Truss Failure Theory Inconsistent; Critically Flawed

Thank you Valhall for that succinct explanation.

another scientific paper on the subject.

Originally posted by HowardRoark
Thank you Valhall for that succinct explanation.

another scientific paper on the subject.

This paper is funny...

On page one they state: "This investigation does not take into
account the structural damage caused by the terrorist attack."

Then on page 30: "This softening would be particularly severe if it is assumed that the truss members had lost significant proportion of their fire protection at impact (as all the truss components were rather light and would heat up very quickly without protection). This case is covered by the analyses which assume rapid rise of compartment temperature (values of a=0.005)."

So, they say they are not accounting for impact damage... then they do! Nice paper howard Roark.

When was it peer reviewed?
By who?

This is my favorite quote from the article you posted: "Beyond this point they conjecture that the large deflections would lead to tensile membrane action in the slab and the resultant tension would lead to connection failures and floor collapse, thus setting off a chain of progressive collapse. This theory is also improbable as it relies upon a large number of connection failures in a very short space of time to set off the floor collapses with sufficient kinetic energy."

lol howard roark





[edit on 1-8-2006 by Slap Nuts]

[edit on 1-8-2006 by Slap Nuts]

Slappy. Perhaps you missed the point, so let me explain it to you.

If the exterior columns are sufficiently buckled, then it doesn’t matter what the floors are doing as plastic hinges form in the columns and the building will collapse.


Haven’t you figured that out yet?



Try reading this one:

www.era.lib.ed.ac.uk...

The models were designed to study the effects of the fires, not the impacts. They did not look at the physical damage caused by the impacts, but they did look at the effects of varying amounts of fireproofing. The fact is that the fires were able to produce the buckling effects observed without the physical damage to the structure caused by the impacts. Factor in that damage and the buildings were doomed.

Originally posted by Valhall
Okay, actually it would. This issue here is very much like talking about, say, a failed balcony. Let's say the balcony was rated to 10,000 lbs, and then one day a bunch of people get on it and it fails. And low and behold its found out there were 10,001 lbs of people on it. It wasn't the first 10,000 lbs that failed the balcony, it was the final 1 lb.

How does a balcony compare with a floor of these, in terms of failing simultaneously all the way around?:

And eventually, you'll get to the point that you have crossed the "average strength line" - and at that point it's "Katy Bar the Door".

First, how many perimeter columns would have to be buckled on any given floor, and second, how many did we see? Even with a rough estimate on how many it would take, and a rough estimate on how many we saw, I don't think there's any excuse.

We're going from a few buckled columns to all of them in no time flat. I can't see how you're getting the straw that broke the camel's back when the camel's back is only lightly covered with straw.

This is my favorite quote from the article you posted: "Beyond this point they conjecture that the large deflections would lead to tensile membrane action in the slab and the resultant tension would lead to connection failures and floor collapse, thus setting off a chain of progressive collapse. This theory is also improbable as it relies upon a large number of connection failures in a very short space of time to set off the floor collapses with sufficient kinetic energy."

If the paper HowardRoark posted actually says this, then it seems to be getting at the same point that I am.

[edit on 1-8-2006 by bsbray11]

You're not understanding what I'm saying.

I've made no judgement as to whether enough had failed prior to the point of overloading the elements en masse, what I've said is, that once you do reach that point, it will happen suddenly and instantaneously.

The balcony analogy absolutely applies.

The only point I'm trying to make is that the gradual buckling of columns preceding the entire failure is NOT a contradictory phenomena.

Originally posted by Valhall
[W]hat I've said is, that once you do reach that point, it will happen suddenly and instantaneously.

I agree; to use the camel analogy again, I agree that one failure could have pushed the buildings over their limits instantly, supposing that they had already lost enough integrity.

The problem is that the buildings should have been NOWHERE NEAR the amount necessary, and then collapsed anyway. The explanation is apparently that there was a series of failures all around the floor too fast to be video taped, being propogating by some single initiatory failure. Again, why would a single failure push the buildings over the threshold when they were so far from it from multiple failures already? The additional number needed to initiate a collapse would be way too many to fail so quickly.

Wasn't one of the main reasons you started considering demolition, Valhall, that the fires shouldn't have caused enough damage for a collapse to initiate? This seems related.

The only point I'm trying to make is that the gradual buckling of columns preceding the entire failure is NOT a contradictory phenomena.

I agree with this too, strictly speaking, but in the context of the WTC, it would be contradictory behavior because of how few columns were already buckled, compared to how many needed to be (as in contradictory taking into account an additional "variable", that the structure was not weak enough for a single "straw" to break, and yet somehow still managed to, though of course we weren't able to actually see it). All the additional buckling needed had to have been made up in a very, very short period of time for truss failure theory to work. An extreme example of what this equates to, would be the second truss to fail, suddenly propogating truss failures around the whole floor, while the first truss failure did nothing like it, despite the similarity in how very little damage they would have caused the overall structure.

Not that I want to get involved in this thread, but is anyone here a civil engineer, with knowledge of strengths of materials, as wll as the actual materials used in the construction of the WTC?

Outside of Howard Roark and Valhall, my feeling is that everyone here is posting blind.

Now I'm an engineer -- but a logistics engineer, not a civil one. What little I've read and what little knowledge I have about statics, dynamics, strengths, heats, etc. leads me to believe that 1. the cause of the collapse was supports weakened by heat; and 2. although the idea of the WTC being intentionally demolished by charges, while theoretically possible, is improbable to the point of "might-as-well-be-impossible".

But again, I'd like some good data to look at, including the type of construction, load-bearing considerations, etc. Otherwise, I have to go with Valhall and Howard. Howard's stuff, in particular, at least makes sense.

bsbray

We meet again. I have been following your posts about this since I gave up on that one a few months back, but here i am again, i just cant listen to it anymore without saying something.

Let me see if I understand YOUR viewpoint and correct me if im wrong. You believe that in order for this tower to collapse under its own demise, then you would witness something like this..... Top of the tower begins to fall, as it impacts the closest floor, its momentum is resisted, slowing down the impact, and then the top leans over in one big chunk and falls to the side?

Or you believe that the buckling would be such that a slow failure of one side, with the building slowly tilting and we actually being able to see individual columns buckling inwards.

Heres the problem with that.

There was progressive buckiling from the point of impact to the point of collapse, but it happens on a scale too small to be witnessed by someone watching, you wont see the gradual buckling of a column over a 45-1 hr time frame, moving ever so slowly. As these columns slowly deformed, so did the load transfer occur, ever so slowly, shifting the remaining weight to stiffer members.

And it only gets worse from here. The deformed columns, do not return to normal conditions, even if completely cool. So as the fire proressed, and more damage was done, more columns experienced minor to major buckling.

I do not believe that a failure in load trasfer caused the collapse. I believe it was the soul result of collapsing floor trusses which caused the collapse because as the floor fell, it greatly reduced the lateral stability of MANY columns, and that is why u have a sudden collapse, because of the lateral failure of multiple columns all at once.

The load of the tower is so great, it just smashes through the rest of the remaining columns which already have no chance of taking the increased load.

Train

Originally posted by Off_The_Street
Not that I want to get involved in this thread, but is anyone here a civil engineer, with knowledge of strengths of materials, as wll as the actual materials used in the construction of the WTC?

I am a CIVIL engineer...more so a Structural Engineer...at least that's my title. But, unfortunately, I.... like you..... have a problem obtaining the actual drawings/specs or even as-built drawings for these buildings. I have tried to find past permits on the NYC buildings site (a government site for buildings in NYC to list permits/complaints/Environmental issues etc. of a building in NYC.) to no avail. How do you get information that has been classified?

Also, Valhall is more than qualified....probably even more so than myself. You, being an engineer, should know better than most that a mechanical enginner is more qualified to investigate than a structural engineer when MOVEMENT of the building started. Once that happened, STATICS is thrown out the door.

Outside of Howard Roark and Valhall, my feeling is that everyone here is posting blind.

Outside of Howard Roark and Valhall, Everyone?

Now I'm an engineer -- but a logistics engineer, not a civil one.

Hmm...and I thought only civil engineers could have an opinion?

What little I've read and what little knowledge I have about statics, dynamics, strengths, heats, etc. leads me to believe that

Maybe that's the problem?

1. the cause of the collapse was supports weakened by heat;

Remember that not ALL supports would be weakened/collapse at once. There would have been a partial collapse here, then there, then everywhere. Not all at once...IMO.

and 2. although the idea of the WTC being intentionally demolished by charges, while theoretically possible, is improbable to the point of "might-as-well-be-impossible".

Why is it impossible? Are you going on normal demolition charges? I'll speculate no further.

But again, I'd like some good data to look at, including the type of construction, load-bearing considerations, etc.

You and me both brother.....AMEN!!!!

Otherwise, I have to go with Valhall and Howard. Howard's stuff, in particular, at least makes sense.

Howard does make sense and I'll be the first to state that he makes me think about my own theories and all. I do have to say BSBray....I'm going with Valhall and Howard on this issue. Only because I feel the core was taken out before all this even started.

Originally posted by BigTrain
I do not believe that a failure in load trasfer caused the collapse. I believe it was the soul result of collapsing floor trusses which caused the collapse because as the floor fell, it greatly reduced the lateral stability of MANY columns, and that is why u have a sudden collapse, because of the lateral failure of multiple columns all at once.

I have a question about this. When the trusses were failing, do you believe that they all fell at once or do you believe they fell chaotic? If they fell chaotic, wouldn't they then give lateral support by kinda forming a diagonal type support? That is if one side fell while the other side stayed connected. Just a question.

Or, would taking out the core result in floors sagging/trusses failing/exterior columns being "pulled" in (i.e. buckling)/ and when the load became too strong it collapsed at the weekest part of the building (the impact zones)?

Originally posted by bsbray11

Wasn't one of the main reasons you started considering demolition, Valhall, that the fires shouldn't have caused enough damage for a collapse to initiate? This seems related.

Right, I'm questioning whether "we got to that point" (especially in WTC 1 - and then there's a whole other batch of questions for WTC 2). I'm not stating - "silly, we got to that point". I'm saying - the statement that gradual buckling preceding catastrophic buckling being contradictory is not correct. That's all I'm saying.

The important question really is - did we get to that point?

Then the second statement I would make is:

Exactly how does the truss failure theory apply to WTC 2? How do they apply the "the hat truss failed and then the core fell" theory to WTC 2 when the approx. 20 degree tilt is taken into account.

bsbray11, Slap Nuts.....



Seriously though, your theory has been slaughtered. Sit back down! Move on, let go.

shane,

Seriously, I have to say to you that this isn't a competition. And it's actually the tendency of these discussion to degenerate into a sophomoric pissing contest between "the two sides" that usually turns these discussions to a worthless waste of time.

There really aren't two sides when we're talking about the physics and failure theories. Unless some one is in one of these discussions to do nothing more than prove their pet theory extraneous to physics and failure modes - (like the government blew the building up, or - there was nothing but the plane impact and the fire because NIST said so). If the discussion is trying to get to the proper failure mode and whether the physics of a failure theory are correct or not, then there's only one side actually, that of trying to get to the physical facts.

As I've said before, we can each take a different path in search of the truth (due to whatever personal bias we might have) but if we all continue to seek the truth we'll all end up in the same location eventually - because the truth is absolutely standing still...waiting on every one of us.

[edit on 8-3-2006 by Valhall]

Valhall I totally agree that the facts are in fact the facts and thats where the truth resides, and the physics of the event are indeed the physics of the event, but there is no way to absolutlely determine what exactly happened short of having a 'wayback machine' that would put us inside the building at the time the collapse was happening with a 360 degree unobstructed view in slow motion of what was happening at the time it was happening. No investigation of a complex event is 100% explained. You have to go with the most likely event based on the data. Raw data based on design..load specs etc. are in a sense kinda of 'cookie cutter' and reality rarely is. During construction,was something altered?..a bracket raised 1/4 "..missing or substandard bolts in used in areas? Howard posted a pic of the actual floor trusses that showed a substandard application of fireproofing, a modification that in normal situations would most likely not matter .....unless something happened like a huge frikken plane flies into it at 530 mph and then explodes.
At that point it would seem like all conclusions that require 100% satisfaction based on analysis of the raw data of design and load ratings goes out the window because of the impossibility of knowing all the factors to plug into the equation.
At that point the only valid conclusion is the one most likely to have occured based on the data and the evidence.

If the counter theory is that the buildings were brought down by explosives, in order for it to be considered not only as valid but more valid than the official conclusion, the same degree of 100% certainty in all aspects has to be met in order for it to be accepted as valid or there is a bias involved.. As far as I can see the counter theory not only does not meet this level of certainty, there is in fact no actual evidence of explosives or demo that can be shown at all.

If the criteria of satisfaction is one that demands that everything be 100% explained and settled once and for all, I'm afraid that will never be accomplished because it is simply impossible.

Vushta,

Once again I'll repeat:

1. That the evidence referenced in the NIST report does not,
2. Support their conclusions which rely on,
3. Weakened steel at extreme temperatures for sustained times,
4. and
5. because they won't share their data,
6. we are left with,
7. the authoritative conclusions being worthless because it contradicts its own evidence...
8. in its own report.

Now - NO, we can never know for sure what happened in the buildings. But we can take what the NIST states in their report and say - applying physics, thermodynamics and material science - your evidence does not support your conclusion. So in the big "lets make a good working theory on what happened to make the towers collapse" effort - NIST doesn't bring that effort to closure.

[edit on 8-3-2006 by Valhall]

Originally posted by Valhall
Vushta,

Once again I'll repeat:

1. That the evidence referenced in the NIST report does not,
2. Support their conclusions which rely on,
3. Weakened steel at extreme temperatures for sustained times,
4. and
5. because they won't share their data,
6. we are left with,
7. the authoritative conclusions being worthless because it contradicts its own evidence...
8. in its own report.

Now - NO, we can never know for sure what happened in the buildings. But we can take what the NIST states in their report and say - applying physics, thermodynamics and material science - your evidence does not support your conclusion. So in the big "lets make a good working theory on what happened to make the towers collapse" effort - NIST doesn't bring that effort to closure.

[edit on 8-3-2006 by Valhall]

This is just a point and it's all I'll say because it is ...well...off topic.

But.

7. the authoritative conclusions being worthless because it contradicts its own evidence...

How do you know this if you don't have all the data and the referenced data may not be all the data involved in the conclusion?

I'm pretty sure that the scope of the final report did not include the explaination of not only every bit of data but an explantion of the complexity of the forensic methods used.
Can you imagine the problems this could cause as far starting an endless arguement over minutia? I mean come on..we have an endless arguement going on now...is a 'squib' a 'squib'?..did it fall 'into its own footprint' or not?..somebody 'smelled something'..'didn't look right'..etc. Releasing all the data would then require releasing the minutia of methodology..which would require a herd of people to explain the 'whys' of the methodology..which would require endless responses to peoples questioning the methodology of not only evaluating all the data but of accumulating all the data etc, This would just be a real dumb move and set precedent for all future and past similar investigations.

My point is that its possible that what you're saying is a contradiction in the report may simply be a result of the report not explaining every bit of data and every step of the methodology involved that lead to the conclusions because that was not the scope of the report.

Originally posted by Vushta

My point is that its possible that what you're saying is a contradiction in the report may simply be a result of the report not explaining every bit of data and every step of the methodology involved that lead to the conclusions because that was not the scope of the report.

I understand what you are saying Vushta, but why would they include the contradiction if they weren't "explaining every bit of data"? Why wouldn't they just ommit the contradiction if they are willing to ommit other things? Just doesn't make sense to me to pay an agency how many million to have them ommit things in their findings.

Originally posted by Vushta


How do you know this if you don't have all the data and the referenced data may not be all the data involved in the conclusion?

Vushta,

Have you read the report? Because this question makes me think you haven't.

Okay, you're the NIST and you've been tasked (and paid) do perform an exhaustive investigation, analysis and modeling of what happened with the towers. And you issue your final report and use your one shot at reviewing the metallurgical evidence on this statement (I'll paraphrase because I'm not going to go find this portion of the report for the 14th time):

Of all the steel we looked at none of it looked like it got over 250 C except for two pieces that we think got to 600 C - and by the way, we think those two pieces got that hot while they were buried in the debris pile - not before collapse. And further more, we don't think any structural element saw elevated temperatures of fire for the whole duration of the fire. FURTHERMORE, they go and self-implicate themselves in their sloppiness by saying - we think we might have picked debris from the debris pile kind of wrong. WTF?

And then you go on to present a theory of failure that is based on "weakened steel due to extreme temperatures over long period of times that induce creep" (and then misuse what the affects of creep are) that you've already admitted IN YOUR ONE SHOT TO TELL THE WORLD THE FACTS, you couldn't find!

This isn't "omitting data".

In fact, what it is is ADDING DATA. It's...

looking for what you wanted to find,
not finding what you wanted to find,
adding what you wanted to find,
instead of what you found.

And it gives the appearance (which can't be verified not to be correct because they won't share their data) that you....

created a model FIRST,
and then waved your hands at the data that didn't fit,
and ran with your model anyway.

P.S. And ANYBODY who wants to make that claim against them is within their full rights as far as I'm concerned - UNTIL FULL DISCLOSURE OF THE DATA THE MODEL WAS BASED ON ALONG WITH THE MODEL AND METHODOLOGY takes place.

[edit on 8-3-2006 by Valhall]