Merged Applicability of Bazant's model to the real world

[carlitos]

From what he posts his logic has not, at that stage, ruled out demolition.

In my own explanatory posts I routinely leave the option of demolition open until I have reached the stage where demolition can be ruled out. Call it "honesty in debate" or some such ethical scruple. I don't like presuming that which I have not shown if it is a central issue under contention. For brevity in debate I will often make assertions on secondary matters on the implied or explicit justification that I am prepared to give "proof" if called on.

So, for an example, "The initial collapse stage for the twin towers, the stage where the top block started to fall, resulted from some process weakening the structure in the impact zone. That process was either aircraft impact damage plus accumulated fire damage alone OR the same impact and fire damage PLUS assistance from demolition...."
...should not be read as me supporting demolition. I am simply leaving one option open because at that stage it is still a possibility of logic.

It's a fair point, but given the massive amount of evidence against demolition, at what point is it dishonest to include the possibility? These analyses aren't being done in a vacuum; they are being done in the real world where we know that bombs make noise and thermite burns gravitationally, etc.

 

[bill smith]

Because you asked about the upper block.

Now you're asking why I didn't abruptly change the subject? Because I rely on you for that. Specialization and division of labor promotes efficiency. I answer your questions, you abruptly change the subject. That's how it works, why change?

Respectfully,
Myriad

I was just making the point that Bazant has nothing to do with the real collapse event of WTC1. You are in full agreement I take it ?

We can therefore dispense with Bazant altogether ? Or if not maybe you can explain the value and significance of Bazant's work as it relates to the authentic event.

To be frank Myriad I can feel Bazant fading into insignificance- finally..

 

[leftysergeant]

I was just making the point that Bazant has nothing to do with the real collapse event of WTC1. You are in full agreement I take it ?

His math was right, he just went a little off track on the sequence of crush-up, crush down.

We can therefore dispense with Bazant altogether ? Or if not maybe you can explain the value and significance of Bazant's work as it relates to the authentic event.

Bazant demonstrated that the energy to do the job was available. Verinage proves that what he describes is the way that buioldings will, generally, perform.

Gage is left looking like a moron as the Balzac-Vitry structure crushes itself to oblivion exactly as Bazant describes.

 

[Myriad]

We can therefore dispense with Bazant altogether?

Hey, no one can stop you from dispensing with anything altogether. You can dispense with food, you can dispense with arithmetic, you can dispense with words, you can dispense with gravity, you can dispense with sight, you can dispense with traffic laws, you can dispense with safety warnings on power tools, you can dispense with breathing, you can dispense with truth, you can dispense with sanity.

You can even dispense with all the consequences of dispensing with these things.

What you cannot do is prevent those consequences from occurring.

Respectfully,
Myriad

 

[femr2]

Bazant demonstrated that the energy to do the job was available.

Agreed.

Verinage proves that what he describes is the way that buildings will, generally, perform.

Ah. Not agreed. Verinage is a very specific case, not borne out by generalised building performance. The numerous failed demolitions are case-in-point there. Like these...

or


Given the thread purpose, it's pertinent to make this point.

 

[bill smith]

Hey, no one can stop you from dispensing with anything altogether. You can dispense with food, you can dispense with arithmetic, you can dispense with words, you can dispense with gravity, you can dispense with sight, you can dispense with traffic laws, you can dispense with safety warnings on power tools, you can dispense with breathing, you can dispense with truth, you can dispense with sanity.

You can even dispense with all the consequences of dispensing with these things.

What you cannot do is prevent those consequences from occurring.

Respectfully,
Myriad

But you missed out the consequences of dispensing with Bazant....if there are in fact any. .

 

[bill smith]

His math was right, he just went a little off track on the sequence of crush-up, crush down.



Bazant demonstrated that the energy to do the job was available. Verinage proves that what he describes is the way that buioldings will, generally, perform.

Gage is left looking like a moron as the Balzac-Vitry structure crushes itself to oblivion exactly as Bazant describes.

Hmmm.........

 

[ozeco41]

It's a fair point, but given the massive amount of evidence against demolition, at what point is it dishonest to include the possibility? These analyses aren't being done in a vacuum; they are being done in the real world where we know that bombs make noise and thermite burns gravitationally, etc.

It depends entirely on the context of the specific discussion and the scope of that discussion and whatever stage my discussion with the other party has reached on the topic.

In the general situation if I was debating with a person who was possible an interested sceptic and who had made some valid points which fell within the whole context of the "Demolition or not?" topic then I would feel obliged to be rigorous in laying out my explanation. I could foreshadow my long established opinion as to "no demolition" but in laying out the logic and any necessary supporting evidence I would not be entitled to presume the "no demolition" outcome until I had laid out the case to support that conclusion.

In this current thread the global topic is "applicability of Bazant's model to the real world"

A sub set contained within the global scope of that topic is "applicability of Bazant to WTC 1, 2, 7" and my comments are further limited to WTC 1 & 2.

My position has been stated as accepting Bazant as globally valid i.e. there was more than enough energy to sustain the global collapse of each of the twin towers. I have stated reasons why I do not regard Bazant as valid if taken further into detail for WTC1 & 2 - irrespective of Bazant' general applicability to other structures.

Major_Tom has pointed out that Bazant applies to the "global collapse" stage of WTC1 & 2 collapses but not to the "initial collapses" (My terminology used to state M_T's position)

He and I (and others) have explored some details of our differing approaches to the WTC global collapse.

M_T has indicated that the "initial collapse" is outside the scope of Bazant's work. We have not discussed "initial collapse". And it falls outside the scope of this thread. However, explaining briefly, although I hold that "initial collapse" occurred without demolition, we have not reached that stage of logic in our discussions. The point therefore is on the table till our discussions progress. And that includes if our discussion progress - they may well not but that does not change the fact that he and I have not discussed "initial collapse" nor does it preclude me from saying to him "I've explained this many times previously - here are the links".

I am aware that most of the preceding is no longer current practice on threads such as these. "We" seem to have polarised into a two camp polarised situation between "truthers" and "debunkers" - both sides having several rude names of denigration.

I recall that "we" used to have three parties - genuine (or apparently genuine) sceptics being the third group. I still tend to give benefit of doubt and accept positions which oppose mine as being possibly genuinely held sceptic positions.

The question of "...given the massive amount of evidence against demolition, at what point is it dishonest to include the possibility?" ...does not arise in the situations I have described. It would arise if I, or a person like me, started to advocate "demolition" against my better professional judgement. Doing so seriously (not in fun/irony/poe) would be dishonest.

I leave it to you to muse on how that principle applies to Richard Gage and the other high profile claimants pro demolition.

 

[bill smith]

It's beginning to look as though it's not only Bazant that is feeling the chill . Even NIST are being overridden and explosives are back on the table.

We are certainly making progress.

 

[ozeco41]

It's beginning to look as though it's not only Bazant that is feeling the chill . Even NIST are being overridden and explosives are back on the table.

We are certainly making progress.

Wishful thinking there Bill on your three points:
1) "We" are all agreed that Bazant was right - there was sufficient energy to complete the global collapse of the twin towers.
2) "We" are all agreed that NIST was right - no demolition of the towers AND once collapse started "global collapse was inevitable" AND
3) recent discussions here show that the only place explosives are on the table is where honest professionals explain the "no demolition" case to genuine sceptics.

And "we" don't need to make progress but we have. There are few genuine sceptics still enquiring about truther rubbish.

...and few, if any, genuine truthers still posting...

 

[pgimeno]

I was just making the point that Bazant has nothing to do with the real collapse event of WTC1.

You were just making a wrong point. The real collapse event of WTC1 is one of the many collapse scenarios that Bazant proved would be unstoppable once initiated.

And please stop your latest derailing.

 

[pgimeno]

Agreed.


Ah. Not agreed. Verinage is a very specific case, not borne out by generalised building performance. The numerous failed demolitions are case-in-point there. Like these...

or


Given the thread purpose, it's pertinent to make this point.

Both failed demolitions prove that in neither case was the KE enough to cause failure. Both are arrested at the point where the explosives were not used. Not very useful for any purpose related to this thread.

 

[ozeco41]

Both failed demolitions prove that in neither case was the KE enough to cause failure. Both are arrested at the point where the explosives were not used. Not very useful for any purpose related to this thread.

In fact BOTH cases could have benefited from a Bazant Model assessment before they tried and failed.


Remembering that Bazant's Model is conservative, and ultra conservative for steel structures similar to the WTC towers. I am unsure as to whether it would be equally as conservative for those two buildings.

 

[leftysergeant]

The failed buildings appear to be rather robustly-built structures and were not adequately pre-weakened., nor do they seem to have dropped far enough to develop sufficient momentum

 

[ozeco41]

The failed buildings appear to be rather robustly-built structures and were not adequately pre-weakened., nor do they seem to have dropped far enough to develop sufficient momentum

Yes. Or in pgimeno's words "not enough KE"

 

[leftysergeant]

Yes. Or in pgimeno's words "not enough KE"

You may have noticed that I am not an engineer.

But then, I don't think you need to be an engineer to see through most twoofishness. Just trying to put it into my own native language and hoping that that makes it accessible to the other side.

Apparently, that is still not dumbed-down enough for some people.

 

[ozeco41]

You may have noticed that I am not an engineer...

...you are quite switched on as an obviously practical thinking person. And it doesn't need any more than that to understand the basics. Dealing with the more technical stuff such as "Where is the line where Bazant ceases to apply to WTC1 & 2?" starts to get into the areas where many "run of the mill" engineers would fumble.

...But then, I don't think you need to be an engineer to see through most twoofishness....

..agreed wholeheartedly

Just trying to put it into my own native language and hoping that that makes it accessible to the other side.

Apparently, that is still not dumbed-down enough for some people.

..a valiant and worthwhile goal. Setting aside my several recent posts here which have touched on some esoteric matters I usually write with the "interested and reasonably intelligent non-engineer" as the target.

So keep up the good work BUT don't lose sight of "there's none so blind as those who will not see..."

 

[Major_Tom]

Leftysergeant, verinage demos do not show that the crush down phase happens before the crush up phase as Bazant claims for his 1-D stick model.

We find many different crush up, crush down ratios in verinage demos, but I haven's seen a single case of crush down before crush up, have you?

We notice close to a 1:1 crush up crush down ratio in the Balzac demo. A 1:1 ratio makes sense, but that is not what Bazant claims. He claims crush down, then crush up.

>>>>>>>>>>>>>>>>>>>>

Why is it an extreme stretch to apply the Bazant 1-D stick model based on column buckling for up and down propagation to 3-D objects and real buildings?

Because Bazant justifies very little early crush up based on the fact that there is insufficient upward force to buckle the columns upwards.

Hence the concept of "crush down, then crush up".

Now let's use the same logic for a real building: Does any thinking person believe that the upper columns will ride on the debris zone B, which provides insufficient upward force to prevent the columns from collectively buckling upward, hence the upper portion of the building will remain largely undamaged?

Can you see how absurd it is to claim that no upward buckling saves the upper portion of a real building from crush-up?

In a steel building with concrete and metal floor slabs, the upper columns may just spear through the flooring with ease. There are many possiilities, but their buckling strength is certainly not going to save the upper portion from serious, serious damage.

WHen you apply the Bazant 1-D stick model and the concept of crush down, then crush up to real buildings, you are assuming that the column strength and it's resistance to buckling upwards will save the upper portion from early crush up.

That is obviously crazy, so why do so many people do it, including R Mackey and Myriad?

I think it is because people do not realize that the Bazant argument for no early crush up depends on the upward force not exceeding the upper column yield strength (in BV and BL).

They forget on what the argument depends, and try to apply it to the 3-D world anyway.

 

[carlitos]

I am not an engineer!

Since you started your post with my username, I get the impression that you were intending to reply to my post, but I don't see any connection at all between my post and your response.

Three-hinge buckling is definitely part of Bazant's collapse model, and three-hinge buckling definitely cannot take place in one dimension, so any claim to the effect that every aspect of Bazant's collapse model is limited to one dimension is clearly false. Does that help?

Respectfully,
Myriad

Leftysergeant, verinage demos do not show that the crush down phase happens before the crush up phase as Bazant claims for his 1-D stick model.

...

Why is it an extreme stretch to apply the Bazant 1-D stick model based on column buckling for up and down propagation to 3-D objects and real buildings?

...

WHen you apply the Bazant 1-D stick model and the concept of crush down, then crush up to real buildings, you are assuming that the column strength and it's resistance to buckling upwards will save the upper portion from early crush up.

That is obviously crazy, so why do so many people do it, including R Mackey and Myriad?

I think it is because people do not realize that the Bazant argument for no early crush up depends on the upward force not exceeding the upper column yield strength (in BV and BL).

They forget on what the argument depends, and try to apply it to the 3-D world anyway.

Can someone clarify the obvious disconnect above, between three hinge buckling and "1-D sticks." Thank you in advance.

 

[Major_Tom]

The truth is many people apply the concept of crush down, then crush up to 3-D situations. Consider a great example from BLGB. Bazant writes:

From BLGB, pg 894,5: “Generalization of Differential Equation
of Progressive Collapse

The gravity-driven progressive collapse of a tower consists of two
phases—the crush-down, followed by crush-up (Fig. 2 bottom)—
each of which is governed by a different differential equation
(Bažant and Verdure 2007, 312–313). During the crush-down
phase, the falling upper part of the tower (C in Fig. 2 bottom),
having a compacted layer of debris at its bottom (zone B), crushes
the lower part (zone A) with negligible damage to itself. During
the crush-up, the moving upper part C of the tower is crushed at
the bottom by the compacted debris B resting on the ground.
The fact that the crush-up of entire stories cannot occur simultaneously
with the crush-down is demonstrated by the condition
of the dynamic equilibrium of compacted layer B, along with an
estimate of the inertia force of this layer due to vertical deceleration
or acceleration; [see Eq. (10) and Fig. 2(f) of Bažant and
Verdure (2007)]. This previous demonstration, however, was only
approximate since it did not take into account the variation of
crushing forces Fc and Fc ‘ during the collapse of a story. An accurate
analysis of simultaneous (deterministic) crush-up and
crush-down is reported in Bažant and Le (2008) and is reviewed
in the Appendix, where the differential equations and the initial
conditions for a two-way crush are formulated. It is found that,
immediately after the first critical story collapses, crush fronts
will propagate both downward and upward. However, the
crush-up front will advance into the overlying story by only about
1% of its original height h and then stop. Consequently, the effect
of the initial two-way crush is imperceptible and the original hypothesis
that the crush-down and crush-up cannot occur simultaneously
is almost exact.”

Fig. 2. (Top)Scenario of collapse; (bottom) crush-down and crush-up phases of collapse; (A) intact stationary (lower) part; (B) dense layer of crushed debris; and (C) intact moving (upper) part



Is Bazant applying his crush down, then crush up model to the WTC towers in this quote and in the figures, or is he only describing and and illustrating the theoretical scenario best able to survive as an extreme case (which we do not expect to match the actual towers)?

I see no mention of this only as a theoretical case most optimal for survival. Are we to assume so?

He never refers to the diagrams as only an extreme, theoretical case based on assumptions most optimal for survival.

Myriad or others, should we assume this is only the case most optimal for survival?