WTC: Rate of Fall (rate of crush)

[lee h oswald]

But neither NLM nor special relativity are anything to do with buckling girders.

Neither is Verinage; nor VW cars, bowling balls, sheets of glass, brick chimneys. Annoying these discussion things have a nasty habit of evolving, much faster than people, too. NLM can, are and should be used to calculate how much force (Q: what is measured in Newtons?), mass, acceleration etc. was present - that's what they do! How do you calculate those values without NLM?! You over complicate things on purpose, it seems. It doesn't need to be broken down to sub atomic levels - we're not in need of a molecular investigation here, but you appear to be claiming just that. Newton's laws will do just fine to give a broadly accurate picture of forces, masses, accelerations, energy, and I suspect you know it. Did you take that refresher I offered? I doubt it. He's very well qualified, the lecturer, and quite engaging.

Almost as annoying as an evolving discussion is being continually logged out by your site, hanging, freezing, ages to load pages - and that's been for a while now, but much worse last two or three days. It's pretty much impossible. Anyone else?

How about some answers?

1) Have you sought the answer from your engineer pals on whether Verinage demo would be considered for the towers? Do you still think it could be? (Forget all other constraints except the ability to do the job)

2) Do you still think the top part of the tower under construction looks 'relatively spindly'? Or would you now allay fears of the dreaded spindly sledgehammer?

3) Do you think the photograph you chose from the many available, to represent a tower, was an honest accurate representation? Likewise your graphic.

4) Why did you choose that photograph?

These aren't rhetorical.

 

[George B]

Yes, Lee, I have been having difficulty in editing, using quotes, adding images and so forth . . . and yes seems Mick is always quick to say how any demonstration is too difficult, too expensive or would be dismissed out of hand if it were contrary to doubters beliefs . . .

 

[lee h oswald]

Yes, Lee, I have been having difficulty in editing, using quotes, adding images and so forth . . . and yes seems Mick is always quick to say how any demonstration is too difficult, too expensive or would be dismissed out of hand if it were contrary to doubters beliefs . . .

Right.

Mick is also very quick to say that the pictures of the core spire appearing to turn to dust are 'very misleading' or 'seriously misleading', whatever it was, But his hollow glass tube, bleached out picture 'had all the structural steel in place, so why isn't it representative' or similar. A clear case of Doubles all round, then! Double standards

Dicussion? You're having a giraffe mate

 

[Mick West]

Almost as annoying as an evolving discussion is being continually logged out by your site, hanging, freezing, ages to load pages - and that's been for a while now, but much worse last two or three days. It's pretty much impossible. Anyone else?

It was doing some maintenance yesterday which required me to restart the server a few times. That might have been it.

1) Have you sought the answer from your engineer pals on whether Verinage demo would be considered for the towers? Do you still think it could be? (Forget all other constraints except the ability to do the job)

I don't have any qualified engineer pals, and all the Verinage experts are French. But I think the primary problem would be that you could not jack the steel columns on a single floor. Verinage seems to work by pushing over weakened reinforced concrete walls. I'm not sure why it would not work if you could destory the columns though. What do you think?

2) Do you still think the top part of the tower under construction looks 'relatively spindly'? Or would you now allay fears of the dreaded spindly sledgehammer?

Relative to the photo of the base, yes.

3) Do you think the photograph you chose from the many available, to represent a tower, was an honest accurate representation? Likewise your graphic.

4) Why did you choose that photograph?

I chose it because it's representative of the length of the unsupported floor spans. There are plenty of other photos of the building in this thread that show the actual construction. I'm not claiming that the building has no exterior structure, quite clearly it does, you can see it in the other photos.

 

[Mick West]

Right.

Mick is also very quick to say that the pictures of the core spire appearing to turn to dust are 'very misleading' or 'seriously misleading', whatever it was, But his hollow glass tube, bleached out picture 'had all the structural steel in place, so why isn't it representative' or similar. A clear case of Doubles all round, then! Double standards

Dicussion? You're having a giraffe mate

I wasn't trying to misrepresent anything. I was just trying to show that in my 2D sketch of the structure of the building my columns were about in the right place, and the floor spans were about the right length. I wasn't claiming anything at all unusual about that image.

That's totally different from actually claiming that some steel turned to dust, and then creating before and after images that miss the steel actually falling away.

 

[Mick West]

Yes, Lee, I have been having difficulty in editing, using quotes, adding images and so forth . . . and yes seems Mick is always quick to say how any demonstration is too difficult, too expensive or would be dismissed out of hand if it were contrary to doubters beliefs . . .

Are you still having those problems today?

I just think you are being highly unrealistic with your suggestions for demonstrations.

 

[RolandD]

A lot of grain elevators are built very solidly. I know that many of the ones around here have had to be demoed by hand, instead of implosion because of that. That has saved a one or 2 of them so they could be repurposed

That reminds me of a couple of grain elevators just east of St. Louis, on the Illinois side. They were already abandoned when I was little. One took over forty years to collapse and the other was still standing, last I looked.

 

[lee h oswald]

It was doing some maintenance yesterday which required me to restart the server a few times. That might have been it.



I don't have any qualified engineer pals, and all the Verinage experts are French. But I think the primary problem would be that you could not jack the steel columns on a single floor. Verinage seems to work by pushing over weakened reinforced concrete walls. I'm not sure why it would not work if you could destory the columns though. What do you think?


Relative to the photo of the base, yes.



I chose it because it's representative of the length of the unsupported floor spans. There are plenty of other photos of the building in this thread that show the actual construction. I'm not claiming that the building has no exterior structure, quite clearly it does, you can see it in the other photos.

You said in another thread that you have friends who are engineers and that if there was something wrong with the 911 explanations they would say something. It was just the other day. That's why I asked the question. I can draft a letter in French if you want to send an email.

I chose it because it's representative of the length of the unsupported floor spans.

I think language and pictures we use are very important. Unsupported floor spans? What was 'unsupported' about them? The floors, all in all, were 33 inches thick including two lots of steel beams at right angles to one another carrying the corrugated steel decking onto which the concrete was poured. I assure you the floors were very well supported.

 

[lee h oswald]

Originally Posted by Mick

But neither NLM nor special relativity are anything to do with buckling girders.

Neither is Verinage; nor VW cars, bowling balls, sheets of glass, brick chimneys. Annoying these discussion things have a nasty habit of evolving, much faster than people, too. NLM can, are and should be used to calculate how much force (Q: what is measured in Newtons?), mass, acceleration etc. was present - that's what they do! How do you calculate those values without NLM?! You over complicate things on purpose, it seems. It doesn't need to be broken down to sub atomic levels - we're not in need of a molecular investigation here, but you appear to be claiming just that. Newton's laws will do just fine to give a broadly accurate picture of forces, masses, accelerations, energy, and I suspect you know it. Did you take that refresher I offered? I doubt it. He's very well qualified, the lecturer, and quite engaging.

You missed a bit.

 

[Mick West]

Neither is Verinage; nor VW cars, bowling balls, sheets of glass, brick chimneys. Annoying these discussion things have a nasty habit of evolving, much faster than people, too. NLM can, are and should be used to calculate how much force (Q: what is measured in Newtons?), mass, acceleration etc. was present - that's what they do! How do you calculate those values without NLM?! You over complicate things on purpose, it seems. It doesn't need to be broken down to sub atomic levels - we're not in need of a molecular investigation here, but you appear to be claiming just that. Newton's laws will do just fine to give a broadly accurate picture of forces, masses, accelerations, energy, and I suspect you know it. Did you take that refresher I offered? I doubt it. He's very well qualified, the lecturer, and quite engaging.

Okay, let's try it in terms of Newtonian mechanics, and discuss the issues:

Force is measured in Newtons, but force is also measured in pounds, which illustrates one of the problems here. People confuse force with weight. This leads them to confuse static loads with dynamic loads.

Weight is force, but force is not weight.

Weight is the force that gravity exerts on a mass. When a mass is being supported by something then it's applying a downwards force on that thing equal to its weight. In Newtons, this would be the mass in Kg multiplied by the acceleration of gravity, g = 9.91 m/s2​. In pounds force it would just be the weight in pounds.

That is a static load. It's the weight of one thing resting upon another. The bottom part of the building can support the weight, or the static load of the top part.

Dynamic forces are when something is moving encounters something that resists it. Like if the top of the building were to fall ten feet, and then hit the bottom of the building, the force exerted on the bottom part of the building would be a dynamic load.

What is the magnitude of this dynamic load? What does it measure in Newtons? Or in pounds.

F = ma, Force = mass * acceleration

The mass we know, but what is the acceleration? Well, that's a little more complex, but let's assume for a second that in that collision between the top part of the building and the bottom, then the acceleration (actually a deceleration) is a constant. Then the acceleration a is simply:

a = change in velocity / time

Let's say, for the sake of argument, that the building drops ten feet onto the lower part, and then stops. Bam, like a brick falling on the ground. What actual dynamic force is exerted on the lower part? How much bigger is it than the static force?

The velocity of something dropped ten feet (let's call that three meters, a height h = 3.0m) can be found with the equation:

v = sqrt(2*g*h) (where sqrt = square root, and * is multiplication)

If that thing stops in time t, the acceleration a, is:

a = sqrt(2*g*h)/t

What is t? How long does it take one thing to stop when it falls on another? It's nearly instantaneous. Let's say for now 0.01 seconds, so we have:

a = sqrt(2*9.81*3)/0.01
a = 767 m/s2​
a = 78 * g

So if something stops in 0.01 seconds after falling 10 feet, it has to withstand a force about 80 times that of gravity. That's somewhat equivalent to a static force eighty times the mass of the upper part of the building.

Except that's not the whole story of course, it's all a bit more complicated than that. But can we agree to the above before getting into the nitty-gritty? Any problems with the above?

 

[George B]

Okay, let's try it in terms of Newtonian mechanics, and discuss the issues:

Force is measured in Newtons, but force is also measured in pounds, which illustrates one of the problems here. People confuse force with weight. This leads them to confuse static loads with dynamic loads.

Weight is force, but force is not weight.

Weight is the force that gravity exerts on a mass. When a mass is being supported by something then it's applying a downwards force on that thing equal to its weight. In Newtons, this would be the mass in Kg multiplied by the acceleration of gravity, g = 9.91 m/s2​. In pounds force it would just be the weight in pounds.

That is a static load. It's the weight of one thing resting upon another. The bottom part of the building can support the weight, or the static load of the top part.

Dynamic forces are when something is moving encounters something that resists it. Like if the top of the building were to fall ten feet, and then hit the bottom of the building, the force exerted on the bottom part of the building would be a dynamic load.

What is the magnitude of this dynamic load? What does it measure in Newtons? Or in pounds.

F = ma, Force = mass * acceleration

The mass we know, but what is the acceleration? Well, that's a little more complex, but let's assume for a second that in that collision between the top part of the building and the bottom, then the acceleration (actually a deceleration) is a constant. Then the acceleration a is simply:

a = change in velocity / time

Let's say, for the sake of argument, that the building drops ten feet onto the lower part, and then stops. Bam, like a brick falling on the ground. What actual dynamic force is exerted on the lower part? How much bigger is it than the static force?

The velocity of something dropped ten feet (let's call that three meters, a height h = 3.0m) can be found with the equation:

v = sqrt(2*g*h) (where sqrt = square root, and * is multiplication)

If that thing stops in time t, the acceleration a, is:

a = sqrt(2*g*h)/t

What is t? How long does it take one thing to stop when it falls on another? It's nearly instantaneous. Let's say for now 0.01 seconds, so we have:

a = sqrt(2*9.81*3)/0.01
a = 767 m/s2​
a = 78 * g

So if something stops in 0.01 seconds after falling 10 feet, it has to withstand a force about 80 times that of gravity. That's somewhat equivalent to a static force eighty times the mass of the upper part of the building.

Except that's not the whole story of course, it's all a bit more complicated than that. But can we agree to the above before getting into the nitty-gritty? Any problems with the above?

Continue . . .

 

[Mick West]

You said in another thread that you have friends who are engineers and that if there was something wrong with the 911 explanations they would say something. It was just the other day. That's why I asked the question. I can draft a letter in French if you want to send an email.

I don't have any VERINAGE engineer friends, or any demolition engineer friends, or highrise engineer friends, just regular civil engineering.

I think language and pictures we use are very important. Unsupported floor spans? What was 'unsupported' about them? The floors, all in all, were 33 inches thick including two lots of steel beams at right angles to one another carrying the corrugated steel decking onto which the concrete was poured. I assure you the floors were very well supported.

Of coure they were well supported. They were up to code. They were working just great. The point was to illustrate that they are long span, and there are no supports in the middle of the span. Long span means more leverage when things get out of alignment.

 

[Mick West]

Continue . . .

I'm just waiting to see if lee has any objections.

 

[lee h oswald]

Okay, let's try it in terms of Newtonian mechanics, and discuss the issues:

Force is measured in Newtons, but force is also measured in pounds, which illustrates one of the problems here. People confuse force with weight. This leads them to confuse static loads with dynamic loads.

Weight is force, but force is not weight.

Weight is the force that gravity exerts on a mass. When a mass is being supported by something then it's applying a downwards force on that thing equal to its weight. In Newtons, this would be the mass in Kg multiplied by the acceleration of gravity, g = 9.91 m/s2​. In pounds force it would just be the weight in pounds.

That is a static load. It's the weight of one thing resting upon another. The bottom part of the building can support the weight, or the static load of the top part.

Dynamic forces are when something is moving encounters something that resists it. Like if the top of the building were to fall ten feet, and then hit the bottom of the building, the force exerted on the bottom part of the building would be a dynamic load.

What is the magnitude of this dynamic load? What does it measure in Newtons? Or in pounds.

F = ma, Force = mass * acceleration

The mass we know, but what is the acceleration? Well, that's a little more complex, but let's assume for a second that in that collision between the top part of the building and the bottom, then the acceleration (actually a deceleration) is a constant. Then the acceleration a is simply:

a = change in velocity / time

Let's say, for the sake of argument, that the building drops ten feet onto the lower part, and then stops. Bam, like a brick falling on the ground. What actual dynamic force is exerted on the lower part? How much bigger is it than the static force?

The velocity of something dropped ten feet (let's call that three meters, a height h = 3.0m) can be found with the equation:

v = sqrt(2*g*h) (where sqrt = square root, and * is multiplication)

If that thing stops in time t, the acceleration a, is:

a = sqrt(2*g*h)/t

What is t? How long does it take one thing to stop when it falls on another? It's nearly instantaneous. Let's say for now 0.01 seconds, so we have:

a = sqrt(2*9.81*3)/0.01
a = 767 m/s2​
a = 78 * g

So if something stops in 0.01 seconds after falling 10 feet, it has to withstand a force about 80 times that of gravity. That's somewhat equivalent to a static force eighty times the mass of the upper part of the building.

Except that's not the whole story of course, it's all a bit more complicated than that. But can we agree to the above before getting into the nitty-gritty? Any problems with the above?

Let's say, for the sake of argument, that the building drops ten feet onto the lower part, and then stops. Bam, like a brick falling on the ground. What actual dynamic force is exerted on the lower part? How much bigger is it than the static force?

There's your first issue. The model needs to be applied, not abstract. There's an assumption there is nothing there - which cannot apply. It's the framing of the parameters which is already leaning - a bit like the top of the south tower. This is where we won't be able to agree, I predict. I have just read through the post once, haven't checked the maths but didn't have anything jump out at me either - I'll need to spend a few minutes properly checking it when I have a bit more time - cooking, writing and rendering all at once, well, sort of!

 

[Mick West]

Another way of calculating the dynamic force of an impact is to see the distance that the object continues to travel via deformation while stopping. Here's a calculator showing this:

http://hyperphysics.phy-astr.gsu.edu/hbase/flobi.html

If you enter a value of 0.10204 (1/9.8) for the mass, then the end result will be the multiple of g, i.e. how much you would have to multiply the static load by.

 

[lee h oswald]

Another way of calculating the dynamic force of an impact is to see the distance that the object continues to travel via deformation while stopping. Here's a calculator showing this:

http://hyperphysics.phy-astr.gsu.edu/hbase/flobi.html

If you enter a value of 0.10204 (1/9.8) for the mass, then the end result will be the multiple of g, i.e. how much you would have to multiply the static load by.

That's handy

 

[Mick West]

There's your first issue. The model needs to be applied, not abstract. There's an assumption there is nothing there - which cannot apply. It's the framing of the parameters which is already leaning - a bit like the top of the south tower. This is where we won't be able to agree, I predict. I have just read through the post once, haven't checked the maths but didn't have anything jump out at me either - I'll need to spend a few minutes properly checking it when I have a bit more time - cooking, writing and rendering all at once, well, sort of!

Therein lies the difficulty - what actually happened inside the tower? Maybe though for the sake of argument we can assume it was something like a verinage collapse? You seem to have been saying earlier that verinage would not work at all (even if ignoring the difficult of pushing over the columns)

I await your full critique.

 

[Mick West]

That's handy

Not entirely accurate as it assumes the force is constant, but it's in the ballpark.

 

[lee h oswald]

I'm just waiting to see if lee has any objections.

You don't have to stop for me - you've seen my comment, I can check numbers later, at my leisure. I love a busman's bloody holiday, not!

 

[lee h oswald]

Therein lies the difficulty - what actually happened inside the tower? Maybe though for the sake of argument we can assume it was something like a verinage collapse? You seem to have been saying earlier that verinage would not work at all (even if ignoring the difficult of pushing over the columns)

I await your full critique.

Yes - it's a problem - and most probably the main problem.

Accepting your assumption 'it was something like a Verinage' - yes - ok, but with these additions: Isolate that to just the amount of force required to shear every single steel structural member or coupling on the collapse floor in 1 second or less. We can know the steel values in all necessary areas (thickness of, box column dimensions, shear strength, bending moment etc) - dimensions can be checked at a level in one tower or the other, as an example.

I think that would be an interesting example to follow. Any thoughts?

 

[Mick West]

Yes - it's a problem - and most probably the main problem.

Accepting your assumption 'it was something like a Verinage' - yes - ok, but with these additions: Isolate that to just the amount of force required to shear every single steel structural member or coupling on the collapse floor in 1 second or less. We can know the steel values in all necessary areas (thickness of, box column dimensions, shear strength, bending moment etc) - dimensions can be checked at a level in one tower or the other, as an example.

I think that would be an interesting example to follow. Any thoughts?

How about we also calculate the force required to buckle all the columns? Just as an upper bound?

 

[George B]

How about we also calculate the force required to buckle all the columns? Just as an upper bound?

Where are you going to get the numbers for the force required to buckle the columns?

 

[Mick West]

Hmm, I was just looking up some reference on buckling, and found this quite useful overview.

http://www.me.mtu.edu/~mavable/Book/Chap11.pdf

I was quite surprised they had a section on the WTC collapse, although no actual numbers. However it kind of bolsters the argument that experts in the various fields (here, in buckling) find nothing wrong with the official story. (Of course they could be part of some conspiracy.... but still).

Anyway, what is the buckling force of the interior and exterior columns?

 

[Mick West]

Where are you going to get the numbers for the force required to buckle the columns?

Google? I'm sure lee will offer corrections if I get the wrong figures.

 

[George B]

Hmm, I was just looking up some reference on buckling, and found this quite useful overview.

http://www.me.mtu.edu/~mavable/Book/Chap11.pdf

I was quite surprised they had a section on the WTC collapse, although no actual numbers. However it kind of bolsters the argument that experts in the various fields (here, in buckling) find nothing wrong with the official story. (Of course they could be part of some conspiracy.... but still).

Anyway, what is the buckling force of the interior and exterior columns?

I would like to see a reference to buckling that does not reference the WTC situations . . . makes me think they have drunk the same Kool Aid . . . give me some pre - 911 . . . data, formulae and findings . . . http://www.me.mtu.edu/~mavable/Book/Chap11.pdf page 11. . .

 

[Mick West]

I would like to see a reference to buckling that does not reference the WTC situations . . . makes me think they have drunk the same Kool Aid . . . give me some pre - 911 . . . data, formulae and findings . . . http://www.me.mtu.edu/~mavable/Book/Chap11.pdf page 11. . .

You think they would change all the reference books after 9/11? How would they build things?

 

[George B]

You think they would change all the reference books after 9/11? How would they build things?

In essence, yes, the idea of how shear forces are extrapolated from aircraft collision to verticals column elastic strength . . . yes, I think it has greatly influenced them . . .

 

[Mick West]

Okay, I'm going with critical load Pcr = Pi2​ * E * I / (K2​ * L2​)

Where

Pi = 3.14
E = Material elasticity (Elastic Modulus, Youngs Modulus)
I = Area Moment of Intertia
K = End fixity condition coefficient
L = Length

Here's a good reference
http://www.engineersedge.com/calculators/section_square_case_10.htm

Here's a good lay discussion of this equation:
​

Any objections?

 

[Mick West]

In essence, yes, the idea of how shear forces are extrapolated from aircraft collision to verticals column elastic strength . . . yes, I think it has greatly influenced them . . .

So..... they now vastly over-estimate the strength of things?

Wouldn't that cause things to collapse?

 

[Jazzy]

Okay, I'm going with critical load Pcr = Pi2​ * E * I / (K2​ * L2​)

Which is Note 33 on this thread.

Page 1.

 

[Mick West]

Which is Note 33 on this thread.

Page 1.

Indeed it is, also from Wikipedia:
http://en.wikipedia.org/wiki/Buckling

Which give these definitions, and values for K:

= maximum or critical force (vertical load on column),

= modulus of elasticity,

= area moment of inertia,

= unsupported length of column,

= column effective length factor, whose value depends on the conditions of end support of the column, as follows.

For both ends pinned (hinged, free to rotate),

= 1.0.
For both ends fixed,

= 0.50.
For one end fixed and the other end pinned,

= 0.699...
For one end fixed and the other end free to move laterally,

= 2.0.

is the same as Pcr, the critical force. Other terminology is the same.

 

[George B]

So..... they now vastly over-estimate the strength of things?

Wouldn't that cause things to collapse?

No, I don't want any of the assumptions from WTC to influence the calculations . . . I want it to be a classic hypothetical problem . . . and the data should be entered as though a Verinage demolition was to be performed on an existing building . .

 

[Jazzy]

Indeed it is:

For one end fixed and the other end free to move laterally,

= 2.0.

Which is the case in point.

 

[Mick West]

No, I don't want any of the assumptions from WTC to influence the calculations . . . I want it to be a classic hypothetical problem . . . and the data should be entered as though a Verinage demolition was to be performed on an existing building . .

I think you'd struggle to find something like this that has changed because of WTC. We are talking about Euler's buckling equation, which has been around since 1757. Everything I linked to regarding buckling is just fundamental physics.

 

[Mick West]

Which is the case in point.

Although you could argue a (highly unlikely) worse case of K=0.5. With K=2 you are assuming the top of the column is no longer connected to the floors.

Oh wait, no you wouldn't, if all the columns buckled in the same direction....

Complicated, but I think it's worth calculating for extreme upper bounds. Of course the collapse would not be symmetrical either, which makes it even more complex (and likely not at all close to that upper bound).

 

[George B]

I think you'd struggle to find something like this that has changed because of WTC. We are talking about Euler's buckling equation, which has been around since 1757. Everything I linked to regarding buckling is just fundamental physics.

I trust you . . . just stressing a point . . . . pun intended

 

[Jazzy]

you are assuming the top of the column is no longer connected to the floors

Considering the tower top did move temporarily out of line, and began to rotate, it seems a safe bet to assume the column "tops" below the "fold"were no longer connected. But it is complicated by the lateral constraints of the horizontal steelwork, which was, of course, a broken hoop at the failure point. There's no simple equation for that.

 

[Jazzy]

acceleration due to gravity is only relevant when there is only the normal impedance due to air resistance and cannot be applied where further resistance is encountered.

That's the purest BUNK. Science works on the precept that natural laws work continuously and everywhere. Even an object hurled upward still has the force of gravity applying to it.

Long span flooring sections are in common use and I think it important that people should be assured that the same design faults as allegedly caused wtc1, 2, & 7 to fall, are not inherent in all these other buildings.

More absolute bunk. Such design faults will always present as failure, wherever and whenever they may be.

As for asbestos and other toxins... I think it typical of the cover up and disinformation that is put out and is appalling.

Everything is relative. Asbestos has been known to be dangerous only since cancer studies picked it up in the fifties. But dust has been killing miners for thousands of years.

Politics over science... would they really do that?

Why not? YOU do.

 

[Mick West]

Number of A&E discussion moved to:
https://www.metabunk.org/threads/11...s-what-percentage-actually-disagree-with-NIST

 

[slenderbeam]

There is no need for calculations for buckling capacities.

All you need to accept is the momentum of the upper floors pulverised the floors below, because those floors' truss connections were miniscule.

Neither the core nor the perimeter walls had the ability to freestand once the floors were obliterated. That is why they toppled radially out over such a massive debris field. Both core and exterior column panels.