Merged Discussion of femr's video data analysis

[ozeco41]

...It provides a mechanism by which the upper perimeter (and so eastern upper block) can pass inside the lower eastern block rapidly, to instigate ROOSD and subsequent perimeter peeling.

Yes.

It is one of (at least) three mechanisms which I have postulated in my explanations of collapse initiation - and the transition to the global collapse by the mechanism for which we now have the label "ROOSD".

Whether the top block ended up inside the lower tower perimeter or outside we still have similar mechanisms to explain the initiation of ROOSD - each of those two options being "upside down" relative to the other. I have usually discounted the third option of "part inside - part outside" - but that leaves the question of "what happened at the corners". (EDIT oops that is ambiguous - I meant "inside" or "outside" for each complete face of the block)

(Does that make me some sort of a sinner - for trying to understand what actually happened beyond what NIST said? )

 

[Reactor drone]

I think, due to the staggered nature of the wall panels, interaction between the column ends and the floors and whether wall sections are inside or outside won't have a significant effect on the overall collapse. The majority of the force that breaks the floor/column connections will come from the floor impacts rather than column end and spandrel impacts.

 

[ozeco41]

I think, due to the staggered nature of the wall panels, interaction between the column ends and the floors and whether wall sections are inside or outside won't have a significant effect on the overall collapse. The majority of the force that breaks the floor/column connections will come from the floor impacts rather than column end and spandrel impacts.

Except that at the very start of ROOSD - apart from the floor bits and pieces already damaged by aircraft impact or fire or directly involved in initiating collapse:
1) The 'other' floors are still tied to the outer perimeter (and core at the other end);
2) Where do you get the impetus to fail the first floor of the ROOSD process; AND
3) How do you stop the perimeter columns applying force to the floors if you want it to be "floor on floor"?

Then, probably more important in understanding the details, at what stage do the staggered ends of broken columns become available relative to the shearing of the floors at that level?

The answer to that is easy for floor levels below the initiating zone once ROOSD is under way. The floors are stripped THEN the perimeter fails so the staggered ends of perimeter only become available after the floors are fallen - so your statement appears valid once ROOSD is under way. Floor on floor is the mechanism but I realise that is not the stage you were addressing.

It ain't so obvious for the impact and fire damage levels where the collapse initiates and transitions into ROOSD.

Which naturally is one of the answers that femr2 is working towards if only those people who don't want more info than NIST provides could let him get on with the process. The perennial circling on the theme of "I'm not interested in those details so what right have you to be interested" - flavoured by the sauce of personal comments.

The only thing that is near certain for my money is that at the start of the process it is floors attached to top block perimeter and core (and maybe hat truss) which combine to give sufficient falling weight to shear the first floor or two or three or...

After that falling floor mass with accumulated debris is sufficient to sustain ROOSD.

 

[femr2]

Except that at the very start of ROOSD - apart from the floor bits and pieces already damaged by aircraft impact or fire or directly involved in initiating collapse:
1) The 'other' floors are still tied to the outer perimeter (and core at the other end);
2) Where do you get the impetus to fail the first floor of the ROOSD process; AND
3) How do you stop the perimeter columns applying force to the floors if you want it to be "floor on floor"?

Watch this annotated segment a few times...

The white line follows the NE edge of the building, and so provides a *virtual* running location of where the lower NE corner of the upper section would be, if intact.

The vertical red line is static, and shows the lower NE edge with the top of the line set to the initiation location (molten metal yada yada)

The horizontal red line shows the location of the upper edge of the lower east face.

The purpose of the image is to show the wedging action of the upper block on the lower east perimeter.

However, it is also useful to see that the east face dust ejecta (which indicates the lowest visible sign of ROOSD crush front) remains in very close proximity to the lower NE corner of the descending upper block.

Such may indicate, however unlikely, that that lower edge remained *effective* in imparting significant force upon lower floors...for quite a while...until ROOSD took over.

(I have large versions of the clip kicking around. It's only small to keep GIF filesize down)

Then, probably more important in understanding the details, at what stage do the staggered ends of broken columns become available relative to the shearing of the floors at that level?

Speculative, but it may be that the lower ends of the upper East face fold in and help protect the *wedge* ??

Which naturally is one of the answers that femr2 is working towards if only those people who don't want more info than NIST provides could let him get on with the process. The perennial circling on the theme of "I'm not interested in those details so what right have you to be interested" - flavoured by the sauce of personal comments.

<tips hat>

In addition, I occasionally ask a few questions. Unlikely as it may seem, I'm normally after answers to them, in as much detail as possible.

The only thing that is near certain for my money is that at the start of the process it is floors attached to top block perimeter and core (and maybe hat truss) which combine to give sufficient falling weight to shear the first floor or two or three or...

Not sure about core-side there. May well be that core-side has already detached, or even early core column detachment.

 

[ozeco41]

...The purpose of the image is to show the wedging action of the upper block on the lower east perimeter...

Understood.

...However, it is also useful to see that the east face dust ejecta (which indicates the lowest visible sign of ROOSD crush front) remains in very close proximity to the lower NE corner of the descending upper block...

Yes

...Such may indicate, however unlikely, that that lower edge remained *effective* in imparting significant force upon lower floors...for quite a while...until ROOSD took over.

Could be for that side. Could also be similar but in upside down arrangement for other sides where the top block fell "outside" the lower tower. You and MT are the ones who would know which sides did what.

...Not sure about core-side there. May well be that core-side has already detached, or even early core column detachment.

Recall I'm trying to be clear about the top block remaining structurally integral whilst recognising that integrity would have been lost in the mess of collapse initiation in the impact and fire damage zones. How and when the top block disintegrated is another issue.

 

[BasqueArch]

Originally Posted by BasqueArch
I understand that claiming to still be right while being wrong must be frustrating

What claim are you referring to ?

Here are the claims I am referring to:

Quote:
femr2
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.

Originally Posted by femr2
.....
Would you say that "the east wall buckled inward" ?
I wouldn't.

Originally Posted by femr2

Originally Posted by Reactor drone
And the significance of bolts breaking and material being expelled following the initiation of collapse is?

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.

So answer these questions:
1) The column assemblies buckled. Yes or no.
2) The columns buckled. Yes or no.
3) The east wall buckled. Yes or no.
4) The floor assemblies pulled in the perimeter columns to the point where the perimeter buckled. Yes or no.

I note you have failed to answer my questions...

I answered your questions, you ignored it.

Quote BasqueArch
Ask a structural engineer, seriously. Have you ever discussed your propositions with a SE?

What governs the direction of the fracture ?

What fracture, the bolts ? The direction of the reaction forces and momentum. Some bolts did not fracture.

What governs the direction of an elastic buckle ? (around the axis with the lowest moment of inertia I suppose)

No, in this case the direction of the tensile force applied by the sagging trusses. The perimeter framed tube columns had nearly equal moments of inertia in both horizontal axis.

Individual direction for each half of the fractured member ? (which in this case could be the bolts...)

The perimeter members (columns) sprung back, they did not fracture. For the bolts ref above. As the progressive collapse continued, the other columns, exterior and interior did fracture, and at a small angle as Bazant explained nearly 10 years ago.

The lower columns clearly spring back.

After elastic buckling.

The cracks in the bolts probably formed somewhere between in-plane sliding (placing the propogation [sp]direction parallel to the applied shear stress) and out-of-plane sliding (placing the propogation [sp] direction normal to the shear stress). More in-plane I suppose ?

You’re trying too hard to sound engineery. It’s awkwardly phrased Googley-gook. We know you just picked up these phrases on the way home from the store. Since you don’t understand bucking, we know you don’t understand the more complex reasons why connections fail.

If you understood what you just wrote you would have understood the bolt could also have punched through the base plates. I mentioned this a few posts back but you didn’t know what you were looking at. NIST has pictures of this.

Given that the upper column and lower column travel in different directions following failure of the connection between them, what direction would the subsequent buckle be in, and why ?

Don't understand what you are asking.

My original assertions clearly relate to my viewpoint on each column in a panel section being a column in its own right...

Ok.

Makes you wonder why NIST would use the term inward bowing, as a separate phase before buckling.

Where does bowing turn into buckling ?

Bowing is not a separate phase before buckling; it is a change in shape while generally buckling. All bowing in a structural member is buckling, not all bucking in a structural member is bowed. For instance buckling can be local, such as in the crushing of a beer can.

Stick to what you know. There are many ways to be wrong but only one way to be right. Wandering outside your field of competence will result in errors.

 

[femr2]

Here are the claims I am referring to

I see you suffer from selective memory, deliberately ignoring prior responses in order to appear to (though fail to) score "points"...

Read.

So answer these questions

Already have.

Some bolts did not fracture.

Which ones ? What did they do instead ? What is your assertion based upon ?

What governs the direction of an elastic buckle ? (around the axis with the lowest moment of inertia I suppose

No, in this case the direction of the tensile force applied by the sagging trusses. The perimeter framed tube columns had nearly equal moments of inertia in both horizontal axis.

Nearly ? Which was lowest ?

The perimeter members (columns) sprung back, they did not fracture.

I know.

For the bolts ref above.

Ref above.

\\m//

As the progressive collapse continued, the other columns, exterior and interior did fracture, and at a small angle as Bazant explained nearly 10 years ago.

Whoa there. Which columns ? Overwhelming majority of columns, both perimeter and core did not fracture. What are you talking about ?

If you understood what you just wrote you would have understood the bolt could also have punched through the base plates.

When was that discounted ? Quote please

I mentioned this a few posts back but you didn’t know what you were looking at.

ROFL...

What breaks in your opinion ? Bolts or column ends ? (There's some words in t'NIST report on the subject, I imagine )

I see you decided to go and actually read some of the report then

NIST has pictures of this.

Really ?!?!!

Any detail from the staggered break line ?

Don't understand what you are asking.

How convenient, bearing in mind that is the actual point of this *quibble*. NIST state...

With continuously increased bowing and axial loads, the entire width of the east wall buckled inward (Fig. E–13). The instability started at the center of the wall and rapidly progressed horizontally toward the sides.
...and...
When the east wall reached instability and buckled

Sequence -> increased bowing -> buckled/instability started/reached instability -> buckled.

Given the spring-back behaviour, I don't accept *buckled inward*.

We can keep repeating this over and over again if you like though. It's not going away.

Bowing is not a separate phase before buckling

I'm not saying it is. I'm saying that NIST suggest this sequence as above...

Sequence -> increased bowing -> buckled/instability started/reached instability -> buckled.

What on earth that last *buckled* refers to...what's buckling there ? That's post fracture of the bolts (or column ends if you like) and the columns are or have sprung back, so THEY aren't buckling. What is ?

 

[NoahFence]

Then why was this report, so rife with error, used by actual engineers and designers to build a structure that survived a massive fire?

If it was that bad, surely these engineers who are at least in your ballpark as far as engineering prowess is concerned, would have just ignored NISTs findings, no?

Why did those people go with the NIST report, and not [Merged] FEMRs Useless Gif and JPEG party discussion thread at JREF?

Perhaps FEMR missed these questions in all the noise. I'll repost for his benefit.

 

[femr2]

(I have large versions of the clip kicking around. It's only small to keep GIF filesize down)

For reference...



http://www.youtube.com/watch?v=b2I1UMuBWRE

 

[tsig]

Except that at the very start of ROOSD - apart from the floor bits and pieces already damaged by aircraft impact or fire or directly involved in initiating collapse:
1) The 'other' floors are still tied to the outer perimeter (and core at the other end);
2) Where do you get the impetus to fail the first floor of the ROOSD process; AND
3) How do you stop the perimeter columns applying force to the floors if you want it to be "floor on floor"?

Then, probably more important in understanding the details, at what stage do the staggered ends of broken columns become available relative to the shearing of the floors at that level?

The answer to that is easy for floor levels below the initiating zone once ROOSD is under way. The floors are stripped THEN the perimeter fails so the staggered ends of perimeter only become available after the floors are fallen - so your statement appears valid once ROOSD is under way. Floor on floor is the mechanism but I realise that is not the stage you were addressing.

It ain't so obvious for the impact and fire damage levels where the collapse initiates and transitions into ROOSD.

Which naturally is one of the answers that femr2 is working towards if only those people who don't want more info than NIST provides could let him get on with the process. The perennial circling on the theme of "I'm not interested in those details so what right have you to be interested" - flavoured by the sauce of personal comments.

The only thing that is near certain for my money is that at the start of the process it is floors attached to top block perimeter and core (and maybe hat truss) which combine to give sufficient falling weight to shear the first floor or two or three or...

After that falling floor mass with accumulated debris is sufficient to sustain ROOSD.

So it's posters here that are keeping femur2 from completing his process?

 

[femr2]

In a different discussion femr was able to produce a wonderfully high quality gif of the east face falling away from the building:

Indeed, allowing break-line confirmation...


With this higher quality video segment, I assume the break pattern is clear.

MT provided additional information, but his posts were moved here.

 

[rwguinn]

Once again, someone has spent 59 pages of rambling to prove that "A chain is only as strong as its weakest link"
Whoopie...

 

[Major_Tom]

No, I only spent a few posts on that. I showed that it broke pretty much exactly where one could predict with a knowledge of the structure.

Anyway, those posts explaining this were here last night. they are ...somewhere.

 

[ozeco41]

No, I only spent a few posts on that. I showed that it broke pretty much exactly where one could predict with a knowledge of the structure.

Anyway, those posts explaining this were here last night. they are ...somewhere.

I also noticed the changes. Puzzling since they were a direct extension of the application of "femr's video data analysis" which was the topic.



(They also gave some "padding" to hide the fact that I was not responding to the potential derail of tsig's leading question. )

 

[W.D.Clinger]

(They also gave some "padding" to hide the fact that I was not responding to the potential derail of tsig's leading question. )

If you think discussion of the mechanism you credit with impeding femr2's progress would be a derail, then why did you raise that subject?

More plausible mechanisms are known to be at work. Your refusal to answer tsig's question tells us you are unable or unwilling to defend the hypothesis you advanced in this thread.

In scientific discourse, hypotheses that no one is willing to defend are generally presumed to be indefensible.

Which naturally is one of the answers that femr2 is working towards if only those people who don't want more info than NIST provides could let him get on with the process.

So it's posters here that are keeping femur2 from completing his process?

 

[femr2]

So it's posters here that are keeping femur2 from completing his process?

I only have a small amount of spare free time for these "discussions", so the more time wasted on "off topic" banter does indeed mean that I have less time to do "femr2's video data analysis".

As a reminder...

I think the above might need to be spelled out more. Forum management discussions that should take place in the appropriate forum and not here include (but are not limited to) any and all of the following:

- Suggestions or arguments for why and where the thread should be moved, and responses to same.

- Objections to previous threads or posts having been moved, and responses to same. This includes such objections phrased as vague allusions to "censorship" or other nefarious practices.

- Claims and arguments about whose posts are or are not on topic for this thread. (If you believe a post is off-topic, report it in the usual way, and do not respond to it.)

Replying to this modbox in thread will be off topic  Posted By: Myriad

I'll be more than happy if the noise level reduces.

 

[tsig]

I only have a small amount of spare free time for these "discussions", so the more time wasted on "off topic" banter does indeed mean that I have less time to do "femr2's video data analysis".

As a reminder...


I'll be more than happy if the noise level reduces.

Then your best strategy would be not to post till you have your analysis all worked out.

That would reduce the noise level tremendously.

 

[NoahFence]

 

[GlennB]

Then your best strategy would be not to post till you have your analysis all worked out.

That would reduce the noise level tremendously.

Now I don't know whether to report him, you, or myself

 

[ozeco41]

Your refusal to answer tsig's question tells us you are unable or unwilling to defend the hypothesis you advanced in this thread...

Not so. You are confusing "process" with "content". The topic I choose not to explore was a potential derail into process matters. I generally ignore such sidetracks or do no more than identify the derail as I did here.

...In scientific discourse, hypotheses that no one is willing to defend are generally presumed to be indefensible.

Not a valid criticism because my comments amounted to "lets focus on the hypothesis which is the topic of the thread". What I am not willing to defend in this thread are those matters of process which are off topic. There is no need to defend my reluctance to go off topic. The topic is "femr's video data analysis" which subsumes application of those techniques of analysis to WTC Tower collapses.