Layman's terms please! Tower collapse issue

[DGM]

One reason I write for children is:

http://www.telegraph.co.uk/earth/main.jhtml?xml=/earth/2008/03/23/sv_michiokaku.xml

Prof Kaku has a gift for communicating complex scientific ideas in a way that lay people can understand. He argues, moreover, that good physics should be simple, so simple that it can be understood as an image. I'll let him explain. 'A good physicist is driven by a childlike fascination and imagination. If we find ourselves getting jaded or bored we have to try to recapture that childishness. Einstein used to do that. He could be quite childish. He wanted to get access to that feeling of wonderment.
'He also believed that if a theory couldn't be broadly explained to a child it wasn't working. He believed that there should be a picture behind the theory. So his special relativity, for example, can be understood as a 16-year-old boy out-racing a light beam.

Sorry, if my article were too advanced for you. Time to grew up?

This would only be true if you could prove your theory in the first place. You write for children because they will not question you and it makes you feel important. Kind of like the old days when the 'Estonia' was popular.

 

[Hokulele]

While Dr. Kaku believes that scientific theories should be understandable to the lay public, he can provide the hard science and math to back the theories up when addressing a professional audience. Heiwa, can you?

 

[rwguinn]

This would only be true if you could prove your theory in the first place. You write for children because they will not question you and it makes you feel important. Kind of like the old days when the 'Estonia' was popular.

This would also only be true if the science was right.
In Heiwa's place, simple is used in the 14th and 15th definition

 

[Newtons Bit]

One reason I write for children is:

http://www.telegraph.co.uk/earth/main.jhtml?xml=/earth/2008/03/23/sv_michiokaku.xml

Prof Kaku has a gift for communicating complex scientific ideas in a way that lay people can understand. He argues, moreover, that good physics should be simple, so simple that it can be understood as an image. I'll let him explain. 'A good physicist is driven by a childlike fascination and imagination. If we find ourselves getting jaded or bored we have to try to recapture that childishness. Einstein used to do that. He could be quite childish. He wanted to get access to that feeling of wonderment.
'He also believed that if a theory couldn't be broadly explained to a child it wasn't working. He believed that there should be a picture behind the theory. So his special relativity, for example, can be understood as a 16-year-old boy out-racing a light beam.

Sorry, if my article were too advanced for you. Time to grew up?

Are you going to respond to my challenge? It's a five minute calculation. And it's not hard.

 

[pomeroo]

One reason I write for children is:

http://www.telegraph.co.uk/earth/main.jhtml?xml=/earth/2008/03/23/sv_michiokaku.xml

Prof Kaku has a gift for communicating complex scientific ideas in a way that lay people can understand. He argues, moreover, that good physics should be simple, so simple that it can be understood as an image. I'll let him explain. 'A good physicist is driven by a childlike fascination and imagination. If we find ourselves getting jaded or bored we have to try to recapture that childishness. Einstein used to do that. He could be quite childish. He wanted to get access to that feeling of wonderment.
'He also believed that if a theory couldn't be broadly explained to a child it wasn't working. He believed that there should be a picture behind the theory. So his special relativity, for example, can be understood as a 16-year-old boy out-racing a light beam.

Sorry, if my article were too advanced for you. Time to grew up?

You write for children because you feel comfortable addressing your peers. The real engineers here have revealed you to be an incompetent.

 

[Architect]

Who are you calling an engineer?!

...unless you meant........HEY! POMEROO!!!

 

[Heiwa]

While Dr. Kaku believes that scientific theories should be understandable to the lay public, he can provide the hard science and math to back the theories up when addressing a professional audience. Heiwa, can you?

Of course, read the article http://heiwaco.tripod.com/nist.htm . There is first the theory of Bazant comprising six stages. I point out many mistakes in the various assumptions using observations (pictures) and very basic math. Then there is the theory of Seffen treated in a similar manner.

Both scientists treat the problem in 1-D; a rigid upper block of uniform density - like a point - is supposed to freefall on a structure - like a line - and destroy the latter. I think it is too simple.

The point - the upper block - is not rigid and not of uniform density and appears to selfdestruct before any freefall and impact.

The 0.8-0.9 seconds freefall cannot be observed on any videos and therefore no impact is seen.

The line - the lower, intact structure - consists in reality of 280+ load bearing columns - so there are at least 280+ lines to impact by equal number points. Not so easy.

But I do an attempt. The line is not a line but replaced by a spring that is impacted by a point (actually energy). And the spring compresses and bounces back. Explained with simple math.

The point is not really a point but another spring with its energy. And now it gets complicated. One spring (the line) is impacted by another spring (a point)! What happens then? Is there an impact? Does the upper spring remain on the lower spring? Is there a gravity driven global collapse? What is a gravity driven collapse? An avalanche? I kindly ask Bazant and Seffen to redo their analysises with that in mind and clarify the matters.

I have no theory as indicated in the title of the article. To me it looks like the lower structure is destroyed by one or more bombs and I find is strange that it has not been investigated. Maybe the investigators got confused? Like:

"Perplex'd in the extreme; of one whose hand,
Like the base Indian, threw a pearl away
Richer than all his tribe; of one whose subdued eyes,
Albeit unused to the melting mood,
Drop tears as fast as the Arabian trees
Their medical gum. Set you down this;
And say besides, that in Aleppo once,
Where a malignant and a turban'd Turk
Beat a Venetian and traduced the state,
I took by the throat the circumsiced dog
And smote him, thus. "

The great warrior saying this then commits suicide! Fooled by his honest friend! History repeats itself! Children (and adults) love it.

 

[Architect]

Of course, read the article http://heiwaco.tripod.com/nist.htm .

We all have; it's just that you keep ignoring the posts whichpoint out the many, many flaws in your hypothesis.

There is first the theory of Bazant comprising six stages. I point out many mistakes in the various assumptions using observations (pictures) and very basic math. Then there is the theory of Seffen treated in a similar manner.

We're going to have to disagree on that one. You misconstrue and misrepresent their models - look that one up before you respond - without understanding the underlying engineering analysis. For example:

Both scientists treat the problem in 1-D; a rigid upper block of uniform density - like a point - is supposed to freefall on a structure - like a line - and destroy the latter. I think it is too simple.

Density is wholly irrelevant. It is the overall mass impacting the lower structure which matters unless, for example, you are trying to argue that a building structure should perform in the same manner as (say) a fluid. Which would be ludicrous.

The point - the upper block - is not rigid and not of uniform density and appears to selfdestruct before any freefall and impact.

That's just plain wrong, and you've failed to respond to the half dozen posts pointing this out to you. You have unilaterally decided that the initiation zone is the aircraft impact point, when in actual fact initiation is higher (what with the fire and so on). At this point we see fragmentation of the upper section as it impacts the lower structure, which is exactly what we would expect.

But, of course, you expect the upper mass to simply slide off or flow around or somesuch. Which is ... how can I put this gently .... ludicrous.

The 0.8-0.9 seconds freefall cannot be observed on any videos and therefore no impact is seen.

What?!?!

The line - the lower, intact structure - consists in reality of 280+ load bearing columns - so there are at least 280+ lines to impact by equal number points. Not so easy.

How many times has it been pointed out to you that the WTC structure cannot be treated as a birdcage? Tall buildings are not designed that way. All you aredoing is aprading your own lack of knowledge.

But I do an attempt. The line is not a line but replaced by a spring that is impacted by a point (actually energy). And the spring compresses and bounces back. Explained with simple math.

Rubbish. Whilst there is a degree of spring back as the compression load is removed it is happening at the same time as 33,000T on building and debris hit the lower structure, massively exceeding design loads on the new and chaotic load paths.

The point is not really a point but another spring with its energy. And now it gets complicated. One spring (the line) is impacted by another spring (a point)! What happens then? Is there an impact? Does the upper spring remain on the lower spring? Is there a gravity driven global collapse? What is a gravity driven collapse? An avalanche? I kindly ask Bazant and Seffen to redo their analysises with that in mind and clarify the matters.

That's just plain daft.

I have no theory as indicated in the title of the article. To me it looks like the lower structure is destroyed by one or more bombs and I find is strange that it has not been investigated.

You clearly have a theory, and that is controlled demolition. Like many Truthers you disguise this as "asking questions", yet as with the same motley crew we find that your analysis has more holes than the Scottish 1st XV's front row. You clearly have no meaningful grasp of structural design, despite your protestations to the contrary, and no practical understanding of tall buildings.

Just as an aside, I note you ran away from my challenge. On the plus side you have, however, apparently quit calling me a greenhorn.

Maybe the investigators got confused?

Ah yes, I forgot. Some of the best engineers in the world got it wrong but you, a mere naval architect (allegedly), unravelled the whole conspiracy. Silly me. They'd have got away with it too, if it hadn't been for those pesky kids.

Children (and adults) love it.

Yea, well kids love the Mr. Men and Noddy books but I wouldn't use either of them as a benchmark for investigating the WTC collapse either.

 

[Sunstealer]

if a theory couldn't be BROADLY explained to a child it wasn't working.

Capitalised word is of more importance than you will understand. Just because a child of 8 can't understand calculus does not mean that any theory involving calculus is worthless. sheesh!

 

[Heiwa]

Density is wholly irrelevant. It is the overall mass impacting the lower structure which matters unless, for example, you are trying to argue that a building structure should perform in the same manner as (say) a fluid. Which would be ludicrous.

A fluid structure?? Your brain? Have any? Density is very relevant according to Seffen and Bazant (and Nist). And the total upperbody/part mass - with uniform density - must be rigid (i.e. not fluid!) in their theories throughout the process. Otherwise there will be no impact and global collapse! It may be a collision ... but it is completely different and is not treated by Seffen/Bazant ... and normally does not cause global collapse of a very robust steel construction - like a cage. Just some local failures at most.

You know a collision? A non-rigid mass with no uniform density like when a small car hits a big truck from behind. The little car is mostly damaged.

Some people believe the little car impacted the truck but it was only its solid bumper with uniform density ... and it didn't last long - that impacted. The rest was a normal collision.

According Seffen, Bazant and Nist the little car - intact after impact - proceeds through the big truck and destroys it - and comes out intact the other end!!! Imagine what scientists invent!

Like a bullet! It has uniform density and is rather rigid. Shot by a gun! That smokes afterwards.

Actually the complete WTC1,2 collapses are smoking guns!! Could never have been caused by loose upper blocks and gravity (and plane crashes/fires to loosen the block). Any real engineer knows that. Or should.

 

[phunk]

The line - the lower, intact structure - consists in reality of 280+ load bearing columns - so there are at least 280+ lines to impact by equal number points. Not so easy.

And what do you suppose happens when the mass doesn't land on the columns, but falls between them?

 

[X]

A fluid structure?? Your brain? Have any? Density is very relevant according to Seffen and Bazant (and Nist). And the total upperbody/part mass - with uniform density - must be rigid (i.e. not fluid!) in their theories throughout the process. Otherwise there will be no impact and global collapse! It may be a collision ... but it is completely different and is not treated by Seffen/Bazant ... and normally does not cause global collapse of a very robust steel construction - like a cage. Just some local failures at most.

Allow me to quote myself:

I think what Heiwa is overlooking (and Apollo20 too, if he's serious), is that impact is a function of velocity and time together.

Heiwa seems to assume that if the upper block is not "solid", it must be macroscopically fluid, and thus would behave the same as water in stream, and break around the object.
At lower flow rates, you have a small mass of water impacting over a relatively long time, which allows the water to flow around the object.

At higher velocities (like, say, the deluge from a water bomber), the mass of water is huge, and it impacts over a very short time. It packs a helluva punch.

The same thing would happen with a large mass of rubble (rubble for Heiwa's fluid upper block). A lot of rubble (whatever consistency you want) impacting over a short time (and in a small area, since most of the mass is vertical, not spread out horizontally), will impact with a force not appreciably less than if it were rigid.

F = m(dv/dt)

F = impact force
m = mass
dv = change in velocity
dt = change in time

so, if m = 33,00 tons ~ 30x10⁶ kg
dv = v_initial - v_final, which I shall arbitrarily (since I don't know the speed at which the upper block fell) set to a conservative to dv = 5 m/s
dt = time of impact, which I shall arbitrarily set to a generous 1 second

F = 30x10⁶(5/1) = 150,000,000 N

Put another way, that's the same as getting hit with a 1 kg cannon ball (over an impact period of 1 second) traveling at 150,000,000 m/s (half the speed of light!)

It is not an insignificant amount of force, and you can't just wave your hands and say "it never hits the towers", because even assuming the "fluid" upper block is deflected by the lower block, you have to account for the force applied to the lower section as it deflects all that mass over the duration of the impact.

 

[DavidJames]

Heiwa - I would suggest you abandon your attempt to argue as though you were talking to children and begin to present your case like a professional and an adult. You have been presented with many arguments refuting your childlike assertions. Arguments supported with detailed technical analysis. Unless you can refute the calculations and analysis, I can only assume you are unable and will further assume you are ignorant of engineering principles.

 

[Heiwa]

And what do you suppose happens when the mass doesn't land on the columns, but falls between them?

Good question.

The mass is all the parts of the upper block connected to the 280+ columns above.

Let's assume there is a massive local failure up top - all columns fail - and the upper block free falls and is misaligned with the structure below.

The columns of this upper mass miss the columns below and there is no impact columns against columns. Abt. 50% of the wall columns slide outside the structure below, lets call them A, abt 50% of the wall columns slide inside the structure below, lets call them B. The core columns are also out of line.

The A columns will not hit anything after that! The lower floors attached to the A columns, will be punctured by the columns below previously aligned with the A columns. There will be many local failures. Max two, three floors will be punctured.

The B columns will puncture the floors below causing more local failures. The columns of the lower structure previously aligned with the B columns above will not be affected. I assume max two, three floors below will be affected.

It would appear that the upper block telescopes into the lower structure, but the upper block is actually sliced in two big parts but in reality many more parts. Quite a collision!

I would then expect (or suppose) that further local failures would not occur when what remains of the upper block gets entagled in the lower structure. The local failures due to the assumed initial massive failures will not extend more than a few floors.

Evidently 'global collapse will ensue' as suggested by Nist will not take place. The upper damaged block has no possibility to impact anything further. It didn't impact anything in the first place.

Actually the above worst case scenario is why tower steel structures do not collapse completely like houses of cards. In reality the assumed massive failures of all columns at one floor followed by a 3 meters free fall could never take place. Not seen on any videos anyway.

 

[Architect]

A fluid structure?? Your brain? Have any?

Oh Heiwa, my little Scandanavian friend.

One of us designs tall buildings for a living, and has previously provided sufficient creds to the mods for them to confirm professional status. One of us is, in fact, licenced to practice as an architect. One of us has recently picked up a Civic Trust Award for his work.

Hint: It's not you, mate.

Now, if I see one more comment accusing me of being a greenhorn, or being thick, then I will not hesitate to pursue your inane and insensible arguments three quarters of the way around the internet.

I had assumed that, as an alleged professional, the usual courtesies would apply. It would appear, however, that your narrow grasp of engineering also extends to the rules of conduct that most of us labour under.

Disappointed, rather than surprised, it would be fair to say.

Now, let's look at your latest comedic gems:

Density is very relevant according to Seffen and Bazant (and Nist). And the total upperbody/part mass - with uniform density - must be rigid (i.e. not fluid!) in their theories throughout the process. Otherwise there will be no impact and global collapse! It may be a collision ... but it is completely different and is not treated by Seffen/Bazant ... and normally does not cause global collapse of a very robust steel construction - like a cage. Just some local failures at most.

Interesting. Wrong, of course, but interesting.

You have been told time and time again that the cage analogy is irrelevant here. The WTC functioned in a manner akin to a composite girder truss, one element of which was the floors. Failure of floors led to failure of the external envelope and hence global progressive collapse.

It does not matter how often you use the cage analogy.....any engineer who looks at the schematics and details will see how it really works, and your "argument" will fall at the first hurdle.

You know a collision? A non-rigid mass with no uniform density like when a small car hits a big truck from behind. The little car is mostly damaged.

Your analogy is useless. There is no suggestion that the lower frame had sufficient capacity to accept a dynamic load pattern of of the type encountered in collapse. If you believe otherwise, post the detailed structural analysis.

Some people believe the little car impacted the truck but it was only its solid bumper with uniform density ... and it didn't last long - that impacted. The rest was a normal collision.

Stick at the English lessons.

According Seffen, Bazant and Nist the little car - intact after impact - proceeds through the big truck and destroys it - and comes out intact the other end!!! Imagine what scientists invent!

That's not actually what they say; try reading papers properly.

Like a bullet! It has uniform density and is rather rigid. Shot by a gun! That smokes afterwards.

You're only adopting that position because you believe - wrongly - that the debris was somehow of substantially lesser mass and hence would not have had a broadly similar impact. Which is, with respect, completely ludicrous.

Actually the complete WTC1,2 collapses are smoking guns!! Could never have been caused by loose upper blocks and gravity (and plane crashes/fires to loosen the block).

Sigh

Any real engineer knows that. Or should.

And there we have it again. The foremost structural engineers in the world are all wrong, except you, who doesn't even appear to understand basic structural engineering. Amazing.

 

[Architect]

Good question.

The mass is all the parts of the upper block connected to the 280+ columns above.

Let's assume there is a massive local failure up top - all columns fail - and the upper block free falls and is misaligned with the structure below.

The columns of this upper mass miss the columns below and there is no impact columns against columns. Abt. 50% of the wall columns slide outside the structure below, lets call them A, abt 50% of the wall columns slide inside the structure below, lets call them B. The core columns are also out of line.

The A columns will not hit anything after that! The lower floors attached to the A columns, will be punctured by the columns below previously aligned with the A columns. There will be many local failures. Max two, three floors will be punctured.

The B columns will puncture the floors below causing more local failures. The columns of the lower structure previously aligned with the B columns above will not be affected. I assume max two, three floors below will be affected.

It would appear that the upper block telescopes into the lower structure, but the upper block is actually sliced in two big parts but in reality many more parts. Quite a collision!

I would then expect (or suppose) that further local failures would not occur when what remains of the upper block gets entagled in the lower structure. The local failures due to the assumed initial massive failures will not extend more than a few floors.

Evidently 'global collapse will ensue' as suggested by Nist will not take place. The upper damaged block has no possibility to impact anything further. It didn't impact anything in the first place.

Actually the above worst case scenario is why tower steel structures do not collapse completely like houses of cards. In reality the assumed massive failures of all columns at one floor followed by a 3 meters free fall could never take place. Not seen on any videos anyway.

The floors are a vital part of the composite structural system. Failure will lead to deformation of the unbraced external envelope and hence global collapse.

Really, how many times do you have to be told these basics?

Tomorrow: Rain is wet......

 

[X]

Good question.

The mass is all the parts of the upper block connected to the 280+ columns above.

Let's assume there is a massive local failure up top - all columns fail - and the upper block free falls and is misaligned with the structure below.

The columns of this upper mass miss the columns below and there is no impact columns against columns. Abt. 50% of the wall columns slide outside the structure below, lets call them A, abt 50% of the wall columns slide inside the structure below, lets call them B. The core columns are also out of line.

The A columns will not hit anything after that! The lower floors attached to the A columns, will be punctured by the columns below previously aligned with the A columns. There will be many local failures. Max two, three floors will be punctured.

The B columns will puncture the floors below causing more local failures. The columns of the lower structure previously aligned with the B columns above will not be affected. I assume max two, three floors below will be affected.

It would appear that the upper block telescopes into the lower structure, but the upper block is actually sliced in two big parts but in reality many more parts. Quite a collision!

I would then expect (or suppose) that further local failures would not occur when what remains of the upper block gets entangled in the lower structure. The local failures due to the assumed initial massive failures will not extend more than a few floors.

Evidently 'global collapse will ensue' as suggested by Nist will not take place. The upper damaged block has no possibility to impact anything further. It didn't impact anything in the first place.

Actually the above worst case scenario is why tower steel structures do not collapse completely like houses of cards. In reality the assumed massive failures of all columns at one floor followed by a 3 meters free fall could never take place. Not seen on any videos anyway.

Alright, now post up your models and calculations that prove this.
If you want to convince us, that's what it is going to take.
Remember to list your approximations, and show your work.

 

[Architect]

And to at least the same level of detail as Bazaaaaant, Greening, Arup, and so on.

 

[Darkhole]

What I'm looking for is a simple explanation for why the towers could have come down inside of 12-15 seconds or so and still taken into account conservation of momentum.
Any help with this is appreciated.

Thanks.

On this picture you see the rubble falling faster then the building.
Is that proof enough?

http://911research.wtc7.net/wtc/evidence/photos/wtc2exp6.html

 

[phunk]

Good question.

The mass is all the parts of the upper block connected to the 280+ columns above.

Let's assume there is a massive local failure up top - all columns fail - and the upper block free falls and is misaligned with the structure below.

The columns of this upper mass miss the columns below and there is no impact columns against columns. Abt. 50% of the wall columns slide outside the structure below, lets call them A, abt 50% of the wall columns slide inside the structure below, lets call them B. The core columns are also out of line.

The A columns will not hit anything after that! The lower floors attached to the A columns, will be punctured by the columns below previously aligned with the A columns. There will be many local failures. Max two, three floors will be punctured.

The 'A' columns might 'not hit anything' as they fall outside the structure, but the floors that were attached to them will pancake and overload the floors below them. They will cause the columns below the 'A' columns to be pushed and pulled out of alignment so that they can not carry any more load.

The B columns will puncture the floors below causing more local failures. The columns of the lower structure previously aligned with the B columns above will not be affected. I assume max two, three floors below will be affected.

The 'B' columns will not be stopped by any of the floors below, if they fall just inside the columns below, they will easily sever the floor trusses from the outer columns, adding the mass of those floors to the collapsing mass. How do you figure they will be stopped after two or three floors? Like the columns below the 'A' columns, the columns below the 'B' columns will be pushed outward by the 'B' columns falling against their inside faces.

It would appear that the upper block telescopes into the lower structure, but the upper block is actually sliced in two big parts but in reality many more parts. Quite a collision!

And all of those big parts still have all of their mass, only now none of it is sitting on the only things that could hold that mass, the columns.

I would then expect (or suppose) that further local failures would not occur when what remains of the upper block gets entagled in the lower structure. The local failures due to the assumed initial massive failures will not extend more than a few floors.

In the core, when the upper section falls between the columns instead of directly aligned with them, there is nothing to slow it down. It won't just become entangled and stop. As as the upper section of the core falls between the columns, it's mass will easily break loose the horizontal members it encounters, as those are not designed to carry any vertical load. The mass will also impact against the sides of the core columns, pushing them out of alignment (very easily as the horizontal members are being removed also). The mass of the upper core section, if not aligned with the columns below, will easily 'unzip' the core all the way down.

Evidently 'global collapse will ensue' as suggested by Nist will not take place. The upper damaged block has no possibility to impact anything further. It didn't impact anything in the first place.

In what magical world can the upper section fall and have "no possibility to impact anything further"? It's guaranteed to impact the building below. The worst case scenario is the upper block columns shifting out of alignment with the lower block. Once that happens there is nothing to stop a global collapse.

Actually the above worst case scenario is why tower steel structures do not collapse completely like houses of cards. In reality the assumed massive failures of all columns at one floor followed by a 3 meters free fall could never take place. Not seen on any videos anyway.

The 3 meter free fall is not even necessary. All you need is to shift the columns of the upper block out of alignment with the columns of the lower block. Just a few degrees tilt of the upper block will do, for example if one of the outer walls buckles as we saw happen.