The 9/11 Forum

femr2 wrote:....The floor regions were a weak link, but not as weak as being portrayed....

I agree.

femr2 wrote:....Last time I checked we agreed around 6 floors in a static condition. Others suggest up to 10....

When I first explained the two stages of collapse I guesstimated the floor failure load as 5 floors applied static. Cannot remember how I did it at this late stage. Given that whatever hit the first floor down when the "global" or "progression" stage started was dynamic and included weight of top block rather than one or more disconnected floors I was and still am satisfied the loading was "overwhelming'. And therefore I didn't need any more precision. There are a few other factors I have glossed over - all of them in the direction of making global collapse start-up more certain.

ozeco41 wrote:Given that whatever hit the first floor down when the "global" or "progression" stage started was dynamic and included weight of top block rather than one or more disconnected floors

Have to disagree.

Disparity between crush front "release" and propogation rate, when compared to roofline release and rate of descent, suggests that floor region(s) essentially separated from the "upper section" as part of the initiation process.

It may have been that after release of a floor or two upper section mass kicked ROOSD into motion, but it's a grey area in observational terms. ROOSD gets off too rapidly is the problem.

We haven't looked at reduced load capacity in floor regions immediately below initiation zone.

Well basically it was my error in the first place, during a debate about the collapse, I referenced Dave thomas who said that the top section exerted a dynamic load 31 times the static load when falling, now I now know its not that simple but I'm sure that the dynamic load was too much for the lower sections connections to resist. The other poster refuted this by saying what I cited above about the technical error bazent made ( and Dave used). Saying that it was calculated wrong therefore the top section should have been arrested by the lower section.

Wow must be frustrating having all the work lost, I can only imagine.

femr2 wrote:

ozeco41 wrote:Given that whatever hit the first floor down when the "global" or "progression" stage started was dynamic and included weight of top block rather than one or more disconnected floors

Have to disagree....

Great. I'm referring back to my own 2008 thinking - your details most likely better than mine. Could be interesting to work through it though my primary motivation here is to help illuminist14 get a handle on the basics. As you know I'm not all that driven by details unless they change the outcomes.

femr2 wrote:...Disparity between crush front "release" and propogation rate, when compared to roofline release and rate of descent, suggests that floor region(s) essentially separated from the "upper section" as part of the initiation process....

I have had in mind - with zero proof so it is a possible hypothesis only - that floor separation was initiated in two ways - one of them with two sub-sets.

1) The initiation resulting from accumulated damage in the impact and fire zone could well have separated some zones of flooring. I certainly don't envisage anything like a flat floor on flat floor interaction. And (almost??) certainly all the envisionable initiation mechanisms would cause some floor bits to break free.
2) The falling top block had its outer perimeter attached and that outer perimeter fell either inside or outside the lower perimeter - depending on which side of which tower we consider. I understand that you or Major_T know which ones went where. I don't and haven't needed the detail. However my preliminary part of an hypothesis has been that:
Sub set A - where the top block perimeter fell inside it would act as a knife edge putting a big load on the first floor it landed on and initiating disconnection of that floor. Full disconnection most likely a progressive event moving around the tower due to several factors.

Sub set B - Likewise but in reverse, where the Top Block perimeter fell outside the lower perimeter the lower perimeter moving upwards (relatively that is) to the top Block acted as a knife edge and separated floors in the top block.

All of that thinking based purely on thinking about possible mechanisms. Remember my objective has been "sufficient understanding to enable me to explain." For that objective I only need a plausible mechanism. Sure a probable mechanism is better if it is relatively easy to access.

Do you have data which proves what I say OR proves me wrong and supports and defines another mechanism?

femr2 wrote:...It may have been that after release of a floor or two upper section mass kicked ROOSD into motion, but it's a grey area in observational terms....

I would have thought very dark grey. I continue to admire the work you and M_T have done. No way could I either be bothered or do it. but my needs have been very different also.

femr2 wrote:...ROOSD gets off too rapidly is the problem....

I may need to get to understand what that means/implies.

femr2 wrote:...We haven't looked at reduced load capacity in floor regions immediately below initiation zone.

Ditto

Illuminist14 wrote:Well basically it was my error in the first place, during a debate about the collapse, I referenced Dave thomas who said that the top section exerted a dynamic load 31 times the static load when falling, now I now know its not that simple but I'm sure that the dynamic load was too much for the lower sections connections to resist. The other poster refuted this by saying what I cited above about the technical error bazent made ( and Dave used). Saying that it was calculated wrong therefore the top section should have been arrested by the lower section....

It's far too complicated and confused to try to explain all the claims that have been made. Just remember that anyone claiming columns needed to be buckled is near certainly following Bazant and probably is not talking about what actually happened.

Illuminist14 wrote:...Wow must be frustrating having all the work lost, I can only imagine.

Not soul destroying. It happened at a time when I was dealing with depression AND burned out with 9/11 foruming plus some frustrating battles in revising rules and moderating practices. So I resigned my Senior Moderator role and simply walked away from Internet forums for a while. I'm still not driven to the level I was in 2007-8-9 and the amount of meaningful discussion has tapered away to near zero. Mostly trolling and rehashing of long disproved stuff on my other two forums and not all that different here except not the trolling. A lot less "noise" here also

Must have been annoying, It was basically a 'TRUTHER' (god I hate that term) who refutes everything NIST and Bazent says inc that error in calculation, which he think means theres no way the top section falling could overwhelm the lower section....

Illuminist14 wrote:Must have been annoying,..

somewhat but I've had worse - look at the user name ozeco41

Illuminist14 wrote: It was basically a 'TRUTHER' (god I hate that term)

It was an honourable term at its origin - self description by concerned people who were genuinely seeking truth about 9/11 events and the management of those events by Government/Authorities. The word has since been degraded from both sides of the polarised divide that both sides reinforce. Few if any genuine truthers left. Given it is now 10 years the important questions have been answered therefore those still pursuing truth include a large proportion of those determined to never shift belief, a few newcomers with genuine concerns but not many of those in 2012 and a few long time truthers who for whatever reasons are still unsatisfied. With the demographic mix so shifted from (say) what it was 2005-6-7 it is natural that "name calling" becomes prominent and "truther" becomes debased.

Illuminist14 wrote: who refutes everything NIST and Bazent says inc that error in calculation, which he think means theres no way the top section falling could overwhelm the lower section....

There is no way that a rational honest person provided with the evidence and explanations can genuinely hold that opinion in 2012. So at least one of the legs must be sus. So a failure in one or more of these >>"Honest"; "Rational"; "Evidence" or "Explanations"



Good evening - UCT +10 here in Eastern Australia.

ozeco41 wrote:1) The initiation resulting from accumulated damage in the impact and fire zone could well have separated some zones of flooring.

Could do.

2) The falling top block had its outer perimeter attached and that outer perimeter fell either inside or outside the lower perimeter

Likely, and enabling a fairly "low energy" route to stripping the perimeter from the floor regions. Not quite the same at the core end of OOS floor regions, but maaaybe.

Do you have data which proves what I say OR proves me wrong and supports and defines another mechanism?

Probably, though I suggest halting the derail here

femr2 wrote:...ROOSD gets off too rapidly is the problem....

I may need to get to understand what that means/implies.

Based on extremely rapid propogation of "crush front" ejecta for WTC1. WTC2 primary crush front ejecta tended to follow the tipping of the upper section more closely. Will halt the derail in a mo

femr2 wrote:...We haven't looked at reduced load capacity in floor regions immediately below initiation zone.

Ditto

[/quote]
Fir below initiation zone may have weakened connections, making ROOSD easier to start with less mass/force. Derail done Will find a more appropriate thread.

ozeco41 wrote:

Illuminist14 wrote:Must have been annoying,..

somewhat but I've had worse - look at the user name ozeco41

Illuminist14 wrote: It was basically a 'TRUTHER' (god I hate that term)

It was an honourable term at its origin - self description by concerned people who were genuinely seeking truth about 9/11 events and the management of those events by Government/Authorities. The word has since been degraded from both sides of the polarised divide that both sides reinforce. Few if any genuine truthers left. Given it is now 10 years the important questions have been answered therefore those still pursuing truth include a large proportion of those determined to never shift belief, a few newcomers with genuine concerns but not many of those in 2012 and a few long time truthers who for whatever reasons are still unsatisfied. With the demographic mix so shifted from (say) what it was 2005-6-7 it is natural that "name calling" becomes prominent and "truther" becomes debased.

Illuminist14 wrote: who refutes everything NIST and Bazent says inc that error in calculation, which he think means theres no way the top section falling could overwhelm the lower section....

There is no way that a rational honest person provided with the evidence and explanations can genuinely hold that opinion in 2012. So at least one of the legs must be sus. So a failure in one or more of these >>"Honest"; "Rational"; "Evidence" or "Explanations"



Good evening - UCT +10 here in Eastern Australia.

Ah, its afternoon here in UK (Cannot wait for evening) .

Yes this poster is convinced it was CD and that the below floors could not be overwhelmed as there was no deceleration, thats how clear it was put accross.

femr2 wrote:...Not quite the same at the core end of OOS floor regions, but maaaybe.

understood and agreed. And it could be maaaaaaaayyyybbbee

femr2 wrote:...

Do you have data which proves what I say OR proves me wrong and supports and defines another mechanism?

Probably,...

that's a neat two way bet.
One of my standard "both way bet" respnses: Q: "Was the baby a boy or a girl? A: "Yes!"

femr2 wrote:.. though I suggest halting the derail here
.... Will halt the derail in a mo
...

We need to fix the brakes on this train.

femr2 wrote:...Fir below initiation zone may have weakened connections, making ROOSD easier to start with less mass/force....

There are multiple possibilities and we will never know. IMNSHO the real situation was vastly more complex than the homogeneity and one dimensionality assumed by most of the theoretical "explanations" a la Bazant et al. Very few if any other than members here have looked at "what really happened". And it is mostly hidden so even with research of "observables" there will not be enough pieces to complete the jigsaw. However it requires less than all the pieces to define the size and overall layout of a jigsaw. If you have the necessary bits - not just all those of blue sky which are hard to fit in even when the rest of the puzzle is completed.

My thoughts have long been on zip fastener style cascade mechanisms where one more or less point failure leads to overload of the next bit which then fails overloading the next bit which>>>loop till end. Simple probability logic says that it was highly improbable that anything would land level enough onto such equal strength bits which then all broke at the same time. Therefore that was probably not what happened therefore.... And that is not a "false dichotomy". AND Just to be clear I am speaking of the transition from Top Block starts to move initiation to established global collapse progression. i.e. how does downward movement of Top Block lead into ROOSD.

femr2 wrote:..Derail done Will find a more appropriate thread.

Not sure that I can add anything to further exploration but you could link me to your key bits of work -- no hurry.

Illuminist14 wrote:...Ah, its afternoon here in UK (Cannot wait for evening) ....

I was born here - 29 June 1941:

....10 Moor View, Lower Mickletown. It is between Leeds and Castleford and the house was the coalminers house occupied by my "Mam's" family. Delivered in front room by village midwife. Came to Australia 1952.

Illuminist14 wrote:...Yes this poster is convinced it was CD and that the below floors could not be overwhelmed as there was no deceleration, thats how clear it was put accross.

There has been a lot of silly claims based on poor understanding of "free body" physics coupled with poor understanding of the actual WTC collapse mechanisms. That has allowed a lot of what I consider to be poor reasoning from both extremes of the 9/11 discussion. Call them "truthers' and "debunkers" for shorthand. At least as much crap from the "debunker" side - the only thing saving them being that there are a lot more of them and the evidence tends to be in their favour. But the average level of engineering reasoning skills not impressive IMNSHO.

And all that background is where much of the talk of deceleration and the search for big jolts which should not have been there then presumptions about the absence of big Jolts OR large "decelerations" based on the false concepts. Said false concepts not explicitly admitted but nevertheless which are implicitly underpinning the false conclusions.

If you want to go into all that area be warned it is a confused mess. I am one of those who can help clear it up for you but take my advice and don't waste your time. Focus on any concerns you may have - not the problems that other people have in understanding.

Cheers again.

Gang...

There is little evidence I would think that the top face broke uniformly at one level. It likely parted where the column to column connections were and so it would find be a saw tooth edge. Why would it part columns mid section?

Next we can almost say with 100% that entire slabs did not drop as uniform plates after simultaneous failure of all connections to the frame. But it's conceivable that the top section could have frame and floors connected and crash more or less intact onto something below. Axial load alignments would no longer exist but entire floors could conceivably collide.. but not from simultaneous release of the floor slab. The question is how well did the top remain together as it came down? I think at least a fair bit DID descend as a block a stack of slabs and was some crush up crush down. The so called jolts would require some pretty stiff resistance to the spears of columns coming down and the flimsy floor slabs would hardly do it. So it's hard to conceive of the top breaking apart like a house of cards on first impact with the lower section after a one floor drop. Maybe I'm too dumb.

Since we have evidence of parts racing ahead in the ROOSD process... we need to figure out how and why those parts got a head start or why the other parts were slackers? I would look to the size of the parts... short span v long span and the number of support connections to the frame. The corners or the slabs are interesting... they were supported on one end on a transfer truss or girder which was then connected to the corner column... in a major point / concentrated load. The rest of the corner was support on 2 sides some on the truss joists and the adjacent side on the cross trusses.

So the long and short of this is that explanation of why some of the ROOSD parts were ahead of others is likely like driven by how the parts were connected to the frame. And remember that all those truss seats were identical... and it's likely that the loads on them were not! Short span truss joist connection therefore had a larger FOS than the long span ones.

The ROOSD appears to be born from the mass created by the initial crush up crush down... But once created it was on its own.

Sander there is a lot in your previous post and it clearly shows where you are coming from. Too much to respond briefly and at this time. Ditto other comments by Major_Tom et al.

However on this post:

SanderO wrote:Gang...

There is little evidence I would think that the top face broke uniformly at one level. It likely parted where the column to column connections were and so it would find be a saw tooth edge. Why would it part columns mid section?..

Yes. It wouldn't.

SanderO wrote:...Next we can almost say with 100% that entire slabs did not drop as uniform plates after simultaneous failure of all connections to the frame. But it's conceivable that the top section could have frame and floors connected and crash more or less intact onto something below. Axial load alignments would no longer exist but entire floors could conceivably collide.. but not from simultaneous release of the floor slab. The question is how well did the top remain together as it came down? I think at least a fair bit DID descend as a block a stack of slabs and was some crush up crush down. The so called jolts would require some pretty stiff resistance to the spears of columns coming down and the flimsy floor slabs would hardly do it. So it's hard to conceive of the top breaking apart like a house of cards on first impact with the lower section after a one floor drop. Maybe I'm too dumb....

we are getting into areas where:
A) I doubt we will ever know the answers; AND
B) I don't personally have a lot of interest in pursuing. Recall my motivation or WTC collapse has always focussed on being able to explain to lay persons and some fellow professionals (1) Why the towers collapsed i.e. the mechanism in good enough detail to satisfy their interest; AND (2) the answer to "was there demolition?" Naturally I need to understand sufficiently to support my opinions being professionally responsible for the purpose I need to deploy them. BTW that is one of the two big differences of opinion between me and Major_Tom. Probably irreconcilable since I don't pursue detail which is not needed for the purpose.

SanderO wrote:...Since we have evidence of parts racing ahead in the ROOSD process... we need to figure out how and why those parts got a head start or why the other parts were slackers? I would look to the size of the parts... short span v long span and the number of support connections to the frame. The corners or the slabs are interesting... they were supported on one end on a transfer truss or girder which was then connected to the corner column... in a major point / concentrated load. The rest of the corner was support on 2 sides some on the truss joists and the adjacent side on the cross trusses....

Two points:
1) For the reasons of motivation I have stated several times for me it is "may need to figure out" - my "need" may be less absolute than other members;
2) More on the technical variables. your factors about loading are valid candidates. Add in two more for my starters:
(i) Some bits of the first floors to fall may - most likely did - start before others - wouldn't take much in time to give the "head start" Conversely the "slackers" delayed start.
(ii) Variances in floor loads could change the impact forces leading to easier/harder shearing of connections (Yes I'm aware of the risk of dubious physics in the range close to "G" accelerations so I post that whilst I await clearing of current brain fog)

SanderO wrote:...So the long and short of this is that explanation of why some of the ROOSD parts were ahead of others is likely like driven by how the parts were connected to the frame. And remember that all those truss seats were identical... and it's likely that the loads on them were not! Short span truss joist connection therefore had a larger FOS than the long span ones...

probably the same sort of issue I tried to address in my previous comment.

SanderO wrote:...The ROOSD appears to be born from the mass created by the initial crush up crush down... But once created it was on its own.

Be warned - every time I see "crush up crush down" when discussing what really happened I get nervous about Bazantianism.

"Crush up, crush down" also synonymous with "top dies, bottom dies" in 911 Forum jargon.

The expression may be the like the scarlet letter... I don't see this as a continuing process by any means but it could account for the first one or perhaps two slab to slab collisions / destruction post buckling. The core buckling could conceivable mean release of the core side of the slab support... at least where the core columns went all twisty. could this have happened simultaneously to in such a way that the entire inside of the square donuts had no axial support? Remember that side was supported no in individual column connections but on the *belt* girder which connected to the columns and had the truss seats welded to it. It may make even less sense to imagine 100% release from the columns on the core side simultaneously.... And on the facade side there is little buckling... not know as there was the observed pulling in which is more indicative of NO release... or was that from no connection and no bracing allowing buckling? In any case this IB did not occur all around the perimeter and it appears that most of the slabs were still receiving axial support from the facade side in the first instant of the downward motion.

And this leads me to suggest that the first floor to floor collisions or impacts were not from whole floor slabs released. These impacts likely did shatter and dislodge the slabs from the columns and became the seeds of ROOSD. Would crush up crush down be the correct terminology? Dunno... the moving down of the tops HAD to mean the first two slabs would have a date and a nasty fight... and not live to tell about it either.