Merged Applicability of Bazant's model to the real world

[pgimeno]

That is your retort, talk! Wave hands pull a number out of the vapor and that is it?
How would you know? Source and references please.

I believe he is based on Bazant and Zhou 2002 Appendix III, except he ignores the parts that say "(if we assume, optimistically, fixed ends [for the columns])" and "This curve is an optimistic upper bound since, in reality, the plastic hinges develop fracture (Bažant and Planas 1998), and probably do so already at rather small rotations."

 

[Oystein]

This poster is arguing that a jolt, which would have induced column buckling, could have been missed on one hand, and then that freefall would have occurred afterward.

Just so everyone can judge the quality of the above post and the knowledge level of the poster, it is important to note that it is impossible for a freefall to occur in a natural building collapse, as the resistance during column buckling never drops below 25% of the original intact resistance,

You don'tr believe this, do you?? Methinks you're invoking magic here.
As the main failure mode surely was breaking (of bolts and welds) at the joints, I am sure resistance usually dropped to 0%.

and since the columns in the towers had low slenderness ratios with factors of safety of 3.00 to 1 minimum, it would take an impulse significantly higher than 1g to cause them to buckle.

Yes, but these impulses could be very short (small fractions of a second) and easily missed in your low sampling frequency.

 

[Tony Szamboti]

You don'tr believe this, do you?? Methinks you're invoking magic here.
As the main failure mode surely was breaking (of bolts and welds) at the joints, I am sure resistance usually dropped to 0%.



Yes, but these impulses could be very short (small fractions of a second) and easily missed in your low sampling frequency.

There is no evidence of columns breaking at bolts and welds early in the collapse of WTC 1. The loading would have been vertical at that point. The only evidence for it is later on when lateral loads would have been possible.

Ryan Mackey tried to use the same argument in our debate, that you are about the bolts, and he produced examples which were from 5 and 8 stories below the collapse initiation, but nothing from the initiation zone. He had no comeback when I confronted him with that, as apparently the steel from the initiation zone wasn't saved. How interesting.

You apparently still don't get that the impulse itself is not what is observable. It is the velocity loss which is an effect of the impulse and is observable since it takes much longer to recover from.

 

[femr2]

Just so everyone can judge the quality of the above post and the knowledge level of the poster, it is important to note that it is impossible for a freefall to occur in a natural building collapse, as the resistance during column buckling never drops below 25% of the original intact resistance

Your position makes no sense Tony, regardless of MIHOP or not.

Let's assume the resistance of a number of columns is *removed*.

You say that the ~0.7g acceleration is due to resistance of structural members that have not been *removed*.

So...where are the *jolts* caused by axial impact of those structural members ?

 

[Tony Szamboti]

Your position makes no sense Tony, regardless of MIHOP or not.

Let's assume the resistance of a number of columns is *removed*.

You say that the ~0.7g acceleration is due to resistance of structural members that have not been *removed*.

So...where are the *jolts* caused by axial impact of those structural members ?

No, if you read what we said it was that we only considered the first collision and allowed the upper section to then fall without additional collisions just to make the initial point that there was no impulse that caused the collapse continuation as Dr. Bazant had theorized.

You and W.D. Clinger are picking on irrelevant minutia and the jolts you both claim to see are extremely weak and could not possibly have caused failure, making me wonder just what the point of your argument actually is.

 

[Oystein]

There is no evidence of columns breaking at bolts and welds early in the collapse of WTC 1. The loading would have been vertical at that point. The only evidence for it is later on when lateral loads would have been possible.

Assuming this is true. Absence of evidence means... what?

We know however that early on in the collapse, during collapse initiation in fact, columns were pulled laterally inwards, and the top part tilted.
Both mean horizontal shifting and thus the kind of lateral load that the structure was not designed to handle.

You apparently don't read as you still don't get that the impulse itself is not what is observable. It is the velocity loss which is observable and an effect of the impulse and takes much longer to recover.

You apparently don't read as you still don't get that velocity loss is more likely than noit to get smoothed out due to the low sampling rate. W.D.Clinger has shown that your own data is better explained by functions that involve actual decelerations than by functions that do not.
femr2 has come up with a valid and yet unrefuted method to compute the maximum duration of overall deceleration that would be missed by your sampling method.
ozeco41 and others have convincingly argued that many local decelerations do not necessarily translate into an overall deceleration of the entire assembly.
pgimeno and others have reminded you time and again that your "missing jolt" paper rests on Bazant and Zhou's assumption of ideal column to column contact. An assumption that Bazant and Zhou's themselves describe as a best case scenario, as a boundary condition. It has as such practically zero probability of representing reality.

 

[Oystein]

No, if you read what we said it was that we only considered the first collision and allowed the upper section to then fall without additional collisions just to make the initial point that there was no impulse that caused the collapse continuation as Dr. Bazant had theorized.

You and W.D. Clinger are picking on irrelevant minutia and the jolts you both claim to see are extremely weak and could not possibly have caused failure, making me wonder just what the point of your argument actually is.

Ok. Let's assume that all columns had the strength to carry 3 times their normal load. Let's assume all columns were in unblemished state. If a moving top block now falls onto all columns perfectly and absolutely simultaneously, then we would expect to see an (average) deceleration of -2g (for a very brief momentm, until columns are overloaded).
However if only half the columns impact, and the other half an instant later, we'd see only -1g, for twice as long.

But our assumptions are wrong, on several counts:
- Column-on-column impact would not be perfect, and not happen at all in several places
- Not all columns would still have their full strength, as thos impacted early on were already stressed by heat, sagging floors, etc.
- Impacts are not as vertical as the static loads the columns are designed for
- The factor 3 is possibly an overstatement. NIST assumes 1.667, IIRC.

If we correct all assumptions, we will probably find that the maximum expected deceleration would be much closer to 0 than -1g. Which increases the probability that your low sampling rate will miss that peak.

 

[femr2]

No, if you read what we said it was that we only considered the first collision and allowed the upper section to then fall without additional collisions just to make the initial point that there was no impulse that caused the collapse continuation as Dr. Bazant had theorized.

So why is there no massive *jolt* after the *second* collision, or the *third*, or the *tenth*, or ... ?

Again, you say that the ~0.7g acceleration is due to resistance of structural members that have not been *removed*.

So...where are the *jolts* caused by axial impact of those structural members ?

I also note your use of the word allowed there. What exactly do you mean by that ?

Are you saying that *the missing jolt* is simply a refudation of the Bazant limiting case, or that you actually expect the *jolt* in reality...

...but don't expect a *jolt* for the *second* impact ?

You and W.D. Clinger are picking on irrelevant minutia and the jolts you both claim to see are extremely weak and could not possibly have caused failure, making me wonder just what the point of your argument actually is.

The point is to explore the validity and scope of your Missing Jolt claim.

If it's correct, you should have no problem responding, in full detail, to all the questions you have been asked.

 

[Disbelief]

Just so everyone can judge the quality of the above post and the knowledge level of the poster, it is important to note that it is impossible for a freefall to occur in a natural building collapse, as the resistance during column buckling never drops below 25% of the original intact resistance, and since the columns in the towers had low slenderness ratios with factors of safety of 3.00 to 1 minimum, it would take an impulse significantly higher than 1g to cause them to buckle.

Bolding mine. Since you say freefall is impossible in a natural collapse, can you show where freefall occurs in a CD? Thanks.

 

[Patriots4Truth]

Question: How much data has NIST not released so far? What do we know about this data?

 

[carlitos]

If I were a paranoid conspiracist, what would help my incredulous argument vis a vis NIST reporting the most?

a - Assuming that the most relevant data is the data that wasn't released.
b - Reading the released information for comprehension.

 

[Patriots4Truth]

all I know is: "The decision to withhold the data was based on the fact that the capabilities of the WTC 7 collapse initiation and global collapse models are unprecedented, in that they provide validated models that can predict collapse of typical tall buildings. If released, these models would provide a powerful tool to groups and individuals interested in simulating building collapses and devising ways to destroy buildings." pg. 2 - right column (.pdf)

say what???

I repeat: How much data has NIST not released so far? What do we know about this data?

 

[beachnut]

all I know is: "The decision to withhold the data was based on the fact that the capabilities of the WTC 7 collapse initiation and global collapse models are unprecedented, in that they provide validated models that can predict collapse of typical tall buildings. If released, these models would provide a powerful tool to groups and individuals interested in simulating building collapses and devising ways to destroy buildings." pg. 2 - right column (.pdf)

say what???

I repeat: How much data has NIST not released so far? What do we know about this data?

You are off topic, start a thread on why you fail to comprehend NIST like the rest of 911 truth. Bazant's model; get on topic.

911 truth posts off topic and spreads lies, exposing their ignorance on engineering and NIST? Bazant, try to say something about the model, or start your thread of woo ideas on NIST. Stop acting so truthy, spreading nonsense.

I repeat: you are off topic.

 

[W.D.Clinger]

Just so everyone can judge the quality of the above post and the knowledge level of the poster, it is important to note that it is impossible for a freefall to occur in a natural building collapse, as the resistance during column buckling never drops below 25% of the original intact resistance, and since the columns in the towers had low slenderness ratios with factors of safety of 3.00 to 1 minimum, it would take an impulse significantly higher than 1g to cause them to buckle.

Just so everyone can judge the quality of Tony Szamboti's argument from his personal authority:

Tony continues to get his units wrong. Impulses and accelerations do not have the same units.

More generally, Tony is arguing with Zdeněk Bažant^WP:

As generally accepted by the community of specialists in structural mechanics and structural engineering (though not by a few outsiders claiming a conspiracy with planted explosives), the failure scenario was as follows:

Zdeněk Bažant and Mathieu Verdure. Mechanics of progressive collapse: learning from World Trade Center and building demolitions. Journal of Engineering Mechanics 133(3), March 1, 2007, pages 308-319.

No, if you read what we said it was that we only considered the first collision and allowed the upper section to then fall without additional collisions just to make the initial point that there was no impulse that caused the collapse continuation as Dr. Bazant had theorized.

So says the fellow who still doesn't understand the distinction between impulse and acceleration.

You and W.D. Clinger are picking on irrelevant minutia and the jolts you both claim to see are extremely weak and could not possibly have caused failure, making me wonder just what the point of your argument actually is.

The point is that your argument began with a fallacy and went downhill from there.

You may think the distinction between impulse and acceleration is irrelevant minutia, but your ongoing failure to understand that distinction is just one of the many reasons you fear peer review. If you had a legitimate argument, you would submit it to a legitimate journal, such as the Journal of Engineering Mechanics. As it happens, you have nary a technical paper to your name.

You think your personal authority can salvage your argument against Bažant. I've got news for you: Your personal authority is insufficient to salvage your argument against femr2.

 

[Myriad]

say what???

What it means is, that software could be used to figure out the best place(s) to put a bomb to cause a given building to collapse.

That represents a hazard to public safety because psychopaths, criminals, and terrorists would be among the potential users.

Agree or disagree, it's pretty easy to understand. So why all the indignant feigned incomprehension?

Respectfully,
Myriad

 

[ozeco41]

Just so everyone can judge the quality of the above post and the knowledge level of the poster, it is important to note that it is impossible for a freefall to occur in a natural building collapse, as the resistance during column buckling never drops below 25% of the original intact resistance, and since the columns in the towers had low slenderness ratios with factors of safety of 3.00 to 1 minimum, it would take an impulse significantly higher than 1g to cause them to buckle.

Just so everyone can judge the quality of Tony Szamboti's argument from his personal authority:

Tony continues to get his units wrong. Impulses and accelerations do not have the same units...

Sadly it's even worse than that. Every time someone picks one of his errors it seems to let him think he got away with all the other untruths,

And the false claim that columns had to be buckled outranks the error in what he uses to measure the applied impact. The reality is that the global collapse of the twin towers buckled few if any columns. Whether they were buckled by "impulse", by 1g acceleration or by static load. In fact no matter what wrong units he uses to measure what buckles columns the real fact is that few if any were buckled. That is the main reason of the near G - near free fall - collapse rate. Not many columns resisting with full axial loads sufficient to cause buckling.

Where are the buckled outer tube columns?

And remember the standing spire of core columns. What price on even many of the core buckling?

I've been pointing out to Tony and he has been denying that most columns were bypassed without buckling during the global collapse. Something the rest of us could keep in mind when highlighting his other errors.

 

[ergo]

What it means is, that software could be used to figure out the best place(s) to put a bomb to cause a given building to collapse.

That represents a hazard to public safety because psychopaths, criminals, and terrorists would be among the potential users.

Agree or disagree, it's pretty easy to understand. So why all the indignant feigned incomprehension?

Yes, because bringing down buildings is always the terrorist's or psychopath's first line of attack... It's so easy, after all.

 

[ergo]

Anyway, according to you folks, all one needs to do is fly a plane into a building. Why worry about where explosives are placed?

 

[excaza]

Aw, it's ok little buddy

 

[ergo]

The only thing capable of supporting the weight of the upper block is the fully intact and braced columns of the lower block. When the collapse starts, the connection between the columns of the upper block and lower block has severed. The columns of the upper block fall, mostly, onto the floors of the lower block. The floors can't support it and they collapse.

Only 15% were estimated by NIST to have been severed. The remaining 85% were not.

There's also the common misconception by "truthers" that the columns of the upper block should fall aligned with what's left of the columns of the upper block, never mind that the columns on both ends have been horribly mangled during the collapse initiation event.

There's a misconception by "d-bunkers" that, first of all, the upper block would "fall" through the 85% remaining columns, and secondly, that the imagined severing of the 15% damaged columns would produce a radical shift of the upper block, misaligning the remaining composition of columns.