OOS Collapse Propagation Model

[beachnut]

I don't mean to imply anything. I mean to suggest that grid schemes... the concept rejected for the twin towers might not collapse completely... UNDER SOME CIRCUMSTANCES that Hull and Core would.

I don't know how to engineer CD except the few youtubes I've seen.

I see no evidence of CD on 9/11.

So you have no evidence for other buildings can't have a global collapse; it was BS.
There is no proof for your, suggestion. It is simple BS. Got it, you are not interested in more than spreading some BS on the subject, asking questions you can't answer, and generally...

When in Nevada City, I am buying the beer... PM me when that occurs...

 

[JSanderO]

JSanderO, Please read your statement 10 times to yourself and explain how you're not placing the blame on Mr Robertson. Unless your claiming the PANYNJ altered the design or constructions to fit their needs, the blame you suggest has only one place to go.

Of course he and his clients, and agencies having jurisdiction, and Yamasaki are responsible for the design of the project.

Who else would be?

Blame for what?

 

[DGM]

Of course he and his clients, and agencies having jurisdiction, and Yamasaki are responsible for the design of the project.

Who else would be?

Blame for what?

You tell me. You imply that the design was at fault for the global collapse. You also can't show that any other design would not do the samething given the same circumstance.

For me, a Boeing 767 at (near) full load and speed was responsible. I doubt the ESB or any other building would have done much better.

Personally, I think this whole argument is silly.

 

[Newtons Bit]

Assuming the same connection type.... are you saying that a grided structure would completely collapse and a hull and core with long span column free would not? Or they both would collapse the same?

Ugh.

 

[BasqueArch]

You know, it’s pretty ugly for those in the building trades to listen to someone loudly and repeatedly mouth off about things he doesn’t know what he’s talking about.

 

[JSanderO]

You tell me. You imply that the design was at fault for the global collapse. You also can't show that any other design would not do the samething given the same circumstance.

For me, a Boeing 767 at (near) full load and speed was responsible. I doubt the ESB or any other building would have done much better.

Personally, I think this whole argument is silly.

That is a valid POV. I disagree and I am not in the business of proving anything. I think to deny that design plays a role in a collapse is to be in denial.

The discussion is silly because no one is prepared to look into the building's details and see how things unfolded. It IS a childish discussion!

 

[JSanderO]

Ugh.

Thank you for that brilliant answer!

 

[JSanderO]

You know, it’s pretty ugly for those in the building trades to listen to someone loudly and repeatedly mouth off about things he doesn’t know what he’s talking about.

How do you know what I know? or what my qualifications are? What qualifications does one need to have to participate in the discussion of a structural collapse? or a nuclear plant disaster? or the Challenger disaster?

I happen to BE in the "building trade" since 1972... and I worked for Emery Roth & Sons to boot.

Have you ever been inside the Twin Towers?

 

[DGM]

I think to deny that design plays a role in a collapse is to be in denial.

I agree that design plays a role in the collapse, it has to. I never said it didn't. I just don't see how this design (OOS) has been shown to be inferior than any other (practical design). Do you disagree this this (outside of a personal view)?

 

[WilliamSeger]

The discussion is silly because no one is prepared to look into the building's details and see how things unfolded. It IS a childish discussion!

How can you say I'm not prepared to look into the details when I've been begging for them? You say you've looked into the details and it helped you understand what happened, but if you were hunting for design flaws, then it sure seems you've completely missed the target. The structure was designed to withstand a large plane crash, and it did. The problem was, nothing else about the building was designed to withstand a large plane crash -- most critically, the exits and all the fire suppression systems. That's why so many died, not because of OOS.

 

[JSanderO]

How can you say I'm not prepared to look into the details when I've been begging for them? You say you've looked into the details and it helped you understand what happened, but if you were hunting for design flaws, then it sure seems you've completely missed the target. The structure was designed to withstand a large plane crash, and it did. The problem was, nothing else about the building was designed to withstand a large plane crash -- most critically, the exits and all the fire suppression systems. That's why so many died, not because of OOS.

well.... if the was some manner of arrest or not the entire oos floor went....and not total collapse in 10 seconds... maybe more would have survived.

 

[DGM]

well.... if the was some manner of arrest or not the entire oos floor went....and not total collapse in 10 seconds... maybe more would have survived.

Certainly none above the impact zone. If the design was not able to flex and respond to the impact it could have collapsed immediately. Maybe not total but, it makes you appreciate the fact the WTC design flexed and did not collapse right away.

 

[Bravin Neff]

well.... if the was some manner of arrest or not the entire oos floor went....and not total collapse in 10 seconds... maybe more would have survived.

In the B&Z argument - yes, the limit case argument - one conclusion was that the elastic response potential of the building was an order of magnitude insufficient to arrest the collapse, and that's with the ridiculous assumptions in favor of collapse arrest (axial alignment of all columns, etc.). In the actual collapse scenario, it was probably 2 orders of magnitude insufficient.

Using that as a backdrop, you seem to be arguing that in some hypothetical alternate WTC design, one with a more conventional grid, it would have taken up this order-of-magnitude deficiency - and then actually more on top of that. It would have needed to add 2 full orders of magnitude arrest potential above what the WTC towers actually had. There is no way a reasonable person believes this.

But you have to believe it, if you really want to blame the design (and oos).

 

[JSanderO]

Certainly none above the impact zone. If the design was not able to flex and respond to the impact it could have collapsed immediately. Maybe not total but, it makes you appreciate the fact the WTC design flexed and did not collapse right away.

hold on a second... why does it have to flex?

What if the jet just sheared columns etc.. and all the energy of the impact severed them and that's it?

Do you think another design slammed by a jet would topple over? or would have every joint fail?

How many columns CAN a plane actually take out... in a 30x30 foot grid?

Do you think the towers' facade mitigated structural damage?

 

[Bravin Neff]

...it makes you appreciate the fact the WTC design flexed and did not collapse right away.

I think one could reasonably argue the flexing and not-collapsing-right-away feature literally allowed hundreds if not thousands of people to survive.

 

[JSanderO]

In the B&Z argument - yes, the limit case argument - one conclusion was that the elastic response potential of the building was an order of magnitude insufficient to arrest the collapse, and that's with the ridiculous assumptions in favor of collapse arrest (axial alignment of all columns, etc.). In the actual collapse scenario, it was probably 2 orders of magnitude insufficient.

Using that as a backdrop, you seem to be arguing that in some hypothetical alternate WTC design, one with a more conventional grid, it would have taken up this order-of-magnitude deficiency - and then actually more on top of that. It would have needed to add 2 full orders of magnitude arrest potential above what the WTC towers actually had. There is no way a reasonable person believes this.

But you have to believe it, if you really want to blame the design (and oos).

Disclaimer... I am not going to argue a paper I haven't read and probably can't understand if I did.

HOWEVER.. did Mr B assume all the mass from the top section would "drop" or crush or whatever and this would destroy the tower?

Why assume all the mass from above the impact is in play? Why not assume 1/3 of it was "in play?

 

[JSanderO]

I think one could reasonably argue the flexing and not-collapsing-right-away feature literally allowed hundreds if not thousands of people to survive.

Please tell me how a too stiff steel building would ... instantly collapse. Is that what you are saying?

 

[DGM]

hold on a second... why does it have to flex?

For the same reason a race car body has to crumple and tear away. To absorb energy without inflicting damage to structural parts. You're safer in a 2015 Toyota into a tree then a '57' Buick for the same reason.

 

[Bravin Neff]

Why assume all the mass from above the impact is in play? Why not assume 1/3 of it was "in play?

I'm not sure what you're getting at, but you seem to be suggesting that something less than the total is a more realistic assumption.

However, to get to collapse arrest, B&Z would have to assume only 1/10 of the mass was in play, and that's still assuming perfect collisions with columns axially aligned. If my off hand remark is correct, that in the actual scenario the building's arrest potential was 2 orders of magnitude insufficient, then B&Z would then need to assume, corresponding to this estimate, that only 1/100 of the mass was in play.

Why would anyone do that? That's not anything what it looked like.

 

[Bravin Neff]

Please tell me how a too stiff steel building would ... instantly collapse. Is that what you are saying?

I was going along with DGM's statement that the flexing bought some time.