The Collapse of WTC1 and 2

[coughymachine]

Consider this hypothetical scenario:

A decision has been made to bring a WTC-type tower down in a controlled manner. The reasons are legitimate and irrelevant.

Time is taken to prepare the building in the proper way and the site is evacuated in advance.

If all of the core columns were blown simultaneously on one floor - say the 80th - would the building collapse as the towers did on 9/11?

If the collapse mechanism couldn't be replicated by the simultaneous removal of the core columns at one floor, could it be replicated by simultaneously removing the core columns at two floors? If not, how many?

If the collapse mechnism couldn't be replicated, why not?

I started having a similar conversation with one of your members in another forum but, unfortunately, that ended before I got to grips with his line of reasoning.

 

[gumboot]

I think it's possible, but not guaranteed.

What does this have to do with "the collapse of WTC1 and 2" (the title of this thread)?

-Gumboot

ETA. Welcome to the forums.

 

[Mancman]

Blowing away all the core columns at once would make the top of the buildings drop straight down.

This didn't happen. The towers leant. The failure of the perimeter walls initiated the collapsed, not the cores.

 

[jhunter1163]

Most likely, yes, the towers would collapse in the same way. Inertia and all, you know. A building the size of the WTC has tremendous inertia, and pretty much COULD ONLY FALL in the manner seen on 9/11. Someone on this board, probably R. Mackey, calculated how much lateral energy would be required to make the towers topple over rather than collapse straight down. I don't remember the figures, but the impact of a fully loaded 767 wasn't nearly enough.

 

[Dave Rogers]

If all of the core columns were blown simultaneously on one floor - say the 80th - would the building collapse as the towers did on 9/11?

In how much detail do you want to replicate the 9/11 collapse mechanism? In particular, are you trying to reproduce the inward bowing of the perimeter columns prior to collapse, and their inward movement as the collapse initiated? If so, no it wouldn't - there would be no inward bowing (nothing to cause it), and I suspect that if the core columns were removed and the floor trusses remained initially intact, then the perimeter columns would be restrained from collapsing inwards.

If the collapse mechanism couldn't be replicated by the simultaneous removal of the core columns at one floor, could it be replicated by simultaneously removing the core columns at two floors? If not, how many?

If the collapse mechnism couldn't be replicated, why not?

I suspect the latter for the reasons given above, though there are plenty of people here better qualified to judge than I am.

Dave

 

[gumboot]

Just want to point out that I took "replicating collapse" to mean the vertical global collapse we saw on 9/11. If you mean more specifically, in particular the collapse mechanism, then Dave Roger is precisely correcting in pointing out you cannot replicate the 9/11 collapse by destroying core columns as the 9/11 collapse was initiated in the floor trusses, not the core.

-Gumboot

 

[einsteen]

The point is that he wonders if you could reprocude the collapse by blowing up the columns of one story (core and maybe even the perimeter columns), he is interested in the post-collapse initiation process.

The official story indeed says: yes

 

[Architect]

No, it doesn't.

Dropping the core would not explain the deformation and buckling failure of the external envelope.

 

[gumboot]

The point is that he wonders if you could reprocude the collapse by blowing up the columns of one story (core and maybe even the perimeter columns), he is interested in the post-collapse initiation process.

The official story indeed says: yes

Let's wait for him/her to clarify for himself/herself.

To be precise, the NIST study seems to indicate that if you removed four or five floors of the tower at once you would get a global collapse.

-Gumboot

 

[ref]

The point is that he wonders if you could reprocude the collapse by blowing up the columns of one story (core and maybe even the perimeter columns), he is interested in the post-collapse initiation process.

The official story indeed says: yes

Once the upper mass and structure of the WTC drops to the below structure the like of WTC, it will collapse. Didn't Bazant calculate, that only a drop of 0,5 meters for the upper part would have been enough to produce the result we all saw.

 

[coughymachine]

I think it's possible, but not guaranteed.

What does this have to do with "the collapse of WTC1 and 2" (the title of this thread)?

-Gumboot

ETA. Welcome to the forums.

Thanks for the welcome.

The relevance is simply that the hypothetical is based around a building similar to either of the twin towers. I want to try to understand whether there would be any practical difference, in terms of the resulting collapse mechanism, between the initiating event described by NIST and a blast event as set out in the hypothesis.

 

[gumboot]

Thanks for the welcome.

The relevance is simply that the hypothetical is based around a building similar to either of the twin towers. I want to try to understand whether there would be any practical difference, in terms of the resulting collapse mechanism, between the initiating event described by NIST and a blast event as set out in the hypothesis.

What you need to appreciate is that the NIST collapse findings indicate a collapse initiation around the floor trusses and the exterior columns.

Your theoretical scenario is based around failure (due to explosives) of the core columns.

I think it's certainly true that the consensus view is a total failure of one floor would result in a global collapse much like we saw on 9/11.

Would removing just the core at one floor result in an entire floor failure?

Probably, but I don't know. The weight division was meant to be 50/50 and a failure of the exterior columns on 9/11 caused a core failure, so I suppose logically a core failure would result in an exterior column failure.

-Gumboot

 

[coughymachine]

No, it doesn't.

Dropping the core would not explain the deformation and buckling failure of the external envelope.

Presumably, without a core to attach to, the trusses would sag and deform the perimeter.

 

[The Doc]

http://video.google.com/videoplay?docid=-5405555553528290546

The above video clearly shows the perimeter columns of the World Trade Center bow inwards before the collapse. This was due to the sagging floor trusses pulling them inwards as they sagged further and further.

To replicate the collapse of the towers, you would somehow need to get the floor trusses to sag enough to pull those perimeter columns inward. Fire will do this, explosives and thermite will not.

Blowing all the core columns on one floor of the tower would also create a visible and audible explosion outside of the trade centers. This was not seen on 9/11.

 

[Architect]

Let's wait for him/her to clarify for himself/herself.

To be precise, the NIST study seems to indicate that if you removed four or five floors of the tower at once you would get a global collapse.

-Gumboot

Point me in the direction of that, please; a (so far) polite young chap at LCF is questioning me on it and I explained that one would have to fully model it to know. Obviously I don't want to waste his time if someone has done it already.

 

[Dave Rogers]

Thanks for the welcome.

The relevance is simply that the hypothetical is based around a building similar to either of the twin towers. I want to try to understand whether there would be any practical difference, in terms of the resulting collapse mechanism, between the initiating event described by NIST and a blast event as set out in the hypothesis.

The consensus that seems to be emerging, then, is that specific observables relating to the collapse initiation would be visibly different, but that once the collapse had commenced the overall behaviour would be similar (not necessarily identical - the blast hypothesis would need to be asymmetrical to produce the observed rotations of both falling sections). This is consistent with the opinion that NIST were correct to study collapse initiation in detail but not to devote similar effort to modelling the resulting collapse, although I suspect that it would be a circular argument to suggest that one point justifies the other.

Oh yes - welcome to the forum from me too. You've picked an interesting topic to come in with.

Dave

 

[The Doc]

Presumably, without a core to attach to, the trusses would sag and deform the perimeter.

They wouldn't "sag" so to speak. Sagging is a result of the metal bending. Not breaking.

 

[Architect]

Presumably, without a core to attach to, the trusses would sag and deform the perimeter.

Oversimplification. The trusses would collapse.

 

[coughymachine]

I think it's certainly true that the consensus view is a total failure of one floor would result in a global collapse much like we saw on 9/11.

This is the point I wanted to clarify.

 

[coughymachine]

Oversimplification. The trusses would collapse.

You're right - I'm a bit loose with my terminology here.

What I meant to say was that, with the core removed, the trusses would be lost and the perimeter column would have been unable to support the weight of the building above the 'event'.

In such circumstances, the upper portion would have fallen x number of floors without or with limited resistance. In your opinion, if this wouldn't have led to a similar 'global collapse', how might it have looked or behaved differently?