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

[Heiwa]

In your simplistic view of the universe, in which momentum vanishes into nothingness and all structures of all shapes and sizes behave exactly the same, I imagine it would be easy. Especially when you can redefine your terms at will to allow reality to fall into place with your ideals -- in your mind, at least.

Most people who deal professionally with momentum and structures, however, have to contend with the universe we've got, and the laws it imposes on us.

Yes, the momentum (mass times velocity) of a moving object C is affected when C collides with another object A.
Most, >99.9%, structural engineers do static and dynamic analysises of intact structures just to confirm that they will remain intact in service. Some structures can also be tested full-scale and the result compared with theoretical ones. A few engineers do real structural crush tests of various kind, e.g. testing car bodies and also ship structures subject to collision. In these tests the moving object always come to a standstill, i.e. its momentum becomes zero. Also the stricken object normally comes to a standstill afterwards, i.e. its momentum is zero. What the momentums are during collision is of little interest! More interesting are the forces involved acting on the objects and energies applied and absorbed and associated deformations and defects.

In the special case where moving object C (not connected to anything) has same structure as stricken object A (connected to e.g. ground) and when mass A > mass C, it is easy to show that deformations of C and A are of similar magnitudes and that C cannot one-way crush down A.

C cannot apply greater forces on A than C itself can withstand. In the WTC 1 case, where C evidently is weaker than A (A carried C before, but C could not carry A) it should be clear that C cannot one-way crush A! C is too weak to accomplish it!

If, on the other hand, you assume, like Bazant and NIST, that little C is rigid and much stronger than big A (not rigid and weak - cannot absorb strain energy), then you can prove anything ... but it has nothing to do with the real world and correct structural damage analysis.

I wonder why Bazant was so quick to demonstrate the impossible? And why NIST jumped on this obvious false conclusions of zero scientific value?

 

[Dave Rogers]

Most, >99.9%, structural engineers do static and dynamic analysises of intact structures just to confirm that they will remain intact in service. Some structures can also be tested full-scale and the result compared with theoretical ones. A few engineers do real structural crush tests of various kind, e.g. testing car bodies and also ship structures subject to collision.

And how many make up spurious axioms to avoid having to do any of the above?

Dave

 

[Heiwa]

The Björkman's axiom

And how many make up spurious axioms to avoid having to do any of the above?

Dave

After having studied a large number of analysises of structures A subject to gravity or similare impact by a part C of same structure A I noted that C could not one-way crush A. Thus I formulated the following Björkman's axiom:

You cannot crush an isotropic or composite 3-D structure A by a part C of itself (C = 1/10 A) by dropping part C on A using gravity. Part C either bounces on A or gets damaged in contact with A and is stopped by A that is also damaged a little. It is quite basic and all due to forces and that the two parts have identical structure. Materials, size and particulars of the elements of the structure A doesn't matter the least. Part C of A cannot destroy A.
Thus no structures, 1, 2 or 5 meters tall, or 100, 200 or 500 meters tall exist that will one-way crush down, when a small part C is dropped on the remainder part A.

The wording and syntax can no doubt be improved but the conclusion?

 

[BigAl]

After having studied a large number of analysises of structures A subject to gravity or similare impact by a part C of same structure A I noted that C could not one-way crush A. Thus I formulated the following Björkman's axiom:

You cannot crush an isotropic or composite 3-D structure A by a part C of itself (C = 1/10 A) by dropping part C on A using gravity. Part C either bounces on A or gets damaged in contact with A and is stopped by A that is also damaged a little. It is quite basic and all due to forces and that the two parts have identical structure. Materials, size and particulars of the elements of the structure A doesn't matter the least. Part C of A cannot destroy A.
Thus no structures, 1, 2 or 5 meters tall, or 100, 200 or 500 meters tall exist that will one-way crush down, when a small part C is dropped on the remainder part A.

The wording and syntax can no doubt be improved but the conclusion?

Only if you define "no structures" to exclude WTC1 and WTC2.

 

[newton3376]

After having studied a large number of analysises of structures A subject to gravity or similare impact by a part C of same structure A I noted that C could not one-way crush A. Thus I formulated the following Björkman's axiom:

There is no "Bjorkman's axiom".....just saying a bunch of nonsense and then claiming "It's my axiom" doesn't make it so....

Iv'e made my oen axiom...lets call it "newton's axiom".

Bjorkman's axiom is not really an axiom. It is not written in formal or precise mathematical form. It is an informal and loosely stated opinion that lacks the type of detail used in physics to be of any use in theory or in practise.

Lets look at your statement....I have bolded the really ridiculous part....

You cannot crush an isotropic or composite 3-D structure A by a part C of itself (C = 1/10 A) by dropping part C on A using gravity. Part C either bounces on A or gets damaged in contact with A and is stopped by A that is also damaged a little. It is quite basic and all due to forces and that the two parts have identical structure. Materials, size and particulars of the elements of the structure A doesn't matter the least. Part C of A cannot destroy A.
Thus no structures, 1, 2 or 5 meters tall, or 100, 200 or 500 meters tall exist that will one-way crush down, when a small part C is dropped on the remainder part A.

The wording and syntax can no doubt be improved but the conclusion?[/QUOTE]

All an engineer has to see is you saying "materials, size, and particulars of the elements of structure A doesn't matter in the least" to ignore the rest.

Ever since the very first time I read that comment I haven't taken anything you say seriously and have assumed that you are likely wrong whenever you say anything.

You have a big problem here...

If you keep that phrase in the "axiom" it makes anything else you say invalid and makes your axiom so ridiculous even nonengineers can see the blatant error.

If you remove that phrase from the "axiom" then it leaves your viewpoint open to an obvious attack...since it really does matter what the materials, size, and particulars are.

Either way you can't win. Leave it in and you look insane and stupid. Take it out and you look sloppy and stupid.

You are oversimplifying a complex situation to protect your conspiracy views. The sad part is that you are one of the people that should know better and you don't.

 

[aggle-rithm]

After having studied a large number of analysises of structures A subject to gravity or similare impact by a part C of same structure A I noted that C could not one-way crush A. Thus I formulated the following Björkman's axiom:

You cannot crush an isotropic or composite 3-D structure A by a part C of itself (C = 1/10 A) by dropping part C on A using gravity. Part C either bounces on A or gets damaged in contact with A and is stopped by A that is also damaged a little. It is quite basic and all due to forces and that the two parts have identical structure. Materials, size and particulars of the elements of the structure A doesn't matter the least. Part C of A cannot destroy A.
Thus no structures, 1, 2 or 5 meters tall, or 100, 200 or 500 meters tall exist that will one-way crush down, when a small part C is dropped on the remainder part A.

The wording and syntax can no doubt be improved but the conclusion?

I'm curious as to how you come up with these numbers such as 1/10, 200, 500, etc. Are these to be taken as constants, or are they just examples of values?

If they are constants, they come up to suspiciously round, base-10 numbers. I would be interested in how you came up with them. Most constants found in nature, such as pi or the Planck length, are irrational numbers.

If they are just value examples, then this is a very strange sort of axiom. It sounds more like an idle and groundless claim.

 

[aggle-rithm]

All an engineer has to see is you saying "materials, size, and particulars of the elements of structure A doesn't matter in the least" to ignore the rest.

If this were true, then even an unsound structure -- even one in imminent danger of collapse -- would not do so if 10% of its weight were dropped on it.

I'm thinking of the Texas A&M bonfire collapse of 1999. This was precipitated by the careful placement of one too many logs -- considerably less than 10% of its weight -- and killed 12 people.

I'm sure the families of those who died would be relieved to learn that there is an axiom that shows that it could not have happened.

 

[Dave Rogers]

The wording and syntax can no doubt be improved but the conclusion?

Any conclusion of the form "No [X] exists" is extremely difficult to defend, and can be discarded at once on the production of a single verified example of X. I would therefore like to submit for your consideration the collapse of a multistory building in construction at Bailey's Crossroads, Fairfax County, Virginia, USA, in March 1973.

http://www.djc.com/news/co/11155170.html

The 24th floor concrete was being poured at the same time as the shoring was removed from the 22nd floor, which had been curing for two weeks. The 22nd floor was unable to bear the weight of the 23rd and 24th floors, and so collapsed on to the 21st. Although the 21st and lower floors were sufficiently cured to withstand the static weight of the upper structure - they had done so for a week - they were unable to withstand the dynamic loading from the collapsing 22nd, 23rd and 24th floors, and this resulted in a progressive collapse of the entire structure.

No doubt you will argue that the building was incomplete. This is irrelevant to your "axiom", as the structure was capable of supporting its own weight prior to the collapse. In fact, as it was the removal of shoring from the 22nd floor that rendered it unable to resist the weight of the 23rd and 24th floors, it is clear that in this instance the weight of two floors - less than 10% of the total - caused a complete crush-down of a 22-floor lower structure.

A counter-example having been produced, The Björkman's axiom is shown to be spurious.

Dave

ETA: In keeping with the previous post, shall I convey your congratulations to the families of the 14 construction workers who were miraculously resurrected the day you dreamed up your axiom?

 

[Heiwa]

The Björkman axiom

Thanks for comments! An axiom should be one sentence, thus:

The Björkman axiom:

A smaller part of an isotropic or composite 3-D structure, when dropped on and impacting a greater part of same structure by gravity, cannot one-way crush down the greater part of the structure.

Possible proofs of the Björkman axiom:

In order to one-way crush down a structure, elements and their connections of the structure must be broken using forces. A smaller part cannot apply sufficient force by gravity on a greater part of same structure without destroying itself first!

The force a structure C can apply on another structure A is limited by the force that C can withstand itself. If C and A have same structure, both parts will be affected/crushed at impact C on A and thus part C cannot one-way crush down part A by gravity or any force applied on C. If C is smaller than A the result is even more obvious.

Further creative ideas are always welcome! Pls focus on topic/music and do not shoot the pianist.

 

[aggle-rithm]

Thanks for comments! An axiom should be one sentence, thus:

The Björkman axiom:

A smaller part of an isotropic or composite 3-D structure, when dropped on and impacting a greater part of same structure by gravity, cannot one-way crush down the greater part of the structure.

Possible proofs of the Björkman axiom:

In order to one-way crush down a structure, elements and their connections of the structure must be broken using forces. A smaller part cannot apply sufficient force by gravity on a greater part of same structure without destroying itself first!

The force a structure C can apply on another structure A is limited by the force that C can withstand itself. If C and A have same structure, both parts will be affected/crushed at impact C on A and thus part C cannot one-way crush down part A by gravity or any force applied on C. If C is smaller than A the result is even more obvious.

Further creative ideas are always welcome! Pls focus on topic/music and do not shoot the pianist.

Better, but it doesn't account for the exceptions to the rule. For instance, you have said that the axiom doesn't apply if it happens during controlled demolition.
And it evidently doesn't apply to the Texas A&M bonfire collapse either. Why not?

 

[tfk]

The Björkman Bad Joke:

A smaller part of an isotropic or composite 3-D structure, when dropped on and impacting a greater part of same structure by gravity, cannot one-way crush down the greater part of the structure.

Well, at least he's making progress.

This steaming pile is still a steaming pile.

But at least he's now redefined his nonsense such that it excludes the WTC.

Small steps.

Tom

 

[Heiwa]

The Björkman Bad Joke:

A smaller part of an isotropic or composite 3-D structure, when dropped on and impacting a greater part of same structure by gravity, cannot one-way crush down the greater part of the structure.

Well, at least he's making progress.

This steaming pile is still a steaming pile.

But at least he's now redefined his nonsense such that it excludes the WTC.

Small steps.

Tom

Another consequence of the Björkman Axiom is evidently that the smaller, upper part cannot produce and compact rubble that was previously the bigger, lower part.

How are you getting along with your theory of the opposite?

 

[tuc0]

Another consequence of the Björkman Axiom is evidently that the smaller, upper part cannot produce and compact rubble that was previously the bigger, lower part.

How are you getting along with your theory of the opposite?

It's not evident to me. Is the lower part indestructible? Please explain.

Bonus question: According to your new and improved axiom, what happens if you have an isotropic or composite 3-D structure, let's say a building with 20 floors, and you drop the upper 9 onto the lower 11? Use as much detail as you need.

 

[Heiwa]

It's not evident to me. Is the lower part indestructible? Please explain.

Bonus question: According to your new and improved axiom, what happens if you have an isotropic or composite 3-D structure, let's say a building with 20 floors, and you drop the upper 9 onto the lower 11? Use as much detail as you need.

Bonus answer: The upper 9 floors assembly (held together one way or another), when dropped, cannot one-way crush down the lower 11 floors assembly (and what holds it together). The result is only a lot of local failures in what holds together both assemblies at the impact interface and no rubble is compacted.

Try it with any structure! Just drop the upper part on the lower part! If you manage to one-way crush down the lower part with the upper part, pls report details of structure + photos, etc.

 

[beachnut]

Bonus answer: The upper 9 floors assembly (held together one way or another), when dropped, cannot one-way crush down the lower 11 floors assembly (and what holds it together). The result is only a lot of local failures in what holds together both assemblies at the impact interface and no rubble is compacted.

Try it with any structure! Just drop the upper part on the lower part! If you manage to one-way crush down the lower part with the upper part, pls report details of structure + photos, etc.

From what distance did you drop the 9 floors; details please.

 

[twinstead]

What exactly again is supposed to prevent the upper 9 floors from simply crushing floor 11 only? Then, what exactly is supposed to prevent that mass from crushing floor 10 only? I still am not sure how that is supposed to work in Heiwa's Axiom.

I'm also very concerned about the lack of structural engineers who have discovered Heiwa's Axiom. Somebody needs to show them.

 

[tuc0]

Bonus answer: The upper 9 floors assembly (held together one way or another), when dropped, cannot one-way crush down the lower 11 floors assembly (and what holds it together). The result is only a lot of local failures in what holds together both assemblies at the impact interface and no rubble is compacted.

I was hoping for a bit more detail. I'm not so much interested in what doesn't happen as in what does. You say there "is only a lot of local failures" but what then? What is the result of those local failures (that don't produce any rubble)? It evidently can't be a collapse because that would invalidate your axiom.

Also, you don't need to ask me to produce any kind of structure because I won't. I'm interested in what you think the consequence of your axiom is for the whole structure. I'll help you out.

1. local failures

2. no rubble!!

3. ? <- this is where we are at

 

[tsig]

There is no "Bjorkman's axiom".....just saying a bunch of nonsense and then claiming "It's my axiom" doesn't make it so....

Iv'e made my oen axiom...lets call it "newton's axiom".

Bjorkman's axiom is not really an axiom. It is not written in formal or precise mathematical form. It is an informal and loosely stated opinion that lacks the type of detail used in physics to be of any use in theory or in practise.

Lets look at your statement....I have bolded the really ridiculous part....

You cannot crush an isotropic or composite 3-D structure A by a part C of itself (C = 1/10 A) by dropping part C on A using gravity. Part C either bounces on A or gets damaged in contact with A and is stopped by A that is also damaged a little. It is quite basic and all due to forces and that the two parts have identical structure. Materials, size and particulars of the elements of the structure A doesn't matter the least. Part C of A cannot destroy A.
Thus no structures, 1, 2 or 5 meters tall, or 100, 200 or 500 meters tall exist that will one-way crush down, when a small part C is dropped on the remainder part A.

The wording and syntax can no doubt be improved but the conclusion?

All an engineer has to see is you saying "materials, size, and particulars of the elements of structure A doesn't matter in the least" to ignore the rest.

Ever since the very first time I read that comment I haven't taken anything you say seriously and have assumed that you are likely wrong whenever you say anything.

You have a big problem here...

If you keep that phrase in the "axiom" it makes anything else you say invalid and makes your axiom so ridiculous even nonengineers can see the blatant error.

If you remove that phrase from the "axiom" then it leaves your viewpoint open to an obvious attack...since it really does matter what the materials, size, and particulars are.

Either way you can't win. Leave it in and you look insane and stupid. Take it out and you look sloppy and stupid.

You are oversimplifying a complex situation to protect your conspiracy views. The sad part is that you are one of the people that should know better and you don't.[/QUOTE]

It would be interesting to build a "Heiwa structure". We could start with pizza boxes then use bed springs and top it off with lemons.

 

[Heiwa]

I was hoping for a bit more detail. I'm not so much interested in what doesn't happen as in what does. You say there "is only a lot of local failures" but what then? What is the result of those local failures (that don't produce any rubble)? It evidently can't be a collapse because that would invalidate your axiom.

Also, you don't need to ask me to produce any kind of structure because I won't. I'm interested in what you think the consequence of your axiom is for the whole structure. I'll help you out.

1. local failures

2. no rubble!!

3. ? <- this is where we are at

Good that you understand that at impact, assuming no bounce, local failures of structural elements occur and no rubble is formed and elements now in contact rub against each other (friction).

After that the process is always arrested. As per Björkman's axiom.

Reason is that all applied energy by part C/gravity has been used to produce the local failures, etc.

In order to continue destruction you have to add more energy, e.g. by controlled demolition.

 

[tuc0]

Good that you understand that at impact, assuming no bounce, local failures of structural elements occur and no rubble is formed and elements now in contact rub against each other (friction).

After that the process is always arrested. As per Björkman's axiom.

Reason is that all applied energy by part C/gravity has been used to produce the local failures, etc.

In order to continue destruction you have to add more energy, e.g. by controlled demolition.

Again, not as much detail as I'd like but at least it's an unambiguous answer. So, to sum it up, it follows form your axiom that in every collapse where a smaller part drops onto a larger part of any structure, this is what happens after the initial drop from any height (assuming no bounce of course):

1. local failures

2. no rubble!!

3. collapse stops

Is this a correct summary or did I misrepresent your position in any way?