WTC Collapse Simulation using Unity/Besiege

Jeffrey Orling

Senior Member
Damage Caused by Heat

Let's discuss

Where was the acting
in the core - %​
outside the core - %​
both inside and outside the core % & %​
Did the fire spread...
From where to where​
Why?
Where was the main impact:​
Beams in the core​
did the expand and sag​
did they expand and push
did the concrete they supported break up and drop?​
Bar trusses supported the outside the core slabs​
did the expand and sag​
did they expand and push​
over the entire footprint​
in some areas only​
Columns in the core​
did they grow weaker and carry loads​
did they grow weaker and buckle​
did the end connections hold or did they shear
were they displaced by the beam expansion
which were the most and least effected by heat​
Connections​
did they shear and fail
beam stubs to columns
beam stubs to beams​
column to column​
 

Mendel

Senior Member.
A typical office fire starts on a single floor (and stays on a single floor), then the sprinkler system comes on, and a short while later the fire department attends to it and saves the building.
You don't design a building against someone spilling several tons of jet fuel over several floors and setting them alight.

Fire safety is always compromised against cost. What you want in case of a really big fire is for everyone to make it out safely, and for most people in thw WTC below the impact zone with the demolished stairwells, this worked (though analysis identified necessary improvements).
 
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econ41

Senior Member
Why would you design a building so that an unattended fire on a small group of floors can demolish the entire building in under an hour?
You don't. You design for an anticipated level of risk.

Steel framed high rise towers are a compromise. Certainly in the era when WTC Towers were built, they had to be lightweight steel frames. And steel frames are vulnerable to fires causing heat weakening.

So they're a compromise designed with "fire rating" as a major design consideration. "Fire Rating" is expressed in hours. Three hours for most of the WTC Complex.

The purpose of fire rating is to allow time. Time for:
(1) Occupants to escape >>which is the over-riding#1 priority; AND
(2) Time for active firefighting to be implemented. Protect the building - minimise damage - which is the second priority.

The fire rating is based on the normal (expected) progression of an office fire i.e. a fire involving normal office contents within the normal office partitions fit out.
The goal is to prevent steel frames from heating to temperatures that would compromise the structural stability. It is achieved by techniques that include insulation and fire sprinklers.

None of the WTC Towers fires were the fires designed for. The Twin Towers fires were much larger in several dimensions. Instantaneous start of fires on several floors. Fuel concentrated to one side of the building due to "BoeingDozing" (The aircraft pushing office contents and fitout material across the building) and the instant start of fires aided by aircraft fuel acting as an accelerant. PLUS fire sprinkles were disabled.

AND there was no active firefighting which, at minimum, would (a) put firefighters at the fire front with hoses AND would ensure the boosting and replenishment of fire sprinkler supply water.

Bottom line the Twin Towers fires were well outside the designed fire parameters and collapsed well before the fire rating time. WTC 7 was also outside design but not as far. So WTC1 & WTC2 designed for 3-hour fire rating failed well before the three hours. WTC 7 - not taken as far outside parameters - lasted nearly twice its fire rating.
 
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Jeffrey Orling

Senior Member
The answer is that steel's vulnerability to failure are fire protection, suppression and fighting.
Unfortunately in a multi story building... the mass of only several floors "released" by a failure at one level is enough to destroy the floor it falls on and that repeats all the way to the ground. No single floor can be built economically or practically to support these sorts of loads.

It should be noted that the runaway collapse was essentially the overloaded slabs, not the columns. Columns failed from loss of bracing when the floors had collapsed... which provided lateral support/bracing for the columns.

Fire protection and fighting systems need to be robust and redundant. WTC buildings' crippled fire protection and fighting systems all failed to prevent fires from fatally weakening the structure.

Steel typically is protected by "insulation" to prevent temps from rising and lowering strength. This alone is not enough. Active fire fighting/suppression is required. Sprinklers failed and fire fighters were unable to fight the fires.

++++

So design engineers of the WTC buildings used column free floor space outside the cores. Cores were for vertical conveyance and mech shafts and contained bathrooms. These designs has floors spanning from core to perimeter. Traditional high rise steel frames use a grid system of "bays". The floors are "structurally" isolated from one bay to the next. A local floor failure within a bay usually will not spread laterally to other bays. The construction is more expensive... so it was not used.
The wide open office floors facilitated entire floor collapse... and essentially left the core and the perimeter standing. Floor collapses can destroy essential column bracing... the beams that support the floors.

In 7WTC it appears that there was a "local" floor collapse in the NE quadrant which undermined structure at the lowest floors and that involved load transfer structures which rapid spread and undermined the entire core leading to a floor collapse of the entire footprint. This left the facade which fell soon afterward as the floor collapse undermined its support.

The twins fate was sealed when there was a runaway floor collapse... leaving unbraced columns which could not stand without bracing.

Floors are typically designed to carry only about 2-3 times the anticipated superimposed loads. More than that... a runaway collapse is the outcome.
 
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dylbie

New Member
Hi all, sorry not been here for a while.

I've been running some more "simulations" with Besiege recently and think I might have a makeshift solution to simulate the floor collapses.

One problem I had with the previous versions was that the floors to column connections were much too strong (almost indestructible in fact!) so as soon as the mass of the upper moving section hit the intact section below, it 'stalled', ejected a lot of material sideways, and in lots of cases stopped the whole collapse. This obviously isn't consistent with what happened.

The solution I have reduces the strength of the floors so the impact of the collapse, and a lot of the material falling from above, now continues down inside the tube of exterior columns in a much more fluid motion as was seen in real life.

The only problems I have left are the fact the top 'block' does not remain intact. I honestly don't think that this can be overcome with this software, so not much I can do here. Also, the core isn't putting up much of a fight once the floors and exterior columns have fallen down to ground level. This leads me on to some questions...

1. Does anyone have any estimates of total collapse duration times, including the core? All I've seen so far is either 12-13 seconds for 2WTC and 15-16 seconds for 1WTC. The video taken from the boat on the Hudson of 1WTC would suggest the time taken from initiation to complete core failure were much longer than this.

2. Does anyone have any theories as to why the core failed? Both cores were still partially standing after the main collapse. In the simulations I've run, the debris at ground level completely overwhelms the base of the core and destabilises it. Just wondering if this is anywhere near accurate.

3. I've asked this before, but has anything done to calculate the build up of debris at lower levels and any lateral damage this may have caused? Once the debris/material starts building up inside the 'tube' it starts damaging the exterior walls. I notice in some of the photos of ground zero the lower sections which remained intact are bowed outwards. I also noticed a photo where part of the exterior wall is intact, but there is a hole section of steel which appears as if its been punched out. One odd thing which relates to question 2, is that how on earth did the core survive this amount of damage and not collapse immediately. Seems to stay up for 10 seconds or so second before finally giving up.
 
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Landru

Moderator
Staff member
Hi all, sorry not been here for a while.

I've been running some more "simulations" with Besiege recently and think I might have a makeshift solution to simulate the floor collapses.

One problem I had with the previous versions was that the floors to column connections were much too strong (almost indestructible in fact!) so as soon as the mass of the upper moving section hit the intact section below, it 'stalled', ejected a lot of material sideways, and in lots of cases stopped the whole collapse. This obviously isn't consistent with what happened.

The solution I have reduces the strength of the floors so the impact of the collapse, and a lot of the material falling from above, now continues down inside the tube of exterior columns in a much more fluid motion as was seen in real life.

The only problems I have left are the fact the top 'block' does not remain intact. I honestly don't think that this can be overcome with this software, so not much I can do here. Also, the core isn't putting up much of a fight once the floors and exterior columns have fallen down to ground level. This leads me on to some questions...

1. Does anyone have any estimates of total collapse duration times, including the core? All I've seen so far is either 12-13 seconds for 2WTC and 15-16 seconds for 1WTC. The video taken from the boat on the Hudson of 1WTC would suggest the time taken from initiation to complete core failure were much longer than this.

2. Does anyone have any theories as to why the core failed? Both cores were still partially standing after the main collapse. In the simulations I've run, the debris at ground level completely overwhelms the base of the core and destabilises it. Just wondering if this is anywhere near accurate.

3. I've asked this before, but has anything done to calculate the build up of debris at lower levels and any lateral damage this may have caused. Once the debris/material starts building up inside the 'tube' it starts damaging the exterior walls. I notice in some of the photos of ground zero the lower sections which remained intact are bowed outwards. I also noticed a photo where part of the exterior wall is intact, but there is a hole section of steel which appears as if its been punched out. One odd thing which relates to question 2, is that how on earth did the core survive this amount of damage and not collapse immediately. Seems to stay up for 10 seconds or so second before finally giving up.
When did Besiege (a $15 game engine) become good enough to model the collapse? I though you admited it wasn't very good.
 

dylbie

New Member
We've established that it isn't good enough to model the collapse in detail... but for a £15 game, on a consumer grade PC, it doesn't do a bad job. It's also led me to ask some questions that I wouldn't have thought about, and which I haven't seen discussed before.
 

Jeffrey Orling

Senior Member
When did Besiege (a $15 game engine) become good enough to model the collapse? I though you admited it wasn't very good.

Hi all, sorry not been here for a while.

I've been running some more "simulations" with Besiege recently and think I might have a makeshift solution to simulate the floor collapses.

One problem I had with the previous versions was that the floors to column connections were much too strong (almost indestructible in fact!) so as soon as the mass of the upper moving section hit the intact section below, it 'stalled', ejected a lot of material sideways, and in lots of cases stopped the whole collapse. This obviously isn't consistent with what happened.

The solution I have reduces the strength of the floors so the impact of the collapse, and a lot of the material falling from above, now continues down inside the tube of exterior columns in a much more fluid motion as was seen in real life.

The only problems I have left are the fact the top 'block' does not remain intact. I honestly don't think that this can be overcome with this software, so not much I can do here. Also, the core isn't putting up much of a fight once the floors and exterior columns have fallen down to ground level. This leads me on to some questions...

1. Does anyone have any estimates of total collapse duration times, including the core? All I've seen so far is either 12-13 seconds for 2WTC and 15-16 seconds for 1WTC. The video taken from the boat on the Hudson of 1WTC would suggest the time taken from initiation to complete core failure were much longer than this.
I don't have anything for 2WTC... but 1 WTC was I believe: (hard to determine the precise end of the collapse as its shrouded in a huge dust cloud. The floor collapse appears to have reached a "terminal velocity" around 100' / second.
Einstein Puffs_page1.jpg

2. Does anyone have any theories as to why the core failed? Both cores were still partially standing after the main collapse. In the simulations I've run, the debris at ground level completely overwhelms the base of the core and destabilises it. Just wondering if this is anywhere near accurate.

Parts of both cores survived because the ROOSD phase the collapsing floor mass BYPASSED the columns... striped off most bracing beams with the exception of some elevator shaft framing.... which can be seen as "ladder looking" surviving core columns. All columns collapsed post floor collapse from Euler buckling and instability. Tallest surviver was col 501 which was 72 stories tall before it toppled.
3. I've asked this before, but has anything done to calculate the build up of debris at lower levels and any lateral damage this may have caused? Once the debris/material starts building up inside the 'tube' it starts damaging the exterior walls. I notice in some of the photos of ground zero the lower sections which remained intact are bowed outwards. I also noticed a photo where part of the exterior wall is intact, but there is a hole section of steel which appears as if its been punched out. One odd thing which relates to question 2, is that how on earth did the core survive this amount of damage and not collapse immediately. Seems to stay up for 10 seconds or so second before finally giving up.
The core columns were incredibly thick at the bottom of the towers... made from plates up to 2.5" thick. The 5 story"trees" were made from 6" thick plate. I can only guess that the debris mass had largely vertical impulse and the debris mass perhaps braced the columns as it filled in around them. There was a lateral component to the debris pile which would push the facade outward.... which would behave like pouring gravel in one spot.
 
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econ41

Senior Member
When did Besiege (a $15 game engine) become good enough to model the collapse? I though you admited it wasn't very good.
The fundamental problem remains - failing to define the goal. There are two main motivations that seem to be driving the project viz:
(1) Having fun forcing a gaming engine to mimic a structural collapse; AND
(2) Producing something that can help persuade some target class of person to understand the physics of the collapse.

Those two logically "AND"ed not "OR"ed. Both are valid in some balance.

The problem with all the "is it good enough" questions depends on who is the defined target. @dylbie can decide for himself if it provides him with enough fun. BUT the range of targets for persuasion is potentially wide. From raw novice, CT committed truther lay-person across to highly experienced and qualified professional persons. And it won't persuade those at either extreme whether the committed CT OR the experienced professional. The committed CT is not available for persuasion other than indirectly. Whilst, of the experienced professionals, I and several other members here comprehend the WTC collapses sufficiently well that we can advise @dylbie as to the accuracy of the model. Which by definition says it is not of value to persuade us -- we already know.

Bottom line I suggest is we cannot know whether "a $15 game engine" can produce results of persuasive value until we decide the level of "good enough" that is needed for the target audience. Hence the need to define "Who is the target for persuasion"? i.e. "What is the objective"?
 

econ41

Senior Member
@dylbie You asked several questions. I will respond to one - possibly more of them. But for reasons of overall coherent logic I will start with this one:
2. Does anyone have any theories as to why the core failed?
I have certainly presented comprehensive and in-depth explanations of all stages of the WTC Twin Towers collapses. Naturally such explanations include the aspects of core failure. Given this Forums "No Click" policy I won't provide links but can do so or provide quotations if appropriate.

(Others may have done similar work but I am not aware of any. If other members are aware of other comprehensive explanations they can comment separately.)
Both cores were still partially standing after the main collapse.
To be more specific some core columns were left standing and remained so for a few seconds. I suggest that the easiest way to understand why this is so is through understanding all the key features of the four distinct stages of Twin Towers collapses. I'll just outline them here - you can ask for more details if you need them. The "stages" are:
1) "initiation" stage - essentially a process of cascading failure of columns extending over about 1 hour (shorter for WTC 2 - longer for WTC 1) which reached a threshold point when the remaining columns were not strong enough to support their Top Block which then started to move bodily downwards. Causing near-instantaneous failure of the remaining columns which had survived to that point. The key feature of this stage was that of the three main methods of column failure ALL resulted in the "dropping" top part of the failing column moving past - missing or bypassing its lower part of the column. >> Remember "column ends missing" is ALL we need to know for this discussion at this time. Ask questions if you want more explanation.

2) "transition stage" > a chaotic mess. It resulted in a lot of horizontal translation movement associated with "tilting" and starting to "topple". Forget the details for now. All we need to know is that the horizontal motion made double sure that the column ends kept "missing" or "passing" AND - the main point - it imposed concentrated weight from perimeter columns on office space floor joists > starting "ROOSD" which was the driving process of the "progression stage". Proof of "starting ROOSD" is in this graphic which I can explain when/if necessary:
ArrowedROOSD.jpg

3) "progression stage" - which had two distinct "sub-stages":
3)(a) "early progression - the Top Block" and a similar-sized portion of the "lower tower" broke up in mutual destruction >> with falling debris continuing to "miss" or "bypass" the columns >> This substage is of no consequence to us at this stage of discussion.

THEN - the final stage which left those core column "spires" standing.
3)(b) "established progression"... involving "ROOSD" - a truther side inspired acronym meaning "Runaway Open Office Space Destruction". The concept AFAIK was first posted on a forum in Nov 2007 with this graphic:

003c350.jpg

The acronym "ROOSD" and the concept were put into mainstream discussion in 2009. It explains how debris fell down the "OOS" missing the columns. The concept is generally accepted these days (Since about 2010) as what really happened. Note It explains why the perimeter columns were left unbraced, free-standing and subsequently peeled off and toppled. It did not explain the core which @dylbie is your current interest. For reasons of discussion history, nobody paid the issue much attention. In 2013 I extended the original "perimeter only" scope of ROOSD asserting that the behaviour in the core would be analogous. i.e. falling debris missed columns and sheared of floor beams in the same way as the debris falling in the OOS "outer tube" area sheared of the floor joists.

So that much should at least set an agreed context if you want any further discussion to explore more details. Your call.
In the simulations I've run, the debris at ground level completely overwhelms the base of the core and destabilises it. Just wondering if this is anywhere near accurate.
If your focus is on those few "spire" columns - your guess is probably in the right ball park. The core columns remained standing as spires because the progression of the collapse was so fast. And debris fell around the columns With no bias one way or the other to cause toppling. BUT the spires were too tall to remain - they were well beyond the effective length that could remain self-supporting. (The technical details involve a concept of "Euler Buckling" after the person who described it. Put simply a slender column can be too thin to stand up without horizontal bracing. So it will buckle. Buckle under load at some length. If it is even longer it will buckle under its own weight. And it will buckle easier/earlier if it has either imposed force or vibration. Resonant vibration was IMO possibly the trigger for those core column spires.

So does that answer or start to answer this part of your Question #3?
is that how on earth did the core survive this amount of damage and not collapse immediately. Seems to stay up for 10 seconds or so second before finally giving up.
If you need more or a fuller explanation just ask.
 
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econ41

Senior Member
Parts of both cores survived because the ROOSD phase the collapsing floor mass BYPASSED the columns... striped off most bracing beams with the exception of some elevator shaft framing.... which can be seen as "ladder looking" surviving core columns. All columns collapsed post floor collapse from Euler buckling and instability. Tallest surviver was col 501 which was 72 stories tall before it toppled.
Concisely and accurately stated.
 

arsyn

New Member
The fundamental problem remains - failing to define the goal. There are two main motivations that seem to be driving the project viz:
(1) Having fun forcing a gaming engine to mimic a structural collapse; AND
(2) Producing something that can help persuade some target class of person to understand the physics of the collapse.

I would reformulate #2:
(2) Make a visualisation/animation that is close enough to the actual assumed process to make it passable, making textual explanations easier to follow.

To do this, the physics involved does not need to be exact, it only requires that the visual qualities of the game engine simulations (with its inherent simplifications and flaws) reflect the described process closely enough. But of course, it must not be presented as an actual physics simulation of the collapse.

I think it sounds like a fun project :)
 

econ41

Senior Member
I would reformulate #2:
(2) Make a visualisation/animation that is close enough to the actual assumed process to make it passable, making textual explanations easier to follow.
Your language is probably better than mine BUT don't overlook the key issue "some target class of person". Who you want to make "explanations easier" for is IMO the #1 issue
To do this, the physics involved does not need to be exact, it only requires that the visual qualities of the game engine simulations (with its inherent simplifications and flaws) reflect the described process closely enough. But of course, it must not be presented as an actual physics simulation of the collapse.
Which eliminates two of the three main classes of "audience"
I think it sounds like a fun project :)
It would be a lot easier to discuss if people would recognise when that is their #1 objective.
 

arsyn

New Member
Your language is probably better than mine BUT don't overlook the key issue "some target class of person". Who you want to make "explanations easier" for is IMO the #1 issue

Once you have a good enough representation of the collapse in form of an animation (and make it clear that it is just an illustration and not a simulation based on actual representative physics) it can be adapted further to the target audience. Thus, as long as the illustration can be adapted, I don't think it is necessary to first define the audience.

Besides, playing with the tool in question here can be motivation enough to do it. If the result can also be used for someting useful, it is a bonus :)
 

econ41

Senior Member
Besides, playing with the tool in question here can be motivation enough to do it. If the result can also be used for someting useful, it is a bonus :)
Which is what I suggested. Be self-aware as to motivation. And be open about it - it saves a lot of wasted effort by those of us who try to discuss the more serious aspects.
 
I had to revisit this thread after checking whether the Kostack Studio simulation of WTC has been completed yet (it hasn't, most likely IMO it will be available by September 2022).

Re-reading through all the posts helped me understand some things I was originally not understanding, including tilt being a consequence of failure and not the cause, as well as the concept of euler buckling of the temporarily freestanding core columns (along with the ladder-like appearance of the temporarily standing hollowed out core area (as a result of the floor bracing being stripped when the ROOSD mass was tearing through those sections)).
Hi all, sorry not been here for a while.

I've been running some more "simulations" with Besiege recently and think I might have a makeshift solution to simulate the floor collapses.

One problem I had with the previous versions was that the floors to column connections were much too strong (almost indestructible in fact!) so as soon as the mass of the upper moving section hit the intact section below, it 'stalled', ejected a lot of material sideways, and in lots of cases stopped the whole collapse. This obviously isn't consistent with what happened.

The solution I have reduces the strength of the floors so the impact of the collapse, and a lot of the material falling from above, now continues down inside the tube of exterior columns in a much more fluid motion as was seen in real life.

The only problems I have left are the fact the top 'block' does not remain intact. I honestly don't think that this can be overcome with this software, so not much I can do here. Also, the core isn't putting up much of a fight once the floors and exterior columns have fallen down to ground level. This leads me on to some questions...

1. Does anyone have any estimates of total collapse duration times, including the core? All I've seen so far is either 12-13 seconds for 2WTC and 15-16 seconds for 1WTC. The video taken from the boat on the Hudson of 1WTC would suggest the time taken from initiation to complete core failure were much longer than this.

2. Does anyone have any theories as to why the core failed? Both cores were still partially standing after the main collapse. In the simulations I've run, the debris at ground level completely overwhelms the base of the core and destabilises it. Just wondering if this is anywhere near accurate.

3. I've asked this before, but has anything done to calculate the build up of debris at lower levels and any lateral damage this may have caused? Once the debris/material starts building up inside the 'tube' it starts damaging the exterior walls. I notice in some of the photos of ground zero the lower sections which remained intact are bowed outwards. I also noticed a photo where part of the exterior wall is intact, but there is a hole section of steel which appears as if its been punched out. One odd thing which relates to question 2, is that how on earth did the core survive this amount of damage and not collapse immediately. Seems to stay up for 10 seconds or so second before finally giving up.
Your more recent simulation videos seem to be a much better match to what occurred.

In particular, v4 and v5.

v3 still appeared to show the same problem of the lower section exterior columns buckling before the higher section exterior columns did.
Source: https://www.youtube.com/watch?v=GG1e91bjgsc


v4 (simulating collapse of the north tower) and v5 (simulating collapse of the south tower) on the other hand show that this issue is no longer present, and you've managed to have some of the bottom part of the exterior facade columns (along with the higher height of the lobby level compared to the above floors) still standing after the collapse has ended.

Source: https://www.youtube.com/watch?v=MTkpr-MjiEM


Source: https://www.youtube.com/watch?v=5eh3QPA5ux4


How did you manage to do this (specifically on managing to have some of the exterior facade columns at the lobby level still standing after the collapse ended)? In the beginning of the v5 video, it said that the simulation had been tweaked so that you:
"increased floor breaking threshold" and "increased core strength (still not enough)".
Is this what changed the result of the collapse simulation between videos v3 and v4, v5?

Also, are you planning to publish a model of this simulation on the Besiege workshop? In the comments of one of your videos you had said that you might be planning to do that.
 
These simulations are poor representation of the collapse.
In what way are the simulations (v4 and v5) a poor representation of the collapse?

The element of the exterior facade peeling away is still not modeled (nor does it seem possible to do that currently in Besiege), but the problem of lower sections of exterior columns buckling before higher sections of exterior columns (which was present in earlier versions v1 through v3) appears to have been fixed, and settings appear to have been tweaked in some way to allow at least some of the exterior columns at the lobby level to remain standing after the collapse concludes.

@dylbie maybe it would be useful to see if you could model both the towers along side each other (in their offset configuration) and including the basement levels below the towers next just to see if these results still hold up in your simulation with the current settings.
 

Jeffrey Orling

Senior Member
In what way are the simulations (v4 and v5) a poor representation of the collapse?

The element of the exterior facade peeling away is still not modeled (nor does it seem possible to do that currently in Besiege), but the problem of lower sections of exterior columns buckling before higher sections of exterior columns (which was present in earlier versions v1 through v3) appears to have been fixed, and settings appear to have been tweaked in some way to allow at least some of the exterior columns at the lobby level to remain standing after the collapse concludes.

@dylbie maybe it would be useful to see if you could model both the towers along side each other (in their offset configuration) and including the basement levels below the towers next just to see if these results still hold up in your simulation with the current settings.
The top blocks' shells came down and broke up on impact with the lower block.
The insides of the upper blocks may have partially broken up before the descend.
The strongest columns in the core survived the collapse... rows 500 & 1000... 501 stood maybe 60 stories before collapse. The rest of the core columns did not survive the collapse.
As ROOSD destroyed floors the facade panels began to peel away without lateral support from the floor plates. Some came off in huge multi story assemblies.
 

Henkka

Member
Cool work dylbie, enjoyed watching those.

I thought of asking something regarding computer simulations of the WTC collapses that's maybe not worth its own thread. That is, why are there so few simulations of the collapses? When I type in "wtc collapse simulation" on Youtube, here's what I get:

-Smithsonian video on Dr. Frank Greening doing some calculations on the collapses, but it is not a visual simulation.
-Video interviewing survivors.
-National Geographic video simulating the plane impact, not the collapse.
-How to survive airplane crash (???)
-Kai Kostack's simulation. Finally, this is the kind of thing I want to see. But it is unfortunately only the top of the tower. I'm also unsure how much weight to put on simulations made by a single guy in Blender.
-Bunch of videos that have no simulations at all...
-Nicholas Cage movie clip...
-WTC 1 litigation animations that show a simulation of the plane impact and the top of WTC 1 starting to come down. This is the closest to that I'm looking for, a proper simulation created by a team of engineers, that is even overlaid on top of real footage of the collapse. But unfortunately, this also only shows the top descending for a short amount of time, and then it cuts. It's also from 2004.

And then if you keep scrolling, you'll maybe find a few simulations created by hobbyists in various videogames, like what dylbie did here. What I'm surprised by is the lack of simulations made by universities and other such research groups. You would think there would be a great amount of interest in creating a simulation that could be matched to the actual footage. Is the size and complexity of the building still difficult for modern computers to simulate?
 

Mendel

Senior Member.
You would think there would be a great amount of interest in creating a simulation that could be matched to the actual footage. Is the size and complexity of the building still difficult for modern computers to simulate?
you can find some simulations of the aircraft impacts in the scientific literature

simulating the collapse is mostly pointless scientifically because there's really not enough data to validate any model, and the modelling for legal/political purposes has already been done
 

Henkka

Member
simulating the collapse is mostly pointless scientifically

That seems like an odd stance to take, considering that:

1) NIST left the door open for further study by focusing on the initiation
2) Bazant's hypothesis seems controversial, even on here

So it seems like there would be an avenue there for further research with massive public interest. I'm sure 9/11 documentaries would also like to include a simulated 3D visualisation of the collapse.
 

Mendel

Senior Member.
massive public interest
yes, but that does not translate to scientific interest
I don't see any benefits to advancing science that could come from this

and most of the "massive public" interested in this are either truthers, or people unfamiliar with the work that has been done (or both).

there's actually only going to be "massive interest" if the results don't confirm what we already have, and that's simply very unlikely and thus not worth the effort
 
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econ41

Senior Member
@Henkka @Mendel's summary is accurate. These are your points:
So it seems like there would be an avenue there for further research with massive public interest.
Both those two assumptions are optimistic. Both seem to assume a level of interest greater than there actually is.

Academic and professional interest in understanding the WTC collapses has faded. It is "past history".

And any contemporary "public interest" is mostly the remnant interest from those remaining "truthers" who have been fed the nonsense faked simulation from the Hulsey Report as commissioned by AE911Truth.

I'm sure 9/11 documentaries would also like to include a simulated 3D visualisation of the collapse.
There are enough visualisations available for 9/11 documentaries. There is no need for detailed technical rigour in a documentary.
That seems like an odd stance to take, considering that:

1) NIST left the door open for further study by focusing on the initiation
The "progression" stage (and in fact all four stages) are now sufficiently understood by those who want to understand.
2) Bazant's hypothesis seems controversial, even on here
There is little real controversy. I've raised the issue many times on multiple forums. You have identified some of the fatal problems with Bazant's "CD/CU" hypothesis. Most people - both online and in academic circles seem to blindly accept Bazant. It's a complex story but don't expect support for raising the topic.
 

Henkka

Member
I would think there would be scientific interest, considering a simulation of the total collapse has never been done before.

I guess Kai Kostack will have to be my knight in shining armour, then. But as I said, it's hard to judge the scientific validity of a simulation done in Blender rather than some more specialised simulation software. But I'm looking forward to seeing his new WTC sim anyway.
 

econ41

Senior Member
I would think there would be scientific interest, considering a simulation of the total collapse has never been done before.
Why would there be interest?
1) The scientific community thinks that "they" know enough"
2) The "debunker" community also think that they know enough - enough to beat truthers in arguments. Very few debunkers are interested in a more complete understanding.
3) A large proportion of those remaining active truthers think they know better. And they have been spoon-fed faked proof in the Hulsey reports. (Most of the genuine truthers with an interest in WTC collapses have learned and left the active scene.)
4) A few people like playing with simulations. Mostly games programming type IT people. Some like building physical modes. Their real objective is doing the modelling. Usually with some undefined or unclear goal of "helping some one to understand".
5) My personal interest is in understanding the WTC collapses to a personally sufficient professional standard. Neither the academics or professionals have done anything to explain Twin Towers collapses better than what I have worked out for my own purposes. And I can identify the shortcomings in many of them as easily as I can identify wrong logic and false claims by truthers..

SO:
6) What is your interest. <<THAT is the vital question. Do you know what you are trying to achieve? For yourself?
I guess Kai Kostack will have to be my knight in shining armour, then.
Why? What are you looking for? His simulations are outstanding work. Leading in the class. Do they help me? >>> No. Do they help you understand the collapses?
But as I said, it's hard to judge the scientific validity of a simulation done in Blender rather than some more specialised simulation software.
I have no difficulty judging scientific merit as soon as the person asking the question decides "Merit for what purpose"?

Remember the classes of scientific objectives in a model for third parties:
1) Looks like the real thing is good enough to assist laypersons understand. Yes that is low level but still "scientific".; OR
2) Accurate enough to help explain or quantify some professional engineering purpose >> and such a model is unlikely to "look like" the real event. Remember all the laypersons after a "look like" model criticise the NIST WTC7 sim because it doesn't "look like".
But I'm looking forward to seeing his new WTC sim anyway.
I'm interested in curiosity. For both reasons plus a third. 3rd - as an example of even better graphical simulation. Then for "look like" and for "what engineering does it help".
 
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Mendel

Senior Member.
I guess Kai Kostack will have to be my knight in shining armour, then. But as I said, it's hard to judge the scientific validity of a simulation done in Blender rather than some more specialised simulation software. But I'm looking forward to seeing his new WTC sim anyway.
Judging the validity of a simulation software (which is what Kostack is producing) is done same, no matter how it's implemented: by comparing the simulation results to real-world data. The problem with WTC is that most of the data is "there was a huge dust cloud, and then all the rubble was moved to search for survivors". Kostack would do better to use a controlled demolition, install cameras and sensors, which would give him a wealth of data to validate his software with.That'd be actual science.
 

Henkka

Member
Why would there be interest?
It's scientific research that hasn't been done yet on the most significant structural failures in history. I think the interest would be self-evident. But maybe it isn't, judging from the lack of simulations.
The problem with WTC is that most of the data is "there was a huge dust cloud, and then all the rubble was moved to search for survivors".
I disagree, there's a lot more than that... One could overlay the footage of the top of WTC 1 from Sauret with the simulation and see how well it matched until it was covered by the dust cloud. One could compare the overall collapse time. I was also reading an older thread here about the lateral ejections of debris where Mick West was theorising that some girders could have fallen for a time, and then bounced horizontally. You could see if that could be recreated in the simulation.
 

econ41

Senior Member
It's scientific research that hasn't been done yet on the most significant structural failures in history.
You asked about simulations, not research. I identified the status of research. And recognised that there is interest in simulations but primarily from those who like doing simulations or modelling. For the fun of it. I'm not persuaded there is any significant interest in benefitting third parties.
I think the interest would be self-evident. But maybe it isn't, judging from the lack of simulations.
The interest in what? You keep switching from "simulation" to "research". Different topics - a lot of overlap but current interest is not in the overlapping aspects. i.e. learning more about the collapses. None of the recent simulations add to the understanding of WTC collapses. All of them AFAICS rely on the sim or model producer already understanding the actual collapses. AND the audience here on Metabunk has been judging sims/models on the basis of whether they match reality. The reality that the judges already comprehend.
I disagree, there's a lot more than that... One could overlay the footage of the top of WTC 1 from Sauret with the simulation and see how well it matched until it was covered by the dust cloud. One could compare the overall collapse time. I was also reading an older thread here about the lateral ejections of debris where Mick West was theorising that some girders could have fallen for a time, and then bounced horizontally. You could see if that could be recreated in the simulation.
I won't comment about your discussion with @Mendel other than to note that you "beg the question". "You could see if that could be recreated in the simulation." Why would anyone need to see it simulated. The fact is readily observed in video clips.
 

econ41

Senior Member
yeah, but then you still wouldn't know if that really happened, because you have no way to check that, or to know that the simulation matches reality.
We "crossed in posting" - it took me a few minutes to write my post.

Your comment is IMO correct. And I suggest there are two over-riding issues:
1) The bit of physics is too trivial to need simulation. It should be easily understood, from the video clips, by anyone of the likely range of intelligence seen in the discussion of these topics.
2) Most of the assessments of "does it match" reality is being done by the class of persons who already understand reality. So they don't need the simulation. Which puts the spotlight on: "Who can benefit from simulation?" ( and that is not a "null" answer but the number who may benefit may be very small.)
 

Henkka

Member
You asked about simulations, not research. I identified the status of research. And recognised that there is interest in simulations but primarily from those who like doing simulations or modelling. For the fun of it. I'm not persuaded there is any significant interest in benefitting third parties.
Well, I mean researching the collapse through creating a computer simulation of it. Just like how NIST did with WTC 7.
I won't comment about your discussion with @Mendel other than to note that you "beg the question". "You could see if that could be recreated in the simulation." Why would anyone need to see it simulated. The fact is readily observed in video clips.
The movement of the debris is what's observed. Whether or not that movement was caused by bouncing is not observed.
 

econ41

Senior Member
Well, I mean researching the collapse through creating a computer simulation of it. Just like how NIST did with WTC 7
Then answer my previous questions, Why? And for who's benefit?
The movement of the debris is what's observed. Whether or not that movement was caused by bouncing is not observed.
What are you trying to prove and for whom? Why do you (or "we") need to simulate speculation raised by a debunker attempting to disprove a claim? The Burden of Proof is his and if he feels the need for a simulation he is free to perform the simulation. My comments to @Mendel are relevant. It is too trivial to need simulation. "We" do not justify detailed simulation of speculative explanations for several reasons of both logic and efficiency.
 

Mendel

Senior Member.
Well, I mean researching the collapse through creating a computer simulation of it. Just like how NIST did with WTC 7.
The paper I linked in the column 87 thread (at https://www.metabunk.org/threads/was-column-79-the-achilles-heel-of-wtc7.12391/post-271005 ) shows there were several simulations, and they don't agree, even though there are more observations to calibrate them by than the WTC towers have.

You don't have a clear idea what that simulation should do (or if you have, you're not revealing it), and that makes your claim of benefit ring hollow.

The NIST simulation of the WTC towers was to establish a plausible collapse initiation sequence, and it succeeded at that. It's impossible to establish a definite detailed sequence because the data isn't there, and there's nothing to be gained by adding more possibilities.

So where's the benefit? besides entertainment?
The movement of the debris is what's observed. Whether or not that movement was caused by bouncing is not observed.
What debris movement was observed?

Put yourself in Kostack's position. He claims he wants to create a simulation so exact that it can predict hollow spaces in collapsed buildings. You can't calibrate that with a dust cloud, you need a well instrumented, well recorded collapse (demolition) and rubble pile.
 

econ41

Senior Member
Put yourself in Kostack's position. He claims he wants to create a simulation so exact that it can predict hollow spaces in collapsed buildings. You can't calibrate that with a dust cloud, you need a well instrumented, well recorded collapse (demolition) and rubble pile.
And you cannot have "a well instrumented, well recorded collapse (demolition) and rubble pile" until AFTER the building has collapsed. Which defeats the goal of PREDICTION.
 

Jeffrey Orling

Senior Member
The runaway destruction of the floors is settled/trivial engineering. Each floor was massively overload one after the other. Severely overloaded floor with shatter, turn to rubble, dust, chunks of concrete and steel.
The toppling of the remaining columns likewise is "settled engineering" - Euler buckling.
It is the "initiation stage(s) which are more elusive... going from a static building "absorbing" the impact of the jet plane... mechanical damage... to "loss of capacity" in the burning plane strike zone.... leading to the collapse of the upper blocks creating what is the driving "ROOSD" mass - runaway destruction of the the floors below the crash zones.
Did the columns (which ones?) have their strength lowered from heat?
Did the lateral steel bracing the columns and supporting the floor slabs collapse?
Did the lateral steel bracing the columns push them out of axial alignment causing the to buckle?
Did the facade columns lose capacity and buckle?
How much of the facade was "pulled in" but sagging floor trusses?
Was the ROOSD mass created in the collision of the dropping top blocks with the fixed lower blocks?
What role, if any, did the hat truss play?
more
 

Mendel

Senior Member.
And you cannot have "a well instrumented, well recorded collapse (demolition) and rubble pile" until AFTER the building has collapsed. Which defeats the goal of PREDICTION.
My point was that the simulation makes a prediction, and then Kostack can use the recording of the actual collapse to check how accurate that prediction is.

Without such confirmation, the simulation can't be relied upon in unpredicted collapses.
 
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Jeffrey Orling

Senior Member
My point was that the simulation makes a prediction, and then Kostack can use the recording of the actual collapse to check how accurate that prediction is.

Without such confirmation, the simulation can't be relied upon in unpredicted collapses.
Building designs are unique and likely initial damage is unique.... Why would you expect "prediction" and how useful would it actually be?
 

econ41

Senior Member
Building designs are unique and likely initial damage is unique.... Why would you expect "prediction" and how useful would it actually be?
That is the core of my point. How can you predict for a specific building if your calibration is post hoc? And the presumption that a simulation - calibrated on the evidence of one or more specific demolitions could have any relevance to a future collapse of a different building.
 
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