OOS Collapse Propagation Model

[rwguinn]

Some of us here are engineers and have experience. Although not many from the truth movement

Gee. You think? (Same response to both sentrnces...)

 

[Major_Tom]

With the gift of hindsight some of us can admit that the unique architecture of WTC1 and 2 led to an equally unique collapse progression mode.



Consider other comparable towers like the Sears and John Hancock buildings in Chicago, on the far left and right in this image:

To what degree are each of these buildings ROOSD vulnerable? If one were to imagine a Verinage type demolition across a single floor near the top of each building, how would each collapse progression mode differ from the mappings within the ROOSD study?



It is now possible to note that WTC1 or 2 could have been completely destroyed any time since 1972 without removing a single column, simply by initiating a ROOSD avalanche on only one part of one floor.

Are these other buildings vulnerable to total collapse without a single column being weakened, simply by initiating a small, regional ROOSD process?

 

[pgimeno]

http://skreened.com/render-product/...parel-unisex-organic-tee.dijon.w460h520b3.jpg

 

[Oystein]

Tom,

1. Have some details of the (former) Sears and Hancock towers been shown here in this thread? If not, got a link? I just don't know if these buildiungs are steel frame (probably) and if so, what the grid looks like. Are there OOS? Are there steel cores, or reinforced concrete cores?

2. If there are no OOS, then ROOSD seems implausible - obvously.

3. Verinage <> ROOSD. Verinage is about removing vertical supports across one floor without the use of explosives. Bazant's very first paper, while not discussing Verinage, seems to me to show plausibly that any building whose main vertical supports are steel, and those steel elements have a normal "safety factor" (static capacity / static live load) of 3 or less will succumb to a Verinage style attack where one entire floor is made to fall more or less freely through the height of one or two floors.
If this also happens when the attack is done on only part of the floor area would depend on how the floor layout is sectioned or not. I seem to remember that the Sears tower is basically 9 towers in a 3x3 grid. Not sure if each subtower can be described as "OOS" design. If you attack one section, global collapse might be limited to just that section, or perhaps even be arrested if somehow the sections reinforce each other, and not just at joint columns. On the other hand, I find it conceivable that even a local ROOSD-type failure within the Sears might spread to the other sections, if joint columns fail through loss of lateral support on one side, oder by being kicked laterally.

But all that is just the imagination of a non-engineer without any knowledge about the specific designs in question

 

[LSSBB]

With the gift of hindsight some of us can admit that the unique architecture of WTC1 and 2 led to an equally unique collapse progression mode.



Consider other comparable towers like the Sears and John Hancock buildings in Chicago, on the far left and right in this image:

[qimg]http://www.sharpprintinginc.com/911/images/photoalbum/13/wtc_sears_hancock.jpg[/qimg]



To what degree are each of these buildings ROOSD vulnerable? If one were to imagine a Verinage type demolition across a single floor near the top of each building, how would each collapse progression mode differ from the mappings within the ROOSD study?



It is now possible to note that WTC1 or 2 could have been completely destroyed any time since 1972 without removing a single column, simply by initiating a ROOSD avalanche on only one part of one floor.

Are these other buildings vulnerable to total collapse without a single column being weakened, simply by initiating a small, regional ROOSD process?

I notice that you didn't include any building built after 2000.

www.nehrp.gov/pdf/fema354.pdf

 

[Oystein]

According to a meme expressed on page 1 of this thread and revived in 2014, this collapse mode of WTC1 and 2 is 'common knowledge'.

I clicked the links to read the three posts by NewtonsBit, RMackey and jaydeehess, and for the life of me can't find a thing that's totally wrong: FEMA had written early on that the floors "pamcaked" (another words for ROOSD), NIST never suggested anything else, and many here have been cool with this (and/or ROOSD) for a very long time.

It is documented in JEM that Thomas Eagar and Edward Musso didn't understand it nor did any peer reviewers at the time, nor many of the readers.


It is documented that neither Bazant nor David Benson understood it in 2007 and 2008.

Maybe.

Members of this forum were able to freely misinterpret BV eq 12 and 17 and ignore direct quotes from BL and BLGB in order to ignore this contradiction. People still do, openly and freely, within this thread.

I don't see anyone interpreting BV eq 12 and 17 anymore. Perhaps that is your interpretation of whole other things you read?

Such behavior is encouraged here, and one of your moderators actively encourages it and participates himself (from 2010 to 2014).

This has nothing at all to do with moderation. Why, do you expect moderation to enforce your POV? Silly.

Seffen didn't understand it.

Maybe.

It is documented in posts that you didn't understand it. Dave Rogers also didn't understand it as is documented in this thread.

I did not understand what? I have no problem admitting that I did not understand a lot of things 4 years ago. So what? I have learned some, and moved on somewhat.

I understood that BZ 2002 had it right - a simple, limiting case, not claiming to describe the actual WTC collapse scenario, just showing that the towers (and indeed any steel frame structure) were doomed once the top block reached a velocity equivalent to having fallen through one story (if you think about this, this holds true even if there isn't a block anymore!). The real world lesson is that you want to keep building from starting to fall.

I never claimed to have read, let alone understood, let alone have agreed with, any of Bazant's following papers. I did discuss the "crush-up-crush-down" thing for a while, and even opened a thread more than two years ago, asking users to clue me in on an amateur level: Bazant in a nutshell. There, I wrote on June 8th, 2012, that I had understood that the "crush-up-crush-down" model "isn't applicable to the WTC". Besides yourself, femr2 and ozeco41, others provided helpful posts: LSSBB, W.D.Clinger, ... oh well, and then the thread fell asleep, and when it was revived a year later, some Truther snatched it with nonsense, and I stopped reading.

I agree with you that given the actual state of the written record, it is verifiable that this information is not well known even among people that write about examples of progressive collapse as their PhD thesis or among JEM published authors on the subject. Anyone who puts in the effort can verify this for themselves.

Oh how can you agree with me when I haven't stated an opinion? I just asked a question. So you think that ... wait, I asked which relevant journals HAVE published a ROOSD-style description / discussion of the WTC collapse progressions, and your answer to this is - what now? None? I am confused! Just answer:

Which academic journal that a doctoral student of civil engineering can be supposed to have on his radar has published an article that describes ROOSD?

And anyway, what are you doing to improve on this situation? You found a problem, you have devoted years now to pin down this problem - what do you plan to do to fix it? You don't think that debating random users, mostly non-experts like myself, on the internet, will get you anywhere?

But your fellow JREF posters seem to disagree with you.

They can't disagree with me for the same reason why you can't agree with me.

According to them, this collapse mode is well recognized and well documented within available literature and is even 'common knowledge.'

The authoritative source describing the collapse progression mode is NIST, before them FEMA. FEMA told of "pancaking", NIST descibed in little (not much) more detail how floor2column connectors fail when impacted by descending floors from above, i.e. ROOSD. So yes, "this collapse mode is well recognized and well documented within available literature". This notwithstanding, I suppose you may be right that some other literature on the topic muddies the waters by coming up with questionable models.

This is a meme that some of you have been trapped within for years. Many have creatively invented their own versions of BV, BL, and BLGB to conform to the meme. I.m not suggesting posters are aware that this happens, but it happens all the same.

And now the other meme: So what? Why does it bother you that a handful of posters on a rather obscure forum that no practicing engineer would ever go to for advice are - perhaps - wrong?


Tom, your problem is that no one reads you. No one reads you because you don't publish properly. You posting history here is, as someone recently put it, very very boring. You copy and paste long tracts of the same old, same old, and I promise you: No one reads all that stuff.


What is your purpose, and how can you hope to achieve it the way you go about it?

 

[Richard the G]

With the gift of hindsight some of us can admit that the unique architecture of WTC1 and 2 led to an equally unique collapse progression mode.



Consider other comparable towers like the Sears and John Hancock buildings in Chicago, on the far left and right in this image:

[qimg]http://www.sharpprintinginc.com/911/images/photoalbum/13/wtc_sears_hancock.jpg[/qimg]



To what degree are each of these buildings ROOSD vulnerable? If one were to imagine a Verinage type demolition across a single floor near the top of each building, how would each collapse progression mode differ from the mappings within the ROOSD study?



It is now possible to note that WTC1 or 2 could have been completely destroyed any time since 1972 without removing a single column, simply by initiating a ROOSD avalanche on only one part of one floor.

Are these other buildings vulnerable to total collapse without a single column being weakened, simply by initiating a small, regional ROOSD process?

Empire State Building: not susceptible to ROOSD but much more likely to collapse on plane impact as massive reinforced masonry wall is not ductile and if you took a quarter of the building perimeter out you would take the building out. WTC 1&2 much more robust and saved the lives of thousands.

Although according to ae911truth there never has been a failure due to plane impact and fire so it would be ok!

 

[Richard the G]

Tom,

1. Have some details of the (former) Sears and Hancock towers been shown here in this thread? If not, got a link? I just don't know if these buildiungs are steel frame (probably) and if so, what the grid looks like. Are there OOS? Are there steel cores, or reinforced concrete cores?

2. If there are no OOS, then ROOSD seems implausible - obvously.

3. Verinage <> ROOSD. Verinage is about removing vertical supports across one floor without the use of explosives. Bazant's very first paper, while not discussing Verinage, seems to me to show plausibly that any building whose main vertical supports are steel, and those steel elements have a normal "safety factor" (static capacity / static live load) of 3 or less will succumb to a Verinage style attack where one entire floor is made to fall more or less freely through the height of one or two floors.
If this also happens when the attack is done on only part of the floor area would depend on how the floor layout is sectioned or not. I seem to remember that the Sears tower is basically 9 towers in a 3x3 grid. Not sure if each subtower can be described as "OOS" design. If you attack one section, global collapse might be limited to just that section, or perhaps even be arrested if somehow the sections reinforce each other, and not just at joint columns. On the other hand, I find it conceivable that even a local ROOSD-type failure within the Sears might spread to the other sections, if joint columns fail through loss of lateral support on one side, oder by being kicked laterally.

But all that is just the imagination of a non-engineer without any knowledge about the specific designs in question

If there are no bar joist floor trusses then any progressive collapse failure is a lot less likely!

 

[GlennB]

It is now possible to note that WTC1 or 2 could have been completely destroyed any time since 1972 without removing a single column, simply by initiating a ROOSD avalanche on only one part of one floor.

I suspect I'm getting a hint of what might be your eventual purpose.

Are you about (eventually) to suggest that it wouldn't have been necessary to demolish the WTC columns in order to bring those buildings down?

 

[Newtons Bit]

If there are no bar joist floor trusses then any progressive collapse failure is a lot less likely!

Evidence?

 

[Newtons Bit]

Empire State Building: not susceptible to ROOSD but much more likely to collapse on plane impact as massive reinforced masonry wall is not ductile and if you took a quarter of the building perimeter out you would take the building out. WTC 1&2 much more robust and saved the lives of thousands.

Although according to ae911truth there never has been a failure due to plane impact and fire so it would be ok!

A massively reinforcement masonry wall is actually quite ductile if detailed correctly. For reference, consult the ASCE7 and look at the R values and allowed heights of special reinforcement masonry shear walls (building frame or bearing wall) in seismic design category D+. However, the ESB does not have a "massively reinforced masonry wall". The masonry in it is not reinforced at all, it's just attached to the structure and forms part of the facade, it's not load bearing or a sgnificant part of the lateral force resisting system.

 

[Richard the G]

Evidence?

Just a brain.!

If there is a 1in hole in the fire protection of a beam. It will locally become a bit hot. If there is the same hole in the protection of a web joist then the elements is totally unprotected. And if a 1in element in a joist fails then the whole joist is a mechanism. If a 1in part of a beam fails then the restl does the job.

That is why engineers do not use bar joists in tall buildings

 

[Richard the G]

A massively reinforcement masonry wall is actually quite ductile if detailed correctly. For reference, consult the ASCE7 and look at the R values and allowed heights of special reinforcement masonry shear walls (building frame or bearing wall) in seismic design category D+. However, the ESB does not have a "massively reinforced masonry wall". The masonry in it is not reinforced at all, it's just attached to the structure and forms part of the facade, it's not load bearing or a sgnificant part of the lateral force resisting system.

Yes but now when built in the 1920's and it does not have the detailing to be considered special in any way.

The ESB is a steel frame but the masonry provides the effective lateral stiffness and stops massive drifts.

The WTC towers could take the removal of a complete wall. And my analysis indicated that you could remove 3/4 of two adjacent walls, including the corner, before it would fail. The ESB has nothing like that ability to redistribute load.

 

[Newtons Bit]

Just a brain.!

If there is a 1in hole in the fire protection of a beam. It will locally become a bit hot. If there is the same hole in the protection of a web joist then the elements is totally unprotected. And if a 1in element in a joist fails then the whole joist is a mechanism. If a 1in part of a beam fails then the restl does the job.

This doesn't explain why the bar joist is inferior with regards to progressive collapse.

That is why engineers do not use bar joists in tall buildings

Engineers have, and continue to use bar joists in tall buildings. A quick google survey shows that Brookfield's Bay Adelaide Center East Tower (just finished construction) uses bar joists for parts of the flooring. As an engineer myself, I am aware of no limitations in the IBC, ASCE7, AISC or SJI that limits bar joists in tall buildings. There are many more examples.

AISC has a publication on fire-resistive assemblies for steel joists. UL has conducted tests on these assemblies to prove that they work.

As far as I'm concerned, what you're talking about is an urban myth.

 

[Richard the G]

This doesn't explain why the bar joist is inferior with regards to progressive collapse.



Engineers have, and continue to use bar joists in tall buildings. A quick google survey shows that Brookfield's Bay Adelaide Center East Tower (just finished construction) uses bar joists for parts of the flooring. As an engineer myself, I am aware of no limitations in the IBC, ASCE7, AISC or SJI that limits bar joists in tall buildings. There are many more examples.

AISC has a publication on fire-resistive assemblies for steel joists. UL has conducted tests on these assemblies to prove that they work.

As far as I'm concerned, what you're talking about is an urban myth.

I think you have got it wrong mate. If you go to the web sites and search construction you will see its a beam building. And I am sure there are not many more examples.

And do you agree that bar joists are very sensitive to poorly applied fire protection.? It's nuts to use them in high rise.

 

[DGM]

And do you agree that bar joists are very sensitive to poorly applied fire protection.? It's nuts to use them in high rise.

Any system is prone to failure with inferior workmanship. This argument makes no sense. This type of floor system makes perfect sense for tall buildings because it reduces weight that needs to be carried by other members. It's not bullet proof but, without the extraordinary conditions on 9/11, the towers would have stood longer than you or I.

 

[Richard the G]

Any system is prone to failure with inferior workmanship. This argument makes no sense. This type of floor system makes perfect sense for tall buildings because it reduces weight that needs to be carried by other members. It's not bullet proof but, without the extraordinary conditions on 9/11, the towers would have stood longer than you or I.

No that's where you are completely wrong. It makes a lot of sense. The standard of care needed to get a safe bar joist floor is much higher than a typical office made from standard sections. And the bar joist floors are much more vulnerable to damage during their life since a small amount of damage could lead to a mechanism forming in a fire

Bar joist floors should not be used in high rise buildings

 

[Newtons Bit]

I think you have got it wrong mate. If you go to the web sites and search construction you will see its a beam building. And I am sure there are not many more examples.

Check the pictures more closely, parts of the structure is bar joists. There are bar joists shown very clearly in this picture:

http://urbantoronto.ca/sites/defaul...es/2014/06/10195/urbantoronto-10195-36437.jpg

And do you agree that bar joists are very sensitive to poorly applied fire protection.? It's nuts to use them in high rise.

There's very little difference to poorly protected wide flanges and poorly protected joists. Wide-flanges might survive a few more minutes, but when the design needs a 2-hour+ protection, then a few minutes doesn't matter much.

 

[DGM]

No that's where you are completely wrong. It makes a lot of sense. The standard of care needed to get a safe bar joist floor is much higher than a typical office. And the floors are much more vulnerable to damage during their life since a small amount of damage could lead to a mechanism forming in a fire

Bar joist floors should not be used in high rise buildings

That's why we have mandatory fire suppression (sprinklers). Your making excuses for substandard workmanship. It's not hard to do it right. It's also not hard to make sure no one compromises it down the line, it's call using qualified contractors.

Do you think the towers could not deal with a normal fire? They did you know.

 

[Major_Tom]

Tom,
Why do you suppose so many seemed to have missed the *obvious*? To some (many?) the ROOSD process seems to be indistinguishable from *global collapse* and the distinction is of no consequence. At the very least even if there are no code / engineering implications it seems from an intellectual honesty perspective an accurate description should be of interest to all.

This is the statement given by Ms. Regenhard of the Skyscraper Safety Campaign in a congressional session on the NIST WTC investigation:

First of all, I just want to preface my comments with saying I often introduce myself in the way that I am basically just a little mother from the Bronx, and really, that is what I am, and I am not a technical person. However, I do have, over the last four years, you know, the input from my wonderful technical advisory panel, which represents some excellent, excellent people in the academic fields, and certainly, you know, in structural engineering, fire protection, architecture, and evacuation specialists.

So�"but to get back to your question, you know, political correctness. I have seen, and the other families of the victims have seen the aftermath of 9/11 to be somewhat definitely flavored by political correctness in many, many ways, in so many ways. But certainly, with the NIST investigation, I mean, I understand that it is a wonderful organization of scientists, and scientists are not trained to be like NYPD detectives. There is a professional and academic way that these kinds of organizations deal with one and with other entities. And you have other professional people in that investigation that should have been really interrogated, such as the Port Authority, such as their building plans. You know, the Port Authority never turned over their building plans until there was an article about it in the front page of the New York Times condemning them, or not condemning them, but accusing them of really not coming forward. That is one of the examples. People like the chief structural engineer for the first World Trade Center, you know, his work should have been investigated, because after all, he was responsible for the design of that building, and the subsequent, and yet, instead of that, he was sort of dealt with in a friendly basis, and he was actually put on the payroll to explain his plans and all that.

So, there were these very, you know, maybe because I am a layperson, I can't understand why these entities that should have been scrutinized and investigated were sort of taken in and became part of the investigation. You know, that is just one of the examples of where the families were really, really deeply concerned about that. And also, the avoidance of certain things that were not politically correct, like the avoidance of blaming anyone for anything. I mean, we all teach our children to obey the law, and to respect authority, and not to break any laws, but yet, when we have this investigation of the, I would say the needless deaths of nearly 3,000 people, no one is to be blamed. It is handled so gingerly. I mean, there is a reason why nearly 3,000 people are dead, and I feel the majority of them needlessly, but yet, the approach of these investigations is very, very tentative, and no one wants to put anyone on the line, and no one wants to look into what was the effect of the Port Authority immunities from building and fire codes?

If someone said to me what are the two major grievous examples of what went wrong on 9/11 in those buildings? I would say the two things are the Port Authority exemptions and immunities from New York City building and fire codes, and the wholesale failure of the FDNY radio communications, and the wholesale failure of the Emergency Management System of the City of New York and the Port Authority. And these are the crux of the matter. This is the bottom line. Yet, these are the issues that were, you know, skirted around and, you know, tiptoeing through the tulips, instead of�"and still, today, I have to fault both the 9/11 Commission and the NIST investigation for not taking a stand, for not saying that in our country, no building should be above the law, especially the Port Authority buildings that were the tallest and largest buildings in the world, that at that time, was built to contain the largest number of people in the world, and yet, those buildings were allowed to be exempt and immune from building and fire codes, essentially above the law, and now, we are allowing the Port Authority to do the same thing all over again.

The new World Trade Center and the memorial, and every single building down there on that property will be just as exempt and immune from every single New York City building and fire code as the first one. That is an abomination. That is a sin. That is an outrage against humanity. And you know, I am sorry to get emotional. I expected the NIST investigation and the 9/11 Commission to take a stand on that, but you know what, it is only the average Joe Q. Citizen. When we break the law, we have to pay the consequences, but when we have these huge organizations breaking the law, I feel they are not held to the same standard as an average citizen, and that hurts.

From these comments certain key words and phrases can be extracted:

politically correct
avoidance of blame
handled gingerly
no one wants to put anyone on the line
no one wants to look into...
skirted around
tiptoeing through the tulips
not taking a stand
abomination
a sin
an outrage against humanity
should have been investigated
sort of dealt with in a friendly basis



My guess is that she had no idea at the time of what we now sometimes call ROOSD.

My research has verified that her observations hit the mark perfectly.



As a follow-up, it would be interesting to know if the most prominent members of the Skyscraper Safety Campaign are aware of what we call ROOSD. Sander, I believe you mentioned commenting on this subject to James Quintiere, is that true?




Does anyone believe that Ms Regenhard, surviving parent of a deceased firefighter and co-chair of the Skyscraper Safety Campaign, should be given a clear, unambiguous description of the actual collapse modes of WTC1 and 2?

I find the reaction to ROOSD or whatever name one gives to it... baffling.

Within this environment there is an inability to approach the written record of the collapses in a critical way. Offocial = good and wise. All confusion about the collapses is believed to be due to 'truthers' or the 'ignorant laymen in the public'.

The NIST, ASCE or JEM are responsible for....nothing.