9/11: Is this photo consistent with a progressive collapse?

[lee h oswald]

The floor trusses, and the central support columns (which were box girder assemblages)

And this in relation to my question: what steel girders initiated the collapse?

Ok. I can see why you'd say the floor trusses were susceptible to fire, especially if the fireproofing had been knocked off in the collision and explosion. When you say, 'central support columns' are you talking about the core columns?

 

[lee h oswald]

Ok. There was about an acre of concrete slab per floor, I'm sure you know that. What you need to consider is all the possible flex of the building in terms of lateral loads, torsion, all that. Concrete will help stiffen the join between the two tubes of the inner core and the outer perimeter, and in turn the whole structure, but it wouldn't last five minutes without some reinforcing mesh in it. Quite simply, you couldn't pour a concrete slab of 10 square metres at 4 inches and expect it to have any kind of longevity - put some A393 mesh in it though, and it's nails. Concrete without steel reinforcement in poured slabs at that thickness is prone to crack and fail pretty quickly.

It might be pertinent to add to that that the slab would be poured in sections, not one acre (4,000sq metres) in one hit. Shuttering would be made to contain the pour and then, when the shuttering is removed, an expansion joint (a gap filled with a flexible material to allow flex, prevent cracking etc.) fitted between the panels of slabs.

 

[lee h oswald]

I would not be surprised if there there was steel-reinforced concrete in the WTC. But the elements that failed that initiated the collapse were steel girders coated in concrete or some other form of fireproofing, which is not the same thing at all. What were the RC elements? How are they relevant?[/FONT][/COLOR]

I've just thought of a visual reference for steel r/c - remember that disputed photo of 'chunks' from the 911 thread? Fireman with a spade...have a look at that pic - there's quite a bit (if I remember right) of reinforcing mesh sticking out of the disputed 'chunks'.

You're right that steel r/c isn't the same as steel fireproofed using a spray-on cementitious material.

The r/c elements were the floors and the core. They are relevant because they have been misrepresented

 

[Mick West]

This from the NIST recreation, showing there was a welded wire fabric reinforcement.
http://fire.nist.gov/bfrlpubs/build05/PDF/b05042.pdf (Page 30, pdf page 66)

10 in by 4 in W4.2/W4.2 welded steel mesh

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Now it's been correctly represented, how is it relevant? If the trusses sag, then the floor will sag.

 

[Mick West]

And this in relation to my question: what steel girders initiated the collapse?

Ok. I can see why you'd say the floor trusses were susceptible to fire, especially if the fireproofing had been knocked off in the collision and explosion. When you say, 'central support columns' are you talking about the core columns?

Yes.

The truss and perimeter column fire protection was spray on "BLAZE-SHIELD DC/F,", a mixture of cement and "glassy mineral fibers". (ref NCSTAR 1, Page 70-72).

The (steel) core column fire protection was: (page 73)

• Those core columns located in rentable and public spaces, closets, and mechanical shaftswere enclosed in boxes of gypsum wallboard (and thus were inaccessible for inspection).
The amount of the gypsum enclosure in contact with the column varied depending on the
location of the column within the core. SFRM (BLAZE-SHIELD D and DC/F) was applied
on those faces that were not protected by the gypsum enclosure. The thicknesses specified in
the construction documents were 1 3/16 in. for the heavier columns and 2 3/16 in. for the
lighter columns.
• Columns located at the elevator shafts were protected using the same SFRM thicknesses.
They were not enclosed and thus were accessible for routine inspections.

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[Mick West]

I was just reading the NIST report trying to figure out which bits of it you thought were obtained by torture, and I suddenly realized that when you said:

There I go? Where exactly? Maybe you need to read it again, try to take it in this time. It's amusing (only mildy) that you are permitted to say this in instigation: What do you think would happen to a 1,300 foot high building being hit by 300,000 pounds of plane containing 10,000 gallons of jet fuel, travelling at 586 mph? I think what did happen does not seem unreasonable...and I, in response, say: Didn't you mean a quarter mile high steel and concrete structure weighing 300 thousand tonnes hit by a 13.5 tonne aluminium bomb containing 45 cubic metres of jet fuel? It seems very unreasonable to me - if YOU introduce the idea of what YOU think is reasonable, am I not permitted the same luxury? Clearly not. It's also interesting how you avoid such questions as: What kind of 'progressive' collapse ejects matter and pulverizes everything, reducing 110 floors of 4inch thick steel reinforced concrete, miles of carpet, office furniture, computers, wiring, plasterboard, people, to dust and sheared steel columns? Or: You: it's amazing that the terrorist's plan worked so well...Me: I'd be tempted to say 'incredible' rather than 'amazing'. It's even more incredible that at least six of them survived their 'suicide' mission, as subsequently reported by much of even the 'mainstream' media. Some feat that. However, the official narrative remains doggedly in place. A mere detail? And this: But what about the official report? Have you read it and do you think it adequately reflects the truth of what happened?

I had assumed you meant the NIST report, as you were talking about all those technical details of the impact and collapse, but actually you were talking about the 911 commission report, which deals mostly with the events before the impacts.

So to be very clear, when I said:

Yes I've read it. I think it's a very reasonable account of what happened that day.

I was referring to the NIST report. NCSTAR1. I have not read the 9/11 commission report. I do not know how well it reflects the truth of what happened - particularly regarding the planning of the attacks . I am suspicious of evidence obtained by torture.

I apologize for this misunderstanding.

 

[lee h oswald]

This from the NIST recreation, showing there was a welded wire fabric reinforcement.
http://fire.nist.gov/bfrlpubs/build05/PDF/b05042.pdf (Page 30, pdf page 66)

10 in by 4 in W4.2/W4.2 welded steel mesh

Content from External Source

Now it's been correctly represented, how is it relevant? If the trusses sag, then the floor will sag.

I'm not so sure it's been correctly represented, but it does show two layers of steel reinforcement per slab being used, which is a start. Now you know for sure that the slabs in the towers were RC. The panels appear to be about ten foot by ten foot square.

Are you familiar with the methods of increasing the density of concrete poured in situ, and if so do you know if they were used either in the towers or in the recreation?

Can you find the differential in concrete without steel reinforcement as compared to concrete with?

 

[Mick West]

See the NIST fire test doc (unlocked version here)

4.2.6 ConcreteThe concrete design strength for a typical office floor of the WTC was specified to be 3,000 psi, and the
lightweight density was specified as 100 pcf. The concrete for the floor slab consisted of 3/4 in.
lightweight haydite aggregate, sand, Type I Portland cement and water. No records of actual mixture
proportions or cylinder strengths were found in NIST’s review of available documents. The mix design
shown in Table 4–2 was determined by the concrete supplier to produce a 3,000 psi 28-day strength using
lightweight aggregate.

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I get that you are trying establish that the floors were strong. But does this, in your opinion, make a floor collapse from fire totally unfeasible? The concrete load was mostly supported by the trusses after all, and that is what the fire supposedly affected.

 

[lee h oswald]

See the NIST fire test doc (unlocked version here)

4.2.6 ConcreteThe concrete design strength for a typical office floor of the WTC was specified to be 3,000 psi, and the
lightweight density was specified as 100 pcf. The concrete for the floor slab consisted of 3/4 in.
lightweight haydite aggregate, sand, Type I Portland cement and water. No records of actual mixture
proportions or cylinder strengths were found in NIST’s review of available documents. The mix design
shown in Table 4–2 was determined by the concrete supplier to produce a 3,000 psi 28-day strength using
lightweight aggregate.

Content from External Source

I get that you are trying establish that the floors were strong. But does this, in your opinion, make a floor collapse from fire totally unfeasible? The concrete load was mostly supported by the trusses after all, and that is what the fire supposedly affected.

Well, doesn't knowing that the floors were RC and not just a slab poured on top of corrugated steel make a difference to your calculation of all factors?

You can't make a floor collapse from fire totally unfeasible, but it depends on the fire and what the fire is on or in.
Pouring concrete into corrugated moulds makes it very strong again - add to that the reinforcing and you'll have a job breaking up those 10ftx10ft slabs full of steel mesh. The walls of Anderson air raid shelters were built from concrete poured into corrugated iron shuttering; they withstood anything but a direct hit. I have first hand experience of removing Anderson shelters - and it's no fun unless you have a crane and a wrecking ball.

Where exactly did the trusses fail according to Nist?

 

[lee h oswald]

See the NIST fire test doc (unlocked version here)

4.2.6 ConcreteThe concrete design strength for a typical office floor of the WTC was specified to be 3,000 psi, and the
lightweight density was specified as 100 pcf. The concrete for the floor slab consisted of 3/4 in.
lightweight haydite aggregate, sand, Type I Portland cement and water. No records of actual mixture
proportions or cylinder strengths were found in NIST’s review of available documents. The mix design
shown in Table 4–2 was determined by the concrete supplier to produce a 3,000 psi 28-day strength using
lightweight aggregate.

Content from External Source

I get that you are trying establish that the floors were strong. But does this, in your opinion, make a floor collapse from fire totally unfeasible? The concrete load was mostly supported by the trusses after all, and that is what the fire supposedly affected.

Reading the doc it says thay they couldn't find mix ratios prescribed by the engineers in the available information. I think that's highly dubious. It's so basic....anyway, the ratio of the mix seems quite strong to me - approx 4.3:1 when 6:1 might be the average today. The 'C' part of the Haydite (aggregate) content likely refers to its size range. Be good to know what that is.

 

[Mick West]

Where exactly did the trusses fail according to Nist?

They fail in that they sagged, not failed as in snapped. Some of them probably failed at the ends before collapse was initiated, but it was how they pulled on the columns that eventually led to collapse.

Unlocked NIST NCSTAR-1: https://www.metabunk.org/files/NIST-NCSTAR1-909017_unlocked.pdf

WTC1's sequence of events :

After the aircraft impact, gravity loads that were previously carried by severed columns were redistributed
to other columns. The north wall lost about 7 percent of its loads after impact. Most of the load was
transferred by the hat truss, and the rest was redistributed to the adjacent exterior walls by spandrels. Due
to the impact damage and the tilting of the building to the north after impact, the south wall also lost
gravity load, and about 7 percent was transferred by the hat truss. As a result, the east and west walls and
the core gained the redistributed loads through the hat truss.


Structural steel and concrete expand when heated. In the early stages of the fire, temperatures of
structural members in the core rose, and the resulting thermal expansion of the core columns was greater
than the thermal expansion of the (cooler) exterior walls. The floors also thermally expanded in the early
stages of the fires. About 20 min after the aircraft impact, the difference in the thermal expansion
between the core and exterior walls, which was resisted by the hat truss, caused the core columns’ loads
to increase. As floor temperatures increased, the floors sagged and began to pull inward on the exterior
wall. As the fires continued to heat areas of the core that were without insulation, the columns weakened
and shortened and began to transfer their loads to the exterior walls through the hat truss until the south
wall started to bow inward due to the inward pull of the sagging floors. At about 100 min, approximately
20 percent of the core loads had been transferred by the hat truss to the exterior walls due to weakening of
the core, the loads on the north and south walls had each increased by about 10 percent, and those on the
east and west walls had about a 25 percent increase. The increased loads on the east and west walls were
due to their relatively higher stiffness compared to the impact damaged north wall and bowed south walls.


The inward bowing of the south wall caused failure of exterior column splices and spandrels, and these
columns became unstable. The instability spread horizontally across the entire south face. The south
wall, now unable to bear its gravity loads, redistributed these loads to the thermally weakened core
through the hat truss and to the east and west walls through the spandrels. The building section above the
impact zone began tilting to the south as the columns on the east and west walls rapidly became unable to
carry the increased loads. This further increased the gravity loads on the core columns. The gravity loads
could no longer be redistributed, nor could the remaining core and perimeter columns support the gravity
loads from the floors above. Once the upper building section began to move downwards, the weakened
structure in the impact and fire zone was not able to absorb the tremendous energy of the falling building
section and global collapse ensued.

Content from External Source

The "hat truss" is a a vert large and strong structure at the top of the building that was designed to support the antenna mast. Its presence had big effect on the way loads were redistributed.

 

[lee h oswald]

The 'C' part of the Haydite (aggregate) content likely refers to its size range. Be good to know what that is.

three quarters of an inch.

 

[Mick West]

Reading the doc it says thay they couldn't find mix ratios prescribed by the engineers in the available information. I think that's highly dubious. It's so basic....anyway, the ratio of the mix seems quite strong to me - approx 4.3:1 when 6:1 might be the average today. The 'C' part of the Haydite (aggregate) content likely refers to its size range. Be good to know what that is.

http://www.hpbhaydite.com/haydite/properties.html

"C"Coarse Material
A coarse lightweight aggregate for use in concrete, landscaping, and Geotechnical fill applications. Available in a prewetted state for use in concrete and concrete pumping applications

Content from External Source

 

[Mick West]

Oh yeah, they say 3/4". Also other references say C is 3/4. Anyway, does this alter the NIST findings at all? If the collapse was from the floor pulling on the columns, then does the aggregate size affect that much?

 

[lee h oswald]

They fail in that they sagged, not failed as in snapped. Some of them probably failed at the ends before collapse was initiated, but it was how they pulled on the columns that eventually led to collapse.

Unlocked NIST NCSTAR-1: https://www.metabunk.org/files/NIST-NCSTAR1-909017_unlocked.pdf

WTC1's sequence of events :

After the aircraft impact, gravity loads that were previously carried by severed columns were redistributed
to other columns. The north wall lost about 7 percent of its loads after impact. Most of the load was
transferred by the hat truss, and the rest was redistributed to the adjacent exterior walls by spandrels. Due
to the impact damage and the tilting of the building to the north after impact, the south wall also lost
gravity load, and about 7 percent was transferred by the hat truss. As a result, the east and west walls and
the core gained the redistributed loads through the hat truss.


Structural steel and concrete expand when heated. In the early stages of the fire, temperatures of
structural members in the core rose, and the resulting thermal expansion of the core columns was greater
than the thermal expansion of the (cooler) exterior walls. The floors also thermally expanded in the early
stages of the fires. About 20 min after the aircraft impact, the difference in the thermal expansion
between the core and exterior walls, which was resisted by the hat truss, caused the core columns’ loads
to increase. As floor temperatures increased, the floors sagged and began to pull inward on the exterior
wall. As the fires continued to heat areas of the core that were without insulation, the columns weakened
and shortened and began to transfer their loads to the exterior walls through the hat truss until the south
wall started to bow inward due to the inward pull of the sagging floors. At about 100 min, approximately
20 percent of the core loads had been transferred by the hat truss to the exterior walls due to weakening of
the core, the loads on the north and south walls had each increased by about 10 percent, and those on the
east and west walls had about a 25 percent increase. The increased loads on the east and west walls were
due to their relatively higher stiffness compared to the impact damaged north wall and bowed south walls.


The inward bowing of the south wall caused failure of exterior column splices and spandrels, and these
columns became unstable. The instability spread horizontally across the entire south face. The south
wall, now unable to bear its gravity loads, redistributed these loads to the thermally weakened core
through the hat truss and to the east and west walls through the spandrels. The building section above the
impact zone began tilting to the south as the columns on the east and west walls rapidly became unable to
carry the increased loads. This further increased the gravity loads on the core columns. The gravity loads
could no longer be redistributed, nor could the remaining core and perimeter columns support the gravity
loads from the floors above. Once the upper building section began to move downwards, the weakened
structure in the impact and fire zone was not able to absorb the tremendous energy of the falling building
section and global collapse ensued.

Content from External Source

The "hat truss" is a a vert large and strong structure at the top of the building that was designed to support the antenna mast. Its presence had big effect on the way loads were redistributed.

You've posted this one before and I still think it's not right. I'll have to come back to it though...bed time

 

[lee h oswald]

Oh yeah, they say 3/4". Also other references say C is 3/4. Anyway, does this alter the NIST findings at all? If the collapse was from the floor pulling on the columns, then does the aggregate size affect that much?

Not necessarily, I'm just establishing the strength of the RC floors. It's a pretty robust formula for 'lightweight' concrete. Haydite must be quite porous (a high surface area to volume ratio, no?) given its weight.

It seems that what we need to be looking at is the connections of the floors to the core and the perimeter and why they remained functional while the floors themselves didn't - functional enough to allow sagging floors to pull the building down.

 

[Mick West]

You've posted this one before and I still think it's not right. I'll have to come back to it though...bed time

I found it easier to follow by drawing a simplified diagram of just the core columns, the exterior columns, the hat truss, and the floors. Then you can follow the forces.

Here it is. Don't laugh too hard. It's a representation of the top of the tower.

A key thing to remember is that the hat truss is very rigid.

 

[Mick West]

Not necessarily, I'm just establishing the strength of the RC floors. It's a pretty robust formula for 'lightweight' concrete. Haydite must be quite porous (a high surface area to volume ratio, no?) given its weight.

It seems that what we need to be looking at is the connections of the floors to the core and the perimeter and why they remained functional while the floors themselves didn't - functional enough to allow sagging floors to pull the building down.

Not exactly "pull the building down", they pulled some exterior columns out of load-bearing alignment, transferring loads around to other columns.

In a way what (theoretically) happened is rather like verinage, where the supporting columns are pushed or pulled over.

 

[lee h oswald]

Mick - just to backtrack somewhat, would you be so kind as to post the video representation of Purdue on the North Tower strike? The same one you used in the '911 an inside job?' thread. Otherwise please explain how I can do that. Ta

 

[Mick West]

This one?

​

If you "Reply With Quote", you can see how the video is embedded. You can use the little film strip icon above, or do it manually.

I also uploaded a very high resolution version here:

http://contrailscience.com/files/WTC-Purdue.mp4

 

[lee h oswald]

That's the one. Thanks. Is it possible to do a side by side comparison to a still from this and another video, both stopped at the same moment?

Could you put it up? from this

​

if you could put up a freeze frame from this and your video, both stopped at 1.05 that would be great. ta

 

[lee h oswald]

I found it easier to follow by drawing a simplified diagram of just the core columns, the exterior columns, the hat truss, and the floors. Then you can follow the forces.

Here it is. Don't laugh too hard. It's a representation of the top of the tower.

A key thing to remember is that the hat truss is very rigid.

I think a key thing to remember is that the hat truss didn't look like that. It looked like this:

[SIZE=-1] This photograph shows the top of the hat truss of one of the towers during its construction. credit: the Skyscraper Museum [/SIZE]

The fourth primary structural subsystem in each tower was the hat truss -- a lattice of large diagonal I-beams that connected the perimeter walls to the core structure between the 107th floor and roof. This structure was also known as the "outrigger truss system."
The hat truss structure strengthened the core structure, unified the core and perimeter structures, and helped to support the large antenna mounted atop the North Tower. The hat truss, which contained both horizontal and sloping I-beams, connected core columns to each other, and connected the core to the perimeter walls. Most the beams connected core columns to each other, while a set of sixteen horizontal and sloping beams spanned the distance the core and perimeter walls. Eight of these, the outrigger trusses, connected the corners of the core to the perimeter walls, while another eight connected the centres of the core's periphery to the perimeter walls.

Content from External Source

 

[Mick West]

That's the one. Thanks. Is it possible to do a side by side comparison to a still from this and another video, both stopped at the same moment?

Could you put it up? from this

​

if you could put up a freeze frame from this and your video, both stopped at 1.05 that would be great. ta

The one you link to seems to be a different visualization for that segment. The high res one does not show the floors. They do use the visualization with the floors later, when showing the fuel.

Visualization is separate from the physical simulation.

 

[lee h oswald]

Here it is more completely, in an axonometric view


The truss is highlighted in blue so you can see how it interacts with the core

 

[lee h oswald]

The one you link to seems to be a different visualization for that segment. The high res one does not show the floors. They do use the visualization with the floors later, when showing the fuel.

Visualization is separate from the physical simulation.

Great, but could you just post both images, the large one and the inset one at the same size and next to each other?

 

[Mick West]

I think a key thing to remember is that the hat truss didn't look like that. It looked like this:


[SIZE=-1] This photograph shows the top of the hat truss of one of the towers during its construction. credit: the Skyscraper Museum [/SIZE]

The fourth primary structural subsystem in each tower was the hat truss -- a lattice of large diagonal I-beams that connected the perimeter walls to the core structure between the 107th floor and roof. This structure was also known as the "outrigger truss system."
The hat truss structure strengthened the core structure, unified the core and perimeter structures, and helped to support the large antenna mounted atop the North Tower. The hat truss, which contained both horizontal and sloping I-beams, connected core columns to each other, and connected the core to the perimeter walls. Most the beams connected core columns to each other, while a set of sixteen horizontal and sloping beams spanned the distance the core and perimeter walls. Eight of these, the outrigger trusses, connected the corners of the core to the perimeter walls, while another eight connected the centres of the core's periphery to the perimeter walls.

Content from External Source

That photo is clearly just a small part of the hat truss, specifically the bit in the middle directly below the antenna. The hat truss itself was a large complex structure that spanned the entire top of the building. The bit in your image sits above the small square of girders in this full extent model:

 

[Mick West]

Great, but could you just post both images, the large one and the inset one at the same size and next to each other?

They are not the same aspect ratios in the two videos



Here I've manually aligned them.


Did you see something suspicious?

 

[lee h oswald]

At least one of these videos must be wrong - but can you say which? And why? Or could it be both are wrong?

 

[lee h oswald]

The original video you put up does not show the tips of the wings - why not? You've previously commented on this yourself. The video I provided shows the tips of the wings. Why might we not want to see the tips of the wings?

Sorry to be a pain - you should be used to it by now - but would you adjust the contrast in 'your' version of the video (the dark one) so we can see the spandrels/floors please?

 

[lee h oswald]

At least one of these videos must be wrong - but can you say which? And why? Or could it be both are wrong?

And please - just post two full-size static images next to each other

 

[lee h oswald]

Who'll be first to spot the problem?

 

[Mick West]

Why don't you just tell us what you think it is.

I see two different visualizations of the same data. In the newer (HD) one it's been rendered with the floors switched off. It's also been framed differently so the left wingtip is off screen.

Unless you just say what you think is a problem, I'm not going to comment any more.

 

[lee h oswald]

They are not the same aspect ratios in the two videos Did you see something suspicious?

Would you explain how to freeze frame a video and put it in a post please? Suspicious? No, just wrong. The link I provided, on the left, is titled: The first scientifically accurate visualization of the 9/11 attacks and it was produced by some people at Purdue University, who subsequently were awarded a 'Homeland Security Institute' grant for their trouble. The head of the University at the time was also given a place on the board of SAIC - a military contractor with strong connections to NIST, a govt. agency; the same govt. agency tasked with coming up with an explanation for the building collapses on 9/11. The link on the right, provided by you as your first piece of evidence in the closed thread, 9/11 - An Inside Job?, is titled: High Quality, High-fidelity visualization of the Sept 11 attacks on the wtc. It was also produced by Purdue. The commentary over both videos is exactly the same and in exactly the same place. The commentary feels the need to remind the viewer of its 'high quality' 'high-fidelity' 'state of the art' 'scientifically accurate' qualities as it goes along. Do you agree that these videos represent a 'high quality', 'high-fidelity', 'state of the art', 'scientifically accurate' visualization of the North Tower attack?

 

[Mick West]

To freeze a video and put it in a post depends on what your setup is at home. But basically the simplest way is just to pause it, and take a cropped screen shot.

What I do is (on the Mac)
1) Download the video using the "HD Suite" for chrome
2) Play it in Quicktime 7, which lets you single step through frames.
3) Capture the frame using "Skitch"
4) Annotate in Skitch
5) Upload with Skitch

Do you agree that these videos represent a 'high quality', 'high-fidelity', 'state of the art', 'scientifically accurate' visualization of the North Tower attack?

Those are all relative terms. Any simulation can be higher quality, and more accurate. But I think it's pretty reasonable.

You need to understand the distinction between a simulation, and a visualization. Both videos, as far as I can tell, share the same simulation. The simulation is very very slow to run, possibly taking several days for a full run on a very powerful computer. The end product of the simulation is raw data representing the position, orientation, and connectivity of all the elements in the scene at intervals of the timestep (something like 1/1000th of a second).

The visualization (also called a "rendering") takes that data and places a virtual camera in the scene, and renders the scene from the POV of that camera. The data does not change.

They can do different renderings with different camera positions. They can also make parts of the scene invisible so you can better see what is going on - like when they show what is happening to the fuel. renderings can also be done fairly quickly, as they can simplify the visual model. This doe not make it less accurate a simulation, as the underlying simulation is unchanged.

Regarding the difference between the two videos. It looks like they released it first with the lower resolution renderings. Then later they did some higher resolution renderings of the same simulation that looked better, so they simply replaced those segments at the appropriate point in the video.

 

[Mick West]

Here's how Perdue describe what I just said. The "animation" is what I refer to as the visualization or rendering.

http://www.purdue.edu/uns/x/2007a/070612HoffmannWTC.html

"Scientific simulations restrict us to showing the things that are absolutely essential to the engineer," Hoffmann says. "This gives us a simulation that doesn't deliver much visual information to a layperson. Our animation takes that scientific model and adds back the visual information required to make it a more effective communication tool."

The scientific simulation, the completion of which was announced last September, required several test runs before the researchers were satisfied; the final test run required more than 80 hours of high-performance computing. The simulation depicts how a plane tore through several stories of the World Trade Center north tower within a half-second and found that the weight of the fuel acted like a flash flood of flaming liquid, knocking out essential structural columns within the building and removing fireproofing insulation from other support structures. The simulation used lines and dots to show the aircraft and building during the event.
To develop the new animated visualization, Voicu Popescu, an assistant professor of computer science, developed a translator application that creates a link between computer simulations and computer visualization systems to automatically translate simulation data into a 3-D animation scene.

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And more technically:

http://www.cs.purdue.edu/homes/cmh/simulation/phase3/

The simulation uses adaptive time stepping which averages to approximately 0.000001 sec time steps. We generate snapshots of the simulation approximately every 0.0025 sec. The airplane arrives with an initial velocity of 470 mph. Penetration to the core structure of the building takes approximately 0.1 sec.

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So they simulate where everything is every 0.000001 secs, but they record the position of everything (for later rendering) every 0.0025 secs.

 

[Mick West]

The title of the second video comes from this paper, which gives a very detailed explanation of the simulation/visualization issue:

http://www.cs.purdue.edu/cgvlab/papers/popescu/popescuWTCVIS07.pdf

This presentation is great, shows how they did variosu things:
www.cs.purdue.edu/cgvlab/talks/fall06/09-14-1.pdf

 

[lee h oswald]

The title of the second video comes from this paper, which gives a very detailed explanation of the simulation/visualization issue:

http://www.cs.purdue.edu/cgvlab/papers/popescu/popescuWTCVIS07.pdf

This presentation is great, shows how they did variosu things:
www.cs.purdue.edu/cgvlab/talks/fall06/09-14-1.pdf

Mick, I've tried all possible methods for uploading stills from these videos but either your site or my computer, or a combination of the two, won't allow it. I really can't make my point unless the visuals are there - I need three images, all from the 'first scientifically accurate' film I posted. Could you put them up for me? Full size
at times 1.05, 2.30 and 3.21...

 

[Mick West]

Those don't represent the exact same instant, as far as I can tell. I'd have to create a synced version of the clips. Maybe later, if you explain what the discrepancy is.

Sorry about the problem's uploading, I think that was my fault, as some of the image types had very low size limits. I've upped them all to 10MB now, so if you'd like to try again it should work.

 

[lee h oswald]

Those don't represent the exact same instant, as far as I can tell. I'd have to create a synced version of the clips. Maybe later, if you explain what the discrepancy is. Sorry about the problem's uploading, I think that was my fault, as some of the image types had very low size limits. I've upped them all to 10MB now, so if you'd like to try again it should work.

No problem, and thank you for doing that, I know it's a bore. Now, would you be so kind as to count the number of columns severed by the port wing, from its connection to the airframe down to the port wing tip of the aircraft? Beginning with the broken steel perimeter column closest to and in front of the fuselage; the piece which hangs in front of the fuselage from the camera's perspective and is clearly distinguishable from the next broken column going towards the fuselage (which looks as if it's almost directly over the main body of the a/c) should be counted as number 1

 

[Mick West]

18?