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Moderated WTC 1 features list, initiation model / WTC 2 features list, collapse model

Major_Tom

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Any model of the WTC 1 collapse initiation or progression sequence should be based on a carefully prepared list of observations. The following features were observed for WTC 1:

(Links fixed)

Ejection from 75th Fl, E Side During AA11 Impact
Damage to Basement and Lobby
Fire, Smoke Ejections as WTC2 is Struck
Strong Fire Ejections As WTC2 Collapses
Inward Bowing of the S Perimeter
Ejections Witnessed at 10:18
Roofline Smoke Pulses just before Collapse
Upper West Wall Pulls Inward 9.5s before Collapse
Antenna Base Shifts Eastward 9.5s before Collapse
Fire Flair-up along E Face 3s before Collapse
Antenna Sags 2 ft into Roofline before Falling
Concave Roof Deformation
Earliest Row of Ejections from fl 95, W Face, S Side
Over-pressurization of fl 98 before Falling Begins
Upper Portions tilt less than 1 Degree in 0.5s before Falling
Earliest Detectable and Drop Movements Traced and Plotted
All 60+ Columns in W Face Fail Within 0.5s and 1 Degree
Adjacent Perimeter N and W Walls Fail Within 0.5s Interval
Jolts Detected in Earliest Antenna, NW Corner Drops
Upper W Wall Breaks Outward as Large, Unbuckled Pieces
Large W Wall Piece w/ Straight Break Along Bottom
Lower W Wall Pushed Outward Intact
Upper NW Corner Slides Out and Over Lower Portion
Lower NW Corner Remains Standing Below Fl 98
Upper NE Corner Assembly has Straight Break along Bottom
Upper N Wall Breaks Outward as Large, Unbuckled Pieces
E Wall Breaks Outward as Large, Unbuckled Pieces
Early Downward Acceleration Rates
88th Fl S Face Light Grey Ejection
77th Fl Over-pressurization Timing Inexplicable
SW Corner Section is Earliest Free-falling Object
N and W Rooflines Lose Shape and Pull Inwards
Ejections Advancing Down NW and SW corners
Ejections Below WTC1 Collapse Fronts
Mechanical Floor Ejections
Diagonal Ejections Traversing E Face, Fls 50-55
Lower Perimeter Peels Outward after Flooring Destroyed
Large Piece of Antenna Falls Southward
Whole E-W Width of the Core Survives Initial Collapse
Surviving Core Remnant Drops Collectively
Rubble Layout and Column Conditions Recorded



The list is roughly in chronological order. Reading down the list allows you to see the progression of events as they occurred.




I know it is a lot of information, but the true collapse as it was recorded was not a simple event. The earliest motion was one of pure deformity as sub-pixel measuring methods show.

It it interesting to study how well common descriptions of the collapse events match or contradict the recorded events. For example, how does the NIST's description of the initial failure sequence match the actual events as they are recorded and measured?

Do words like "hinge" or "tilt axis" have any real meaning for WTC1? Do the events show south wall failure as the initiating event or does a sagging core pull the building down?



Any model of the collapse initiation sequence must match the visual record, just as any collapse progression model must match all observables. The OOS collapse propagation model was based on a handful of features from this list.

Does any known collapse initiation model match this visual record? (No).
 
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This list makes me nauseous. :)

The work you put into this issue is stunning, Major Tom, and invaluable. Your site has to be one of the best WTC resources on the internet, if not the best, in the English language. I do not know of any others where the intent is so purely focussed on facts over rhetoric (and I'm one who is fond of rhetoric).

(But which is also why I find your OOS collapse argument puzzling, as, imo, the very evidence that you've taken such pains to archive and bring attention to does not match that model, and at times outright contradicts it. But that's for another thread, if ever.)

Just wanted to convey my appreciation. Sorry for the drift.
 
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Major_Tom said:
...It it interesting to study how well common descriptions of the collapse events match or contradict the recorded events. For example, how does the NIST's description of the initial failure sequence match the actual events as they are recorded and measured?...
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This is more or less the common description of events:
1) Airplane strikes tower, does some damage, starts some fires.
2) Fires are not fought allowing more damage to accumulate.
3) The accumulating damage causes load shedding and load redistribution.
4) The load redistribution events build up into a cascading sequence which weakens the impact and damage zone.
5) The damage reaches the point where there is insufficient remaining strength to support the "top block".
6) The impact zone ceases to support the Top Block.
7) The Top Block starts to fall and from that instant "global collapse was inevitable"

So that is my description and, as far as I am aware, it aligns with NIST on the key points which matter.

Any more micro details may be of interest depending on the objective of the person expressing interest.
 
Major_Tom said:
Any model of the WTC 1 collapse initiation or progression sequence should be based on a carefully prepared list of observations. The following features were observed for WTC 1:

...
Any model of the collapse initiation sequence must match the visual record, just as any collapse progression model must match all observables. The OOS collapse propagation model was based on a handful of features from this list.

Does any known collapse initiation model match this visual record? (No).
Click to expand...

I disagree. Some, many or even most of the observations you present are irrelevant to the collapse initiation model. They probably are all effects of the same cause (plane crash and ensuing fires), but that does not mean that the model must explain them all. It is virtually impossible to create a model that predicts every single observable, and it is also unnecessary. A large fire is too complex, too chaotic, to be modelled in every minute detail. The model only needs to predict the relevant parts.

To make this clear with an example:
Suppose I grab a machine gun and fire around at random.
Now you make the following observations:
- A man dies
- A squirrel dies
- A few windows break
- A fuel tank leaks and burns a car to the ground

Now you want to find out what killed the man. In order to do that, it is irrelevant to also explain what killed the squirrel, broke the windows or burned the car. All you need to do is forensically examine the man, examine the crime scene, identify any bullets that may have hit the man, and match them to my gun.

If it turns out that the man has one or more gun shot wounds, died as a consequence of them, you find all the bullets that hit the man, trace them to my gun, and establish that there was a line of sight between my gun and the man, you have a complete and convincing model that explains his death, even if you do not also explain how the squirrel died or the car was blown up.
The man would have died even if you had not observed the squirrel, the car and the windows, and your forensic examination would have yielded the very same result. Your result would even stand if you could show that I could not possibly have shot the squirrel or the car.
 
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Let's make this simpler.

A condensed but thorough summary of how the NIST explain the initial sequence of buckling which led to collapse of WTC1 is in NCSTAR 1-6D, Ch 5, section 5.2, p312 to 318 (draft form from p305 to 312), in a section titled "WTC 1 Collapse Sequence" and 1-6draft 9.3.1, p 287-295 in a section titled "Probable collapse sequence of WTC1". Relevant sections are reproduced below.
...................

1-6D, p 312:

Table 5–1. Summary of main events that led to the collapse of WTC 1.
Event Number........ Event
1 .......................Aircraft impact
2 .......................Unloading of core
3 .......................Sagging of floors and floor/wall disconnections
4........................Bowing of the south wall
5 .......................Buckling of south wall and collapse initiation
Click to expand...


1-6D, pg 314:

Bowing of South Wall

The exterior columns on the south wall bowed inward as they were subjected to high temperatures, pull-in forces from the floors beginning at 80 min, and additional gravity loads redistributed from the core. Figure 5–6 shows the observed and the estimated inward bowing of the south wall at 97 min after impact (10:23 a.m.). Since no bowing was observed on the south wall at 69 min (9:55 a.m.), as shown in Table 5–2, it is estimated that the south wall began to bow inward at around 80 min when the floors on the south side began to substantially sag. The inward bowing of the south wall increased with time due to
continuing floor sagging and increased temperatures on the south wall as shown in Figs. 4–42 and 5–7. At 97 min (10:23 a.m.), the maximum bowing observed was about 55 in. (see Fig. 5–6).

Buckling of South Wall and Collapse Initiation

With continuously increased bowing, as more columns buckled, the entire width of the south wall buckled inward. Instability started at the center of the south wall and rapidly progressed horizontally toward the sides. As a result of the buckling of the south wall, the south wall significantly unloaded (Fig. 5–3),
redistributing its load to the softened core through the hat truss and to the south side of the east and west walls through the spandrels. The onset of this load redistribution can be found in the total column loads in the WTC 1 global model at 100 min in the bottom line of Table 5–3. At 100 min, the north, east, and
west walls at Floor 98 carried about 7 percent, 35 percent, and 30 percent more gravity loads than the state after impact, and the south wall and the core carried about 7 percent and 20 percent less loads, respectively. The section of the building above the impact zone tilted to the south (observed at about 8°,
Table 5–2) as column instability progressed rapidly from the south wall along the adjacent east and west walls (see Fig. 5–8), resulting in increased gravity load on the core columns. The release of potential energy due to downward movement of building mass above the buckled columns exceeded the strain
energy that could be absorbed by the structure. Global collapse ensued.
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1-6draft, p 288, Table 9-5 titled "Observations for WTC1", fifth entry:
and
1-6D, p 312, Table 5-2, last entry

Tower began to collapse – first exterior sign of collapse was at
Floor 98. Rotation of at least 8 degrees to the south occurred before
the building section began to fall vertically under gravity.
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1-6draft p 290, figure 9-8 on probable collapse initiation sequence for WTC1:

3. Collapse Initiation
• The inward bowing of the south wall induced column instability, which progressed rapidly horizontally across the entire south face.
• The south wall unloaded and tried to redistribute the loads via the hat truss to the thermally weakened core and via the spandrels to the adjacent east and west walls.
• The entire section of the building above the impact zone began tilting as a rigid block (all four faces; not only the bowed and buckled south face) to the south (at least about 8º) as column instability progressed rapidly from the south wall along the adjacent east and west walls.
• The change in potential energy due to downward movement of building mass above the buckled columns exceeded the strain energy that could be absorbed by the structure. Global collapse then ensued.
Click to expand...

1-6draft, p 294:

Buckling of South Wall and Collapse Initiation

The inward bowing of the south wall increased as the post-buckling strength of bowed columns continued to reduce. The bowed columns increased the loads on the unbuckled columns on the south wall by shear transfer through the spandrels. Consequently instability progressed horizontally, and when it engulfed the entire south wall, it progressed along the east and west walls. Moreover, the unloading of the south wall resulted in further redistribution of gravity loads on the south wall to the east and west walls and to the thermally weakened core via the hat truss. At 100 min, the north, the east, and the west walls at Floor 98 carried about 7 percent, 35 percent, and 30 percent more gravity loads than the state after impact, and the south wall and the core carried about 7 percent and 20 percent less loads, respectively. The section of the building above the impact zone began tilting to the south at least about 8° as column instability progressed rapidly from the south wall along the adjacent east and west walls, as shown in Fig. 9–13. The change in potential energy due to downward movement of building mass above the buckled columns exceeded the strain energy that could have been absorbed by the structure. Global collapse ensued.
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1-6draft, p 317:

Finding 26: The WTC 1 building section above the impact and fire area tilted to the south as the structural collapse initiated. The tilt was toward the side of the building that had the long span floors. Video records taken from east and west viewpoints showed that the upper building section tilted to the south. Video records taken from a north viewpoint showed no discernable east or west component in the tilt. A tilt to the south of at least 8 degrees occurred before dust clouds obscured the view and the building section began to fall downwards.
Click to expand...



This is the NIST description of WTC1 collapse initiation in a nutshell. If anyone has more relevant quotes on the initiation process, please post them.


Question: Does the NIST description of the collapse initiation sequence match the observables posted in the OP?

My answer: From the observables, we can see the NIST description of the initiation sequence is a fairy tale.

Numerous features point to core-led collapse initiation, not the one the NIST describes.
 
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A similar, much better "features list" is found in NCSTAR1-5A. If one wants to quibble over details, it might do to compare against that list, and focus on the differences.
 
NIST NCSTAR 1-5A: Visual Evidence, Damage Estimates, and Timeline Analysis. Covers the fire progression and observations up to the collapse initiation sequence. Useful for that time interval, but says basically nothing about the initiation failure sequence.


I found their description of the initiation sequence in NCSTAR 1-6D, Ch 5, section 5.2, p312 to 318 (draft form from p305 to 312), in a section titled "WTC 1 Collapse Sequence" and 1-6draft 9.3.1, p 287-295 in a section titled "Probable collapse sequence of WTC1".

I reproduced the most relevant quotes from it a few posts ago. I wish the NIST had more to offer on the initial failure sequence, but that about covers it. If anyone has other useful NIST quotes of the initial failure sequence, please post them.

R Mackey, is that the superior list you had in mind?
 
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Major_Tom said:
...
I found their description of the initiation sequence in NCSTAR 1-6D, Ch 5, section 5.2, p312 to 318 (draft form from p305 to 312), in a section titled "WTC 1 Collapse Sequence" and 1-6draft 9.3.1, p 287-295 in a section titled "Probable collapse sequence of WTC1".
...
R Mackey, is that the superior list you had in mind?
Click to expand...

I am sure R Mackey considers the final version superior to the draft.

Why do you base your stuff on the draft?
 
"Earliest Detectable and Drop Movements Traced and Plotted"



links to w3schools.
 
atecom said:
"Earliest Detectable and Drop Movements Traced and Plotted"



links to w3schools.
Click to expand...

That sucks. Can't fix it now.

Here is the correct link:

Earliest Detectable and Drop Movements Traced and Plotted
http://the911forum.freeforums.org/early-movement-of-wtc1-made-simple-t346.html#p9507

Draft version quotes are identical to the final version or I would not post them. FInal version is protected from copy/paste words and images. Identical sections for collapse initiation description, just shifted about about 13 pages. Easy to find.

I couldn't find much more information on the initiation sequence than the sections quoted. If anyone finds useful info elsewhere, please post it.
 
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femr2 said:
The final versions are protected, disabling copy & paste of text....as-in...because the (draft) PDF allows cut and paste.
Click to expand...

Oh I see. I don't have that issue on Mac OS X - you just open 'em in Preview and you can copy all you like.

If you're on a PC just use a free pdf unlocker. Hope that helps.
 
It is obvious that the NIST describes a perimeter-led collapse initiation sequence. The south wall fails first, somewhere around it's center, and column failure propagates around the perimeter through the east and west walls, and through the core.

Actual observations included in the list of features in the OP show a core-led collapse initiation. Some have suggested that this is only a minor detail, a "quibbling".

The models in the NIST reports study the building up to the moment the building is poised to collapse. Their work, based on long truss span sagging which pulls in the south wall, leading to perimeter failure, is so obviously dependent on a perimeter failure initiation mechanism that even the slowest of readers should understand that.

There is no amount of lipstick you can put on that pig to turn it into core-led collapse initiation model.

It seems a bit ridiculous to call visual evidence of a core-led collapse a minor detail.
 
The NIST's desctiption of WTC1 collapse initiation, and therefore their model of the events leading up to it, are contradicted by the visual record at it's most fundamental level. Collective core failure is a fundamentally different structural process than that of long truss sagging and perimeter pull-in to the point of failure.

No amount of lipstick can change one into the other.

Moreover, one must logically conclude that the inward bowing witnessed on the south side of the building was probably also caused by a fundamentally different process than the one the NIST modelled, like a possible partial core failure in the 1000 row core columns, the ones that support the other sides of the long trusses.

If collective core failure caused the building to collapse at 10:28 as the visual record seems to indicate, is it not reasonable to consider whether partial core collapse was responsible the south wall inward bowing witnessed in the minutes leading up to collapse? Not only reasonable but the logical choice.
 
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Major_Tom said:
Any model of the WTC 1 collapse initiation or progression sequence should be based on a carefully prepared list of observations. The following features were observed for WTC 1:
Click to expand...


You do understand that no sane person on earth cares less exactly what happened?
It does not really matter to a sane person. The exact collapse process is irrelevant as each impact and hence damage was unique, each fire was unique.
All that is important to sane people is that the impact and fire COULD have caused the collapse.
Click to expand...
 
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