False Narrative: "North Tower Antenna Dropped Before Roof Line"

[Joe Hill]

Richard Gage's AE911Truth organization asserts the North Tower antenna dropped straight down into the building at the beginning of collapse, and claims that is evidence the core columns had to be cut with cutter charges. The claim is made in the video, "9/11 Explosive Evidence - Experts Speak Out", at 53:20 here:
As recently as March, 2018, one of the key AE911Truth engineers repeated the claim as fact:

It is clear that the antenna dropping before the exterior roofline in the North Tower collapse shows it was a core column failure that pulled the exterior columns inward and initiated the collapse.

Having found no rebuttal of Szamboti's premise, it seems appropriate, for the record, to submit a thread on the topic. The assertion is patently false, easily discernible by studying collapse initiation from east or west. I used a video taken from the west, on the Hudson river:

It's clear the tower top section and antenna are tilting south as one unit to begin collapse. The motion indicates that the core initially served as the fulcrum for the rotating motion of the tower top, buckled, and was quickly ripped apart.
A closer look shows clearly the antenna did not drop into the building:

Gage and Szamboti use only a view from the north, the optics of which are illustrated here:

Editorial comment:
It is unfathomable that professional architect and engineer researchers would fail to study initiation of collapse from all angles. Initiation, or onset, is actually all that matters in determining why a structure collapsed. It is clear onset of the North Tower was due to failure of the south wall, not the core. The south wall gradually formed an inward sink, long before onset of collapse, seen below, and there is no sign of core failure until after the tower top started tilting south. For Gage and Szamboti to still claim the core failed first reveals utter sloppiness, or outright bias/deceit, neither worthy of the "Truth" moniker.

 

[econ41]

...As recently as March, 2018, one of the key AE911Truth engineers repeated the claim as fact:

Having found no rebuttal of Szamboti's premise, it seems appropriate, for the record, to submit a thread on the topic.

Agreed that there may not be any rebuttal on this forum of Szamboti's specific claim about antenna drop >> caused by core column cutting. Your comments about geometry and viewpoint are probably sufficient of themselves to cast doubt on Szamboti's claim. However I suggest that comprehensive rebuttal is best framed in the context of the "tower top section and antenna are tilting south as one unit to begin collapse". i.e. the full context of the role played by the "Top Block" in the initiation stage...not just the antenna itself.

I'll put some comments in line:

The assertion is patently false, << Agreed easily discernible by studying collapse initiation from east or west. << and also by comprehending the mechanism of Top Block movement ......
It's clear the tower top section and antenna are tilting south as one unit to begin collapse. << Yes The motion indicates that the core initially served as the fulcrum for the rotating motion of the tower top, buckled, and was quickly ripped apart. << I'll offer an alternate explanation for both those points. You accept as premise that the top section tilted as one unit. That suggests that core columns were also failing to allow the tilt. And the "ripping apart" of the "Top Block" occurred later - as the Top Block fell bodily - graphical evidence in a later post.
A closer look shows clearly the antenna did not drop into the building: << Yes - a conclusion supported by your video evidence and also flowing from analysis of the mechanism.

Gage and Szamboti use only a view from the north, the optics of which are illustrated here:

View attachment 37790
<< Fully agreed and probably strong enough as a stand alone argument.

It is unfathomable that professional architect and engineer researchers would fail to study initiation of collapse from all angles. Initiation, or onset, is actually all that matters in determining why a structure collapsed.

Agreed both points.

It is clear onset of the North Tower was due to failure of the south wall, not the core. The south wall gradually formed an inward sink, long before onset of collapse, seen below, and there is no sign of core failure until after the tower top started tilting south.

This is the aspect that IMO needs discussion. The observed fact that the Top Blocks... both of them ... tilted as integral single units conflicts with the asserted no failure of core. We need to be very clear what stage we are discussing. My contention being that the Top Block maintained most of its structural integrity as it tilted - therefore the tilting resulted from differential shortening of columns whether perimeter or core. The integrity of the Top Blocks was destroyed after they started to fall bodily - the Top Block and upper levels of lower tower in mutual destruction... The analogous mechanism for both towers notwithstanding the greater tilt for WTC2.

For Gage and Szamboti to still claim the core failed first reveals utter sloppiness, or outright bias/deceit, neither worthy of the "Truth" moniker.

The underlying issue is that none of the AE911 technical leaders understand the actual mechanism of the collapses. Especially at this stage and the transition into "progression". Both Szamboti and Chandler making similar errors.

 

[Mick West]

Richard Gage's AE911Truth organization asserts the North Tower antenna dropped straight down into the building at the beginning of collapse, and claims that is evidence the core columns had to be cut with cutter charges. The claim is made in the video, "9/11 Explosive Evidence - Experts Speak Out", at 53:20 here:

I don't think that's a great example. He just says:

00:53:11,309 --> 00:53:19,890 before the towers
00:53:16,349 --> 00:53:24,829 started collapsing from the top the
00:53:19,890 --> 00:53:27,839 antenna started to fall and the antenna
00:53:24,829 --> 00:53:30,990 of course was over the middle of the
00:53:27,839 --> 00:53:36,180 elevator shafts. I'm very familiar with the
00:53:30,990 --> 00:53:40,200 interior structure that surrounded the
00:53:36,180 --> 00:53:44,130 elevator shafts and the accessibility
00:53:40,200 --> 00:53:51,390 which the elevator companies had 24/7
00:53:44,130 --> 00:53:54,160 The only way that I can see that the
00:53:51,390 --> 00:53:57,519 towers could have collapsed
00:53:54,160 --> 00:54:00,279 is that the inferior columns were
00:53:57,519 --> 00:54:02,859 compromised

 

[Joe Hill]

That suggests that core columns were also failing to allow the tilt.

Indeed. Core columns would have to buckle, bend, kink, sink, in order for the upper block to tilt. They could still function as fulcrum for observable motion of the upper block while sustaining such failures. Whether it was the core or south wall that initiated vertical failure of the building however, is off topic, and I probably shouldn't have commented on it.

And the "ripping apart" of the "Top Block" occurred later

The "ripping apart" I referred to was the core structure, not the top block. Based simply on motion of the top block, over, then over and down, then down, in rapid succession, the core structure quickly ripped apart.

We need to be very clear what stage we are discussing.

Agreed, and imo, there is nothing more important than initiation, in as tight a frame as is observable.

I don't think that's a great example. He just says:

00:53:11,309 --> 00:53:19,890 before the towers
00:53:16,349 --> 00:53:24,829 started collapsing from the top the
00:53:19,890 --> 00:53:27,839 antenna started to fall and the antenna
00:53:24,829 --> 00:53:30,990 of course was over the middle of the
00:53:27,839 --> 00:53:36,180 elevator shafts. I'm very familiar with the
00:53:30,990 --> 00:53:40,200 interior structure that surrounded the
00:53:36,180 --> 00:53:44,130 elevator shafts and the accessibility
00:53:40,200 --> 00:53:51,390 which the elevator companies had 24/7
00:53:44,130 --> 00:53:54,160 The only way that I can see that the
00:53:51,390 --> 00:53:57,519 towers could have collapsed
00:53:54,160 --> 00:54:00,279 is that the inferior columns were
00:53:57,519 --> 00:54:02,859 compromised

Relative to, "and claims that is evidence the core columns had to be cut with cutter charges" (OP), I agree. I considered that axiomatic.
The video reference was to show that AE uses a view which makes it appear the antenna is sinking as an initial movement, not necessarily the accompanying dialogue.
Relative to the thread topic however,
"00:53:11,309 --> 00:53:19,890 before the towers
00:53:16,349 --> 00:53:24,829 started collapsing from the top the
00:53:19,890 --> 00:53:27,839 antenna started to fall", confirms AE claims the antenna moved, "fell", before any other part of the building.

 

[Abdullah]

Are you sure the narrative that the antenna fell first is necessarily false? FEMA said

Review of videotape recordings of the collapse taken from various angles indicates that the transmission tower on top of the structure began to move downward and laterally slightly before movement was evident at the exterior wall.

 

[Mendel]

Are you sure the narrative that the antenna fell first is necessarily false? FEMA said

... in "World Trade Center Building Performance Study: Data Collection, Preliminary Observations, and Recommendations" (FEMA 403), January 2002, page 2-27
Chapter 2: https://www.fema.gov/pdf/library/fema403_ch2.pdf
Full report: https://www.fema.gov/sites/default/files/2020-07/fema_403_2002.zip

Review of videotape recordings of the collapse taken from various angles indicates that the transmission tower on top of the structure began to move downward and laterally slightly before movement was evident at the exterior wall. This suggests that collapse began with one or more failures in the central core area of the building. This is consistent with the observations of debris patterns from the 91st floor, previously discussed. This is also supported by preliminary evaluation of the load carrying capacity of these columns, discussed in more detail in Section 2.2.2.2. The core columns were not designed to resist wind loads and, therefore, had less reserve capacity than perimeter columns. As some exterior and core columns were damaged by the aircraft impact, the outrigger trusses at the top of the building shifted additional loads to the remaining core columns, further eroding the available factor of safety. This would have been particularly significant in the upper portion of the damaged building. In this region, the original design load for the core columns was less than at lower floors, and the column sections were relatively light. The increased stresses caused by the aircraft impact could easily have brought several of these columns close to their ultimate capacity, so that relatively little additional effects due to fire would have been required to initiate the collapse. Once movement began, the entire portion of the building above the area of impact fell in a unit, pushing a cushion of air below it. As this cushion of air pushed through the impact area, the fires were fed by new oxygen and pushed outward, creating the illusion of a secondary explosion.

 

[Abdullah]

@Mendel ??? The two bolded sections are not related. The first is describing antenna movement whereas the second is explaining the fanning of flames

 

[Mendel]

@Mendel ??? The two bolded sections are not related. The first is describing antenna movement whereas the second is explaining the fanning of flames

The two bolded parts together strongly suggest that the same event that caused the antenna to move also caused the top section of the building to come down. The explanation for that is between the bold parts.

Given that some 9/11 truthers have argued how difficult it supposedly was to hit the WTC, hitting them at the exact height where the charges were (different for each tower!) should've been impossible.

 

[Abdullah]

@Mendel your point being what

 

[AmberRobot]

The two bolded parts together strongly suggest that the same event that caused the antenna to move also caused the top section of the building to come down. The explanation for that is between the bold parts.

Given that some 9/11 truthers have argued how difficult it supposedly was to hit the WTC, hitting them at the exact height where the charges were (different for each tower!) should've been impossible.

Clearly there had to have been charges on every floor.

 

[econ41]

Clearly there had to have been charges on every floor.

If we assume for moot purposes that there was CD then there are potentially two scenarios for "necessary charges".

First in the impact and fire zone to trigger the initiation sage which ended with Top Block moving down. The location of those charges would depend on the chosen plan of attack. If the goal was to "mimic" the actual collapse mechanism the two (semi) plausible options would be cutting office space floor joists - to start perimeter column inward bowing. OR direct cutting of core columns -- to trigger apparent early fall of the hat-truss and antenna. There are many more options that would cause "initiation" but not mimic the actual collapse.

Second, the oft-repeated truther fantasy need for "squibs" at every floor to cut the joist to column connections.

Actually, no charges were needed because the initial damage plus accumulating fire damage was sufficient for both of those locations.

 

[Abdullah]

@econ41 there is no need to touch the exterior at all. The outriggers are not that strong. A building thus caving in from the middle could easily be explained as insulation damage + high temperature.

But is this on topic?

 

[Abdullah]

It is clear onset of the North Tower was due to failure of the south wall, not the core. The south wall gradually formed an inward sink, long before onset of collapse, seen below, and there is no sign of core failure until after the tower top started tilting south.

I disagree. Collapse of the 1000 series core columns could cause inward bowing of the south wall

If these columns failed, entered tension, and detached from the hat truss, it would cause floor sagging in their vicinity from the impact zone up to the hat truss. Like this?:

Top is the NIST measurements based in the image you mentioned. Bottom is NIST's attempt to replicate them using pull in forces only in floors 95 through 99.

You can see that the simulation cannot recreate the measured bowing on floors 94, 100, and 101 on the west side. (The east and center of the higher floors are hidden)

Now recall that the hat truss reinforces the roof, which may cause it to appear as the top of a rigid tilting block. In reality, the core may have been pulling down on the hat truss, and inward on the south wall.

This could maybe be yet another case of "right for the wrong reason".

 

[Henkka]

I'm probably going to go with FEMA's analysis over OP's on this one... Does anyone know if NIST ever remarked on this? I don't think they did but could be wrong.

 

[econ41]

I disagree. Collapse of the 1000 series core columns could cause inward bowing of the south wall

Why don't you take the path I have suggested many times? Understand the actual collapse mechanism. Once you are clear as to the broad outline you have a basis for testing your speculations.

It should be known, accepted and agreed fact that the key process of the initiation stage was the cascading failure of columns losing axial load-carrying capacity in sequence.

So how does your suggested core column failure fit in the reality of a cascading sequence? Where does perimeter inward bowing fit in the same sequence?
That should be an agreed starting point for speculation.

If these columns failed, entered tension, and detached from the hat truss, it would cause floor sagging in their vicinity from the impact zone up to the hat truss. Like this?:

"IF"?

Top is the NIST measurements based in the image you mentioned. Bottom is NIST's attempt to replicate them using pull in forces only in floors 95 through 99.

You can see that the simulation cannot recreate the measured bowing on floors 94, 100, and 101 on the west side. (The east and center of the higher floors are hidden)

The interest should be in "What actually happened"? NOT "Did NIST explain it?" We KNOW that perimeter column IB occurred and therefore MUST have been part of the cascade failure. Whether or not NIST explained it is irrelevant. A side track. Wrong goalpost

Now recall that the hat truss reinforces the roof, which may cause it to appear as the top of a rigid tilting block. In reality, the core may have been pulling down on the hat truss, and inward on the south wall.

May?? May?? (TWICE?) BTW try fitting your speculation into a context. HOW could the core be "pulling down"? How much of the core is pulling? Which part of the core is pulling what? How does that fit in the known context of a sequenced cascade failure?

The Topic Title is: 'False Narrative: "North Tower Antenna Dropped Before Roof Line"' and the referenced AE911 claim is that antenna drop was caused by explosive cutting of the core.
Do you disagree with the OP that it is a "False Narrative"?
Are you claiming there was explosive cutting of core columns?
OR
... are you speculating that the core did somehow drop but without explosive cutting?
If so, how?

 

[Abdullah]

So how does your suggested core column failure fit in the reality of a cascading sequence?

As a catalyst for an initiating event, or a possible initiating event.

Where does perimeter inward bowing fit in the same sequence?

As a possible initiating event, caused by the core failure mentioned.

 

[Abdullah]

We KNOW that perimeter column IB occurred and therefore MUST have been part of the cascade failure. Whether or not NIST explained it is irrelevant.

No, the NIST simulations are very important, as they can be used as evidence for a core-led collapse.

HOW could the core be "pulling down"?

If the core failed irst, it would be trying to shed loads through the hat truss.

How much of the core is pulling? Which part of the core is pulling what?

Such detail is probably beyond the scope of this s topic. All that matters is "the core pulled"

Do you disagree with the OP that it is a "False Narrative"?

Yes. Again, "right for the wrong reason".

Abstract: Points along the top of WTC 1 are traced and plotted during the earliest moments of collapse to determine the initial order of column failure. Positional and tilt data is extracted from 5 video clips
...
>> The traced points show the earliest movement was that of the roof deforming into a concave shape, meaning the collective core must have sagged and failed before any traced point along the perimeter.

https://www.tapatalk.com/groups/the911forum/early-movement-of-wtc1-made-simple-t346.html

 

[Abdullah]

Looks like my answers were dissatisfying. So let's try sgain

So how does your suggested core column failure fit in the reality of a cascading sequence? Where does perimeter inward bowing fit in the same sequence?

If we define "cascade" as occuring at the moment of collapse initiation, then neither the failure of the 1000 line nor the inward bowing of the south perimeter played a role. They merely set the conditions which allowed to tower to fall the way it did, falling core-first and tilting south.

So why am I bringing them up? I am trying to contradict this

The south wall gradually formed an inward sink, long before onset of collapse, seen below, and there is no sign of core failure until after the tower top started tilting south.

It is clear that the OP sees the failure cascade as being south wall→core. He thinks that this is proven by the inward bowing of the wall.

I am saying, no, actually the inward bowing is a sign of impending core collapse, and the collapse sequence was core→south wall.

 

[Abdullah]

HOW could the core be "pulling down"? How much of the core is pulling? Which part of the core is pulling what? How does that fit in the known context of a sequenced cascade failure?

What I'm saying is the collapse initiated with the loss of azial capacity in the core. "Pulling down" is a metaphor for the resulting rapid redistribution r of loads away through to the hat truss.

How much of the core was pulling on the hat truss? All. The initial failure in the south side, inboard of the missing 1000 line, started a rapid northward cascade of core column failures.

As the core displaced downward under the rapidly accumulating loss of axial stiffness, it pulled down the hat truss, redistributing loads to the exterior. Meanwhile, the south wall and the southern parts of the east and west walls had been weakened by pull in forces caused by the failure of line 1000. They thus failed, starting another northward csscade of column failures.

 

[Abdullah]

Are you claiming there was explosive cutting of core columns?
OR
... are you speculating that the core did somehow drop but without explosive cutting?
If so, how?

Neither.

Although the core would be an easier target for demolition because of its lower safety factor, smaller number of columns, and easier access.

If it was fire, then I would speculate that at first the the floors heated up and failed, because they are lighter.

In this photo you can see that the 97th floor appears to have collapsed from columns 344 to 347 and perhaps up to 350

The temperatures were higher in the south side due to prevailing winds and Boeing dozing of combustibles. So eventually the south core columns buckled plsstically. This buckling was made much more severe by the loss of bracing from destroyed floors, which increased the lateral displacement of the columns. And so the 1000 column line lost all compression capacity, entered tension, overloaded the splices at fl 106, detached, and sagged down, pulling in the south wall in the manner observed, and increasing loads on the 900 line. The rising temperatures eventually got the 900 line, starting the collapse.

You asked for my hypothesis, I gave it.

 

[Mendel]

May?? May?? (TWICE?) BTW try fitting your speculation into a context. HOW could the core be "pulling down"? How much of the core is pulling? Which part of the core is pulling what? How does that fit in the known context of a sequenced cascade failure?

The Topic Title is: 'False Narrative: "North Tower Antenna Dropped Before Roof Line"' and the referenced AE911 claim is that antenna drop was caused by explosive cutting of the core.

1) if the hat truss was putting pressure on the facade, then it must've been intact.

3) if the antenna dropped before the roof line, then the hat truss must've been broken (because it supported both the antenna and roof line when it was intact).

2) What broke the hat truss between 1) and 3), @Abdullah?

 

[Henkka]

I'm a bit confused as to what the consensus here is now. Do econ41 and Mendel agree the antenna dropped slightly before the roofline, as claimed by FEMA? Or do you guys think it's just an illusion created by the top tilting, as claimed by the OP?

The cause of the antenna dropping first (If it did so) is an entirely different question.

 

[Abdullah]

What broke the hat truss between

We are talking about displacements in the order of inches. Small enough to not necessarily be destructive, but big enough to be measurable. I have written about this in more detail in a commentary on the Sauret video:¹

13 seconds before collapse, the NW corner begins to shudder up and down with a magnitude of 1-2inches. Then, it jerks downward 10 inches before bouncing back up. Shortly afterwards, the antenna lifts about 2 inches. Then, as it drops back, both it and the corner are yanked east 3.6 inches. Over the next 8 seconds, the eastward displacements reach 7.2 inches, and the antenna sinks 3.6 inches below original position. Then in the 1 second between antenna giving and northwest corner giving, the antenna drops 1 foot, and the eastward displacements reach 2 feet.

To which we may add:²

Notes:

1) The east corner of the building stays pretty still. The whole portion below floor 98 stays pretty still.
2) The NW corner window washer actually wiggles east-west. Almost no downward displacement, but observable eastward displacement.
3) Notice that the whole west corner above floor 98 is being pulled inwards. The pull-in first becomes noticeable just above floor 98 and grows much stronger in the top few floors

References
1.
https://www.metabunk.org/threads/do...rrors-in-the-nist-account-of-9-11.6396/page-2

2.
https://web.archive.org/web/2020081...op=view_page&PAGE_id=176&MMN_position=586:586

 

[Abdullah]

The cause of the antenna dropping first (If it did so) is an entirely different question.

This is something U wanted to say. Thus mess started with OP tying antenna non-drop to core non-failure, and was propagated by @econ41 who asked questions like

How much of the core is pulling? Which part of the core is pulling what? How does that fit in the known context of a sequenced cascade failure?

Are you claiming there was explosive cutting of core columns?
OR
... are you speculating that the core did somehow drop but without explosive cutting?
If so, how?

Which I answered at risk to the topic and myself.

 

[econ41]

I'm a bit confused as to what the consensus here is now. Do econ41 and Mendel agree the antenna dropped slightly before the roofline, as claimed by FEMA? Or do you guys think it's just an illusion created by the top tilting, as claimed by the OP?

@Abdullah is speculating as to the causes of antenna drop - without framing his speculation in what should be the known starting point reality of cascading column failures. Neither Mendel nor I are making the claims. I have simply been asking @Abdullah to base his argument on known facts.

In effect @Abdullah is treating antenna drop as a stand-alone anomalous factor - not connected to the overall known context of the collapse mechanism. Hence my (repeated) suggestion:

Why don't you take the path I have suggested many times? Understand the actual collapse mechanism. Once you are clear as to the broad outline you have a basis for testing your speculations.

It should be known, accepted and agreed fact that the key process of the initiation stage was the cascading failure of columns losing axial load-carrying capacity in sequence.

So how does your suggested core column failure fit in the reality of a cascading sequence? Where does perimeter inward bowing fit in the same sequence?
That should be an agreed starting point for speculation.

Both core column failure AND perimeter column inward bowing are plausible triggers for the cascading failure sequence. Both MUST have occurred. Part of the explanation should address which came first as a subset of how did all the column failures occur in the cascade sequence.

@Abdullah's speculation about core failure is overlooking the reality of context. His speculations therefore MUST be assessed in that known context of cascading failure of columns.

The cause of the antenna dropping first (If it did so) is an entirely different question.

It is not "a different question" - it is an effect - a consequence. The relationship presumed by @Abdullah ulla is one of "cause <> effect" with core column failure the presumed cause of the antenna drop effect.

I think that antenna "drop" is an optical illusion rather than a true result of core column failure. BUT we are NOT discussing my opinion. @Abdullah has suggested what he thinks could have happened. I'm asking him to support HIS concept so discussing my opinions is irrelevant. And @Abdulla's speculations could be progressed with more assurance IF he stays within the context of known facts. I SUSPECT that, if he tries to explain the claim incontext, he wil find that i cannot be supported. BUT - once again - we are discussing @Abdullah's speculations NOT my half formed opinions. AND, until he puts his claim in context, there is no basis for a more detailed critique.

 

[Abdullah]

Both core column failure AND perimeter column inward bowing are plausible triggers for the cascading failure sequence. Both MUST have occurred.

What I am saying is that inward bowing, just like antenna drop, is an effect of core failure, cascading or otherwise. Therefore, inward bowing cannot be a meaningful trigger of cascading failure.

 

[econ41]

What I'm saying is the collapse initiated with the loss of azial capacity in the core.

I know that. You have said it several times. The question I asked is "How?" And, specifically, how did that loss of capacity relate to the known feature of the cascading failure sequence?

"Pulling down" is a metaphor for the resulting rapid redistribution r of loads away through to the hat truss.

Why is it a "metaphor?" What actual mechanism are you trying to describe?

How much of the core was pulling on the hat truss?

So two new issues: (1) You take a couple of quantum leaps in speculation. HOW does "pull down" at the lower level of the Top Block" act ONLY on the hat trust; AND (2)

All.

How does "ALL" of the core cause that pull down?

The initial failure in the south side, inboard of the missing 1000 line, started a rapid northward cascade of core column failures.

Still gross speculation. How does that ("initial failure in the south side") trigger
cause that conclusion ("initial failure in the south side")?

Then you repeat the global claim speculation whilst still not explaining how you think it happened:

As the core displaced downward under the rapidly accumulating loss of axial stiffness, it pulled down the hat truss, redistributing loads to the exterior.

... and this:

Meanwhile, the south wall and the southern parts of the east and west walls had been weakened by pull in forces caused by the failure of line 1000. They thus failed, starting another northward csscade of column failures.

... merely repeats the same gross, overall, speculation without explaining how it happens.

 

[Landru]

@Abdullah please provide evidence and support for your assertions.

 

[econ41]

@Abdullah I think we "crossed in posting" you posted whilst I was editing my post and I did not see your post at that time. BUT your latest comment is sufficiently focussed for me to be able to comment:

What I am saying is that inward bowing, just like antenna drop, is an effect of core failure, cascading or otherwise. Therefore, inward bowing cannot be a meaningful trigger of cascading failure.

Sorry but there is a fundamental error in your logic. It is a form of "false dichotomy". There are I think 3 "layers" of error but let me take the primary one - the "false dichotomy":

Your assertions identify TWO plausible trigger mechanisms.
The FIRST is your preferred speculation: "...inward bowing, just like antenna drop, is an effect of core failure,.." That is nearly correct. It should be "...may be an effect of core failure.." >> it is not unconditionally true. It may be true. It may be false. And you haven't proved it either way.
THEN
SECOND, you conclude "...Therefore, inward bowing cannot be a meaningful trigger..." which is the issue of false logic. Inward bowing is also a plausible trigger. So the claim should be "...inward bowing may be a meaningful trigger of cascading failure." >> And the two options are a true dichotomy - either one or the other may be the trigger but not both.

Then the next level of subtlety - the next "layer" of logic. IF you explain (prove, posit an hypothesis for) your first preference of core driven triggering it STILL does NOT establish which of the two options was in fact the actual trigger. i.e. "core" or "perimeter" triggering. If you prove that it could be true you have not proved that it is true. So the first main step is taken but there is still one more step needed to determine which was the actual trigger.

 

[Abdullah]

I think that antenna "drop" is an optical illusion rather than a true result of core column failure.

Why?

easurement of the large antenna, SW corner fire and NW corner washer drops from the NW NBC viewpoint shows once again that the antenna was moving downward before the SW and NW corners of the building.

(notes: Black - Antenna
Red - Washer
Purple - SW Fire

59.94 fps - Resolution Doubled. 1 pixel on the graph is 0.5 pixels on the original video.



Measurements from both viewpoints show early antenna movement when compared to any point on the perimeter of the building. All drop measurements and all visual evidence shows the antenna sinking into the perimeter

https://web.archive.org/web/2020081...op=view_page&PAGE_id=176&MMN_position=586:586

 

[Henkka]

I think that antenna "drop" is an optical illusion rather than a true result of core column failure.

Ok, I tried capturing it in a gif from the Sauret footage. I set it to loop back and forth to make it more clear:

You can see how the antenna is bobbing up and down independent of the roofline there. However, it's a very slight motion. I don't think it's even perceptible in the video OP was using. But I do believe this is the motion FEMA also noticed. They probably also used tracking software to verify it.

 

[Gamolon]

Ok, I tried capturing it in a gif from the Sauret footage. I set it to loop back and forth to make it more clear:

You can see how the antenna is bobbing up and down independent of the roofline there. However, it's a very slight motion. I don't think it's even perceptible in the video OP was using. But I do believe this is the motion FEMA also noticed. They probably also used tracking software to verify it.

But the roofline does move down slightly as the antenna does. Can't this be due to the tilt?

 

[Henkka]

But the roofline does move down slightly as the antenna does. Can't this be due to the tilt?

Yeah I suppose it could be. But FEMA claims they saw this from "various angles" (See post #6 in this thread), and they don't seem to think it was from tilting. I'm not sure what other angles they were looking at, though.

 

[benthamitemetric]

Ok, I tried capturing it in a gif from the Sauret footage. I set it to loop back and forth to make it more clear:

You can see how the antenna is bobbing up and down independent of the roofline there. However, it's a very slight motion. I don't think it's even perceptible in the video OP was using. But I do believe this is the motion FEMA also noticed. They probably also used tracking software to verify it.

Could you please provide the exact quotes from FEMA that support your summary of their methodology and position?

 

[Mendel]

You can see how the antenna is bobbing up and down independent of the roofline there.

looks like it's tilting to me

 

[Henkka]

Could you please provide the exact quotes from FEMA that support your summary of their methodology and position?

I don't claim to know more about it beyond what Mendel already quoted in post #6 in this thread.

Looking at the gif though, I do agree it could be the top ever so slightly tilting away from the camera rather than the antenna dropping. I don't have an argument against it other than FEMA saying they think it's dropping, and they apparently checked it from "various angles".

 

[Landru]

Recommendations" (FEMA 403), January 2002, page 2-27
Chapter 2: https://www.fema.gov/pdf/library/fema403_ch2.pdf
Full report: https://www.fema.gov/sites/default/files/2020-07/fema_403_2002.zip

Review of videotape recordings of the collapse taken from various angles indicates that the transmission tower on top of the structure began to move downward and laterally slightly before movement was evident at the exterior wall. This suggests that collapse began with one or more failures in the central core area of the building. This is consistent with the observations of debris patterns from the 91st floor, previously discussed. This is also supported by preliminary evaluation of the load carrying capacity of these columns, discussed in more detail in Section 2.2.2.2. The core columns were not designed to resist wind loads and, therefore, had less reserve capacity than perimeter columns. As some exterior and core columns were damaged by the aircraft impact, the outrigger trusses at the top of the building shifted additional loads to the remaining core columns, further eroding the available factor of safety. This would have been particularly significant in the upper portion of the damaged building. In this region, the original design load for the core columns was less than at lower floors, and the column sections were relatively light. The increased stresses caused by the aircraft impact could easily have brought several of these columns close to their ultimate capacity, so that relatively little additional effects due to fire would have been required to initiate the collapse. Once movement began, the entire portion of the building above the area of impact fell in a unit, pushing a cushion of air below it. As this cushion of air pushed through the impact area, the fires were fed by new oxygen and pushed outward, creating the illusion of a secondary explosion. Content from External Source

@Henkka the original quote is here.

 

[Abdullah]

The antenna falls vertically. The NW corner and SW fire do not fall.

 

[Abdullah]

For clarity, here are the antenna and fire magnified 10 times

And here magnified 100 times

(Intensity increased in the fire shot)

If this doesn't prove that the antenna fell first, I don't know what will.

 

[Henkka]

The antenna falls vertically. The NW and SW corner fire do not fall.View attachment 57362

Yeah here it's pretty clear that the slight movement is independent of the "top block", which has not started tilting or descending yet. This seems to contradict NIST, who say:

The subsequent unusually large number of jet-fuel ignited multi-floor fires (which reached temperatures as high as 1,000 degrees Celsius, or 1,800 degrees Fahrenheit) significantly weakened the floors and columns with dislodged fireproofing to the point where floors sagged and pulled inward on the perimeter columns. This led to the inward bowing of the perimeter columns and failure of the south face of WTC 1 and the east face of WTC 2, initiating the collapse of each of the towers.

https://www.nist.gov/world-trade-center-investigation/study-faqs/wtc-towers-investigation Question 11

They say the collapse initiated with the perimeter columns. But in the video, we can see the first visible movement is that of the antenna, which was sitting directly on top of the core columns. So something seems to have happened to the core columns about a second, or fraction of a second, before the perimeter columns gave way.