Video simulation of WTC tower collapse removes the smoke and debris

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In the real footage, so much is hidden by fire, dust, debris, distance, and chaos that many people come away with the impression that the towers simply dropped straight down into their own footprints.

But that is not really what happened.

These simulations make it much easier to see that the collapse begins in the heavily damaged and fire-weakened region, the upper section starts moving and tilting, and the destruction then propagates downward through the structure.

The towers do not simply disappear vertically into their own footprints. Large portions of the upper structure and exterior are moving outward and to the side as the collapse develops. Much of that motion is simply obscured in the real videos once the enormous debris cloud forms.

And this is also why I find these simulations useful when people describe the collapses as looking like “controlled demolition.”

Strip away the smoke and dust and the resemblance becomes much less convincing.

What you see is a highly asymmetric structural failure beginning around the aircraft-damaged and fire-affected floors, followed by an enormous moving mass progressively overwhelming the structure beneath it. There is tilting, rotation, exterior columns peeling away, debris being thrown far outside the building footprint, and structural failure occurring chaotically as the collapse moves downward.

That is very different from the neat mental image usually implied by “controlled demolition,” where structural supports are deliberately severed in a carefully timed sequence to produce a predetermined collapse.

And importantly, we already know what preceded these collapses.

Both towers suffered massive aircraft-impact damage. Fireproofing was stripped from portions of the structure. Large, uncontrolled fires then burned across multiple floors - for about 56 minutes in the South Tower and about 102 minutes in the North Tower - heating and weakening structural components until collapse initiated.

Once that upper mass began moving, the loads imposed on the floors and structure beneath became vastly greater than anything they had been designed to carry.

The result was progressive collapse.

No, an animation is not proof simply because it looks convincing, and these are not official NIST simulations. They are visualizations built under particular assumptions.

But as visualizations, I think they are extremely useful.

They let you see something the original footage often cannot show clearly: beneath that enormous cloud of smoke and debris was a complicated, violent, asymmetric structural failure - not two buildings neatly dropping straight down into their own footprints.

A note on the simulation: this is not intended to reproduce the collapse down to the exact motion of every beam, floor panel, and fragment of debris. No practical simulation could do that. Its value is in modeling the large-scale structural behavior - how the major sections deform, move, tilt, separate, and progressively fail. Think of it as a visualization of the mechanics and overall collapse behavior, not a frame-by-frame reconstruction of where every piece of steel ultimately landed.

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