WTC7 and the girder walk-off between column 79 and 44

[Grizzly Bear]

Congratulations to Tony for disproving shotguns and avalanches.

More like pulling an Adam Savage with the principals of net values relevant to force and acceleration.... oy...

 

[BasqueArch]

.......
One example you did not provide is that brought up by Anders Bjorkman concerning his claim that rubble can't destroy a building. What rubble actually can't do very well is to provide a dynamic load, but if there is enough of it falling onto floors below quasi-static failures will take place. .....

Incorrect. The concrete dust produced by the collapsing towers is proof that the energy required to comminute the concrete was provided by kinetic impact (dynamic loading) not from “quasistatic” loading. One can't pour rubble slowly over time and produce the concrete dust seen.

“It is shown that the observed size range 0.01–0.1 mmof the dust particles of pulverized concrete is consistent with the theory of comminution caused by impact, and that less than 10% of the total gravitational energy, converted to kinetic energy, sufficed to produce this dust.” - Bazant
http://www.civil.northwestern.edu/people/bazant/PDFs/Papers/476%20WTC%20collapse.pdf

Pulverization of the concrete is another point that I don't necessarily see as proving things one way or another. The dust found away from the buildings was largely gypsum and I don't believe there was more than about 15% of the concrete actually fully pulverized to a fine dust......

Incorrect also.
“ About 67% of the mass of all slabs gets pulverized into dust during the crush-down, which explains the dust clouds seen jetting out.”
ibid.

 

[Tony Szamboti]

Incorrect. The concrete dust produced by the collapsing towers is proof that the energy required to comminute the concrete was provided by kinetic impact (dynamic loading) not from “quasistatic” loading. One can't pour rubble slowly over time and produce the concrete dust seen.

“It is shown that the observed size range 0.01–0.1 mmof the dust particles of pulverized concrete is consistent with the theory of comminution caused by impact, and that less than 10% of the total gravitational energy, converted to kinetic energy, sufficed to produce this dust.” - Bazant
http://www.civil.northwestern.edu/people/bazant/PDFs/Papers/476%20WTC%20collapse.pdf



Incorrect also.
“ About 67% of the mass of all slabs gets pulverized into dust during the crush-down, which explains the dust clouds seen jetting out.”
ibid.

I am not saying that there weren't dynamic loads by individual pieces which would explain concrete communition. I am saying the structure as a whole did not generate a dynamic load which is generally observed in natural collapses.

I am also on record as agreeing with the fact that only about 15% of the concrete was pulverized into dust, as that is what the percentage by weight of it was found to be in the dust. The concrete in the towers was mostly of the lightweight variety which is not as hard to pulverize as standard concrete which is about 50% denser. Additionally, most of the dust was gypsum which requires a lot less energy to pulverize.

By the way, I have started providing information to MHM on the girder walk-off issue.

 

[BasqueArch]

While we wait for Tony's girder, seat analysis

Started new thread for the question of dynamic vs static forces.
Not that it matters much. The Towers were not CD'd.

 

[Tony Szamboti]

Started new thread for the question of dynamic vs static forces.

I don't have the time to be all over the map here so you will have to excuse me if I don't join in on the new thread you started. I have a full time job and home to maintain and doing the analysis on WTC 7 girder was on my own time in addition to that. There is only so much time in a day. I think I have explained why loose rubble does not generate a dynamic load relative to its overall mass in a fairly straight forward way here.

Not that it matters much. The Towers were not CD'd.

Of course, that is just what you would like to think. Sorry if reality interrupts your thought process.

 

[Animal]

I don't have the time to be all over the map here so you will have to excuse me if I don't join in on the new thread you started. I have a full time job and home to maintain and doing the analysis on WTC 7 girder was on my own time in addition to that. There is only so much time in a day. I think I have explained why loose rubble does not generate a dynamic load relative to its overall mass in a fairly straight forward way here.

Troofer speak translation: It is another topic I will get slapped around like a red headed step child if I delve into it so I will ignore it instead.

Of course, that is just what you would like to think. Sorry if reality interrupts your thought process.

 

[Grizzly Bear]

As I alluded to in the other thread, a dynamic load is by definition a load that changes... claiming that even as a whole assembly, the building didn't experience any such thing borderlines either complete misunderstanding, or complete negligence of the entire concept as far as I'm concerned.

 

[Tony Szamboti]

As I alluded to in the other thread, a dynamic load is by definition a load that changes... claiming that even as a whole assembly, the building didn't experience any such thing borderlines either complete misunderstanding, or complete negligence of the entire concept as far as I'm concerned.

The load does not change when something is continually accelerating such as the upper section of WTC 1.

It is apparent that you either don't have the experience to understand what I am saying, or are being deliberately ignorant for some reason.

I don't have the time to continuously correct all of the obtuseness seen here. Do an experiment with a solid object or even loose rubble in a bag that a structure can take statically, like a bag of sugar, but that you know it will break the structure when dropped onto it. Then do the same with loose rubble of the same overall mass, or the sugar from the bag, poured onto a duplicate of the structure. Let us know how that works out.

 

[tsig]

The load does not change when something is continually accelerating such as the upper section of WTC 1.

It is apparent that you either don't have the experience to understand what I am saying, or are being deliberately ignorant for some reason.

I don't have the time to continuously correct all of the obtuseness seen here. Do an experiment with a solid object dropped onto a structure you know it will break with a reasonable margin and then loose rubble of the same overall mass poured onto a duplicate of the structure. Let us know how that works out.

So you're claiming that the upper stories were turned into rubble then gradually poured onto the bottom stories?

 

[Tony Szamboti]

So you're claiming that the upper stories were turned into rubble then gradually poured onto the bottom stories?

That is somewhat true. I also said in the case of the floors that the rubble would break them and continue the collapse once there was enough of it to cause a quasi-static overload. The amount of rubble needed wouldn't be generated until about eight or nine floors worth were generated.

The problem is that there wasn't enough rubble early in the collapse to do that and there is no evidence of the overall dynamic load necessary to break the structure at that point.

 

[Justin39640]

That is somewhat true. I also said in the case of the floors that the rubble would break them and continue the collapse once there was enough of it to cause a quasi-static overload. The amount of rubble needed wouldn't be generated until about eight or nine floors worth were generated.

The problem is that there wasn't enough rubble early in the collapse to do that and there is no evidence of the overall dynamic load necessary to break the structure at that point.

No it isn't.

The two parts of the building weren't rubble when the towers first started collapsing. They were relatively intact for the first impact. Simple observation of the videos shows that.

What the **** is quasi-static? A way to say dynamic loads when you don't want to use the word dynamic?

 

[Justin39640]

Let us not forget either, Tony, that some of your "harmless rubble" bits were on the order of hundreds of tons by themselves.

 

[Tony Szamboti]

No it isn't.

The two parts of the building weren't rubble when the towers first started collapsing. They were relatively intact for the first impact. Simple observation of the videos shows that.

What the **** is quasi-static? A way to say dynamic loads when you don't want to use the word dynamic?

Simple measurement of the videos shows no deceleration during the time when an impact should have been taking place, meaning there was no dynamic load, and that something was removing the integrity of the structure below rather than the load above overcoming its resistance due to dynamic amplification.

Quasi-static loading is due to a response which generates slightly more load than a dynamic situation, but is not a true dynamic load.

 

[Grizzly Bear]

The load does not change when something is continually accelerating such as the upper section of WTC 1.

It is apparent that you either don't have the experience to understand what I am saying, or are being deliberately ignorant for some reason.

This is complete nonsense... what do you think net values mean in reference to acceleration and force? Out of all the times we've had this kind of discussion, how many times have you referenced that significance? The answer is absolutely none. It's a very simple concept and by ignoring it you immediately invalidate any details you follow up with.

Do an experiment with a solid object or even loose rubble in a bag that a structure can take statically, like a bag of sugar, but that you know it will break the structure when dropped onto it. Then do the same with loose rubble of the same overall mass, or the sugar from the bag, poured onto a duplicate of the structure. Let us know how that works out.

Simple fact; that's been explained to you already. If you don't displace enough of that mass over enough time it's the same amount of force "loose" as it is "contained". If you hit water at 60 miles an hour you're about as well off as hitting pavement.

Until you can properly address such things I can personally care less about what you think of my qualifications.

 

[Tony Szamboti]

This is complete nonsense... what do you think net values mean in reference to acceleration and force? Out of all the times we've had this kind of discussion, how many times have you referenced that significance? The answer is absolutely none. It's a very simple concept and by ignoring it you immediately invalidate any details you follow up with.



Simple fact; that's been explained to you already. If you don't displace enough of that mass over enough time it's the same amount of force "loose" as it is "contained".

Until you can properly address such things I can personally care less about what you think of my qualifications.

You never cease to amaze with the fact that you don't explain anything but harp that the other person doesn't understand. You are the one who simply doesn't understand mass participation and timing in a dynamic loading situation.

You speak in a way that would drive a saint to sin.

 

[Carlos]

The load does not change when something is continually accelerating such as the upper section of WTC 1.

Makes no sense to me.

Well, if you know Dynamics of Structures you must know the Equation of Motion for a Single-Degree-of-Freedom-Structure is.

m.u''(t) + c.u'(t) + k.u(t) = F(t)

or

m.a(t) + c.v(t) + k.s(t) = F(t)

In other words:

Inertia Forces (m.a or m.u'') + Damping Forces (c.v or c.u') + Elastic Forces (k.s or k.u) = External Forces Applied (F)

where:
m -> mass
c -> damping constant
k -> spring constant / stifness

Another way to write the same equation is:

m.u''(t) + c.u'(t) - F(t) = - k.u(t)

but F(t) in this case is equal to m.g, then

m.u''(t) + c.u'(t) - mg = - k.u(t)

or

k.u(t) = mg - m.u''(t) - c.u'(t)

So, according to you, if u''(t) > 0 or a(t) > 0 the elastic force k.u(t) will have the same value for t=0, t=1, t=2, t=3... isn't it?

 

[Justin39640]

Simple measurement of the videos shows no deceleration during the time when an impact should have been taking place, meaning there was no dynamic load, and that something was removing the integrity of the structure below rather than the load above overcoming its resistance due to dynamic amplification.

Quasi-static loading is due to a response which generates slightly more load than a dynamic situation, but is not a true dynamic load.

It didn't fall straight down! Things don't usually fall apart perfectly. The chances of that diminish as things get larger and/or more complex. Your missing jolt idea is a VERY simplistic view of the destruction of a immense and nightmarishly complex object.

Did you mean static situation? Dynamic would indicate anything other than the static force and variable. Dynamic simply means the forces changed from the static state to most people. That would include your "quasi" state I would think.

 

[Justin39640]

And, not for nothing, the buildings NEVER had a true static load. They were designed for dynamic loading. From wind loads to the motion of large numbers of people moving about inside. So are wind loads "quasi-static?"

 

[Grizzly Bear]

You never cease to amaze with the fact that you don't explain anything...<snip>

Acceleration is the change in velocity over change in time. A net acceleration refers to the sum of all the acceleration values in a system, like a net force is the sum of all the forces in a given system. If you have acceleration in one direction considered "positive", and another acceleration value going the opposite direction "negative" your "net" acceleration is the sum of the two values. If A1=9.81 m/s/s and A2= 3 m/s/s then A1+A2 = 9.81-3 = a net acceleration of 6.81 m/s/s and both the resulting change in velocity and the resulting changes in potential energy remain positive. It is still "accelerating."

I kind of expect not to have to explain this when I assume your experience grants you knowledge about something this rudimentary.

So to your point I reiterate:
"The load does not change when something is continually accelerating"

Do you consider the significance of net values in a statement like this? From what I'm reading you don't.

 

[DaveThomasNMSR]

No, a deceleration requires a loss of velocity and there was no loss of velocity. Constant acceleration at values less than g are due to resistance which is less than the static load.



The experiment I described was actually relative. You can use any mass you want but you will also need a scale to match it and a way to handle the loose rubble.

Here is something anyone can do. Take a 5 lb. bag of sugar or 2 lb. box of rice and put some sides around a scale with ounce graduations with at least a 10 lb capacity, and pour the sugar or rice from the same height as what Dave Thomas dropped his bag of rice from. I'll bet you don't see much more than 5 lbs. for the sugar or 2 lbs. for the rice if any at all.

Y'know, you should be careful what you wish for!