OOS Collapse Propagation Model

[ozeco41]

Well, the reason I brought this up is that I don't (yet) accept the first premise (except in the sense that "at one extreme," floor spans begin at zero?). I believe it's virtually impossible in a conventionally designed building to crush columns by loading floors (with impact or otherwise), so your premise would require that with shorter spans, there would be proportionally more cases where columns directly received enough additional force to buckle. While there might be more columns crushed, having more columns also means each is less significant in the overall collapse. Also, as I said, I believe the total column load capacities and floor connection shear capacities depend on floor loads rather than on column spacing, so it's not immediately obvious to me that failure mode proportions would change much with different (practical) spacings.

I was aware of your concerns hence the reason I accepted the offer to discuss. My original suggestion which I thought we agreed was that the Bazant column crushing model could be more valid for application to the real WTC 9/11 collapses IF the energetics bit of the maths was made floor joist shearing energetics rather than column crushing energetics. Your current position rejecting the Bazant starting point - which was the basis of the proposed discussion - makes any further discussion moot.

And since we're apparently not going to hear any more about ROOSD from Major_Tom, have you given any thought to the supposed "funnel" effect? I think it's the second most misleading part of ROOSD. Most of debris went straight down because of gravity, not the perimeter wall, and furthermore whatever minor effect the wall had, it would have been exactly the same with shorter column spacing.

Are you discussing details from some of Major_Tom's explanations? If so where from?

My own view aligns with what you say EXCEPT the reference to column spacing which I cannot recall from any of M_T's explanations.

More importantly IMO the amount of "constraint" imposed by the perimeter wall has zero effect on the point of contention under discussion here. That point being that the mechanism which actually happened - whatever we call it - was the one which saw material falling in the office space tube cause floor joist disconnections which in turn precipitated perimeter peel off. How is that misleading?

 

[Crazy Chainsaw]

I was aware of your concerns hence the reason I accepted the offer to discuss. My original suggestion which I thought we agreed was that the Bazant column crushing model could be more valid for application to the real WTC 9/11 collapses IF the energetics bit of the maths was made floor joist shearing energetics rather than column crushing energetics.

That's the exact mechanism of BLGB.

More importantly IMO the amount of "constraint" imposed by the perimeter wall has zero effect on the point of contention under discussion here. That point being that the mechanism which actually happened - whatever we call it - was the one which saw material falling in the office space tube cause floor joist disconnections which in turn precipitated perimeter peel off. How is that misleading?

Homogeneous crush front falling fast in countering little structural resistance.
Again BLGB.

Floor slabs go boom boom boom, in rapid sugcession, do to rapidly falling mass.

 

[WilliamSeger]

I was aware of your concerns hence the reason I accepted the offer to discuss. My original suggestion which I thought we agreed was that the Bazant column crushing model could be more valid for application to the real WTC 9/11 collapses IF the energetics bit of the maths was made floor joist shearing energetics rather than column crushing energetics. Your current position rejecting the Bazant starting point - which was the basis of the proposed discussion - makes any further discussion moot.

Oh, I thought we were going to discuss why you wanted to also put in a factor for column spacing, but that's okay.

Are you discussing details from some of Major_Tom's explanations? If so where from?

Mainly from the ROOSD acronym itself; otherwise I should think it would just be called Runaway Floor Destruction.

My own view aligns with what you say EXCEPT the reference to column spacing which I cannot recall from any of M_T's explanations.

More importantly IMO the amount of "constraint" imposed by the perimeter wall has zero effect on the point of contention under discussion here. That point being that the mechanism which actually happened - whatever we call it - was the one which saw material falling in the office space tube cause floor joist disconnections which in turn precipitated perimeter peel off. How is that misleading?

That has never been a point of contention with me. As long as I've been in this thread, I've been trying to discuss what "open office space" has to do with any of it (other than the trivial fact that that's what it was). That's what I consider misleading.

 

[ozeco41]

....problems with classical mechanics generally stem from mis-specifying the system under consideration.

Exactly. And that is the fatal error for several of the contentious issues related to Bazant's work. Two of them which I have characterised for several years as "both sides got the starting point wrong":
1 Missing Jolt where the Bazant derived concept of a block falling through a gap to impact NEVER happened. But most discussion has focused on measurement of fall velocity to identify "jolts". Usually missing - or not paying sufficient regard to the reality that Bazant's Limit Case starting assumption was not a description of the initiation mechanism. It was a valid means of setting up the start point for the Limit Case. Which is progression stage. Bazant legitimately fudged the "initiation" because that is not what he was discussing. Too many people - not just T Sz - still have "falling to impact" as their mind set. T'wasn't so.

2 "tilt versus axial impact" (causes or prevents - depending on which side you take. ) BOTH sides wrong. The mechanism to CAUSE tilt was column failure unevenly distributed. Column failure causing the magnitude of top block drop needed to cause tilt has ALREADY made sure the ends of column are bypassing.

So - those are only two prominent examples - but - back to the point - both are errors which flow...

from mis-specifying the system under consideration.

Exactly.

And this is, I think, the problem with a 1-D model that ozeco41 is getting at.

It is one of them. My base position is:
1) The initiation stage cascade failure CANNOT be explained by less than 3D mechanics. (4D if you prefer to include time or sequence as a "D"); AND
2) The progression stage CANNOT be explained by less than 2D mechanics.

Rigorous argument for both those assertions available if anyone itnterested.

In a 1-D collapse model, the debris can only accumulate between the top and bottom blocks. The prediction of the 1-D model is that the debris, in effect, crushes the bottom block while the top block rides on it. In some cases that may be a very good approximation; there are, for example, some verinage demolitions of concrete framed buildings that appear to show very much that behaviour. But in a real, 3D, steel framed building, where the support columns are a very small fraction of the cross-sectional area, it's trivially easy for the debris to outstrip the column collapse and fall between the columns, leaving the top block to continue to impact the bottom block.

Whilst I agree with your statement the actual WTC collapses are IMO far easier to explain from observation of what actually happened without the risks of confusion arising from models or analogies to Verinage etc.

I suggested years ago that there were at least four separate processes going on in the WTC collapses. Firstly, there's the internal collapse of the floors under the weight of the debris, which is fast because the floor connections absorb relatively little energy. Then, lagging behind it (as it must, because it's dependent on it), is the collapse of the perimeter columns, partly because their unbraced length is too great for them to remain stable, but also partly due to repeated partial impacts between top and bottom blocks - the micro-jolts seen in femr2's derivative data - for as long as the top block survives. Next, the hat truss must have impacted the core columns, destroying the former and at least a significant part of the latter, but again lagging behind the floor collapse. And finally, when everything else had progressed to ground level, the remnants of the core also fell due to excessive unbraced length and whatever damage they'd suffered from the earlier processes. And any analysis that doesn't consider all these aspects is not going to be accurate.

That - in your words - is broadly how I describe the progression stage as three mechanisms. The first two from 2007 - never needed to explain the core until about 2010 - see my "one step ahead of the truthers" comment in the next section.

.
And any analysis that doesn't consider all these aspects is not going to be accurate.

Spot on.

.
From a point of view of debunking conspiracy theories, none of this is particularly important, which is probably why it hasn't been extensively studied here; << I like most "debunkers" only needed to be a step ahead of the "truthers". Which is the main reason I never added the core to the "Three Mechanisms " until ~2010 the debris alone can cause collapse, and nothing could have stopped it, so no more explanation is needed to exclude the necessity of explosive assistance to collapse propagation. << True It's also probably too complex to be tractable to analysis, << Maybe. IMO it is valid to give generic analyses as per my series of posts on "initiation" - a lot of technical people are not happy until they can say precisely which bit went when. (It's a "left brain" thing ) But you don't need that to explain the mechanisms. which is why simpler models are generally used. But I think it may account for why those simpler models don't necessarily give the right answer. << Agreed both

Dave

 

[ozeco41]

Oh, I thought we were going to discuss why you wanted to also put in a factor for column spacing, but that's okay.

Will do - wanted to BUT you pulled the plug on the starting point.

We had two lots of energetics - one dominated by column crushing - the other dominated by floor joist shearing. And I thought we agreed that the actual WTC collapse - progression stage - was dominated by FJ Shearing and not by column crushing. So those were the two mechanisms. And I thought we had agreed that the Bazant maths would apply better to WTC real collapse if the column crush energetics factor was replaced by floor joist shearing energetics. So we seemed to have reached agreement on two models.

I the made what I thought was the obvious next step. Divide the gap between the two extreme mechanisms into some part of one and part of the other. So 1/2 and 1/2 midpoint and possibly 1/4 - 3/4 at the other two quartile points. All that just starting point suggestions. And a lot of details for someone to deal with defining whatever those intemediate points could be.

So - if someone could fill the range between the two extremes - it could give Bazant his goal of an accurate generic model. To me "column spacing" was the obvious difference. You didn't see that. OK - so I started by setting out the range - never mentioned column spacing - just the two extremes FJ Shear the major factor <<>> column crushing the major factor. THEREFORE (should be next step of logic IMO) - some in between steps. How we calculate the steps is the challenge for anyone who wants his name on the model. I think column spacing and "subdivision into cells or tubes" are obvious candidates for the classification. So the state of my thinking is:
1) There are two ends of the line;
2) There must be some points in between;
3) If someone works out how to define those points they have the model Bazant wants but on a safer foundation.

And I thought:
(a) we had agreement to "1)" and
(b) "2)" is dogs balls obvious - if you have two ends there must be some in betweens - then
(c) someone can work out the in betweens. Say at the 1/4, 1/2. & 3/4 points (of mechanism difference NOT physical space). That is where all the comments you make about loading on floors transferring to load columns becomes ....."interesting"

But you appeared to reject "1)" which I thought was the starting line. And by repeating the challenging details when we haven't even started the race.

Mainly from the ROOSD acronym itself; otherwise I should think it would just be called Runaway Floor Destruction.

I don't understand how changing the acronym avoids confusion OR how ROOSD causes confusion in the first place.

That has never been a point of contention with me. As long as I've been in this thread, I've been trying to discuss what "open office space" has to do with any of it (other than the trivial fact that that's what it was). That's what I consider misleading.

Why? ROOSD is descriptive. Doesn't change anything for me if you want to say CDBFJSE and CDBCBE - or call it ZXTYPOTL or agree two terms of ten words each and repeat the ten words every time rather than use shorthand. So what?

 

[JSanderO]

Gun powder like reaction of carbon black in air.

Would that make different sounds?

I believe there were ear witness reports of BOOM BOOM BOOM BOOM which probably was not bombs but massive sections of floors dropping and impacting the slab below. If this is the correct explanation it would probably mean that this was at the onset of the collapse in the top as it was being gutted and jostled laterally just before downward movement. These sorts of impact sounds where lost in the noise of the extremely energetic ROOSD phase... which is heard as a roar (blending of mechanical impacts).

I proposed a concept of how the top was hollowed out - initiation phase - called it "sink hole top drop" and no one wanted to discuss the merits or refute it. Message me with an email and I will send you my graphics which explain my thinking (not formulas).

+++++

I believe the column free OOS is key to the collapse and Ronan Point somewhat supports this. So these were no JUST runanaway collapses but OOS runaway collapses and that....

is the sort of radical idea which I believe suggests that the designs DID play some role in the collapse... at leat in the FORM, or the totality of the collapse.

+++++

I also believe that 7wtc came completely down not from one column failure migrating to other column failures but the failure was total because of the massive interconnected load transfer structures which when they failed engaged / every other part of the structure so it all cam down.

+++++

Lesson is that structures NEED some design mechanism (perhaps) to be able to ISOLATE "serious" local structural failures /collapses. These 2 designs did not and in fact their designs had elements which would INVOLVE/engage the entire footprint / plan in what would be a "global collapse". The twins were way outlier in the initiating damage. Mechanically they sustained it! But the fire suppression was not able to deal with the fires... again this was an outlier condition... thousands of gallons of burning jet fuel.

7WTC was not very outlier in the that it was failure of the fire suppression system which led to a single column failure and that to global collapse. In a sense if that explanation "works" then any high rise building in which fire breaks out and the fire suppression system fails (for whatever reason)... is a goner.

Yes or no? Or maybe?

 

[Crazy Chainsaw]

Would that make different sounds?

I believe there were ear witness reports of BOOM BOOM BOOM BOOM which probably was not bombs but massive sections of floors dropping and impacting the slab below. If this is the correct explanation it would probably mean that this was at the onset of the collapse in the top as it was being gutted and jostled laterally just before downward movement. These sorts of impact sounds where lost in the noise of the extremely energetic ROOSD phase... which is heard as a roar (blending of mechanical impacts).

I proposed a concept of how the top was hollowed out - initiation phase - called it "sink hole top drop" and no one wanted to discuss the merits or refute it. Message me with an email and I will send you my graphics which explain my thinking (not formulas).

+++++

I believe the column free OOS is key to the collapse and Ronan Point somewhat supports this. So these were no JUST runanaway collapses but OOS runaway collapses and that....

is the sort of radical idea which I believe suggests that the designs DID play some role in the collapse... at leat in the FORM, or the totality of the collapse.

+++++

I also believe that 7wtc came completely down not from one column failure migrating to other column failures but the failure was total because of the massive interconnected load transfer structures which when they failed engaged / every other part of the structure so it all cam down.

+++++

Lesson is that structures NEED some design mechanism (perhaps) to be able to ISOLATE "serious" local structural failures /collapses. These 2 designs did not and in fact their designs had elements which would INVOLVE/engage the entire footprint / plan in what would be a "global collapse". The twins were way outlier in the initiating damage. Mechanically they sustained it! But the fire suppression was not able to deal with the fires... again this was an outlier condition... thousands of gallons of burning jet fuel.

7WTC was not very outlier in the that it was failure of the fire suppression system which led to a single column failure and that to global collapse. In a sense if that explanation "works" then any high rise building in which fire breaks out and the fire suppression system fails (for whatever reason)... is a goner.

Yes or no? Or maybe?

The sound created by a black powder like reaction depends on containment.

Yes in an unprotected structure fire will destroy it.

 

[WilliamSeger]

Will do - wanted to BUT you pulled the plug on the starting point.

We had two lots of energetics - one dominated by column crushing - the other dominated by floor joist shearing. And I thought we agreed that the actual WTC collapse - progression stage - was dominated by FJ Shearing and not by column crushing. So those were the two mechanisms. And I thought we had agreed that the Bazant maths would apply better to WTC real collapse if the column crush energetics factor was replaced by floor joist shearing energetics. So we seemed to have reached agreement on two models.

I the made what I thought was the obvious next step. Divide the gap between the two extreme mechanisms into some part of one and part of the other. So 1/2 and 1/2 midpoint and possibly 1/4 - 3/4 at the other two quartile points. All that just starting point suggestions. And a lot of details for someone to deal with defining whatever those intemediate points could be.

So - if someone could fill the range between the two extremes - it could give Bazant his goal of an accurate generic model. To me "column spacing" was the obvious difference. You didn't see that. OK - so I started by setting out the range - never mentioned column spacing - just the two extremes FJ Shear the major factor <<>> column crushing the major factor. THEREFORE (should be next step of logic IMO) - some in between steps. How we calculate the steps is the challenge for anyone who wants his name on the model. I think column spacing and "subdivision into cells or tubes" are obvious candidates for the classification. So the state of my thinking is:
1) There are two ends of the line;
2) There must be some points in between;
3) If someone works out how to define those points they have the model Bazant wants but on a safer foundation.

And I thought:
(a) we had agreement to "1)" and
(b) "2)" is dogs balls obvious - if you have two ends there must be some in betweens - then
(c) someone can work out the in betweens. Say at the 1/4, 1/2. & 3/4 points (of mechanism difference NOT physical space). That is where all the comments you make about loading on floors transferring to load columns becomes ....."interesting"

But you appeared to reject "1)" which I thought was the starting line. And by repeating the challenging details when we haven't even started the race.

Sorry if I misunderstood; I don't reject "1)" in the model or "real world." (I don't believe a column would buckle from floor-only loading, but some could get hit with enough direct force to buckle.) If I'm jumping too far ahead to column spacing, then please proceed however you prefer.

I don't understand how changing the acronym avoids confusion OR how ROOSD causes confusion in the first place.

Originally Posted by WilliamSeger
That [floor shear vs. buckling] has never been a point of contention with me. As long as I've been in this thread, I've been trying to discuss what "open office space" has to do with any of it (other than the trivial fact that that's what it was). That's what I consider misleading.

Why? ROOSD is descriptive. Doesn't change anything for me if you want to say CDBFJSE and CDBCBE - or call it ZXTYPOTL or agree two terms of ten words each and repeat the ten words every time rather than use shorthand. So what?

Well, it just seems to me that in a thread titled "OOS Collapse Propagation Model" discussing something called ROOSD, one might assume that the OOS has some special significance, and perhaps that there is something significant about a "runaway OOS" that's qualitatively different from other types of progressive collapse. My question: if so, what is the significance; and if not, why is it in there? I don't think I'm being pedantic; I'd say I've seen more than a few hints that some might be thinking that "open office space" is a "vulnerability or design flaw." If there's a case for that or any other generalization I'd like to hear it, and if not, then OOS is misleading. I don't know how to explain it better than that.

If ROOSD is simply a description of a WTC collapse, then I think the term "WTC collapse" is well worth the few extra keystrokes. Anyone wanting technical details of the collapse propagation is well advised to at least begin with BZ, which has a brief but quite clear description of "what really happened" before getting into the logic of why it happened. With that foundation, anyone wanting to augment their understanding and/or mental visualization with details would probably find M_T's "mappings" to be very interesting. My question about ROOSD, however, has always been, "So what are you getting at?"

 

[JSanderO]

Well, it just seems to me that in a thread titled "OOS Collapse Propagation Model" discussing something called ROOSD, one might assume that the OOS has some special significance, and perhaps that there is something significant about a "runaway OOS" that's qualitatively different from other types of progressive collapse. My question: if so, what is the significance; and if not, why is it in there? I don't think I'm being pedantic; I'd say I've seen more than a few hints that some might be thinking that "open office space" is a "vulnerability or design flaw." If there's a case for that or any other generalization I'd like to hear it, and if not, then OOS is misleading. I don't know how to explain it better than that.

If ROOSD is simply a description of a WTC collapse, then I think the term "WTC collapse" is well worth the few extra keystrokes. Anyone wanting technical details of the collapse propagation is well advised to at least begin with BZ, which has a brief but quite clear description of "what really happened" before getting into the logic of why it happened. With that foundation, anyone wanting to augment their understanding and/or mental visualization with details would probably find M_T's "mappings" to be very interesting. My question about ROOSD, however, has always been, "So what are you getting at?"

I happen to think that the OOS design is very different from the column grid which I believe has more built in redundancy and ability to isolate locale failures and mitigate them from going "global".

From a conceptual point of view... the designers made the claim that what they did is take the typical grid columns which carry floor loads and move them to a structural skin... which would be part of the wind load strategy by acting as a membrane and offering the stiffness of a 4 sided box. Clever...

But in so doing...not that they removed column cross sectional area.. but the removed all the connections and bracing in a grid... and put all the connections to the axial system probably measurably less reserve capacity and demonstrably less ability to isolate disaster. Think of this analogy:

Say you have a river to cross and you need to build a bridge. You can do one large clear span or have several shorter spans... one after the other. In the first if the span drops the entire bridge is kaput. In the second case if one span fails the rest of the bridge remains and the repair is certainly not as expensive. In both cases the river crossing function has been lost.

I am not arguing anything other than the column free design is like the long span bridge and a failure will likely take the entire building out. If the building was like the Empire State Building with a grid of columns... it would likely survive and even possibly be repairable.

I would argue that as clever as the engineering was... it also contained vulnerabilities to runaway total collapse.

I think the load transfer system in 7wtc contained the same vulnerability to total collapse.

Neither design had engineered into them the ability to PREVENT runaway total collapses.

Is this something engineers should consider? Who knows? But it's never a good idea to put all your eggs in one basket.

I am almost positive the OOS column free design was driven by cost and the "need" to be innovative and allow those building to be built quickly.

++++

DO you think the ESB would have survived such an strike?

 

[WilliamSeger]

DO you think the ESB would have survived such an strike?

I don't know, but I do believe that if the entire top few stories started falling, then it would collapse completely. If you want to understand why, then it's a shame you don't have any interest in BZ. The exact design of the WTC towers is obviously important in understanding how the collapses started, and anyone wishing to design a building that can withstand high-speed 767 crashes should take heed. What we're discussing here, however, is collapse propagation, and my questions still is, "What's OOS got to do with it?"

 

[Bravin Neff]

If ROOSD is simply a description of a WTC collapse, then I think the term "WTC collapse" is well worth the few extra keystrokes. Anyone wanting technical details of the collapse propagation is well advised to at least begin with BZ, which has a brief but quite clear description of "what really happened" before getting into the logic of why it happened. With that foundation, anyone wanting to augment their understanding and/or mental visualization with details would probably find M_T's "mappings" to be very interesting. My question about ROOSD, however, has always been, "So what are you getting at?"

That's for making a succinct point covering the vague feeling I couldn't put words to.

 

[JSanderO]

I don't know, but I do believe that if the entire top few stories started falling, then it would collapse completely. If you want to understand why, then it's a shame you don't have any interest in BZ. The exact design of the WTC towers is obviously important in understanding how the collapses started, and anyone wishing to design a building that can withstand high-speed 767 crashes should take heed. What we're discussing here, however, is collapse propagation, and my questions still is, "What's OOS got to do with it?"

The OOS lacked the columns and "bays" which would isolate a collapse to a bay. That's not a hard concept to grasp.

You might disagree, but the bays are like barriers and a column free light wight floor system with joists spanning 60 feet will fail over 60 feet... but one with 2 intervening columns would have probably a failure that was or could be isolated to 20'.

Yes or no?

++++

No the ESB would have not completely collapsed if it was hit 28 floors from the top by that jet.

 

[DGM]

No the ESB would have not completely collapsed if it was hit 28 floors from the top by that jet.

Do you think we need to go back to building tall buildings like the ESB?

Is there a significant risk associated with OOS? WTC 7 performed better then required.

 

[JSanderO]

Do you think we need to go back to building tall buildings like the EPS?

Is there a significant risk associated with OOS? WTC 7 performed better then required.

I can't answer that question.

I don't think WTC7 did very well. It's fire systems failed and it had the load transfer system which was what brought the entire thing down.

OOS might be more survivable with much more robust floors I suppose or much more robust beams and beam to column connections than the trusses and seats that were used.

I am not an engineer and I don't know.

 

[DGM]

I can't answer that question.

I don't think WTC7 did very well. It's fire systems failed ...................

Was there a vary unusual circumstance, maybe even past any reasonable expectations for the failure of these systems? Is there reason to believe if they didn't fail, the building wouldn't survive?

 

[JSanderO]

Was there a vary unusual circumstance, maybe even past any reasonable expectations for the failure of these systems? Is there reason to believe if they didn't fail, the building wouldn't survive?

I know I am wandering OT.

I don't think the failure was from "office" fires on floor 13. I think ...guess ... that there wasn't enough "fuel" to do what is claimed. I think that the fires would probably burn out but not trigger a total building collapse.

I think something else related to fire and it was in the load transfer region.

 

[DGM]

I think something else related to fire and it was in the load transfer region.

Doesn't matter. If the water (sprinklers) were not cut off the building would have survived. It was not a design problem, it was circumstances way outside of consideration. Do you not agree?

 

[WilliamSeger]

The OOS lacked the columns and "bays" which would isolate a collapse to a bay. That's not a hard concept to grasp.

Except that it isn't necessarily true. The initial blast at the Oklahoma City Murrah Building only took out some of the exterior columns near the truck, but the progressive collapse propagated 3 bays in and ended up taking down half the building. The Skyline Towers collapse began with a single bay but it took down the whole building up to an expansion joint. But anyway, the specific issue here is what if anything OOS had to do with the WTC total progressive collapse, and what if anything can be generalized from that.

You might disagree, but the bays are like barriers and a column free light wight floor system with joists spanning 60 feet will fail over 60 feet... but one with 2 intervening columns would have probably a failure that was or could be isolated to 20'.

Yes or no?

Insufficient information to answer, and irrelevant to the topic, but I'll answer anyway: That isn't necessarily a "vulnerability" that's worth the expense of preventing. If you had a partial building collapse, whether 20-foot bays or 60, would you try to reuse the remaining building or tear it all down anyway?

 

[WilliamSeger]

OOS might be more survivable with much more robust floors I suppose or much more robust beams and beam to column connections than the trusses and seats that were used.

I am not an engineer and I don't know.

This is where understanding BZ would come in handy, and you don't need to be an engineer to understand it. If the floor connections had been strong enough to transfer all that load, the columns would have collapsed instead.

 

[JSanderO]

This is where understanding BZ would come in handy, and you don't need to be an engineer to understand it. If the floor connections had been strong enough to transfer all that load, the columns would have collapsed instead.

No they wouldn't... that's incorrect.