Kai Kostack's WTC7 Collapse Simulation using BCB and Blender

Mick West

Staff member
Source: https://www.youtube.com/watch?v=VAkTbyENZ5s

Kostack Studio
Published on Sep 11, 2017

Simulated with completely new developed software designed for structural simulation, this revision of my earlier WTC7 simulation attempt serves as validation case for the software.

New in this simulation compared to the old one:
- Multiple constraints per connection are used to represent individual degrees of freedom (DOF)
- Breaking thresholds are computed from real world parameters
- Correct steel thicknesses and beam dimensions are used
- Plastic deformation is now simulated

While this simulation of World Trade Center 7 is still not 'perfect' it resembles much better the specific characteristics observed in reality than the older model. This simulation confirms mostly the findings of NIST, it is safe to say that the columns 79 to 81 were the first columns which gave way because the removal of other columns led to much different collapses. More than that is hardly determinable, such a system behaves just to chaotic to tell what exact connection failed first. In this regard NIST might be wrong by declaring a specific failure point. However, I consider this not being an important question given the fact how compromised the structure around these three columns must have been exposed to fire for hours, a situation beyond any imaginable safety design specification.

Having said that, I want to emphasize that this video is not intended to prove or disprove 9/11 conspiracy theories. I'm deleting comments that include hate speech, so you better think twice before starting an argument about the reasons of 9/11 here. Instead, I recommend to read a neutral source like: https://en.wikipedia.org/wiki/9/11_co... to get some pros and cons instead of watching YouTube videos.

This is a private project. There are no third parties involved. There is no scientific report available. No peer review has taken place. Thanks for watching.
Content from External Source
An impressive project for one individual, Kostock's simulation is an amazing static model of WTC7, and gives a reasonable facsimile of the collapse, given the limitations of what he is doing.


People will surely pounce on the fact that the outer skin does not behave the same as the real event.

But as with the NIST simulation, this demonstrates an interior collapse followed by the exterior bucking and falling.

Overall a very impressive effort.

It also provides some new viewpoints, that might be helpful perspective.


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Jeffrey Orling

Senior Member
What he seems to ignore are the impact of the transfers in the form of the collapse. He presents the model as if there were NO transfers. Whether the collapse of the region around col 70 was at floor 13 or 12 or whatever floor... the descending floor masses and steel surely dislodged/destroyed the load transfer structures... which would show a different collapse FORM and SEQUENCE. Once the transfers failed... and their failure likely was east to west... the entire inside would collapse INCLUDING undermining the facade... which likely lagged just a bit behind the collapse of the interior.


  • WTC 7 TTF r5.pdf
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Nada Truther

Active Member
He showed the 3d scan of the debris pile, but I wonder how an actual photo of the pile vs. his pile would compare. How would the skin sections compare? I found some, but don't have the know-how to super-impose and all of that for comparison.

Also, besides what Jeffrey posted in post #2, how open for "tweaking" is this simulation to sway it toward what we "want" to see? How easy will it be for some to argue that you could make the collapse look like whatever you want it to look like to reflect your own personal opinion?


Senior Member
As long as the tweaking is within a plausible envelope of the unknown variables, it is fine. If such tweaking shows that lots of forms and features are possible, including those actually observed, this would to pad the credibility of the "no demolition devices after initiating local failure" class of theories.

Invalid tweaks would include adding entities that weren't actually there, like extra elements, unrealistic life loads, or indeed demolition devices.

Mick West

Staff member
What he seems to ignore are the impact of the transfers in the form of the collapse.

It's far from a perfect model, and much less exact than NIST's models. But the point here is an illustration of the very broad principles of collapse. Compare it with an attempt I made for WTC1:

Kostack's model is the best independent model available. Unfortunately as it's not exactly the right collapse people will nit-pick. However the intent is, like with mine, to illustrate general principles and characteristics. Here he failed columns 79-81, and the collapse was as shown, similar to the real world in many aspects.

I think the benefit here is that people will look at the actual structure of WTC7, and perhaps understand more about how the "interior then exterior" collapse might work.

Mick West

Staff member
Another thing he does is add damage to the model to match the photos. Now this is a little speculative, as we don't have great close-ups of the damage, but there's a reasonable visual match.




Mick West

Staff member
His southwest corner damage seems wrong though, as the corner column (15) is intact


Whereas photos and the NIST analysis suggest otherwise.


(Figure 12-33)

Jeffrey Orling

Senior Member
My point is that the collapse sequence likely involved the collapse of the transfers EARLY on... THEN the structure above in the center and west came down.

sequence would be something like this:

failure at column line 79 and 80 (this could occur anywhere from floor 5 - 13 or higher even. But for the falling mass to collapse transfer trusses below it would likely have to be multiple floor masses from above as those trusses supported 40 stories and were massive.

collapse of transfer truss 1 and 2 (don't know which came first) This led to the kink in the north face and then collapse of the EPH thru the building

collapse of the main East-West girder at floors 3-5 at the north side of the core which led to:

collapse of the MG 23 which were supported on main East-West girder on their west side which led to:

collapse of the center of the tower up to:

collapse of transfer truss 3 which led to the collapse of the WPH which led to the collapse of the braced frames of the facade on floors 1-7 which led to the collapse AND counter clockwise rotation and folding inward at column line 47 or 48 of the facade which pivoted about the structure on the west side up to floor 8

The facade fell on and folded over the collapsed materials.

The collapse was driven by FAILURES at the transfer structure level... We don't know what triggered those failures... falling debris from above... or connection (bolt) failures on one of the trusses (bolts being the way the members were connected one to the other.

Mick West

Staff member
My point is that the collapse sequence likely involved the collapse of the transfers EARLY on... THEN the structure above in the center and west came down.

Well, perhaps you should encourage someone to simulate that. But this is getting a bit off topic.


Senior Member.
rereading this thread since someone just linked to Kostacks simulation and i'm struck again at how much I trust "computer guys" to do computer simulations over engineering students :) (ie Hulseys wtc7 report and data dump)
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