Merged Discussion of femr's video data analysis

[femr2]

It is virtually impossible to determine whether the observed plastic buckling occurred prior to or after collapse initiation.

What plastic buckling are you referring to ?

Nobody disagrees that elastic buckling could result in failure at the splices.

Your point ?

By your own admission, ad many as 33% of the columns could fail in the middle (per your diagram) t[h]at way.

Could ?
By my admission ?
My diagram ?

What on earth are you talking about ?

For the region being discussed, the answer is...they didn't. The failures ocurred along bolted seams, not in *the middle*.

Are you trying to deflect from Dave Rogers' suggestion of inelastic buckling and hinge formation in the region ?

An additional 33% had splices at the floor, and the last 33% had splices at the floor above.
The splices could also fail due to the column buckling elastically.

They didn't.

Do you pay ANY attention to the scope of discussion ?

Dance, dance, dance...

You and Dave Rogers do appear to be doing so.

Try ensuring you are aware of the region being discussed.

I guess I'm jumping the gun when I say...

As long as everyone is aware that the break ocurred at the bolted seams along the staggered path highlighted, it's all good.

 

[DGM]

I guess I'm jumping the gun when I say...

As long as everyone is aware that the break ocurred at the bolted seams along the staggered path highlighted, it's all good.

You go on and on but, this fact has been known for years. Why would we expect a member NOT to yield at it's weakest point? So far it looks like the "anomaly" here is you're understanding of the term "buckle".

 

[femr2]

You go on and on but, this fact has been known for years.

Great. Perhaps you'd like to ask Dave Rogers why he wrote this...

You're confusing the inelastic buckling and hinge formation that happened during collapse initiation with the elastic buckling and inward bowing that preceded it.

Do you know what inelastic buckling Dave Rogers is referring to ? (He left the discussion when I asked him)

 

[DGM]

Great. Perhaps you'd like to ask Dave Rogers why he wrote this...


Do you know what inelastic buckling Dave Rogers is referring to ? (He left the discussion when I asked him)

I think you missed his point. Besides that, do you think there was NO inelastic buckling during "collapse initiation"?

Is there actually a point to this "debate"?

 

[ozeco41]

An interesting sequence. RE-ordered to put responses after the relevant post.

You're confusing the inelastic buckling and hinge formation that happened during collapse initiation with the elastic buckling and inward bowing that preceded it. Dave

Whoa there.

What inelastic buckling are you referring to ?

What hinge formation are you referring to ?

The discussion has been about some features in the initial collapse stage. But now Dave seems to be differentiating two stages one of "inelastic bucking" which occurred after some "elastic buckling and" So two stages. And the thought that occurs to me is "why is he differentiating and what are the two aspects he is seeing relevant to the section of wall being addressed. femr2 asks the same question as I would have posed BUT in slightly different words than I would have used. "what is this inelastic buckling".

So are you trying to argue that the columns could only have failed at the connections,...

We get no answer to the question - only a guess as to what femr2 may be getting at. Why the leading inference? Why not answer the question? It seems that we have gone from one step under discussion to two separate actions in sequence - so why not explain that? Instead we get:

... therefore any failure anywhere else indicates deliberate weakening of column trees?

Which looks like a quantum leap into implied MIHOP. Why?

So femr2 responds:

Why are you so paranoid ?

Where do you think I have suggested such ?

One thing I am doing is highlighting that something you just said "seems impossible" did in fact occur.

Well, not sure I would have used "paranoid" BUT femr2 gets a lot of these false accusations about MIHOP which is not under discussion at this stage even if it could be a future possibility.

Forget it. I've had enough of playing dance-around-the subject....

At this stage there has been no dancing but Dave opts out.

Then the totally uncalled for:

...and he'll answer

...and you'll belittle him

....MT will join in

....rinse and repeat. Same story since the thread started nearly 9 months ago

...where the only hook to hang "belittle" on is that one word "paranoid" which is fully understandable in the ongoing context of polarised debate with bi-directional needling "(alleged) truthers"<<<>>>"debunkers".

Why was there no comment on the inference in the bit of pre-judgement "indicates deliberate weakening".

As I said "An interesting sequence".

Now both sides can come down on me I suppose.

 

[DGM]

Now both sides can come down on me I suppose.

SHILL!

I think this all came from a discussion (starting around post 2240) about the theoretical "three hinge" that drifted into "show me this".

Started out good.

 

[femr2]

I think this all came from a discussion (starting around post 2240) about the theoretical "three hinge"

No, it's about the form of the break in the WTC2 East face perimeter, reaching back to post 2062 within which I asked you...

What was the WTC1 initiation sequence ?

...which resulted in...

I tend to think the building was "done" when the perimeter columns were pulled in. The actual sequence is of little concern for me.

...

Did IB result in perimeter column buckling ?

...

No, Overload did.

...
etc.

The break follows the purple line...

Given the discussion originated between you and I, I would have thought you'd be clear where it came from.

 

[BasqueArch]

 

[DGM]

No, it's about the form of the break in the WTC2 East face perimeter, reaching back to post 2062 within which I asked you...

...which resulted in...

...

...

...
etc.

The break follows the purple line...
[qimg]http://www.sharpprintinginc.com/911/images/photoalbum/13/ejection__locations.jpg[/qimg]

Given the discussion originated between you and I, I would have thought you'd be clear where it came from.

Then it drifted around to the definition of buckling and NB explaining how a member can "buckle" without failing itself. I know I was there. I also know Dave was talking about the usefulness of the "hinge/ inelastic buckling" discussed by Bazant.

Do you agree what he was referring to was not necessarily "observable"?


BTW: What is the point of beating this obvious fact to death (splice failure)?

 

[Newtons Bit]

Then it drifted around to the definition of buckling and NB explaining how a member can "buckle" without failing itself. I know I was there. I also know Dave was talking about the usefulness of the "hinge/ inelastic buckling" discussed by Bazant.

Not quite. A compression member that has buckled elastically has still failed. The compression capacity decreases over time at the same rate as the bending moment in the member increases. However at no time do the stresses in the member actually exceed the yield stress (hence no plastic hinges or permanent deformation).

I've also seen you misuse the term yield. You should know that that yield isn't always a failure in collapse prevention engineering. Yield just means that the peak stress in the shape exceeds the yield stress. This is not the point of maximum strength of the member. The tensile or rupture stress is higher. For instance, in typical A36 steel, the spec requires a yield stress of 36ksi and a rupture stress is 58ksi.

 

[femr2]

We get no answer to the question - only a guess as to what femr2 may be getting at.

The basic task in hand was to check whether folk were actually aware of the behaviour of the buildings, with the specific break line being the *feature* being knowledge checked. Seems to be some *dancing* ocurring from some when they are unclear.

 

[femr2]

Do you agree what he was referring to was not necessarily "observable"?

No, I think he misunderstood the scope of the discussion, jumped in and started discussing totally separate potential behaviours, then opted out when asked to clarify what he was talking about.

As I've said a fair few times now...

As long as everyone is aware that the WTC2 East face break ocurred at the bolted seams along the staggered path highlighted in purple in the oft-posted diagram, it's all good.

 

[DGM]

Not quite. A compression member that has buckled elastically has still failed. The compression capacity decreases over time at the same rate as the bending moment in the member increases. However at no time do the stresses in the member actually exceed the yield stress (hence no plastic hinges or permanent deformation).

I've also seen you misuse the term yield. You should know that that yield isn't always a failure in collapse prevention engineering. Yield just means that the peak stress in the shape exceeds the yield stress. This is not the point of maximum strength of the member. The tensile or rupture stress is higher. For instance, in typical A36 steel, the spec requires a yield stress of 36ksi and a rupture stress is 58ksi.

I appreciate the correction.

This is why I have an SE that figures out how it needs to be done (without him I'd most likely build it way stronger than it needs to be).

That said. I think femr2 and Major_Tom are missing the ball by attempting to define each step of the collapse as one particular event. It was a whole series of chaotic events stacked together (and different for each building)that is almost impossible to describe in the detail they think should have been done.

 

[DGM]

No, I think he misunderstood the scope of the discussion, jumped in and started discussing totally separate potential behaviours, then opted out when asked to clarify what he was talking about.

As I've said a fair few times now...

As long as everyone is aware that the WTC2 East face break ocurred at the bolted seams along the staggered path highlighted in purple in the oft-posted diagram, it's all good.

Maybe you should have just said this instead of going on about what your definition of "buckling" was.

 

[femr2]

Maybe you should have just said this instead of going on about what your definition of "buckling" was.

...

the point is to highlight that failure occurred along the bolt seams

Again, the point is to highlight that failure occurred along the bolted seams between individual box column sections

As long as everyone is fully aware of the fact that the break along the East face of WTC2 occurred along the bolt seams, resulting in the break following the pattern highlighted in purple...
[qimg]http://www.sharpprintinginc.com/911/images/photoalbum/13/WTC2_IZ_model2.jpg[/qimg]
...it's all good.

As long as everyone is aware that the break ocurred at the bolted seams along the staggered path highlighted, it's all good.

As long as everyone is aware that the break ocurred at the bolted seams along the staggered path highlighted, it's all good.

As long as everyone is aware that the break ocurred at the bolted seams along the staggered path highlighted, it's all good.

First one of those was back on the 27th June. Too much *free thinking* back in the 60's ?

 

[DGM]

In what manner ?


(the vast majority of) The perimeter columns did not buckle.

Is your knowledge of these events gleaned from observation, or simply *what NIST said* ?

In other words, what makes you think the perimeter columns buckled ?

Firstly, it contradicts the NIST hypothesis of the mechanism in action...floor assemblies did not pull in the perimeter to the point where the perimeter buckled.

Secondly, it raises the question...what occurred at the point in time when the bolt seams fractured (in detail)...
[qimg]http://femr2.ucoz.com/_ph/5/2/786877858.gif[/qimg]

If MT's threads had not been removed from this sub-forum, you'd have in-depth resource to refer to on this specific behaviour...


Trace data extraction for the NW corner of WTC7 is complete, sure. Other traces have been performed, and additional traces may be required (especially given the gradual increase in available decent quality footage)


For the purpose of generating acceleration profile graphs for WTC7 NW corner with the Dan Rather dataset, yes, Savitzky-Golay is the most appropriate and practical method available. Other traces gleaned from higher quality footage, such as the WTC1 data extracted from the Sauret footage, have not required the use of such intensive smoothing methods, though it may well be useful to take another look at S-G processed data from such.


Analysis of trace data has already resulted in quite an array of conclusions, from the initial identification of the ejecta streams resulting in formulation of the ROOSD hypothesis, to indication of incorrect NIST WTC1 initiation sequence, to identification of a plethora of issues with the NIST WTC7 motion study.

The view of many members here seems to be...it doesn't matter how much of the NIST report is wrong, the NIST report is right.

There are, of course, many areas of the reports I am not satisfied with, though not all of those will overlap with video data analysis.

You said earlier that you had read the911forum content. Did you miss all discussion about the geometry of IB ?

Yes ? Okay, how much *sag* would be required to produce the maximum IB identified on the East face of WTC2 ? (Vertical sag distance)

I assume you have seen diagrams in this form before...
[qimg]http://femr2.ucoz.com/_ph/1/109569697.gif[/qimg]
[qimg]http://femr2.ucoz.com/_ph/6/180678443.gif[/qimg]
[qimg]http://femr2.ucoz.com/_ph/6/2/617303571.gif[/qimg]
[qimg]http://femr2.ucoz.com/_ph/6/160048563.gif[/qimg]


But you STATE buckling. Based upon what ? Guess ?

Did you notice the perimeter sections *springing-back* into a nice straight form once the bolt seams failed ?

LOL. You can believe whatever you please. You lack the information to make such a statement.


I'm aware of what buckling is, thanks


LOL. So you are treating multiple separate columns bolted together as a single column ? Oh dear. A rather flimsy way to try and make a (non)point, don't you think ?


Dear me. The assemblies did not buckle. Instead the connection between one assembly and the one above broke along the bolted connections across the width of the building. The columns which make up each of those assemblies did not buckle.


Show me. (aka prove it)

The visual evidence does not agree with you...
[qimg]http://femr2.ucoz.com/_ph/5/2/69989840.gif[/qimg]
[qimg]http://femr2.ucoz.com/lateperimeterpeel.gif[/qimg]

(I'll dig out some other views for you )

Here's that upper edge shape (yes, I know it's on a South Face base image)...
[qimg]http://www.sharpprintinginc.com/911/images/photoalbum/13/bolt_line.jpg[/qimg]

There's a photo kicking around of the upper edge of that section (in two halves iirc) sticking out of the ground, showing no buckling, but instead a remarkably clean break along the bolt seams as indicated above.


I am indeed.



See above.

The columns didn't buckle due to pull-in from the floor assemblies, instead the joint between separate perimeter assemblies broke along the bolt seams, leaving the columns unbuckled.

How much simpler can I make this for you ?


I define a column as a column. Two columns bolted together does not result in one column. It results in two columns bolted together.

If either of those columns which are bolted together buckle, then the appropriate column will have ...buckled...

If the bolted connection between those two separate columns breaks, then neither of those two columns has buckled. Similarly, if you undid the bolts with a wrench, you wouldn't be buckling the column now, would you.

Please stop this keep-the-faith NISTian-supporter nonsense.

...













First one of those was back on the 27th June. Too much *free thinking* back in the 60's ?

Go back a few more days. 60's ........................................................................What?

 

[femr2]

Go back a few more days. 60's ........................................................................What?

ROFL. Maybe when I asked you about the behaviour, you should have highlighted the very same staggered bolt seam fracture outline.

 

[DGM]

ROFL. Maybe when I asked you about the behaviour, you should have highlighted the very same staggered bolt seam fracture outline.

I figured it was obvious (and everyone knew). I think someone mentioned it in a lengthy report.

 

[femr2]

I figured it was obvious (and everyone knew). I think someone mentioned it in a lengthy report.

Do you mean the break along the bolt seam (purple outline) on the oft referenced image was created by NIST ?

Could you tell me where in the lengthy report you mention the behaviour (staggered fracture along the bolt seam on the East face of WTC2) was discussed ?

 

[Reactor drone]

Rather off on a tangent....although...there are photographs of sections of WTC1 (iirc) which show totally straight (non-staggered) perimeter break lines during peeling.

The staggering of the perimeter columns was discontinued at the mechanical floors. Straight sections would probably come from those areas.