Is there a legitimate reason to question the official narrative*?

[BasqueArch]

Core Suddenly Drops 23 Feet​

Wall Slowly Brends 54 Inches​

http://www.internationalskeptics.com/forums/showthread.php?postid=9060359#post9060359​

 

[Tony Szamboti]

For those who have difficulty understanding, in their report on the Twin Towers NIST admitted that the sagging trusses did not cause inward bowing of the exterior in their model and stated that they had to add artificial lateral forces to the columns to cause it to happen.

So all the belly aching about catenary forces etc. isn't going to change the reality that they couldn't get it to happen in their model. I am not saying catenaries don't generate horizontal forces, just that it apparently wasn't enough force in this case to be the cause for the inward bowing of the exterior columns.

 

[LSSBB]

For those who have difficulty understanding, in their report on the Twin Towers NIST admitted that the sagging trusses did not cause inward bowing of the exterior in their model and stated that they had to add artificial lateral forces to the columns to cause it to happen.

So all the belly aching about catenary forces etc. isn't going to change the reality that they couldn't get it to happen in their model. I am not saying catenaries don't generate horizontal forces, just that it apparently wasn't enough force to be the cause for the inward bowing of the exterior columns.

Why are you clinging to NIST?

 

[Tony Szamboti]

Why are you clinging to NIST?

Do you have a better basis than NIST, where you can show sagging trusses caused the inward bowing of the exterior columns? They said they couldn't show it, and my own analyses say the same thing, so I believe them.

 

[BasqueArch]

Some years back I claimed:
"catenary sag is an effective force multiplier" - which a couple of truthers denied - pretended they didn’t comprehend. And, sadly, both of them engineers.

I counter claimed that my (then) 5yo grandson could understand it.

A couple of days later grandson visited and we did the experiment.

A catenary between two columns.

A polarity change to use horizontal vector modelling vertical pull of gravity.

Modelling the "inwards pull" induced by the "catenary sag force":

The comparson with force directly applied to cause "Inward Bowing" of the "column":

Subsequent interview of the experimental candidate:
Q: "which was easier to move the tree, Aiden, pushing the rope ot pushing the tree?"
A: "Pushing the rope made it move grandpa - I couldn't move the tree when I pushed it."

Glossary of language modifications to suit vocabulary of the volunteer participant:
Tree == column
Rope == catenary
Move == inwards bowing
etc.

The more distant "column" was of significantly smaller section modulus/moment of inertia
Section modulus/MoI == thinner

Q: "Which tree moved further Aiden"?
A: "that one Grandpa - its thinner."

I didn't explore the aspects of bending moment of columns subjected to horizontal force.
...or the more esoteric aspects of section properties.

I'm not sure about that example, it looks more like torque and the distance the force is applied from the tree . If he were pushing or pulling the rope where it is attached, the before and after might be the same.

When the compression joist top chord is bearing on the column the vector forces are all or mostly vertical. When the truss sags the top chord is in tension and the horizontal component force is maximum at the connection.

Maybe a physicist here can help.

 

[DGM]

For those who have difficulty understanding, in their report on the Twin Towers NIST admitted that the sagging trusses did not cause inward bowing of the exterior in their model and stated that they had to add artificial lateral forces to the columns to cause it to happen.

So all the belly aching about catenary forces etc. isn't going to change the reality that they couldn't get it to happen in their model. I am not saying catenaries don't generate horizontal forces, just that it apparently wasn't enough force in this case to be the cause for the inward bowing of the exterior columns.

We all know. Now, how does this help you?

Bet you have nothing.

 

[jaydeehess]

Do you have a better basis than NIST, where you can show sagging trusses caused the inward bowing of the exterior columns? They said they couldn't show it, and my own analyses say the same thing, so I believe them.

Over the years there have been several other theories for the inward bowing that do not involve ficticious explosives. Certainly in your perusal over those years you've noticed them?

In one it is considered that the NIST fea did not transfer as much load to the perimeter as was the case in reality. Increased load PLUS catenary forces then cause inward bowing.

For that matter its been noticed that its possible that a fire induced core column creep shortened the core over time and that contributed to inward bowing.

Now, when did inward bowing begin, and when did the antenna drop?

 

[BasqueArch]

Physicists Breathe Sigh of Relief​

Some Guy on the Internet Admits​

That Catenaries Do After All Produce Horizontal Forces​

 

[ozeco41]

I'm not sure about that example, it looks more like torque and the distance the force is applied from the tree . If he were pushing or pulling the rope where it is attached, the before and after might be the same.

When the compression joist top chord is bearing on the column the vector forces are all or mostly vertical. When the truss sags the top chord is in tension and the horizontal component force is maximum at the connection.

Maybe a physicist here can help.

Are you sure you are not missing the simple point by making it too complicated?

You said "Some Guy on the Internet Proves
By Sheer and Repeated Force of Will
That Catenaries do not Produce Horizontal Forces"

I said "catenary sag is an effective force multiplier"

In other words "a little bit of force in the sag direction causes a much bigger inwards pull".

I sought to prove it by a semi humorous example demonstrating that point.

I'd better cover my arse:

My apologies to all who do not appreciate a bit of humour used to illustrate a simple bit of physics.

I'll overlook the snide comment "Maybe a physicist here can help."

 

[BasqueArch]

Are you sure you are not missing the simple point by making it too complicated?

You said "Some Guy on the Internet Proves
By Sheer and Repeated Force of Will
That Catenaries do not Produce Horizontal Forces"

I said "catenary sag is an effective force multiplier"

In other words "a little bit of force in the sag direction causes a much bigger inwards pull".

I sought to prove it by a semi humorous example demonstrating that point.

I'd better cover my arse:

My apologies to all who do not appreciate a bit of humour used to illustrate a simple bit of physics.

I'll overlook the snide comment "Maybe a physicist here can help."

Snide - derogatory or insulting.
It was not a snide comment. You should relax and not be so personally uptight. You're starting to sound like those people.

 

[ozeco41]

Over the years there have been several other theories for the inward bowing that do not involve fictitious explosives. Certainly in your perusal over those years you've noticed them?

In one it is considered that the NIST fea did not transfer as much load to the perimeter as was the case in reality. Increased load PLUS catenary forces then cause inward bowing.

For that matter its been noticed that its possible that a fire induced core column creep shortened the core over time and that contributed to inward bowing.

Now, when did inward bowing begin, and when did the antenna drop?

Surely the problem here is that we are chasing Tony's arse about logic? Lets come at it from the right end. I'll do it wearing my engineering manager's hat.

There was inward bowing seems to be accepted fact.
Something caused it should go without saying.
It was either some consequence of CD OR a consequence of so called "natural" processes.
There was no CD - more rigorously there is not and never has been a pro CD hypothesis to prima facie standard to qualify as worthy of consideration.
THEREFORE for purposes of legitimate argument it was Natural until someone presents a pro CD hypothesis OR we agree to discuss a moot scenario rather than the known facts.
NIST gave some explanations.
NIST reported years after 9/11 2001
THEREFORE whether NIST was right or wrong cannot change what happened.
THEREFORE two different objectives.
Objective #1 explain what happened
Objective #2 see if NIST got it right.
We cannot assess #2 til we understand #1
So what caused it to happen?
Despite all the complicated ways of trying to explain it there seem to be only two factors.
Factor #1 Axial load
Factor #2 Pull in
Factor #3 Heating of the perimeter
(If I've missed any someone tell me and I will include it/them.)
Hypothetical assertion #1 It is highly probable that floor failure effects would cause pull in. (And that there could have been initial push out due to thermal expansion BUT that initial movement swamped by far higher pull in effects as the event progressed. That assertion open to reasoned support or disagreement.
Hypothetical assertion #2 Some quantification of the magnitude of pull in force may be of assistance. But lets avoid the traditional engineer's mistake of trying for quantification BEFORE we know WTF we are measuring. Again - open to comment.
Hypothetical Assertion #3 We can ignore temperature effects - I doubt that they were significant BUT ignoring them at this stage is conservative anyway. Same disclaimer.
Hypothetical Assertion #4 The key issue for quantification will be the interaction between axial loading including any effects from load redistributions AND pull in needed to initiate the direction of bowing and the extent of bowing up to the p delta critical point where self propagation of buckling will take over.

Now that should set a legitimate context.

And I bow out as the manager of engineers - I check the framing of the task with suitable peer referees then delegate the number crunching task to a technical level practising engineer to sweat the numbers. His use of FEA probably better than my use of slide rule. Provided he doesn't lose the plot.
(OK - my humour still not constrained. Tough.)

Ignore NIST for now and ignore CD effects until the CD proponents present a prima facie hypothesis. Or my political overlords ask CD questions.

 

[ozeco41]

Snide - derogatory or insulting.
It was not a snide comment. You should relax and not be so personally uptight. You're starting to sound like those people.

No problem - couldn't decide whether to comment or not.

You could be right. These circling troll chasing discussions do get frustrating.

Which was why I decided inject the light hearted comment - which had a bit of a sting in the principle illustrated.

Your raising the similar theme presented the opportunity.

 

[LSSBB]

Do you have a better basis than NIST, where you can show sagging trusses caused the inward bowing of the exterior columns? They said they couldn't show it, and my own analyses say the same thing, so I believe them.

Oz.

 

[jaydeehess]

Over the years there have been several other theories for the inward bowing that do not involve ficticious explosives. Certainly in your perusal over those years you've noticed them?

In one it is considered that the NIST fea did not transfer as much load to the perimeter as was the case in reality. Increased load PLUS catenary forces then cause inward bowing.

For that matter its been noticed that its possible that a fire induced core column creep shortened the core over time and that contributed to inward bowing.

Now, when did inward bowing begin, and when did the antenna drop?

Surely the problem here is that we are chasing Tony's arse about logic? Lets come at it from the right end. I'll do it wearing my engineering manager's hat.

There was inward bowing seems to be accepted fact.
Something caused it should go without saying.
It was either some consequence of CD OR a consequence of so called "natural" processes.
There was no CD - more rigorously there is not and never has been a pro CD hypothesis to prima facie standard to qualify as worthy of consideration.
.......

Covered it in my first sentence. No evidence of explosives being installed or existing therefore any contention of their use is simply born of the imagination, thus "fictitious".

ETA: IIRC there was a fight with some truthers to even acknowledge that there was inward bowing of portions of the perimeter. In similar fashion there was a great fight to get even the possibility of over 'g' being determined to have occurred,,, and then it suddenly became, somehow, evidence of CD.

 

[Grizzly Bear]

For those not catching on, tony is subtly inserting that "pancake initiation" collapse mechanism. Bear your responses with that in mind and avoid letting the conflation take hold

 

[NoahFence]

Do you have a better basis than NIST, where you can show sagging trusses caused the inward bowing of the exterior columns? They said they couldn't show it, and my own analyses say the same thing, so I believe them.

NIST didn't need to account for idiotic controlled demolition notions. They didn't need to test fire vs explosives.

Common sense and reality does that. There was no CD. Therefore we don't need NIST. Why do you?

 

[ozeco41]

Do you have a better basis than NIST, where you can show sagging trusses caused the inward bowing of the exterior columns? They said they couldn't show it, and my own analyses say the same thing, so I believe them.

Oz.

Thanks.

"Do you have a better basis than NIST." is a reasonable question but it reveals the confusion of objectives which underpins much of Tony's work. Whether NIST was right or wrong or - this case - NIST couldn't demonstrate something - does not change historic fact. So "Do you have a good and persuasive explanation...?"
1) There was Inward Bowing; AND
2) There has never been a prima facie hypothesis for CD; THEREFORE
3) IF we are interested in the cause of the IB We don’t need to consider mechanisms using CD.
4) Reasoning by competent engineers suggests a combination of axial overload and initiating pull in from floor structures. Until it passed the critical point and became self propagating.

"...where you can show sagging trusses caused the inward bowing of the exterior columns?" Strawman - the cause was multi factorial - the contribution of pull in probably defined the direction as "in" and assisted buckling that way in combination with axial loading. Dunno about heating of the columns - doubt it was significant.

"They said they couldn't show it.." I believe them. So what?

I cannot prove my hypothesis that it was Santa's custard..and I've argued that one more persuasively than most truther arguments.

"... and my own analyses say the same thing,.." We know Tony's record - the tendency to get things wrong. In AU the Evidence of Tendency is not admissible unless we have given him "reasonable notice in writing". I reckon we have written and published enough posts telling him we don't accept his arguments.

"...so I believe them." That would be true - his whole foundation is based on "belief".

 

[ozeco41]

For those not catching on, tony is subtly inserting that "pancake initiation" collapse mechanism. Bear your responses with that in mind and avoid letting the conflation take hold

I'm not sure that those two words fit in the same sentence.

Agreed. He is avoiding facing the major foundation error in all his Twin Towers claims. His posts show zero comprehension of the 3D cascade failure mechanism.

So - any port in a storm - "pancaking" will do, By his rules he doesn't need to be consistent or coherent in argument.

 

[ozeco41]

Covered it in my first sentence.

Agreed on the conclusion. I was just laying out the steps.

 

[chrismohr]

Do you have a better basis than NIST, where you can show sagging trusses caused the inward bowing of the exterior columns? They said they couldn't show it, and my own analyses say the same thing, so I believe them.

Tony I think this may be one of CTBUH's critique of NIST, because they said that NIST did not account for thermal contraction after the beams in the burned out areas of the buildings began to cool down. So we had thermal expansion, bowing against the resistance of the perimeters, sagging, then the steel stiffening as it cools down a bit AND shrinking in size while frozen in the sagged position. That pulled the buildings inward in ways not fully explained by the NIST Report, if I understood their critique correctly.