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Split from: First Impressions are everything...

jmercer said:

I split this thread so you folks could continue your discussion while not disrupting TAM's thread.

Carry on. :)

Replying to this modbox in thread will be off topic  Posted By: jmercer
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Thanks, I don't feel so guilty about posting now.
 
Augustine said:
Frankly I am astonished that anyone working as an engineer would write this kind of tripe.
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Yes, most people's initial reaction when confronted with this is astonishment. It's a similar feeling to the one you get when you realise that your childish notions of things being "all good" and "all bad" get blown away by education.

I will ask you one question. If we only base engineering decisions on truth why do safety factors exist?

Why do the designers in my field spend days modelling theoretically "perfect" stresses and temperatures and then put a safety factor of 2.5 on the design? The model must be the truth because it is based upon indisputable facts about the material it is modelling? Why waste the cost of the redundancy in the design just because the designer only has an opinion that he needs it when the facts say he doesn't?

Why is the theoretical thermal simulator we use unable to predict a certain defect in a component when all the data and modelling it contains are based upon facts? Is the computer lying?
 
William Rea said:
Sorry to break it to you Beachnut but, there aren't as many facts in the world as you might like to think. Being an Engineer I'm sure you've also used phrases like "The most likely outcome will be..." or "On balance our opinion is that the best way forward is...".

It's not like answering an Engineering exam paper where the questions all have nice discrete answers. With so much going on during the collision and collapse in such a complex building it is impossible to be certain. They have simply created a model of the collapse that fits what was observable. What was not observable?

Doesn't mean NIST is wrong, just means they could be.
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I think you've hit on a distinct reason why skeptics and conspiracy theorists disagree on such a fundamental level. For me, I'm a logical positivist. I believe that science is the pursuit of innumerable possibilities for explaining phenomena that are observable, measurable and reproducible.

If the possibilities are infinite, then the only truth that we can pursue is the most likely theory. Nothing is proven, but rather, theories pass experimental verification and remain valid until they fail to do so. Competing theories are based on whether or not they encompass most of the observable data, and whether they pass experimental verification.

You say the NIST theory could be wrong. As a positivist, I have to accept that as a possibility, just like I have to accept the possibility that our concept for the fundamental structure of matter is wrong. If NIST's theory fails experimental verification, it's wrong, and I can never say (with any credibility) that no one can conceive of an experiment that would prove NIST wrong.

On the flip side, NIST's self-initiated collapse mechanism does satisfy the positivist definition of the "best" or "most likely" theory. It does encompass the majority of the observable data, and it does provide a working theory whose basis is experimentally verifiable. Competing theories do not approach NIST's level of scientific value. The controlled demolition theory has failed to establish the fundamental fact of the existence of explosives as shown before the collapse. I would also point out that showing the NIST theory is wrong or faulty does not prove that controlled demolition was the correct theory.
 
Darth Rotor said:
Physics, and the properties of steel under thermal stress, are not subject to your opinion.
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It is correct that it is difficult to argue with the facts of a text book list of attributes databases for steels measured under controlled conditions. Of course, these properties are based upon thousands of tests whereas I can only count one very imperfect test of the Twin Towers.

How the steel might subsequently be used and how it would perform in that use are very much subject to my educated opinion. Otherwise I wouldn't be in the highly paid job I am in because, a low paid Technician would be able to look it up in a text book and decide the design.
 
The Almond said:
I think you've hit on a distinct reason why skeptics and conspiracy theorists disagree on such a fundamental level. For me, I'm a logical positivist. I believe that science is the pursuit of innumerable possibilities for explaining phenomena that are observable, measurable and reproducible.

If the possibilities are infinite, then the only truth that we can pursue is the most likely theory. Nothing is proven, but rather, theories pass experimental verification and remain valid until they fail to do so. Competing theories are based on whether or not they encompass most of the observable data, and whether they pass experimental verification.

You say the NIST theory could be wrong. As a positivist, I have to accept that as a possibility, just like I have to accept the possibility that our concept for the fundamental structure of matter is wrong. If NIST's theory fails experimental verification, it's wrong, and I can never say (with any credibility) that no one can conceive of an experiment that would prove NIST wrong.

On the flip side, NIST's self-initiated collapse mechanism does satisfy the positivist definition of the "best" or "most likely" theory. It does encompass the majority of the observable data, and it does provide a working theory whose basis is experimentally verifiable. Competing theories do not approach NIST's level of scientific value. The controlled demolition theory has failed to establish the fundamental fact of the existence of explosives as shown before the collapse. I would also point out that showing the NIST theory is wrong or faulty does not prove that controlled demolition was the correct theory.
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An incredible post The Almond. It was worth reading all this other nonsense just to read yours. Thank you.
 
William Rea said:
Why do the designers in my field spend days modelling theoretically "perfect" stresses and temperatures and then put a safety factor of 2.5 on the design? The model must be the truth because it is based upon indisputable facts about the material it is modelling? Why waste the cost of the redundancy in the design just because the designer only has an opinion that he needs it when the facts say he doesn't?
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Speaking as a civil engineer, the reason we multiply the live load by 1.6 to achieve the design load is more of an acknowledgment that the loads caused by people moving around in a structure are extremely variable. It's not a reflection on our ability to calculate the loads or related stresses, but rather a way of accounting for the new fax machine and the time of day when all of the fat employees jump up and down.

NIST did an extensive analysis of the variability of the system. They isolated variables that had large effects on the simulations. Page 129 in NCSTAR 1 talks about the variability of the fuel load and aircraft impact damage in the WTC collapse model. Page 126 is also helpful in understanding the methods NIST used to control such variability.
 
William Rea said:
Why do the designers in my field spend days modelling theoretically "perfect" stresses and temperatures and then put a safety factor of 2.5 on the design?
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You're an engineer? And you ask THAT question?

jeez.

The saftey factor is there to allow for the extraordinary.

In a building it would be to prevent the disproportionate collapse of the structure should an event occur which would not be allowed for in the original design parameters.

A structure close to a road would have an additional safety factor built in so that the structure could survive the reasonably predictable impact of a vehicle. They don't expect, invite or want a vehicle to hit their building, but they will design it it such a way that a given vehicular impact scenario could be survived.
 
William Rea said:
An incredible post The Almond. It was worth reading all this other nonsense just to read yours. Thank you.
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I'm glad you liked it. It's my opinion that you've been misjudged around here, but (without being critical or apologetic) I think I know why.

We tend to get a lot of black/white disagreement in this forum. That's because most of the opposing viewpoints are centered around the idea "The NCSTAR is wrong, therefore a space microwave melted the towers." Naturally, such a false dichotomy is silly, but that doesn't stop people from making such claims. I'm sure you would agree that some of the things written by TruthSeeker1234 are downright laughable.

Your posts don't seem to indicate that you subscribe to an alternative hypothesis, and that you are far less likely to convince us that mini-nukes and thermite were the culprit. However, your insistence that the NCSTAR is only "probable" has likely lead others to believe that you endorse something like thermite demolition over self-initiated collapse.
 
The Almond said:
I'm glad you liked it. It's my opinion that you've been misjudged around here, but (without being critical or apologetic) I think I know why.

We tend to get a lot of black/white disagreement in this forum. That's because most of the opposing viewpoints are centered around the idea "The NCSTAR is wrong, therefore a space microwave melted the towers." Naturally, such a false dichotomy is silly, but that doesn't stop people from making such claims. I'm sure you would agree that some of the things written by TruthSeeker1234 are downright laughable.

Your posts don't seem to indicate that you subscribe to an alternative hypothesis, and that you are far less likely to convince us that mini-nukes and thermite were the culprit. However, your insistence that the NCSTAR is only "probable" has likely lead others to believe that you endorse something like thermite demolition over self-initiated collapse.
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I think you've hit the nail on the head, up to a point, but it's their problem not mine, I am not responsible for their reactions to the situation.

Thanks for the analysis.
 
William Rea said:
It is correct that it is difficult to argue with the facts of a text book list of attributes databases for steels measured under controlled conditions. Of course, these properties are based upon thousands of tests whereas I can only count one very imperfect test of the Twin Towers.

How the steel might subsequently be used and how it would perform in that use are very much subject to my educated opinion. Otherwise I wouldn't be in the highly paid job I am in because, a low paid Technician would be able to look it up in a text book and decide the design.
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Did you bother to read the entire NIST report? It took me four weeks off and on to read all of the .pdf's posted by them on the web, some of which were harder for me to work through than others.

You impugning of their method is stranger than most, if you are in fact an engineer and not having us on.

DR
 
Darth Rotor said:
Did you bother to read the entire NIST report? It took me four weeks off and on to read all of the .pdf's posted by them on the web, some of which were harder for me to work through than others.

You impugning of their method is stranger than most, if you are in fact an engineer and not having us on.

DR
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How have I impugned their methods?
 
William Rea said:
Yes, most people's initial reaction when confronted with this is astonishment. It's a similar feeling to the one you get when you realise that your childish notions of things being "all good" and "all bad" get blown away by education.

I will ask you one question. If we only base engineering decisions on truth why do safety factors exist?

Why do the designers in my field spend days modelling theoretically "perfect" stresses and temperatures and then put a safety factor of 2.5 on the design? The model must be the truth because it is based upon indisputable facts about the material it is modelling? Why waste the cost of the redundancy in the design just because the designer only has an opinion that he needs it when the facts say he doesn't?

Why is the theoretical thermal simulator we use unable to predict a certain defect in a component when all the data and modelling it contains are based upon facts? Is the computer lying?
Click to expand...

You have not answered any question of mine, but I will answer your "one question".

Safety factors exist because the risk of failure is so unacceptable in an engineered structure in terms of lives. Historically they have existed for over a century and a half. They have steadily declined as our knowledge advances, but I do not ever envision a world where we design structures to perform at precisely their limit. Would you be comfortable in a building where you knew one extra pound would exceed the ultimate strength of the structure? Where one extra mile per hour of wind speed would cause it to fail? So we use safety factors to provide that margin of safety where the risk of failure is suitably small (I might say miniscule in the United States, as building failure is very rare), regardless of load uncertainty, material defect, construction defect, or design defect. (The fact that a mistake may be made in design does not imply that we do not understand structural behavior; it only means that human error exists.)

I am disappointed - you are either an engineer who should know better muddying the waters for those who do not have any engineering experience, or you are not a very competent engineer. I recall the muddying of the jurors minds in the OJ trial, where "reasonable doubt" somehow became "any doubt, regardless of total lack of evidence and no feasible or conceivable explanation" by cynical lawyers who should have known better. This is not a world where "how the towers fell" is simply "a matter of opinion" and NIST is "one opinion" and there is a wide divergence of opinion and debate as to what occurred. NIST may be a "theory" but it is supported by the facts and the analysis of experts and the consent of the engineering community. It may not be "exactly" what happened, but it is easily 95%.

I ask you again: what "could be wrong" with the NIST theory? Anything significant? Or are you quibbling over the details in the margins?
 
The Almond said:
I think you've hit on a distinct reason why skeptics and conspiracy theorists disagree on such a fundamental level. For me, I'm a logical positivist. I believe that science is the pursuit of innumerable possibilities for explaining phenomena that are observable, measurable and reproducible.

If the possibilities are infinite, then the only truth that we can pursue is the most likely theory. Nothing is proven, but rather, theories pass experimental verification and remain valid until they fail to do so. Competing theories are based on whether or not they encompass most of the observable data, and whether they pass experimental verification.

You say the NIST theory could be wrong. As a positivist, I have to accept that as a possibility, just like I have to accept the possibility that our concept for the fundamental structure of matter is wrong. If NIST's theory fails experimental verification, it's wrong, and I can never say (with any credibility) that no one can conceive of an experiment that would prove NIST wrong.

On the flip side, NIST's self-initiated collapse mechanism does satisfy the positivist definition of the "best" or "most likely" theory. It does encompass the majority of the observable data, and it does provide a working theory whose basis is experimentally verifiable. Competing theories do not approach NIST's level of scientific value. The controlled demolition theory has failed to establish the fundamental fact of the existence of explosives as shown before the collapse. I would also point out that showing the NIST theory is wrong or faulty does not prove that controlled demolition was the correct theory.
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Nice post. A perfect example is Darwin's Theory. Still just a theory, but so strong, so backed up, so logical, it has moved closer than any other theory to being the actual "truth".

TAM:)
 
William Rea said:
I think you've hit the nail on the head, up to a point, but it's their problem not mine, I am not responsible for their reactions to the situation.

Thanks for the analysis.
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I might go one step further and say that it's no one's problem. In the strictest sense, NIST is beholdent only to the Congress for judgement about their reactions. It wasn't NIST's job to convince everyone in the country that their theory was correct, and by extension, they could probably care less what you think about their report. Perhaps that's a cynical view of things, but we do live in a rather cynical world, after all.

Again, taking the positivist view, you have one of two options. You could accept the NIST view as the most likely one given the evidence, or you could use the evidence against the NIST theory to support an alternative collapse theory. If you refuse the NIST theory, other theories like it (that is, supported by similar amounts of evidence) must also be refused.
 
uk_dave said:
You're an engineer? And you ask THAT question?

jeez.

The saftey factor is there to allow for the extraordinary.

In a building it would be to prevent the disproportionate collapse of the structure should an event occur which would not be allowed for in the original design parameters.

A structure close to a road would have an additional safety factor built in so that the structure could survive the reasonably predictable impact of a vehicle. They don't expect, invite or want a vehicle to hit their building, but they will design it it such a way that a given vehicular impact scenario could be survived.
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You were doing reasonably well until you got to the example in the fifth paragraph. Building a structure beside a road to resist collision with a vehicle is not building in safety factor. As you yourself said, safety factors are for the extraordinary, not for an event that is reasonably predictable.

By the definition of your fourth paragraph the unknown event is not a fact. The designer is using educated opinion to judge that his calculations do not contain all the facts so he has to add an X factor for the unknown.

I wish you hadn't used the incredulity at the start. I have stated my status as an Engineer, may I now ask yours?
 
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The Almond said:
Speaking as a civil engineer, the reason we multiply the live load by 1.6 to achieve the design load is more of an acknowledgment that the loads caused by people moving around in a structure are extremely variable. It's not a reflection on our ability to calculate the loads or related stresses, but rather a way of accounting for the new fax machine and the time of day when all of the fat employees jump up and down.
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I have a question, if you were designing an office complex, why would you include things like people and fax machines in the safety factor? Surely these are expected and predictable events in an office. I think I may have misunderstood what you have said, could you explain further?

What multiple factor do you apply to the static load?
 
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