David Chandler jumps the shark

[beachnut]

Because I've normalized the variables to roughly equivalent floors (mass and stability), and importantly know that if the actual numbers were to deviate to any degree, they would deviate toward arrest as the 'upper block impact floor' would be lighter and damaged and the 'lower block impact floor' would be more massive and stable. The released KE of B is naught if the work it might have done is used to crush the upper section, thereby rapidly depleting v.
It's like Bazant's limit case, except I didn't ask COM to wait till the bottom.

...

How is the lower floor more massive than 12 or more floors? Show the math... lol

What are you talking about? It is not physics.

 

[Oystein]

Because I've normalized the variables to roughly equivalent floors (mass and stability),

Ok, please present your normalized numbers for A and B:
A = The kinetic energy dissipated by structural resistance, crushing, etc
B = The kinetic energy won from PE by descend through some vertical space "y"
So we can check whether A > B

and importantly know that if the actual numbers were to deviate to any degree^[1], they would deviate toward arrest as the 'upper block impact floor' would be lighter and damaged^[2] and the 'lower block impact floor' would be more massive and stable^[3]. The released KE of B is naught if the work it might have done is used to crush the upper section, thereby rapidly depleting v^[4].

Several "if"s and "would"s. Have you checked whether these premises are true?
Please present your reasons why you assume them to be true. Oh, and define them properly first:
^[1] Which numbers, specifically? Deviate from what towards where? Do they deviate?
^[2] Can you delimit what you mean by 'upper block impact floor'? Why do you think it would be damaged? What is its mass? Are you claiming that the lowest floor of the falling top section is fully detached from the floors above such that their mass does not come into play at all?
^[3] Can you delimit what you mean by 'lower block impact floor'?
^[4] How and why would the upper section be crushed but the lower not?

I think you will want to tell us in your answer to ^[2] that only one floor from the upper section interacts with the lower section, and in your answer to ^[4] that the entire upper section interacts with the lower section as it gets destroyed. This will of course be contradictory. So think a bit harder about your answers!

It's like Bazant's limit case, except I didn't ask COM to wait till the bottom.

I have no idea what that means.

 

[Notconvinced]

Well, no: energy is the driver and velocity is the result. Estimating the velocity just unnecessarily complicates the problem, in fact, because then you have to try to figure out how much force there is in the impact. I admit I thought you would need to do that, too, but reading Bazant's 2002 energy argument was like "doh!" -- if you can't dissipate the energy due to gravity, then the collapse proceeds, and the velocity is an irrelevant detail.

Rofl... Bazant only gets away with that because his special case ignores natural laws until "crush up phase" begins. The professional cutouts got themselves too deep on this one.


Sent from our shared looking glass platform

 

[Crazy Chainsaw]

Rofl... Bazant only gets away with that because his special case ignores natural laws until "crush up phase" begins. The professional cutouts got themselves too deep on this one.


Sent from our shared looking glass platform

Not correct that was confirmed in the Greening computer model.

 

[jaydeehess]

Because I've normalized the variables to roughly equivalent floors (mass and stability), and importantly know that if the actual numbers were to deviate to any degree, they would deviate toward arrest as the 'upper block impact floor' would be lighter and damaged and the 'lower block impact floor' would be more massive and stable. The released KE of B is naught if the work it might have done is used to crush the upper section, thereby rapidly depleting v.
It's like Bazant's limit case, except I didn't ask COM to wait till the bottom.

<<sigh>> no, just, no.

Since impacts are primarily on the floorspace rather than on columns, nothing changes as far as resistance to collapse falling mass.

 

[JSanderO]

The collapse began with mass falling... and destroying the floor plates... CD guys simply cannot see how this could happen unless columns were blown up.

The prevailing explanation of how the mass was "freed" from the axial alignment I have to admit is not well described... we hear things like - columns buckled... well sure... buckled columns leads to destruction of load paths and axial alignment. But this WAS a progressive process... it was not an on off situation. Sure there was a "moment of release" when the remain capacity was consumed and fell below the service loads. All of this are "theoretical" constructs and true. But this is no more a detailed mechanism than a black box CD explanation.

No one seems to want to attempt to propose a model of how the heat "undid" the frame... even with assumptions on where the heat was, how hot it was... how long it was "there" and what did it "do to 'there'".

Of course proposing an actual "sequence" opens one up to charges of... where is the actual "evidence" of this happening as described. These charges need to be ignored. What needs to be done is a credible 4 D model is proposed which in comprehensible and honors the properties of the building's materials. If one, for example, assumes all fire protection spray on insulation was blasted off... FINE... It may not be true... but in the model it may be a requirement to get the steel to do "x, y or z"... then at least it might explain how ONE model of the frame "came undone".

Are there too many variables that a seemingly real set of assumptions cannot be input into some sort of FEA and result in the loss of column capacity and alignment and mimic the "things" we witnessed in the videos?

To the truthers... the refusal of their opponents to model the initiation makes it magic... just as the refusal of truthers to model their CD looks like magic.

It appears that neither side can produce what it takes to convince the other side that the undoing was done as they assert.

I don't think anyone disputes that the building could be CDed... but there is no evidence that they were. Tony's corner ejections are not "evidence" in my book.

 

[jaydeehess]

The collapse began with mass falling... and destroying the floor plates... CD guys simply cannot see how this could happen unless columns were blown up.

Neither can they explain how it would be accomplished with explosives that do not produce the telltale loud bangs.

The prevailing explanation of how the mass was "freed" from the axial alignment I have to admit is not well described... we hear things like - columns buckled... well sure... buckled columns leads to destruction of load paths and axial alignment. But this WAS a progressive process... it was not an on off situation. Sure there was a "moment of release" when the remain capacity was consumed and fell below the service loads. All of this are "theoretical" constructs and true. But this is no more a detailed mechanism than a black box CD explanation.

True.
Yes, over the course of time between aircraft impacts and collapse there was a progressive loss of load carrying capacity diversely distributed throughout the fire involved levels. The distortions in he structure indicate changes to load distributions in the structure. This in turn caused some columns to reach their limit(which in some columns was reduced by heat damage). At some point, further creep induced load redistribution pushed those columns upon which new loads were transferred, to fail and no other columns could take more loads. That is the moment of so called 'release' when failures progressed quickly across the remaining columns. While this period was short it was not instantaneous and it caused distortion, most notable in the increased tilting.

No one seems to want to attempt to propose a model of how the heat "undid" the frame... even with assumptions on where the heat was, how hot it was... how long it was "there" and what did it "do to 'there'".

Of course proposing an actual "sequence" opens one up to charges of... where is the actual "evidence" of this happening as described. These charges need to be ignored. What needs to be done is a credible 4 D model is proposed which in comprehensible and honors the properties of the building's materials.

Which may be better done now as opposed to a decade ago.

If one, for example, assumes all fire protection spray on insulation was blasted off... FINE... It may not be true..

Indeed such detail necessarily cannot be well known. Similarly the fire sim program NIST did for WTC 7 assumed all doors to be open (not an issue in the OOS towers)

Are there too many variables that a seemingly real set of assumptions cannot be input into some sort of FEA and result in the loss of column capacity and alignment and mimic the "things" we witnessed in the videos?

I'd say its almost a guarantee that you won't get an exact match to observed collapse. If half the columns only had half their insulation eroded the damage pattern will be different, if more or fewer columns were damaged, at impact, slightly more or less than predicted, the collapse may be different, different offices would have had different mass distributions, which would also affect the collapse pattern.

To the truthers... the refusal of their opponents to model the initiation makes it magic... just as the refusal of truthers to model their CD looks like magic.

At the very least NIST did do some modeling, especially of the fire spread and intensity. They checked this modelling against known fire damage to some recovered structural components and the model was found to have correctly predicted (within acceptable range) the damage to those components.
CD proponents ignore this or discount it because no severe damage components were used (not possible for several reasons) to check the model.

It appears that neither side can produce what it takes to convince the other side that the undoing was done as they assert.

I don't think anyone disputes that the building could be CDed... but there is no evidence that they were. Tony's corner ejections are not "evidence" in my book.

Ahhh, but then there is the null hypothesis. The known events of hijacked aircraft flown into buildings, the large area, multi-floor, fires that were in effect seconds after impact are all there as drivers of collapse. The 'theories' of CD are all purely speculative, even TSz's opinion of ejections.

 

[WilliamSeger]

Rofl... Bazant only gets away with that because his special case ignores natural laws until "crush up phase" begins. The professional cutouts got themselves too deep on this one.


Sent from our shared looking glass platform

No, you're confused about several things, one of which is that the Bazant & Zhou 2002 paper with the energy argument says nothing at all about any "crush up phase," so that claim is just a lie. Furthermore, it indicates that you really don't understand the energy argument at all, which is a shame, but your lack of understanding is not a rebuttal.

 

[Grizzly Bear]

Basically he thinks for the collapse to have self propagated it would have had to have initiated at the 50th floor or lower...

 

[Gamolon]

Because I've normalized the variables to roughly equivalent floors (mass and stability), and importantly know that if the actual numbers were to deviate to any degree, they would deviate toward arrest as the 'upper block impact floor' would be lighter and damaged and the 'lower block impact floor' would be more massive and stable. The released KE of B is naught if the work it might have done is used to crush the upper section, thereby rapidly depleting v.
It's like Bazant's limit case, except I didn't ask COM to wait till the bottom.


Sent from our shared looking glass platform

How do you explain this:

Additionally, to take down the Twin Towers it wouldn't be necessary to be artificially removing structural integrity all the way down the building, as at some point the falling debris is enough to cause overload. Something like ten to twenty stories would work and after that the collapse would be self-propagating.

 

[ozeco41]

How do you explain this:

Additionally, to take down the Twin Towers it wouldn't be necessary to be artificially removing structural integrity all the way down the building, as at some point the falling debris is enough to cause overload. Something like ten to twenty stories would work and after that the collapse would be self-propagating.

Actually that paragraph is noteworthy because TONY got that much right.

Sadly he got the next step - the next paragraph wrong...but:

"One small step for T Sz - one giant leap for trutherkind." (Apologies to Armstrong. N 1969)

 

[Notconvinced]

Gamolon, can you cite the post # you claim I made? And which thread of course...

I don't recall using that language.


Sent from our shared looking glass platform

 

[GlennB]

Gamolon, can you cite the post # you claim I made? And which thread of course...

I don't recall using that language.

The quote includes a little arrow to your original post. Click the arrow.