How WTC 7 was pulled down

[R.Mackey]

In all bifurcation processes (such as buckling) breakdown of symmetry in the response leads to instability. Symmetry-breaking is a general principle throughout nature (for example, it’s the operating principle in failed controlled demolitions). WTC7’s lack of loss of symmetry at collapse implies that it suffered no change of state (e.g. stability to instability), but that it was stable (strict minimum) throughout. For this reason we can treat it isentropically, and directly compare the input energy to the output energy. This is analogous to the original example of dropping a brick.

Let me get this straight -- you think WTC 7's collapse was isentropic??

You may be the funniest Truther in history.

 

[Furcifer]

You raise a good point because, in general, unless we take into account the PE, we cannot judge the cause of collapse solely by looking at the output response. This was not previously explained.

The energy and entropy regimes are different approaches to the same problem. The condition for which a system is unstable in the entropy regime (ΔS > 0), will occur at the same point in the potential energy regime (det Π_ij = 0 ). So for purposes of determining stability, the two approaches are equivalent.

However, the entropy approach was taken so that we wouldn’t have to solve the entire Π for WTC7. The reason we are able to simplify the problem into directly comparing the output to input energy is because of the fortuitous, straight down, free-fall phase. This allows us to relate the symmetry to stability. In all bifurcation processes (such as buckling) breakdown of symmetry in the response leads to instability. Symmetry-breaking is a general principle throughout nature (for example, it’s the operating principle in failed controlled demolitions). WTC7’s lack of loss of symmetry at collapse implies that it suffered no change of state (e.g. stability to instability), but that it was stable (strict minimum) throughout. For this reason we can treat it isentropically, and directly compare the input energy to the output energy. This is analogous to the original example of dropping a brick.

hehe, this won't work here, nobody is stupid enough to fall for your flawed application of thermodynamic laws. You can't even setup the equation

Got anything with some real substance, some real balls to it, we can debunk? No more of these softballs, give us your bestest.

 

[ElMondoHummus]

Ok, I had to look up what the term "isentropic" meant. The definitions I'm finding basically amount to "with unchanging entropy; at constant entropy".

And to this, I must go "Treat WTC 7 isentropically?? Buh"?

Maybe I'm ignorant here, but: Given that the 7 World trade went from a highly ordered to a disordered system, and that it went from having elements of itself having a gravitational PE built up (from the process of constructing the tower) to having those components have far less due to being on or very near the ground, how can anyone posit that there is no entropy change? That simply makes no sense to me. It seems to me that, if you try to make an analysis describe 7 World Trade's collapse as having constant entropy, you're going to fail because clearly energy was dispersed in the collapse. Treating it "isentropically" seems to me to posit a sort of collapse that's reversible without an additional input of energy. And clearly, that has no chance in hell of happening. So why use the term? Or am I, the layman, misunderstanding the concept here?

Ps. Yes, I understand we're dealing with a word salad chef. What I'm trying to do is teach myself a bit more about how to consider that aspect of his salad, and that's why I'm posting. Am I treating the concept correctly, and have I reached a correct understanding of what the implications of considering the collapse "isentropically" are? That's why I'm posting. That man is self-refuting, but I gain nothing by not learning when I have an opportunity to.

 

[R.Mackey]

Here, I'll make it easy for you:

Isentropic processes are reversible.

Try not to laugh. Just try.

 

[W.D.Clinger]

The energy and entropy regimes are different approaches to the same problem. The condition for which a system is unstable in the entropy regime (ΔS > 0), will occur at the same point in the potential energy regime (det Π_ij = 0 ). So for purposes of determining stability, the two approaches are equivalent.

However, the entropy approach was taken so that we wouldn’t have to solve the entire Π for WTC7.

You do realize, of course, that det Π_ij = 0 means you can't solve for Π?

(Note to those of you who actually understand the words mzelinski used: Yeah, I know, but mzelinski doesn't, so let's wait for him to answer, mmm?)

 

[CompusMentus]

I dropped an egg this morning, as it fell gracefully through the air it also lost no symmetry. Until it hit the floor and the cat licked it up. How so very very isentropic.

Compus

 

[mzelinski]

You go wrong in the very first sentence, and spiral downward from there.

Thermal expansion does NOT generate the kinetic energy that later does the work we are interested in. Thermal expansion only transfers some of the chemical energy of office contents via the heat of fires into mechanical work at the collapse initiation zone: bending, buckling, and pushing the girder over the cliff.

Once that has happened, gravity and potential energy take over.You have been reminded many times that the big elephant in the room is potential energy, you again fail to consider that energy. Why?

In posts #151, #215, #252, #333, the initial input energy is simply the work due to thermal expansion (force of compression) over 3 inches, which, given our numbers, is about
-T*ΔS_internal = F_expansion *Δx = 1.7E+06 J
That’s less than 1% of the total heat input to the girder ΔQ.
(the stress is about 9E+08 N/m²)

Sorry that wasn’t more clear.

If that amount is not absorbed by the structure, then we want to compare it to the output KE_{upper section} = 2.263E+10 J.

Our other option is to try the brute force route, where we use the 3 inch deflection Δx to solve the potential energy.
To see a nice example of how the stability condition for potential energy is applied to tipping over a rigid block, please see Bazant & Cedolin, Stability of Structures, pg. 214.

 

[Furcifer]

In posts #151, #215, #252, #333, the initial input energy is simply the work due to thermal expansion (force of compression) over 3 inches, which, given our numbers, is about
-T*ΔS_internal = F_expansion *Δx = 1.7E+06 J
That’s less than 1% of the total heat input to the girder ΔQ.
(the stress is about 9E+08 N/m²)

Sorry that wasn’t more clear.

*snicker

That's not much of a thermal expansion.

 

[Dave Rogers]

However, the entropy approach was taken so that we wouldn’t have to solve the entire Π for WTC7. The reason we are able to simplify the problem into directly comparing the output to input energy is because of the fortuitous, straight down, free-fall phase. This allows us to relate the symmetry to stability. In all bifurcation processes (such as buckling) breakdown of symmetry in the response leads to instability. Symmetry-breaking is a general principle throughout nature (for example, it’s the operating principle in failed controlled demolitions). WTC7’s lack of loss of symmetry at collapse implies that it suffered no change of state (e.g. stability to instability), but that it was stable (strict minimum) throughout. For this reason we can treat it isentropically, and directly compare the input energy to the output energy. This is analogous to the original example of dropping a brick.

So your argument reduces to the tired old lie that WTC7's collapse was symmetric, therefore it violates the Second Law of Thermodynamics.

Putting aside the fact that WTC7's collapse included a visible southward rotation, and therefore was not even symmetric about a vertical axis, I would invite you to consider the symmetry of WTC7 about any horizontal axis while the collapse was in progress.

Dave

 

[Architect]

Hey, another Truther that tries to apply broad-brush physics (wrongly, but what the heck) but seems unable to explain why such flawed application is preferrable to structural analysis!

I wonder why none of them seem to willing to defend that position?

 

[ozeco41]

Hey, another Truther that tries to apply broad-brush physics (wrongly, but what the heck) but seems unable to explain why such flawed application is preferrable to structural analysis!...

Obfuscation.

But that may be my pragmatic structural engineer's brain objecting to the use of thermodynamics to analyse a structure.

Sorry but I cannot think of an analogy to show how stupid the concept seems.

And lets not forget there is an even easier way than structural analysis to answer the question of "Demolition or not?"

It wasn't because there was simply no way it could have been demolition without evidence becoming available and the perpetrators' actions revealed.

And let's not for get an even more global approach to the question.

Why would anyone need to do it?

But whilst we can have fun discussing the details it suits us to overlook those "bigger picture" questions.

 

[Furcifer]

Sorry but I cannot think of an analogy to show how stupid the concept seems.

Now there's an interesting question.

Since this first came up I was trying to think of an analogy. It's really hard to incorporate the level of stupidity and remain technically accurate.

So far the best I could come up with is that it's akin to trying to paint a picture of Niagra Falls while looking at it through a microscope.

That gives it the impression of being utterly futile. It also gives the sense of it's ever changing nature while conveying the microscopic vs. macroscopic differences in thermodynamics and conservation of energy.

We can then relate the isolated or closed system as a picture of Niagra Falls. An open system, with things constantly changing as you try to look at them would be almost impossible to paint. If you were even going to try and paint the falls looking at it through a microscope you'd want it to be the same every time you looked at it.

This isn't a perfect analogy however, and I think you'd need to know enough physics to connect these subtle similarities and not get confused in the process.

 

[ozeco41]

...This isn't a perfect analogy however, and I think you'd need to know enough physics to connect these subtle similarities and not get confused in the process.

That's why I gave up.
Making parody analogies takes skill and a very high order understanding of the field of knowledge you are parodying.

 

[Furcifer]

That's why I gave up.
Making parody analogies takes skill and a very high order understanding of the field of knowledge you are parodying.

It's frustrating because then along comes an Anders Bjorkman who is himself a parody. It just comes so naturally for some people.

 

[ElMondoHummus]

...Treating it "isentropically" seems to me to posit a sort of collapse that's reversible without an additional input of energy. And clearly, that has no chance in hell of happening.

Here, I'll make it easy for you:

Isentropic processes are reversible.

Try not to laugh. Just try.

Yeah, that's sorta what I was taking from what I've been reading.

And: Laughter. I've already failed. Once I realized what concept he was invoking, that chuckle escaped. I couldn't help it. But what's replaced it is jaw-hanging astonishment. This is clearly a case of a person trying to baffle with bull(*HONK*). I don't honestly believe he himself honestly believes what he's posting because it is just that full of BS. Attempting to analyize the collapse like that is akin to... oh, I don't know, someone trying to study crowd dynamics by analyzing the entropy of a seated vs. standing room only crowd at a concert. Yes, elements of the definition are present - ordered state vs. disordered randomness - but come on, that's a completely inappropriate application of the concept.

Blech... guy's just trying to see how many different ways he can rearrange thermodynamic terms. I betcha he couldn't actually set up a proper, applicable equation if he had a gun to his head.

 

[Oystein]

The taller you make them the less likely they will fall because they will have more building below them.

Bigger building -> higher entropy increase when collapse -> more energy needed to increase entropy -> less likely that fires could provide that much energy

Conclusion: The bigger the building, the less likely it is to collapse.


That is why Richard Gage has only worked out the engineering structure of small buildings in his professional career: You don't need structural engineering for the large ones, as those can't collapse anyway

 

[Oystein]

You raise a good point because, in general, unless we take into account the PE, we cannot judge the cause of collapse solely by looking at the output response. This was not previously explained.

The energy and entropy regimes are different approaches to the same problem. The condition for which a system is unstable in the entropy regime (ΔS > 0), will occur at the same point in the potential energy regime (det Π_ij = 0 ). So for purposes of determining stability, the two approaches are equivalent.

However, the entropy approach was taken so that we wouldn’t have to solve the entire Π for WTC7. The reason we are able to simplify the problem into directly comparing the output to input energy is because of the fortuitous, straight down, free-fall phase.

At what point did you add PE to the input energy?

This allows us to relate the symmetry to stability. In all bifurcation processes (such as buckling) breakdown of symmetry in the response leads to instability. Symmetry-breaking is a general principle throughout nature (for example, it’s the operating principle in failed controlled demolitions). WTC7’s lack of loss of symmetry at collapse implies that it suffered no change of state (e.g. stability to instability), but that it was stable (strict minimum) throughout.

Is this true for the point in time at which free-fall ensued (That is 1.75s after the north face started falling, and on the order of 10s after thermal expansion caused a first floor to fail)? Would you argue that WTC7 had not lost symmetry by then, and was stable throughout?

For this reason we can treat it isentropically, and directly compare the input energy to the output energy. This is analogous to the original example of dropping a brick.

By the time the free-fall started, how much PE had already been used up in mechanical work (increased entropy)? You should be able to provide upper and lower bounds for this, using observevations and measured data.

 

[Oystein]

...
Ps. Yes, I understand we're dealing with a word salad chef. What I'm trying to do is teach myself a bit more about how to consider that aspect of his salad, and that's why I'm posting. Am I treating the concept correctly, and have I reached a correct understanding of what the implications of considering the collapse "isentropically" are? That's why I'm posting. That man is self-refuting, but I gain nothing by not learning when I have an opportunity to.

This.

 

[Oystein]

In posts #151, #215, #252, #333, the initial input energy is simply the work due to thermal expansion (force of compression) over 3 inches, which, given our numbers, is about
-T*ΔS_internal = F_expansion *Δx = 1.7E+06 J
That’s less than 1% of the total heat input to the girder ΔQ.
(the stress is about 9E+08 N/m²)

Sorry that wasn’t more clear.

If that amount is not absorbed by the structure, then we want to compare it to the output KE_{upper section} = 2.263E+10 J.

No. The KE is not the output of the thermal expansion. It is the output of the PE input. You again forgot to input PE_{upper section} = 2.263E+10 J

Our other option is to try the brute force route, where we use the 3 inch deflection Δx to solve the potential energy.
To see a nice example of how the stability condition for potential energy is applied to tipping over a rigid block, please see Bazant & Cedolin, Stability of Structures, pg. 214.

Potential energy was not input by fire. It was input during construction by cranes, pumps and the like. You keep forgetting that.

 

[Dave Rogers]

Ahem.

I invite you to consider the symmetry of WTC7 about any horizontal axis while the collapse was in progress.

Dave