 is an initial impact producing a rubble layer part B that overloads part A, etc.

No logic anywhere.

Where do I say the lower segment (?) will NEVER collapse? Segment? I have never used that word, ever.

Re "There is no mechanical theory that says that a smaller segment can never cause a collapse in a larger lower structure", topic is dropping a part C of a structure on another part A of similar structure. In the latter case part A will neither collapse nor be crushed down. I describe why in my articles.

 

[GStan]

The ejection of large steel pieces is referred to in a sentence about air pressure. There is no mention of ejection of large steel pieces anywhere else in the document.

If you don't want to put 2 and 2 together then Bazant did not account for the the energy necessary to eject the large steel pieces nor the mechanism to hurl them up to 600 feet.

His theory is therefore incomplete and is not an explanation for the collapse of the towers.

There is no need to explain why a few anomalies in the debris distribution occurred during a collapse of this magnitude, and a collapse that you yourself have acknowledged as falling mostly within its own footprint. What level of detail do you require?

No investigations are required to know that planes hit the buildings and fires started. Multiple investigations have confirmed the fires were hot enough to weaken the steel to the point of a failure in the impact zone. Multiple investigations have confirmed that this failure released enough energy so that the first intact floor of the lower mass could not possibly have enough strength to arrest the collapse of the upper mass (Despite Heiwa's rock solid evidence to the contrary). It does not take an engineer (but it helps) to recognize that if first intact floor of the LM cannot arrest the UM, then there is no way the next intact floor could arrest UM+1 and so on.

Once it is established that the collapse cannot be arrested, there is no useful point in attempting to quantify and model the rest of the ridiculously complex, chaotic and unpredictable collisions that occured beyond the point of no return, simply to try to predict the precise or even just probable mechansisms that ejected a few heavy peices of debris beyond the predominant debris field. The amount of energy available in the collapse progression is more than enough to account for it. The number of possible permutations of random collisions that can occur between the building components is ludicrously high relative to the confidence level one could ever hope to achieve in studying which collisions actually did occur.

There is no reason to believe that some explosive force in addition to the energy of the falling mass was required to explain these anomalous ejections.

 

[Heiwa]

The ejection of large steel pieces is referred to in a sentence about air pressure. There is no mention of ejection of large steel pieces anywhere else in the document.

If you don't want to put 2 and 2 together then Bazant did not account for the the energy necessary to eject the large steel pieces nor the mechanism to hurl them up to 600 feet.

His theory is therefore incomplete and is not an explanation for the collapse of the towers.

In order for a sub-part of an intact steel structure to become a 'large steel piece' to be ejected, it must evidently be cut in two places.

So, first it is cut at on end! Failure 1. Then it is cut at the other end! Failure 2. It has become a 'large steel piece'. You would expect that piece to drop down by gravity but then it is ejected sideways.

Now, questions. How can gravity cut a structural sub-part in two locations so it becomes a steel piece, then prevent the piece from dropping down and instead eject is sideways?

 

[Christopher7]

What complete rubbish. The force required to accelerate large steel pieces associated with the fraction of mass shed per floor is very clearly calculated at the bottom of the paragraph you are quoting. This is a very dishonest thing to say.

That's a cool looking equation. Care to plug some numbers into it and explain how it calculates the energy required to eject all the 4 ton framework sections up to 600 feet sideways?
Where does it explain how downward energy is converted into horizontal energy?

I've forgotten all of my college trig and calculus but I know you have to plug some numbers into an equation to get any usable results.

If you can't actually use that equation and get usable results then you are just blowin' smoke by posting it.

 

[DGM]

In order for a sub-part of an intact steel structure to become a 'large steel piece' to be ejected, it must evidently be cut in two places.

So, first it is cut at on end! Failure 1. Then it is cut at the other end! Failure 2. It has become a 'large steel piece'. You would expect that piece to drop down by gravity but then it is ejected sideways.

Now, questions. How can gravity cut a structural sub-part in two locations so it becomes a steel piece, then prevent the piece from dropping down and instead eject is sideways?

Still trying to impress the "children" I see. BTW your question is a "strawman" of the highest order. Your not very good at this but, considering your only trying to impress "children" you'll probably do OK.

 

[Christopher7]

There is no need to explain why a few anomalies in the debris distribution occurred during a collapse of this magnitude,

Get outta town!
A few anomalies?

 

[GStan]

In order for a sub-part of an intact steel structure to become a 'large steel piece' to be ejected, it must evidently be cut in two places.

So, first it is cut at on end! Failure 1. Then it is cut at the other end! Failure 2. It has become a 'large steel piece'. You would expect that piece to drop down by gravity but then it is ejected sideways.

Now, questions. How can gravity cut a structural sub-part in two locations so it becomes a steel piece, then prevent the piece from dropping down and instead eject is sideways?

Heiwa, forget for a moment the mechanisms that initiated the collapse and allowed it to progress, whether it be fire and gravity or bombs or thermite is irrelevant to this question. Are you expecting all the steel to drop straight down? Can you conceive of nothing in the collapse that would cause debris to go to move laterally? Nothing? What would that pile look like? A giant debris pile in the shape of 208 ft X 208 ft X n ft tall cube? If all the steel is expected to fall straight down, why would any pile of any matter whatsoever ever spread out to a cone or pyramid shape; that is if:

You would expect that piece to drop down by gravity but then it is ejected sideways.

 

[Dave Rogers]

Here, Christopher7 claims that a horizontal motion was imparted to the upper block, but doesn't specify the mechanism by which it was imparted. He then makes claims about the magnitude of an effect without making any calculations to back them up.

Newton's first law says an object in motion will remain in motion unless acted on by an external unbalanced force.

The top section was in motion to the side and down.
Both motions continued as the collapse progressed.
The side motion would continue and the top section would fall off the side of the building unless some external balancing force were applied.

Here, Christopher7 tries to claim that it's impossible for "downward energy", a physically meaningless concept, can be converted into "horizontal energy", an equally meaningless concept, despite his earlier claim that this did in fact happen on a very much larger scale. He also points out that claims are worthless if the calculations they are based on have not actually been carried out.

Where does it explain how downward energy is converted into horizontal energy?

I've forgotten all of my college trig and calculus but I know you have to plug some numbers into an equation to get any usable results.

Christopher7 is not just a liar, but an inconsistent liar.

Dave

 

[GStan]

Get outta town!
A few anomalies?

Come on, at least you were making an honest intellectual effort in 10 S H v1.0, but this is downright laziness. You seem to think that there is some reason to study why pieces of steel were ejected so far away from the footprint. There isn't. It has been demonstrated by multiple sources that there was more than enough energy available in the collapse to achieve this. No additional energy from explosives was necessary to achieve it. You have not shown why those sources were incorrect in their calculations of the available energy.

Additionally, yes, anomalies. You consistently cling to the vague claim that debris was ejected up to 600 feet away, or more specifically, that steel was ejected horizontally up to 600 feet away. How much of it was thrown that far? How many pieces? What percentage by weight was thrown that far? Is it statistically significant? What was the percentage distribution by weight of the collapse radius? How much was in the footprint? How much was within 200 feet? within 500 feet? How much energy would have been required to achieve this distribution? Was that amount of energy available to produce this distribution?

Someone making a claim that these ejections could not have occured without an energy source external to the collapse energy itself would know this kind of stuff. Do you?

 

[GStan]

<snip>
His theory is therefore incomplete and is not an explanation for the collapse of the towers.

I almost forgot. Speaking of these, do you have one that is complete?

 

[e^n]

They are talking about ejection velocities.
What accounts for the ejection velocity of the large steel pieces if not air pressure?

The force imparted by the falling upper block accounts for both air and steel ejection.

The energy necessary to hurl a great many large steel pieces up to 600 feet in all directions is very significant and must be accounted for.

Which it was, as I have shown.

Furthermore, the mechanism that transferred all that energy to the 4 ton frame work pieces and ejected them up to 600 feet laterally must be explained for any analysis to be considered complete.

Only if you feel that this is somehow surprising. BLBG does not cover the mechanism by which these pieces were ejected as it is principally addressed at educated engineers, who have no trouble understanding this.

The mechanism by which they were ejected is impact force, the upper block imparts forces onto all objects it touches, in resisting this force these objects will be accelerated depending on the forces applied to them.

This is why I doubt your credentials. That statement is glibly dismissive of two critical factors in the collapse.

What credentials? I have none, I am just slightly better educated on the topic than yourself, it seems.

Double talk. What makes it go sideways instead of down?

Force does. I suspect this is not the answer you're looking for so a more complete answer is that the columns are restrained vertically, but unrestrained horizontally (to any significant degree). If thought of as an avalanche of falling debris, such an avalanche will (even if through only pure statistical chance ala brownian motion) exert a horizontal force component.

The precise details of forces applied and resultant accelerations differs for each piece of ejected steel. If you wish to pick one specifically we can look at the evidence available and determine the likely sources of energy.

That's a cool looking equation. Care to plug some numbers into it and explain how it calculates the energy required to eject all the 4 ton framework sections up to 600 feet sideways?

You are free to, the terms are simple and explained in the paper, although without some experience it may be difficult to understand the derivation of position to velocity to acceleration.

Where does it explain how downward energy is converted into horizontal energy?

There is no such thing as horizontal or vertical energy. Energy is a scalar quantity. You probably mean momentum, but as I have explained above there is nothing special needed to accelerate an object horizontally, drop a pencil at an angle other than the vertical on a desk and you will find a horizontal force component.

If you can't actually use that equation and get usable results then you are just blowin' smoke by posting it.

Please read BLBG. This is an equation quoted directly from the bottom of the paragraph you quoted. It shows how they accounted for the energy required to eject air and steel. If you do not understand how the equation works then it is hardly my job to teach you. I am responding to your claim that the energy was not accounted for.

Do you concede that the energy was in fact accounted for?

 

[Christopher7]

What accounts for the ejection velocity of the large steel pieces if not air pressure?

The force imparted by the falling upper block accounts for both air and steel ejection.

Where does Bazant explain how the falling 'block' ejected the large steel pieces up to 600 feet laterally?

The energy necessary to hurl a great many large steel pieces up to 600 feet in all directions is very significant and must be accounted for.

Which it was, as I have shown.

When, where? How much energy did it take?

Furthermore, the mechanism that transferred all that energy to the 4 ton frame work pieces and ejected them up to 600 feet laterally must be explained for any analysis to be considered complete.

Only if you feel that this is somehow surprising. BLBG does not cover the mechanism by which these pieces were ejected as it is principally addressed at educated engineers, who have no trouble understanding this.

Wrong! You cannot just leave out things you can't explain and call it science or an adequate explanation.

The mechanism by which they were ejected is impact force, the upper block imparts forces onto all objects it touches, in resisting this force these objects will be accelerated depending on the forces applied to them.

You left out one little detail, how do you get all that energy to make a 90 degree turn?

 

[Christopher7]

Please read BLBG. This is an equation quoted directly from the bottom of the paragraph you quoted. It shows how they accounted for the energy required to eject air and steel. If you do not understand how the equation works then it is hardly my job to teach you. I am responding to your claim that the energy was not accounted for.

I knew you were blowin smoke. An equation is just a formula. It is not the answer, only the tool to get the answer. You have to put your numbers into it and calculate the results. The results are the answer.

 

[GStan]

<snip>

You left out one little detail, how do you get all that energy to make a 90 degree turn?

 

[Disbelief]

I knew you were blowin smoke. An equation is just a formula. It is not the answer, only the tool to get the answer. You have to put your numbers into it and calculate the results. The results are the answer.

Why should anyone do the calculations for you, considering how many times calculations have been requested of you and you fail to do any.

 

[e^n]

Where does Bazant explain how the falling 'block' ejected the large steel pieces up to 600 feet laterally?

It is explained in terms of energy sinks. Bazant does not deal with the physical mechanisms because as I have explained

• These are well understood by the target audience of the paper
• They differ for individual steel sections
• The mechanism does not affect the amount of energy subtracted

When, where? How much energy did it take?

I have explained it in my last two posts, the energy it took depends on what values you use for [latex]K_e[/latex] and [latex]K_{out}[/latex]. You may refer to BLBG for suggested values or justify your own.

Wrong! You cannot just leave out things you can't explain and call it science or an adequate explanation.

Who said things cannot be explained? See above for why it was left out.

You left out one little detail, how do you get all that energy to make a 90 degree turn?

You impart a force upon an object, in this case the force was the resistance of the lower block to the force imparted by the upper block.

Here is an experiment for you to do. I assume you are American, and I assume like us Brits, you have soft sandwich spread. Please place a layer of spread between two solid plates (crackers will do, or any sort of biscuit unlikely to deform). Carefully drop a weigh upon this block, taking lots of care to ensure that the weight drops only vertically and impacts squarely.

Explain the mechanism by which soft sandwich spread shot out at 90 degrees to the direction of force.

I knew you were blowin smoke. An equation is just a formula. It is not the answer, only the tool to get the answer. You have to put your numbers into it and calculate the results. The results are the answer.

The equation is simple, it is after all just a minor variation on the forumla for Kinetic Energy. Just because you don't understand it does not mean I am "blowin smoke". The terms are very clearly stated in the paper, and the suggested range of values also. If you want to put these values in, you can put them in, but if you are unable to comprehend how vertical force can result in horizontal motion, then I don't expect you will understand the results of your calculation.

 

[alexi_drago]

You left out one little detail, how do you get all that energy to make a 90 degree turn?

Ever shattered something with a hammer? bits go in all directions.

Ever hammered a wedge in between 2 blocks? blocks move 90 degrees to the applied force.

Ever played on a see saw when you were a kid? oops, that's a 180 degree turn.

You ask how a force/movement/momentum or whatever in one direction can give rise to movement in other directions, there you go but i guess in your world none of those things happen.

 

[Christopher7]

It is explained in terms of energy sinks. Bazant does not deal with the physical mechanisms because as I have explained

• These are well understood by the target audience of the paper

• Yea, a bunch of sheep that will believe anything their government tells them.

They differ for individual steel sections
The mechanism does not affect the amount of energy subtracted

True

I have explained it in my last two posts, the energy it took depends on what values you use for

and

. You may refer to BLBG for suggested values or justify your own.

This is Bazant's theory. He has to come up with the numbers and justify how he arrived at those numbers. Posting a formula isn't proof of anything.
How many tons of steel was ejected? Provide a number.
How far was it ejected? Provide a number.
How do you get all that kinetic energy to make a 90 degree turn?

Until Bazant answers these questions, his hypothesis is incomplete.

 

[twinstead]

• Yea, a bunch of sheep that will believe anything their government tells them.

Give me a break. Is THAT your answer to his post? All those experts who disagree with you do so because they're a bunch of sheep that will believe anything their government tells them?

That's some kind of joke, right, because if not it makes you look like a fool.

 

[beachnut]

Ok, so you are credentialed and qualified to talk about Air Force Mishaps. Have you posted in any threads here about Air Force Mishaps in which your expertise or credentials were questioned?

That was my training. Was he pushing it as his? You can see BEA ...

...Yea, a bunch of sheep that will believe anything their government tells them.
How do you get all that kinetic energy to make a 90 degree turn?

Sheep?

Shoot a gun at the concrete floor in your garage by accident; you will have proof in your legs of kinetic energy making more than 90 degree turns. lol - the accidental KE experiment.