OOS Collapse Propagation Model

[1stClassAlan]

Unfeeling like a banana is the opposite of donuts and broom handles. I am sure there is a better food analogy somewhere. And it's not pizza boxes.

Ah thanks for pointing out an errant inference! I agree that The Towers did unpeel like banana - my allusion to a doughnut down a broom handle refers to the progression of the collapses - there is a continual blooming outwards of dust and debris ( I point this out to fly in the face of those fond of quoting "pancaked into their own footprints etc., ) to reveal some of the core still standing but almost devoid of beams - considerable lenghts (or rather, heights ) of column can be seen to fall out of the cloud - yet another dent in CD Conspiracy as these would be the first items CD professionals would cut.

The initial collapse is easy.

Well, yes, a flippin' great plane hit it at not far under full power! We can all surmise the initiation but the 400 or so NIST experts seemed rathe shy in publishing a definitive cause - misintrepretated by Conspiracists!

Every floor truss is made from bar joists and they are impossible to fire protect every bar. Any defect turns in any bar turns the joint into a mechanism and the fire is hot enough to quickly get lots of bars failing. There are many pics around showing damage to the fire protection before 9/11.

I've never credited even perfect spray on fire protection to be worthy of the name and I speak as someone who has witnessed many a fire test at both our accredited testing facilities here in the U.K. It also makes me laugh to read how self assured many posters are of how hot the fires were in The Towers - couldn't possibily reach high temperatures, wrong colour smoke, etc., etc., and of course, my favourite - oxygen starved!! For chrissakes - no one who says that has ever worked on a highrise with the windows out!

Over here, the news broadcasts at first said a "small" aircraft had hit one tower but once it became clear that it was a large airliner - I had the sneaking suspicion that another would soon hit the other one and both would collapse. Some buildings might be able to resist many of their upper floors crashing down on the remainer but I think thay are few and far between - most are vunerable. However; now this outrage has occurred - it will have to sink from living memory before security around aircraft slackens sufficiently for others to try it again.

 

[DGM]

I've never credited even perfect spray on fire protection to be worthy of the name and I speak as someone who has witnessed many a fire test at both our accredited testing facilities here in the U.K. It also makes me laugh to read how self assured many posters are of how hot the fires were in The Towers - couldn't possibily reach high temperatures, wrong colour smoke, etc., etc., and of course, my favourite - oxygen starved!! For chrissakes - no one who says that has ever worked on a highrise with the windows out!

Excellent point that most "truthers" never get. One of the most important fire protection strategies is to keep the fires contained within a floor and not to allow "chimney" air to feed the fires. This is why all floor stairwells feature self-closing heavy doors. The fact the planes and the collapse of the towers (for WTC7) rendered floor to floor isolation useless doomed these building as much as the lack of water.

 

[Newtons Bit]

That wasn't the point.... I suppose if all the outside the core space is one slab and it collapses it leaves the perimeter columns and the core columns... they may then topple too.

if one bay collapses it leaves all the other slabs intact and most of the frame and it likely will remain standing.....

no?

I don't understand what you're trying to get at with this line of posts. Are you saying that one bay of a typical low-rise grid will collapse with the same ease as the entire shell area of the WTC? I can't see any other purpose for comparing a 30'x30' bay of a hypothetical building with the entire shell area of the WTC. And I certainly can't see any sort of mechanism that would unzip the WTC shell floors.

 

[Myriad]

Comparison of strength or robustness only makes sense relative to demand.

One might think that a pyramid of nearly solid stone would necessarily be extremely robust. And yet, one ancient Egyptian pyramid, built with a slightly steeper angle than normal, collapsed, either just before or soon after completion. Large stone pyramids are not strong compared with their own weight. (The sides actually bulge out under the strain.)

One thing I've learned from all this discussion is how fragile large things are, in relation to the demands upon them, compared to familiar small objects. As I've pointed out elsewhere, if you had a wine goblet made with the same ratio of strength to demand that a skyscraper has, you'd have to put the wine in gradually with an eye dropper, or else it would shatter. (Don't even think about picking it up.)

The ESB, even though made of stronger members more closely interlocked and also having step-backs that give it a rough overall pyramid shape, is not necessarily any more resistant to progressive collapse, because its components are also correspondingly heavier. Remember, even a solid stone pyramid can collapse.

 

[Major_Tom]

Now know? This isn't an original idea of yours, Major_Tom. Every single one of the buildings I have ever designed would experience a total and catastrophic collapse if two the floor slabs suddenly detached. This isn't unique to my buildings, either. It's true for just about every single building ever built.

See step 2.


Mathematical approach to the study of ROOSD propagation:

Step 1: GAIN AN OVERALL CONCEPTUAL AND VISUAL UNDERSTANDING OF WHAT ONE IS LOOKING AT

Step 2: RESEARCH AVAILABLE LITERATURE ON THE SUBJECT OF FLOORS IMPACTING FLOORS

Step 3: MEASURE THE COLLAPSE PROPAGATION RATE AS ACCURATELY AND COMPLETELY AS POSSIBLE

Step 4: EXAMINE A VARIETY OF PHYSICS-BASED MATHEMATICAL APPROACHES TO THE COLLAPSE OF STACKED SYSTEMS

Step 5: COMPARE MODELS IN STEP 4 TO INFORMATION IN STEPS 1 - 3 to see which models could match propagation behavior or teach something about it.



Could you please link to literature on floor slabs impacting floor slabs? I'd like to compare it to the literature I have already found.

May I see and read the literature you use to justify your comment?

 

[beachnut]

See step 2.


Mathematical approach to the study of ROOSD propagation:

Step 1: GAIN AN OVERALL CONCEPTUAL AND VISUAL UNDERSTANDING OF WHAT ONE IS LOOKING AT

Step 2: RESEARCH AVAILABLE LITERATURE ON THE SUBJECT OF FLOORS IMPACTING FLOORS

Step 3: MEASURE THE COLLAPSE PROPAGATION RATE AS ACCURATELY AND COMPLETELY AS POSSIBLE

Step 4: EXAMINE A VARIETY OF PHYSICS-BASED MATHEMATICAL APPROACHES TO THE COLLAPSE OF STACKED SYSTEMS

Step 5: COMPARE MODELS IN STEP 4 TO INFORMATION IN STEPS 1 - 3 to see which models could match propagation behavior or teach something about it.



Could you please link to literature on floor slabs impacting floor slabs? I'd like to compare it to the literature I have already found.

May I see and read the literature you use to justify your comment?

Could you amplify Steps 1 - 5? More details please.

Step 1,000,547: post the steps again - and again - how is that "gravity collapse is an illusion" going, does this debunk yourself?

 

[JSanderO]

I don't understand what you're trying to get at with this line of posts. Are you saying that one bay of a typical low-rise grid will collapse with the same ease as the entire shell area of the WTC? I can't see any other purpose for comparing a 30'x30' bay of a hypothetical building with the entire shell area of the WTC. And I certainly can't see any sort of mechanism that would unzip the WTC shell floors.

Done be so dense... if one *bay* of the ESB collapsed the rest of the bays and the building would stand...

right or no?

 

[DGM]

Done be so dense... if one *bay* of the ESB collapsed the rest of the bays and the building would stand...

right or no?

Why only one bay? The damage to the towers inflicted by the planes was far greater than one 30' bay.

Compare apples to apples. A don't think the EPS would do so well.

 

[JSanderO]

Why only one bay? The damage to the towers inflicted by the planes was far greater than one 30' bay.

Compare apples to apples. A don't think the EPS would do so well.

My point was that a grid system of columns would isolate the damage and the open plan column free would not... yes or no?

 

[DGM]

My point was that a grid system of columns would isolate the damage and the open plan column free would not... yes or no?

No.

The towers did have an extensive grid system that redistributed the loads very well. An open grid needs to redistribute the loads through not so optimal paths. I think the ESB would have failed immediately on impact.

 

[rwguinn]

My point was that a grid system of columns would isolate the damage and the open plan column free would not... yes or no?

Under the conditions of 9/11/2001?
Hell, No.
Under other conditions? Possibly. Define the conditions, and we can discuss it is Science and Technology.

 

[Newtons Bit]

Done be so dense... if one *bay* of the ESB collapsed the rest of the bays and the building would stand...

right or no?

Probably, though it's not a guarentee. There's no reason to compare a single bay to the entirety of the WTC floor shell, though. Hell, I even asked if that was what you were trying to do and you said "that wasn't the point". Perhaps you should try forming more complete thoughts.

 

[Newtons Bit]

Could you please link to literature on floor slabs impacting floor slabs? I'd like to compare it to the literature I have already found.

May I see and read the literature you use to justify your comment?

I don't need literature to justify my comment. The floors of phase 1 of a hospital I'm working on has a dead load of 170psf and a design live load of 80psf. A SINGLE floor detaching and gently lowered on to the floor below would cause a global failure.

That building opened before you and I ever had a single conversation.

 

[Major_Tom]

I don't need literature to justify my comment. The floors of phase 1 of a hospital I'm working on has a dead load of 170psf and a design live load of 80psf. A SINGLE floor detaching and gently lowered on to the floor below would cause a global failure.

Do you think the same was true for WTC1 and 2?

Considering that the WTC 1 and 2 collapses were the largest chain of progressive floor collapses ever, One would think that these exact questions would have come up in the NIST studies.



What are the most vulnerable floor regions of a typical WTC1, 2 floor?

What is the minimum threshold to set off a ROOSD progression in the most vulnerable OOS floor spaces in the buildings?


In the OOS model total floor space is divided into 9 distinct regions:


A typical WTC 1 floor can be divided into 2 main sections having different strengths, one within the core area and another outside the core:

Open office space flooring (OOS)
Flooring within the core (CF)



The total OOS floor space can be divided into 8 smaller floor regions:

1) OOS directly north of the core (OOS n)
2) OOS directly east of the core (OOS e)
3) OOS directly west of the core (OOS w)
4) OOS directly south of the core (OOS s)
5) OOS northwest corner region (OOS nw)
6) OOS northeast corner region (OOS ne)
7) OOS southwest corner region (OOS sw)
8 ) OOS southeast corner region (OOS se)

 

[Animal]

Excellent point that most "truthers" never get. One of the most important fire protection strategies is to keep the fires contained within a floor and not to allow "chimney" air to feed the fires. This is why all floor stairwells feature self-closing heavy doors. The fact the planes and the collapse of the towers (for WTC7) rendered floor to floor isolation useless doomed these building as much as the lack of water.

Well, actually the self closing doors (as well as positive air pressure in the stairways) is intended to keep the stairways safe as long as possible to evacuate the building occupants. Secondary to evacuating the occupants, preventing floor to floor movement of fire is found throughout the code....it is not so much about "chimney air" as it is about preventing a fire to rapidly spread through multiple floors. Fire dampers in ductwork is a simple example...

 

[Newtons Bit]

How was that a response to my post, Major_Tom?

 

[Newtons Bit]

Well, actually the self closing doors (as well as positive air pressure in the stairways) is intended to keep the stairways safe as long as possible to evacuate the building occupants. Secondary to evacuating the occupants, preventing floor to floor movement of fire is found throughout the code....it is not so much about "chimney air" as it is about preventing a fire to rapidly spread through multiple floors. Fire dampers in ductwork is a simple example...

Right. The architects I work with are frequently concerned with vertical shafts (stairways or mechanical) being smoke risers. Trying to navigate out of the building through a smoke filled stairway would be unpleasant...

 

[JSanderO]

Do you think the same was true for WTC1 and 2?


[qimg]http://www.sharpprintinginc.com/911/images/photoalbum/13/reducedliveload.png[/qimg]

NB that these "reduced" live loads were requests from the developers to save money 9 materials and the code called for 100# LL

 

[jaydeehess]

Right. The architects I work with are frequently concerned with vertical shafts (stairways or mechanical) being smoke risers. Trying to navigate out of the building through a smoke filled stairway would be unpleasant...

I work at a TV station and its a very old building so there's not much opportunity to run cables in walls(plaster & lathe). We then run them above the drop ceiling tiles but that requires entry/exit holes in the tiles. Last time we renovated some offices had cables removed but the ceiling tiles remained as is. Fire Dept came and did an inspection (voluntary on our part) and recommended replacing all tiles with holes in them.

Frankly would't make a big difference to fire spread IMHO. Its a 3 storey masonry exterior and timber interior built in 1919. If there were a fire here , the masonry exterior walls would very quickly become one of the biggest chimneys in the world. Our fire drills have everyone out in 90 seconds including fire wardens. IMHO that gives us a buffer of about 8:30 before the building would become a funeral pyre for anyone still inside.

 

[Newtons Bit]

NB that these "reduced" live loads were requests from the developers to save money 9 materials and the code called for 100# LL

Live Load Reduction is a very well understood statistics based analysis and is allowed by both the modern code and the code the WTC was designed to. They don't need scare quotes around them.