WTC7 falls at free fall speed? Why does the official story defy known laws of physics?

Originally posted by ANOK
Yes it does.

But what it doesn't confirm unequivocally is that force is enough to cause the columns to be pulled in.

So please state this explicitly so I can save the link for future reference. You are saying here that fire affected trusses in the WTC can fall into tension and exert an inward pulling force on the columns, yes?

Did you actually read what I quoted from that PDF? How can you still claim it says sagging trusses can pull in columns when clearly it explains how sagging effects only the truss and the connections. It says NOTHING about columns failing.

Here it is again in case you missed it...

The problem here is that you are not quoting from a study that investigates the effects you are talking about. The study is of a steel beam, not a truss. They are radically different structures and that is why the paper I linked you to is a study of representative trusses from the WTC, a much more specific study and conducted in part by the same firm (Arup, who are pretty well reputed).

I'll go through your quotes below.

In the initial stages of heating the restraint from the surrounding structure tends to resist the expansion of a beam...

As I have been saying, heating of the truss/beam causes it to expand, and push against the columns. It cannot push the columns outwards, because "the surrounding structure tends to resist the expansion of a beam".

You are incorrect here. The phrase 'tends to resist' does not mean that there is no motion. In Fig 4(a) you can clearly see a compression element. This is 'push out' and indeed the more detailed study I linked confirms that:

Trusses CAN sag but that is all that that says.

If the heating of the truss/beam causes run-away deflection, and the connections survive, the beam fails, not the columns.

www.fire-research.group.shef.ac.uk...

Do you not understand what that is saying? Obviously not.

This is a woeful misunderstanding of the beam study. It does not purport to investigate the conditions of columns or a representative structure. It is a technical paper on improvements in simplified simulations. This seems to have escaped you.

Luckily there's a way we can easily resolve this. You've referenced this paper as a reliable source and imbued it with authority which inherently transfers to its authors. In this case I happen to know of another paper produced by Ian Burgess and Roger Plank. It is designed to study trusses not beams and is an investigation into their behaviour, not a simplified model.

You can find it here: www.sciencedirect.com...

I believe it can also be found online for free as a PDF.

Originally posted by exponent
So please state this explicitly so I can save the link for future reference. You are saying here that fire affected trusses in the WTC can fall into tension and exert an inward pulling force on the columns, yes?

No, the trusses do not sag into tension when they are SAGGING. How can truss be both sagging from heat and fall into tension? That would be an oxymoron.

The PDF PLB supplied explains quite well what happens, but you have to read and understand it.

The problem here is that you are not quoting from a study that investigates the effects you are talking about. The study is of a steel beam, not a truss. They are radically different structures and that is why the paper I linked you to is a study of representative trusses from the WTC, a much more specific study and conducted in part by the same firm (Arup, who are pretty well reputed).

But wait, that PDF was perfectly fine when PLB tried to use it to prove the hypothesis. So now I have shown he was wrong, suddenly it's no good because it says beam instead of truss? Hilarious.



That is truss deflection, I have already said trusses can deflect, that is not the argument. What can't happen is that deflection pulls in columns. You are making an uneducated assumption.

This is a woeful misunderstanding of the beam study. It does not purport to investigate the conditions of columns or a representative structure. It is a technical paper on improvements in simplified simulations. This seems to have escaped you.

Yes it does. So why did PLB try to use it then? Maybe you should be debating him and his claim?

Luckily there's a way we can easily resolve this. You've referenced this paper as a reliable source and imbued it with authority which inherently transfers to its authors. In this case I happen to know of another paper produced by Ian Burgess and Roger Plank. It is designed to study trusses not beams and is an investigation into their behaviour, not a simplified model.

LOL OK then find a paper that says trusses and not beams eh? I didn't bring up these papers, you guys did.

All science tests use simplified models, now you are just making lame excuses to ignore, and deflect my points.

You can find it here: www.sciencedirect.com...

I believe it can also be found online for free as a PDF.

Oh yes another article you don't understand.

Here is what it says....

A numerical investigation of the structural behaviour of long-span composite truss systems, typically used in multi-storey floor construction, under fire conditions is presented. The non-linear finite element program, Vulcan, which has been specifically developed at the University of Sheffield for the analysis of structures at elevated temperatures, has been used extensively throughout. The in-fire performance of both restrained and unrestrained composite trusses is determined. The contribution of each group of members (i.e. top chord and slab, web members, bottom chord and supporting column) is investigated whilst considering various parameters such as the level of fire protection, structural modifications and deflection patterns. It is shown that, for a truss which is restrained against horizontal movement at its ends, the load-carrying mechanism undergoes a transition from bending to catenary action. Furthermore, at elevated temperatures there is a possibility of progressive buckling in the compressive web elements, which may not have been the identified failure mechanism in design. This is seen to be initiated by a significant rise of the thermal stress in the web members located within the high-shear zones towards the ends of the truss. The knowledge obtained is suitable for use when implementing performance-based design.

www.sciencedirect.com...

It doesn't even mention columns, let alone that a runway deflection of beams, or trusses, would pull in the columns they are attached to.

BTW you didn't go though all my quotes, you addressed one, which you are wrong about.

Originally posted by ANOK

Originally posted by exponent
So please state this explicitly so I can save the link for future reference. You are saying here that fire affected trusses in the WTC can fall into tension and exert an inward pulling force on the columns, yes?

No, the trusses do not sag into tension when they are SAGGING. How can truss be both sagging from heat and fall into tension? That would be an oxymoron.

That's not what I said, and I've included my quote so others can see. I said that trusses can fall into tension due to being affected by fire.

The PDF PLB supplied explains quite well what happens, but you have to read and understand it.
...
But wait, that PDF was perfectly fine when PLB tried to use it to prove the hypothesis. So now I have shown he was wrong, suddenly it's no good because it says beam instead of truss? Hilarious.

You realise I am not PLB right? I didn't link you to that PDF nor endorse it. I also hope you realise that beam vs truss is not a simple word replacement. They are entirely different elements.

That is truss deflection, I have already said trusses can deflect, that is not the argument. What can't happen is that deflection pulls in columns. You are making an uneducated assumption.

The left hand axis on that graph is Column Displacement. What do you think that means?

Yes it does. So why did PLB try to use it then? Maybe you should be debating him and his claim?

I'm debating you and your claim, you quoted from and relied upon that paper. I presented you with a better one by the same authors. You once again just read the abstract and assumed you were right.

You clearly don't have the education or practical knowledge you claim, you've made several major errors just in discussing a trivial beam paper.

LOL OK then find a paper that says trusses and not beams eh? I didn't bring up these papers, you guys did.

I am not PLB. We are not the same person. I didn't bring that paper up at all. The two I've linked you to are proper formal studies on the performance of trusses in fire. Exactly the topic you claim to have knowledge on, yet you don't read these papers and don't accept their results or conclusions.

All science tests use simplified models, now you are just making lame excuses to ignore, and deflect my points.

Certainly, but all that paper shows is that their simplified model matches up well with a real model. It does not investigate the performance of a representative structure in fire. The ones I linked do, because that's how science works. You don't just pick a paper in a sorta similar subject, assume that beams and trusses are the same and then make guesses.

BTW you didn't go though all my quotes, you addressed one, which you are wrong about.

I'm not about to go skimming over every post. If I missed something important please link it or requote it, thanks.

reply to post by exponent


Please refer back to this reply for your answer...

www.abovetopsecret.com...

That PDF explains quite clearly what centenary action does when a beam, OR TRUSS, heats up and expands when pined between two columns. Thank you PLB for pointing it out to me.

Surely the PDF is still valid right, or is it not valid now I have explained it doesn't say what you all want it to?

I can't help it if you can't, or you refuse, to understand it.

Originally posted by ANOK
reply to post by exponent

 

Please refer back to this reply for your answer...

www.abovetopsecret.com...

That PDF explains quite clearly what centenary action does when a beam, OR TRUSS, heats up and expands when pined between two columns. Thank you PLB for pointing it out to me.

Surely the PDF is still valid right, or is it not valid now I have explained it doesn't say what you all want it to?

Your understanding is not correct and I have already replied explaining it. No matter how many times you repeat yourself 'tends to resist' does not mean 'deflection is impossible'.

I can't help it if you can't, or you refuse, to understand it.

I am not the one who needs help, the studies I posted are reviewed, specific and relevant. You refuse to do anything but repeat yourself over and over and over again.

Please, talk to a local professional, perhaps they can convince you.

reply to post by exponent


www.abovetopsecret.com...

www.abovetopsecret.com...

Originally posted by ANOK
reply to post by exponent

 

www.abovetopsecret.com...

www.abovetopsecret.com...

So no matter what I say to you, you're just going to repeat the same thing over and over again.

Thank you for proving your position is dogmatic, not based on facts. My position is based on the actual reality of what occurred. The reality that more than one organisation has demonstrated exactly what you say is impossible and when shown it you put your fingers in your ears and deny it's been said at all.

Face reality ANOK. Trusses can exert an inward pulling force, something you've now admitted. That force can overwhelm columns, something several papers have proven. That effect brought down the WTC. Something NIST proved and video footage clearly shows.

You have destroyed your own case with your hubris. Congratulations.

Originally posted by ANOK
reply to post by exponent

 

www.abovetopsecret.com...

www.abovetopsecret.com...

You're fighting a losing battle Anok, 'exponent' will never listen. They have fixed ideas and will not deviate from those ideas, whether they are right or wrong.

Judging by what they write, it seems they are just here to troll, I've seen so many errors and made up BS in their comments, that quite frankly I do not bother to read them from the like of 'exponent'.

Your comments 'Anok' are always on point, maybe because you understand what it is your discussing, and other just try and rubbish your comments with some of the worse pseudo-science I've ever read, they probably work for NIST, where no lie is too big!

Originally posted by DeeKlassified

Originally posted by ANOK
reply to post by exponent

 

www.abovetopsecret.com...

www.abovetopsecret.com...

You're fighting a losing battle Anok, 'exponent' will never listen. They have fixed ideas and will not deviate from those ideas, whether they are right or wrong.

The irony is that you are quoting someone who is simply repeating himself without answering his critics. That you can't see that is frankly very funny to me.

Apologies for the fairly substance-less post but I think I have illustrated my position and the facts quite clearly.

Originally posted by DeeKlassified
You're fighting a losing battle Anok, 'exponent' will never listen. They have fixed ideas and will not deviate from those ideas, whether they are right or wrong.

But I have to reply, because some stared his post.

Just ask esdad.