OOS Collapse Propagation Model

[Oystein]

I personally am not interested in the behavior of people in the debate discussion....
At this point all that interests me would be discussions about initiation of the collapses. I personally am not troubled by the collapse phase... ...
I don't care what NIST or AE911T or others said in the past or even today... or who said what when.

Then this thread is not for you.

 

[LSSBB]

A three step process for Major_Tom:

Step 1: for Major_Tom, learn how to read introductions and what the authors of papers say what their purpose is.
Step 2: learn how to look at pictures in those papers:
[qimg]http://www.internationalskeptics.com/forums/imagehosting/thum_16329544116e124fcb.png[/qimg]
Step 3: Stop pretending to be the smartest person in the room. You're not.


You've noticed that BV uses terms like m(z) to define the mass of the upper block. And then you still claim z is used for something else. Bizarre...

He won't even say what his ROOSD coordinate frame is, because he still doesn't present his own theory mathematically. He won't put his own car in the race, yet wants to be declared the victor based on his perception of the other cars and who he thinks the fans are of the other drivers and what they believe. What an eccentric performance.

 

[Oystein]

The point is simple. You do not have the capacity to properly assess the ROOSD model because you cling to the dinosaur Bazant paper BV with religious conviction.

Who is "you" here, M_T? Not me!
Yet you keep bringing up long past posts of mine.
Does this further understanding of the ROOSD model? No.
Does this further understanding of what caused the WTC collapses? No.
Does this further understanding of any 9/11 conspiracy theory? No.
Does this further understanding of my psychology? No.
Does this bring us any closer to having a proper mathetical model for collapse progression? No.
Does this help you improve your book, rid it of erroneous titles and make it a more concise and pleasant read? No.
Does this educate anyone? No.
Does this serve any purpose other than annoy me along with everybody else? No!

Please drop the condescending and pompous personalisations! They are a tedious waste of time!


A couple of days you announced a mathematical approach to ROOSD.
There wasn't a mathematical approach to ROOSD.
When will you present your mathematical approach to ROOSD? I am waiting!
The Bazant papers aren't ROOSD
My psychology isn't ROOSD.
This thread isn't ROOSD.

Is this thread about ROOSD? Major_Tom, please answer this one question: Is this thread about ROOSD?
Then please let it be a thread about ROOSD, and do not derail it into a thread about my or "our" psychology or mental capacity.

In other words: Cut the crap. Cut to the chase. 4 years plus, and counting, and not a single high rise is any closer to becoming safer, no emgineering textbook is any closer to being improved, no silly CT is any closer to being debunked, and no history book is any closer to being rewritten.
Do not wait for MY mental capacity to grow to a state where I can as effortlessly and brillantly as you see through Bz's ******** and crush up and down his equations. There is no purpose served in this, and I will not ever follow your pompous, tedious and condescending guide tour through every paragraph and every equation ever written by every author who ever publiched on the collapses.

Don't wait for me to crawl in the dust before you. I won't. Nobody will.

The ROOSD model is the best existing lens through which to examine all other models and claims of the WTC1 and 2 collapse progressions, including Bazant.

Just bring on your mathematical approach to ROOSD - if ever there will be one.
Or, if there is already one, put the header "Mathematical approach to ROOSD" on top of it, instead of on top of a section that presents something entirely different.

 

[Newtons Bit]

He's "chiding" us for not understanding an equation, posts a "quiz" on a variable, and then gets the answer wrong. FFS, Bazant defines the variable in a diagram, how can he get that wrong?

 

[DGM]

The point is simple. You do not have the capacity to properly assess the ROOSD model because you cling to the dinosaur Bazant paper BV with religious conviction.

The ROOSD model is the best existing lens through which to examine all other models and claims of the WTC1 and 2 collapse progressions, including Bazant.

I'll ask you a simple question. Do you consider your ROOSD model to be the same type of model as Bazant et al?

A simple yes or no will do. If yes, I think an explanation would be in order.

 

[beachnut]

The point is simple. You do not have the capacity to properly assess the ROOSD model because you cling to the dinosaur Bazant paper BV with religious conviction.

The ROOSD model is the best existing lens through which to examine all other models and claims of the WTC1 and 2 collapse progressions, including Bazant.

What.

What does it mean.

Actually I think a floor can only hold 29,000,000 pounds, and the mass above the collapse area is greater; is the best "lens" to explain why the WTC collapse progression exists. Maybe a level of abstraction too simple for a super acronym system like ROOSD, the likes I have not seen since we did acronyms at AFWAL/FIGR, like MAGIC, or DAVID.

Are you going to use Bazant's math as model for ROOSD math models. Or what.

Why do you make up lies about people, like, we did not read Bazant. Papers on my computers for 6 to 7 years.

Summarize in your own words how and why the best existing lens through which to examine all other models and claims of the WTC1 and 2 collapse progressions, is ROOSD?

God that is so much BS, it is worse than water-boarding for me.

Sorry MT, I will try to get some help to understand what you are saying, it is way over my head, i am a :just plain, you know, ... I am but a simple pilot, and only went to engineering school to give me something to think about with digging ditches, and sweeping the factory floor at Fitzgerald Engineering in Atlanta... although pulling 7.33 g chasing clouds has it moments, and the afterburner was cool... (and gee, i did not want to go to get a masters the USAF made me get the master in engineering, now i have too much to think about when digging ditches, or plowing the south 40...)

So I will seek help to understand the "just plain"ness of my failure to be...

 

[tsig]

I suppose those who feel they are attacked respond in kind... but that is perhaps almost as bad. I find the ad homs absurd.

It appears to me that Tom has presented a theme which is about how the collapses were botched for years and there was an absence of critical thinking and a sort of follow the herd mentality from people who should have been smarter. I was not involved in the debate/discussion at all until late 2009. I simply never looked closely and basically took the two positions... CD and non CD on face value. It appears that the CD position has no merit at all and the non CD explanations were essentially off the mark. That's pretty interesting considering all the intelligent people weighing in.

I don't know if it's important for mea culpas and it's not very important to harangue people who got it wrong. The record speaks for itself. What is disappointing to see is the fact that the discussion has stalled and no serious study / discussion / debate is taking place about the initiation phase from plane strike to top drop. It also appears to me that Tom's approach was to turn careful observations in a hypothesis and not set off with some theoretical mathematical approach a la Mr Bz et al. Conceptually that seems to me to make sense... describe what you see and THEN do the math, I suppose. To me the technical explanations for the ROOSD process are all settled physics and engineering with perhaps a fog about how the concrete was so completely pulverized with is counter intuitive. Truthers go on and on about no recognizable telephones or PCs but that doesn't surprise me. My intuition say such things would be crushed to tiny unrecognizable bits in the midst of a collapse of hundred of thousands of tons.... and massive steel members would survive largely intact. I think materials science and physics/mechanics confirms this.

The part which confounds truthers and is not well explained by the official story is how the heat was able to disintegrate the structure and cause the tops to drop. It is know that heat does degrade materials, distort them and so forth. But how much and where and what materials did what to cause the top to drop is where we need more clarity in my opinion. I'd like to see discussion about that. But perhaps this is less knowable from observations since we can't SEE heat and we can't see INSIDE the tops during the post plane strike period. It's like trying to diagnose a patient without xray, cat scans, MRIs, and blood work for example and just looking at them. And this is where theoretical models may have to suffice.

Maybe.

Are you trying to locate hot spots in the fire?

If you want to have a discussion with MT then why don't you just have one and cease berating others who have had much more interaction with him?

 

[JSanderO]

I am interested in the initiation period/mechanisms not in the collapse phase or who said what when.

 

[DGM]

I am interested in the initiation period/mechanisms not in the collapse phase or who said what when.

So ROOSD really is of no interest to you? Why post in this thread?

Nothing M_T has posted fits your description of interest.

 

[JSanderO]

So ROOSD really is of no interest to you? Why post in this thread?

Nothing M_T has posted fits your description of interest.

It is as part of the continuum of many processes/mechanisms which destroyed the tower.

For those who claim trusses caused the inward bowing... explain this:

https://www.metabunk.org/data/MetaMirrorCache/15d987530fb19f490198129171c8d200.gif

Clearly what you see is the overloading and BUCKLING of the facade at the corner... so the cartoon posted above has no applicability.

 

[Major_Tom]

You've noticed that BV uses terms like m(z) to define the mass of the upper block. And then you still claim z is used for something else. Bizarre...

You need a little help?





What is Bazant doing in the paper?

Abstract:

Progressive collapse is a failure mode of great concern for tall buildings, and is also typical of building demolitions. The most infamous paradigm is the collapse of the World Trade Center towers. After reviewing the mechanics of their collapse, the motion during the crushing of one floor or group of floors and its energetics are analyzed, and a dynamic one-dimensional continuum model of progressive collapse is developed. Rather than using classical homogenization, it is found more effective to characterize the continuum by an energetically equivalent snap-through. The collapse, in which two phases—crush-down followed by crush-up—must be distinguished, is described in each phase by a nonlinear second-order differential equation for the propagation of the crushing front of a compacted block of accreting mass. Expressions for consistent energy potentials are formulated and an exact analytical solution of a special case is given. It is shown that progressive collapse will be triggered if the total internal energy loss during the crushing of one story equal to the energy dissipated by the complete crushing and compaction of one story, minus the loss of gravity potential during the crushing of that story exceeds the kinetic energy impacted to that story. Regardless of the load capacity of the columns, there is no way to deny the inevitability of progressive collapse driven by gravity alone if this criterion is satisfied for the World Trade Center it is satisfied with an order-of-magnitude margin. The parameters are the compaction ratio of a crushed story, the fracture of mass ejected outside the tower perimeter, and the energy dissipation per unit height. The last is the most important, yet the hardest to predict theoretically. It is argued that, using inverse analysis, one could identify these parameters from a precise record of the motion of floors of a collapsing building. Due to a shroud of dust and smoke, the videos of the World Trade Center are only of limited use. It is proposed to obtain such records by monitoring with millisecond accuracy the precise time history of displacements in different modes of building demolitions. The monitoring could be accomplished by real-time telemetry from sacrificial accelerometers, or by high-speed optical camera. The resulting information on energy absorption capability would be valuable for the rating of various structural systems and for inferring their collapse mode under extreme fire, internal explosion, external blast, impact or other kinds of terrorist attack, as well as earthquake and foundation movements.

He is deriving a one-dimensional continuum model for crushing front propagation of a collapsing building that meets 4 simplifying assumptions.



Key derivations within the paper:

Differential equations of progressive collapse or demolition

Equation 12

Equation 17

Equivalent versions of equations 12 and 17 are equations 20 and 21





What does Bazant believe his eq 12 represents?



Bazant states in BV:

Eqs. (12) and (17) show that Fc(z) can be evaluated from precise monitoring of motion history z(t) and y(t), provided that m(z) and lamda(z) are known. A millisecond accuracy for
z(t) or y(t) would be required. Such information can, in theory, be extracted from a high-speed camera record of the collapse. Approximate information could be extracted from a regular video of collapse, but only for the first few seconds of collapse because later all of the moving part of the WTC towers became shrouded in a cloud of dust and smoke (the visible
lower edge of the cloud of dust and debris expelled from the tower was surely not the collapse front but was moving ahead of it, by some unknown distance)."

From the BV quote above, does Bazant consider the identification of the crush front or the measurement of the displacement of the WTC crush front to be possible?

No. According to him the shroud of dust and smoke blocked moving parts of the WTC towers, like the collapse front, from view.





BV eq 12 is a second order differential equation in one variable, z. A differential equation like this is merely a relationship between the displacement, velocity, and acceleration of an object or a point on an object. From these relations one tries to find the displacement z(t).


The variable z(t) represents the displacement of what point?

In Seffen's eq 12 the variable maps the collapse front of WTC1.

In BV eq 12 there are 2 dynamic points along the collapsing building that can be measured: the crush front and the roofline. z(t) maps the crush front.





DERIVATION OF EQ 12

How did he model the WTC collapse in order to derive equation 12?


The variables, parameters and assumptions used to derive BV eq 12 are all described in a single section titled, "One-Dimensional Continuum Model for Crushing Front Propagation", reproduced below:

APPLICATION OF EQ 12

Does Bazant make physical predictions about the propagation of the actual WTC collapse front from his paper by using eq 12?


Yes. The BV paper is re-examined in discussions by Gourley and Szuladzinski and a closure by Bazant and Le, which is clearly an intended point-by-point rebuttal of the Gourley and Szuladzinski discussions. Bazant makes a couple of physical predictions in BV within the quote below, but he makes quite a few more predictions about the actual WTC collapses in the closure paper.



His implications and conclusions for these equations are clearly listed on page 318:

Implications and Conclusions

1. If the total internal energy loss during the crushing of one story representing the energy dissipated by the complete crushing and compaction of one story, minus the loss of
gravity potential during the crushing of that story exceeds the kinetic energy impacted to that story, collapse will continue to the next story. This is the criterion of progressive collapse trigger Eq. 5. If it is satisfied, there is no way to deny the inevitability of progressive collapse driven by gravity alone regardless of by how much the combined strength of columns of one floor may exceed the weight of the part of the tower above that floor . What matters is energy, not the strength, nor stiffness.

2. One-dimensional continuum idealization of progressive collapse is amenable to a simple analytical solution which brings to light the salient properties of the collapse process.
The key idea is not to use classical homogenization, leading to a softening stress-strain relation necessitating nonlocal fi-
nite element analysis, but to formulate a continuum energetically equivalent to the snapthrough of columns.

3. Distinction must be made between crush-down and crush-up phases, for which the crushing front of a moving block with accreting mass propagates into the stationary stories below, or into the moving stories above, respectively. This leads to a second-order nonlinear differential equation for propagation of the crushing front, which is different for the crush-down phase and the subsequent crush-up phase.

4. The mode and duration of collapse of WTC towers are consistent with the present model, but not much could be learned because, after the first few seconds, the motion became obstructed from view by a shroud of dust and smoke.
`
5. The present idealized model allows simple inverse analysis which can yield the crushing energy per story and other properties of the structure from a precisely recorded history
of motion during collapse. From the crushing energy, one can infer the collapse mode, e.g., single-story or multistory buckling of columns.

6. It is proposed to monitor the precise time history of displacements in building demolitions—for example, by radio telemetry from sacrificial accelerometers, or high-speed optical
camera—and to engineer different modes of collapse to be monitored. This should provide invaluable information on the energy absorption capability of various structural systems, needed for assessing the effects of explosions, impacts,
earthquake, and terrorist acts.

Is it possible to fact-check the dynamic predictions of Bazant using information within the OOS propagation model?

Absolutely.



Limits in Bazant's understanding of WTC collapse mode and collapse features:



Why didn't Bazant compare his prediction to actual measurements of the collapse front speed?


The following quotes explain why he didn't.

BV from the abstract:

The parameters are the compaction ratio of a crushed story, the fracture of mass ejected outside the tower perimeter, and the energy dissipation per unit height. The last is the most important, yet the hardest to predict theoretically. It is argued that, using inverse analysis, one could identify these parameters from a precise record of the motion of floors of a collapsing building. Due to a shroud of dust and smoke, the videos of the World Trade Center are only of limited use. It is proposed to obtain such records by monitoring with millisecond accuracy the precise time history of displacements in different modes of building demolitions. The monitoring could be accomplished by real-time telemetry from sacrificial accelerometers, or by high-speed optical camera. The resulting information on energy absorption capability would be valuable for the rating of various structural systems and for inferring their collapse mode under extreme fire, internal explosion, external blast, impact or other kinds of terrorist attack, as well as earthquake and foundation movements.

From BV conclusions:

4. The mode and duration of collapse of WTC towers are consistent with the present model, but not much could be learned because, after the first few seconds, the motion became obstructed from view by a shroud of dust and smoke.

5. The present idealized model allows simple inverse analysis which can yield the crushing energy per story and other properties of the structure from a precisely recorded history
of motion during collapse. From the crushing energy, one can infer the collapse mode, e.g., single-story or multistory buck ling of columns.

6. It is proposed to monitor the precise time history of displacements in building demolitions—for example, by radio telemetry from sacrificial accelerometers, or high-speed optical
camera—and to engineer different modes of collapse to be monitored. This should provide invaluable information on the energy absorption capability of various structural systems, needed for assessing the effects of explosions, impacts,
earthquake, and terrorist acts.

These were the limitations in WTC observation and measurement Bazant faced in 2007.


At that time it was commonly accepted that it wasn't possible to map motion of the crush fronts. It was believed that it was only possible to measure WTC1 roofline motion for only the first few seconds of the collapse and combine that information with seismic records which may indicate the moment of completion of the collapse.

After these papers were written these limitations were removed and much more accurate mappings became available for the first time since the collapses.

 

[Major_Tom]

In his own words, he defines all variables right in front of your nose.

 

[Major_Tom]

It is as part of the continuum of many processes/mechanisms which destroyed the tower.

For those who claim trusses caused the inward bowing... explain this:

https://www.metabunk.org/data/MetaMirrorCache/15d987530fb19f490198129171c8d200.gif

Clearly what you see is the overloading and BUCKLING of the facade at the corner... so the cartoon posted above has no applicability.

The same pull-in seen on the WTC2 north face in the gif is also seen on the west face of WTC1.

If you are as bored as I am in this thread we can go back to discussing the initiation mechanisms now.

A good place to do that would be in the following threads, set up for that purpose:


October 26, 2010: WTC 1 Feature List


June 1, 2011: WTC 2 Feature List


But we cannot use these because they were removed from this forum. It was reasoned that they "had nothing to do with conspiracy theories."


In my posting history here I was allowed to start only 2 threads. We could use the other if you like.

 

[JSanderO]

Mr B seems to imply/state that structural material from inside the tower was ejected outward. It looks to me that some material spilled over the side when at the release zone when the top came down... but the the material shooting out through the glass AHEAD of the falling debris/crush front was not structural material but contents on / between the slabs... forced out by over pressure from escaping air. The facade peeled the core toppled... the slabs crushed down along with some heavy steel outside the cores on the mech floors. Open your eyes!

 

[Newtons Bit]

z(t) is the distance from the top of the upper block to the bottom of the upper block, Major_Tom. We refer to that as the height of the upper block around here. I don't care to play your semantic games if that's what you're trying to do. In any event, if you want to be a pendant, you need to try and be more consistent.

 

[JSanderO]

Mr Bit... could you respond to my points about the so called pull in of the facade... the explanation of which you felt was in the links. This may be OT.... and relate more to the initiation than the collapse.

I am not here to argue but to learn.

 

[rwguinn]

One of the things engineers have learned over the years is that consistency leads to accuracy.
terms like x, y, and z are axes of a coordinate system. terms like u,v,and w arre also axes of a coordinate system, rotated with respect to x,y, and z. Almost universally, x and y are the plan view as seen from above, with "z" being the vertical axis. (This is so imbedded that all CAD programs I know of start with that assumption).
The variable "t" is, unless otherwise specified, time. A term with "(t)", or "(anything)" after it; e.g., z(t), a(x), is that variable as a function of whatever is inside the (). a "." over a term is the first derivative of that term with respect to time. 2 "."s are the second derivative of that term with respect to time. (Since that is hard to do on a typewriter or word processor, the " ' " has come into use, thus x'=first derivative of distance wrt time (Velocity) and x'' is 2nd derivative (acceleration)
These things are so universally known and taught that any competent engineer can pick up a paper and immediately know just what the hell the other guy is talking about. And just to make sure, virtually all papers have, at the front, a definition of terms section to reiterate this, and to define variables that are used in possibly ways that might not be familiar to the reader.

Doest that assist you in any way, M_T?

 

[DGM]

For those who claim trusses caused the inward bowing... explain this:

https://www.metabunk.org/data/MetaMirrorCache/15d987530fb19f490198129171c8d200.gif

Clearly what you see is the overloading and BUCKLING of the facade at the corner... so the cartoon posted above has no applicability.

The inward bowing came before the buckling. I don't believe anyone claims the trusses caused the exterior columns to buckle, they just helped get the process started.

 

[JSanderO]

Although I was not focused on the technical discussions in the early years post collapse I don't recall seeing ANYONE doing any sort of detailed analysis - motion studies from the vids etc. until years after *they* figured it out and published papers!

 

[rwguinn]

Although I was not focused on the technical discussions in the early years post collapse I don't recall seeing ANYONE doing any sort of detailed analysis - motion studies from the vids etc. until years after *they* figured it out and published papers!

This is off-topic and has been discussed and analyzed ad infinitum over the past 13 years.
The topic here is what happened after the initial event; i.e., from t=0+e onwards.