Building Collapses in Rio

Originally posted by ANOK
Again your opening statement shows you are confused.

FoS is NEVER meaningless, it is the structural capacity of the building. A 'messy' collapse doesn't mean physics is ignored.

The only one ignoring things here is you. IWW has been explaining it to you in excruciating detail. Your response? Skim his explanation, pluck something from it, frame it out of context, and shower the thread with some more physics-challenged asininity.

"doesn't mean physics is ignored"

What physics? Your ACME physics where equal and opposite forces means equal and opposite damage, and where FoS is somehow applicable in off-axis collision interaction?

You can penetrate steel with air. (High explosives) Penetrate steel with water (Water jet cutters)

Hell, in the domain of hypervelocity, you can do grave damage to a satellite or spacecraft in orbit when a speck of space dust hits it.

A 1-kg object impacting at 10 km/s, for example, is probably capable of catastrophically breaking up a 1,000-kg spacecraft if it strikes a high-density element in the spacecraft. In such a breakup, numerous fragments larger than 1 kg would be created.

Wikipedia: Space Debris

Come again, ANOK? Care to "explain" to all of us your loopy bastardization of Newton again? What serves you best right now is silent, attentive humility, not a selective reading and subsequent contextomy of somebody infinitely more qualified, graciously willing to explain it to you, apparently to no avail.

Originally posted by ANOK

Originally posted by IrishWristwatch

Design FOS is meaningless in a messy collapse.

Again your opening statement shows you are confused.

FoS is NEVER meaningless, it is the structural capacity of the building. A 'messy' collapse doesn't mean physics is ignored.

I'm sorry, but this has long since moved past ridiculous.

One of my pet peeves is people who are obviously utterly and totally clueless about physics proclaiming their imaginary version of pseudoscientific mumbo jumbo as fact. The stark contrast between boldly proclaimed falsehoods and reality sticks in my craw, probably because I had to work my ass off with problems of this nature to get passing grades. You are just making stuff up.

Suppose the typical tower had a typical, average FOS of 5, when assembled according to print. Some scholarly estimates put it as low as 2.5, no plausible estimate puts it above 6. Now, I'm going to guesstimate some things for an order of magnitude answer - don't ignore the disclaimer! The widest short axis dimension in any core column is (to the best of my knowledge) 10 inches. The perimeter columns are roughly 14.5 inches square and spaced 40 inches center to center. Therefore, if a tower were to be cut on a horizontal plane and displaced only 15 inches, all perimeter ends and and least half the core ends will be in opposition to - AIR!

Since load was split equally between core and perimeter, that's a reduction in as-built capacity to 25% of the original value, NOT including loss of contact surface in the assumed remaining 25% of columns. The FOS of the optimal configuration (by print) is reduced to 1.25, a mere 25% margin of safety. This residual capacity is barely enough to support the static load, assuming a uniform distribution. It would not even withstand sudden loading (defined to be bringing the load in CONTACT and releasing); that requires a minimum FOS of 2. Forget about arresting any finite drop height at all.

Momentum counts, and it counts in exactly the way I think it does. It is encumbent on you to absorb this remedial physics, and pontificate less.

To reduce the residual capacity to FOS = 1.25, it was only necessary to displace the upper portion by 15", or about 0.6% of its width! Now, let's add some tilt. Recall the article I posted above. Leslie Robertson was concerned with building collapse due to a building undetectably out of plumb. While it is difficult (not impossible) to put numbers on it, I'd say capacity reduces proportionally to eccentricity over a small range of tilt, with at least a reduction in capacity by half at 20 degrees inclination. According to this very generous guess, a 10 degree tilt would would lower the FOS to 1.

At that point, the upper section is on the threshold of overloading the capacity of the lower. If it does, it will descend, even though everything above and below the imaginary cut is intact. The effective FOS is 1, and if overloaded, it will decrease dramatically - that's what steel does when it fails. The first significant resistance the hypothetical collapse will encounter is entanglement of spandrels after 1 - 2m. Of course, it has acquired MOMENTUM by that point, so the resistance is going to have to arrest that motion AND support the static load.

But the spandrels were designed to mediate loads between the perimeter columns in the manner of a Vierendeel truss. This does not equate to an FOS where surfaces which were never meant to be the load bearing regions are impacted. It wouldn't be unreasonable to claim these suboptimal load paths could not even support the static load. The load imposed is is unstable and immediately degenerates to a bending moment. Where spandrel meets in knife-edge orientation, St. Venant's principle dictates deformation until adequate load distribution, which will allow the upper section to drop further, lose more potential energy and, in turn, acquire more kinetic energy and MOMENTUM. Good luck finding equilibrium and arrest.

FOS is meaningless in messy collapse. Get over it.

Thank you, SnowCrash. You have a compactness of expression I envy.

What seems to be mainly at issue here is if the upper block (unfortunate term) is broken up, it becomes incapable of doing damage. Not true. We are talking about an avalanche of debris thundering downward, accumulating and accruing matter as it advances. The rubble is layered: the layer at the collision front isn't as fragmented as the layers on top of that which have already seen multiple collisions. How are the floors, whose connections have roughly the same capacity throughout the building, going to arrest collapse? We are not talking about blocks here, we are talking about a massive accumulation of loosely associated rubble impacting a flat, concrete surface of limited thickness supported by trusses designed to carry desks, chairs, cabinets, office furnishings and people, not a catastrophic collapse, a downwardly accelerating mass of heavy debris. Imaginary physics isn't going to change the hard fact that the floors were overloaded every collapse iteration, with mass reigning down over the 3.7 meter distance from ceiling to ground level.

Originally posted by ANOK

Factor of safety for structural applications is the ratio of the allowable working unit stress, allowable stress or working stress. The term was originated for determining allowable stress. The ultimate strength of a given material divided by an arbitrary factor of safety, dependant on material and the use to which it is to be put, gives the allowable stress.

Your quote applies to structures and subcomponents within the context of design spec only. Do you still hold to the notion that a haphazard jumble of parts has the same properties that the same parts assembled according to print do? Because that is patently false.

Unless you know the FoS of a component you can not claim x amount of force would cause failure. You have to know the FoS to do that calculation.

So? What does that have to do with anything? The FOS can, and has been, approximated MANY times according to sound engineering calculations, usually putting it in the range of 2.5 to 3.0. The only engineering calculation I know of which puts it higher is 6 from Tony Szamboti. Big deal. Call it 10. Sufficient impact velocity will overcome it anyway. MOMENTUM!!!

That is why we laugh when people ask for calculations to prove gravity could not cause the collapses.

Who is we? Are you part of some hive? Do you think for yourself (besides the aluminum cladding IB thing, you're the ONLY person I've seen claim such balderdash in all my years of looking at this)?

There are excellent engineering analyses which show gravity is sufficient to progress collapse. You obviously haven't examined them, nor is there a hope of you understanding them if you did.

You only think it's not important because it's not part of the OS.

Last refuge of a scoundrel with no argument and not a leg to stand on.

Originally posted by ANOK
The top did not have the mass to do any destruction.

Absolutely false. Given the understanding of physics you've displayed to this point, it would be reasonable to assume you're claiming the top did not have any mass, but I'll give you the benefit of the doubt. Most of the 'hive' really do think the mass is 'used up', essentially gone, can do no damage. At least you recognize mass, but stubbornly refuse to recognize momentum.

NIST estimated a floor could hold the mass of 12 floors statically. If the response to sudden loading were linear (which it is not), just bringing 6 floors worth of load in contact and releasing would overload the underlying floor. Drop the load from > 3m, and the floor will only slow it down at collision, because of laws of conservation of momentum. I don't know what the threshold of impinging mass needs to be for any given height, but it could be estimated and I wouldn't be surprised if ONE floor dropping one story overloads the one below.

ps, I see that you choose to not post anymore in the thread where I confronted you with your miserable understanding of physics. I think denial is indeed your best approach to cope with it.

What are you talking about? What thread? Confront me now genius.

You've done me the same way on more than one occasion. Dodging does not an argument make.

Originally posted by IrishWristwatch
Thank you, SnowCrash. You have a compactness of expression I envy.

I'd trade that for a more "Turing-complete" scientific and engineering vocabulary, like yours, combined with some much needed forbearance, any day of the week. Imagine a light bulb slowly ramping up in light intensity when I read your posts.

The dynamic overload of the floors, and even the columns in a hypothetical, picture perfect column-on-column impact, is one thing I accepted quite early. So I was drawn to the "jolt" analysis: if the building is crumbling in an increasingly indistinguishable sequence of closely spaced (in time) "bumps", then where were the jolts?

Turns out I ignored the filter through which I was looking: the video. A television camera is not a high fidelity scientific measuring apparatus, but that's only the tip of the iceberg: the oversimplification of the mechanism, such as proposed by Chandler, too, clouded my perception. And... it seems to escape some that Bazant formulated a scenario most biased towards collapse arrest, so that if the outcome of his analysis was collapse progression, it had to be so in all less optimistic variations, too.

Who here is going to take on the mutually exclusive claims posited by Szamboti & MacQueen on the one hand (succession of jolts) and Chandler on the other (continuous average resistance)? Can we not see they can't both be true, and as such, at the very least one of those two explanations is non-applicable? Wherever my knowledge of mechanics and engineering is lacking, that much I can certainly grasp immediately. However, as we've seen, anything can be artfully hand waved with the right amount of emotion-based reasoning.

This discussion, like all discussions bound for stalemate, is fueled by one giant argument from incredulity: the buildings could not have collapsed the way they did. It should be about how much chemical and physical evidence for explosions we have. Positive evidence, not negative evidence. Where are those explosions relayed by firefighters, captured on cameras close to the WTC, with microphones picking up a continuous roar (this time, it isn't about detecting pixels showing jolt, and the audio sampling rate is thousands of times per second, not 30 as in video) rather than a succession of blasts from start to finish, commensurate with a top-down demolition overkill capable of creating the carnage cited as more evidence for 'controlled' demolition?

And where are the hundreds of photos showing columns cut in similar ways at critical intersections? What do we have? One? Two? Kurt Sonnenfeld anyone? What happened to all the hype? How long can the CD-ers keep their heads in the sand denying every possible explanation at least partially involving natural collapse phenomena with an amalgam of cringe-inducing ACME pseudophysics on par with the guffaw-triggering pseudobiological folly of creationist crackpots?

Almost missed this.

So you're agreeing with me? Sagging trusses could not pull in columns?

Yes.

Originally posted by IrishWristwatch
Almost missed this.

So you're agreeing with me? Sagging trusses could not pull in columns?

Yes.

Yes they can as they cool.

Originally posted by samkent

Yes they can as they cool.

No they can't. The trusses would still not have the energy to pull in columns. What about the bolts, again wouldn't they fail before the columns, or do you think the bolts were stronger than massive box columns?

How in less than one hour did sagging trusses have time to cool?

C'mon think man.

Just to clarify it's not that sagging trusses can't pull inwards, that is a theory dependent on the heat and the components. For example a large truss being held up by small columns that was heated up for long enough could theoretically pull in the columns. But the trusses in the WTC were not large enough to pull in the columns, that were much more massive than the truss, and were connected with bolts that would be the weak point. Bolts would break before columns could be pulled in.

A lot of the times you guys argue theories that can work in some conditions, and pretend that it happens in all conditions.

Originally posted by IrishWristwatch

Absolutely false. Given the understanding of physics you've displayed to this point, it would be reasonable to assume you're claiming the top did not have any mass, but I'll give you the benefit of the doubt. Most of the 'hive' really do think the mass is 'used up', essentially gone, can do no damage. At least you recognize mass, but stubbornly refuse to recognize momentum.

My understanding of physics? But I'm right about the trusses not being able to pull on columns?

I did not say the top had no mass, please learn to read.

Listen carefully, here is the simple version just for you...The top COULD do damage, BUT it could NOT do damage and NOT be damaged ITSELF.

Is that simple enough to understand?

Equal opposite reaction, and conservation of momentum laws explain why. Something OSers keep trying to pretend are not relevant.

Originally posted by ANOK

Originally posted by IrishWristwatch

Absolutely false. Given the understanding of physics you've displayed to this point, it would be reasonable to assume you're claiming the top did not have any mass, but I'll give you the benefit of the doubt. Most of the 'hive' really do think the mass is 'used up', essentially gone, can do no damage. At least you recognize mass, but stubbornly refuse to recognize momentum.

My understanding of physics? But I'm right about the trusses not being able to pull on columns?

Even a broken clock is right twice a day. Besides, I don't know if you or I are correct on this issue. It is my opinion.

I did not say the top had no mass, please learn to read.

I acknowledged it. You learn to read, or at least finish the sentence you started. Skimming doesn't work with me, and it doesn't work for you.

Listen carefully, here is the simple version just for you...The top COULD do damage, BUT it could NOT do damage and NOT be damaged ITSELF.

Another duh. I've never said otherwise. You're tilting at windmills.

Originally posted by samkent

Originally posted by IrishWristwatch
Almost missed this.

So you're agreeing with me? Sagging trusses could not pull in columns?

Yes.

Yes they can as they cool.

Please do elaborate.

Originally posted by IrishWristwatch
Almost missed this.

So you're agreeing with me? Sagging trusses could not pull in columns?

Yes.

Irish, I'm curious, if the trusses did not pull in on the columns, what are the alternate theories as to the cause of the inward bowing?

Actually, I'll take an answer from anyone.

Originally posted by ANOK
C'mon think man.

Is this self-parody?

Originally posted by IrishWristwatch
Even a broken clock is right twice a day. Besides, I don't know if you or I are correct on this issue. It is my opinion.

Very droll, now how would I come to my conclusion, that you agree with, if I didn't understand basic physics?

I acknowledged it. You learn to read, or at least finish the sentence you started. Skimming doesn't work with me, and it doesn't work for you.

You said this...

it would be reasonable to assume you're claiming the top did not have any mass

It's all I felt like replying to, sorry lots of posts to reply to and my back can only stand so much typing at the computer.
Anyway I thought it made the rest of your post irrelevant, because you based it on a misunderstanding in the first place.

Another duh. I've never said otherwise. You're tilting at windmills.

So why do you keep saying I don't know physics? Why do you keep misinterpreting what I say?

Yes you did say otherwise...

it would be reasonable to assume you're claiming the top did not have any mass

Stop changing your story.

Originally posted by snowcrash911

Originally posted by ANOK
C'mon think man.

Is this self-parody?

You think the trusses could heat up enough to sag and cool down in less than an hour?

Really?

You don't think either do you?

Originally posted by ANOK
Just to clarify it's not that sagging trusses can't pull inwards, that is a theory dependent on the heat and the components. For example a large truss being held up by small columns that was heated up for long enough could theoretically pull in the columns. But the trusses in the WTC were not large enough to pull in the columns, that were much more massive than the truss, and were connected with bolts that would be the weak point. Bolts would break before columns could be pulled in.

A lot of the times you guys argue theories that can work in some conditions, and pretend that it happens in all conditions.

So lets review what you were saying very recently:

I have explained to you many times why sagging trusses can not put a pulling force on the columns, and you have failed to address my points every time.

And now that you realize your massive blunder, which demonstrates your understanding in physics is terrible, you pretend as if you always understood that sagging trusses can have an inward pull force. On top of it you create a straw man argument, as if anyone has been claiming "that it happens in all conditions".

You have been exposed as the disingenuous failure at physics that you are.

Originally posted by DrEugeneFixer

Originally posted by IrishWristwatch
Almost missed this.

So you're agreeing with me? Sagging trusses could not pull in columns?

Yes.

Irish, I'm curious, if the trusses did not pull in on the columns, what are the alternate theories as to the cause of the inward bowing?

Actually, I'll take an answer from anyone.

edit on 1/30/2012 by DrEugeneFixer because: (no reason given)

I think core creep led to the south wall being overloaded in WTC1. It's very hard to justify this with an explanation, at least a short one. The belief stems from evidence which demands an explanation. There is some fairly strong evidence the antenna did descend very slowly prior to initiation - true vertical motion which has been typically ascribed to tilt (which did happen). This is why I believe core creep is involved. I can't propose a mechanism for the core failure, and WTC2 is still an engima to me.

On the other side of the coin, I reject pull-in since the caternary sag angle to achieve the effect I estimate to be in excess of 15 degrees, and the study by Vlassis I cited earlier indicated seismically qualified connections generally fail within a rotation angle of 0.05 radians, or less than 3 degrees. 15 degrees is wayyy beyond what the average connection assembly can handle, let alone pull in those perimeters after the plastic deformation, mostly ductile elongation and bending. Those were some mighty special lawnmower bolts.

While I have a problem with sagging trusses getting enough of a horizontal component of force to pull in the perimeters under those conditions, swapping cause with effect poses no issues. The columns can bow, and the floors will distort accordingly, along for the ride. They may sag, or not. At some point, they would definitely be prone to detachment, thus leaving the already failing perimeters unsupported over a greater length, reducing capacity, etc. Vicious circle.

So, between the apparent inability of the connections to hold in this situation, and the apparent evidence of vertical antenna creep, I'm forced to favor core failure.

Originally posted by ANOK

Originally posted by IrishWristwatch
Even a broken clock is right twice a day. Besides, I don't know if you or I are correct on this issue. It is my opinion.

Very droll, now how would I come to my conclusion, that you agree with, if I didn't understand basic physics?

If you'll note my prior post, you'll see there is some overlap in our arguments, but not a lot. Same conclusions, different reason. I'm basing my assessment of your skills on the ongoing stream of pseudophysics much more than an isolated incident, which may just be a lucky call on lawnmower bolts. Or maybe you heard it from someone else. Or maybe we're both wrong.

You said this...

it would be reasonable to assume you're claiming the top did not have any mass

It's good form to include ellipses to avoid being called on obvious quote mining. I said "Given the understanding of physics you've displayed to this point, it would be reasonable to assume you're claiming the top did not have any mass, but I'll give you the benefit of the doubt."

The omission is glaring and dishonest.

So why do you keep saying I don't know physics?

Because of all the mistakes you make, and false claims you identify as physical law. I will say this, you can take a punch and keep coming back like nothing had happened... like you didn't even read it.

Why do you keep misinterpreting what I say?

Aside from your obvious quote mining above, name one instance where I've misinterpreted what you've said.


There are an awful lot of unanwered, completely ignored questions from me to you, stretching a ways back. Perhaps you thought they were rhetorical. Most weren't. Your persistent inability to directly address objections doesn't make them go away. You are wrong as can be about 95% of the time you post. Incredible.