Moderated Steel structures cannot globally collapse due to gravity alone
- Thread starter Heiwa
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Redtail actually has a valid question. Don't laugh at him.
If nano-thermite weren't invented, then it couldn't have been used, correct?
edited to add that I sincerely hope he knows how to google it, and that he will be gracious enough to share his answer with us.
If nano-thermite weren't invented, then it couldn't have been used, correct?
edited to add that I sincerely hope he knows how to google it, and that he will be gracious enough to share his answer with us.
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Dave Rogers
Bandaged ice that stampedes inexpensively through
Again, this is at the heart of your (and Tony Szamboti's) failure of understanding. Bazant has calculated the response of the lower structure to a single simultaneous impact of all the columns of the upper block on the columns of the lower block, a scenario which maximises the ability of the lower block to absorb the energy of the impact, and found that collapse is still expected. He therefore concludes that in a real, non-ideal impact, in which there are miltiple smaller collisions between the upper ans lower blocks, the ability of the lower block to resist must be equal or less, therefore collapse is always expected. He is not stating that a single simultaneous impact is required.
Szamboti is proceeding from the starting assumption that Bazant requires a single, simultaneous impact for collapse to propagate, and goes on to derive from motion data (more correctly in the revised version of the paper, although the fact of the revision had not been published with the paper when last I read it) that this single, simultaneous impact is not observed. Based on his misrepresentation of Bazant's analysis, he therefore erroneously declares it incorrect.
In fact, this paper is a textbook example of the strawman logical fallacy.
Dave
Hokulele
Deleterious Slab of Damnation
Just curious, do you know when they revised the paper? I may have missed an update or two along the way, because as you point out, the fact that the paper has been revised since the original release isn't mentioned anywhere. I would be interested to see how they have changed their arguments since the original release.
Christopher7
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Yes, the force of gravity that was pulling straight down resulted in the top section falling down and to the side.
Once in motion down and to the side, the top section will continue falling down and to the side unless there is another force applied.
The top section suddenly stopped falling to the side.
Something arrested the fall to the side.
Therefore, a force other than gravity was applied to stop the sideways motion.
Are you with me so far?
Christopher7
Philosopher
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Why do you think air pressure can hurl a 4 ton framework section up to 600 feet?
Read the quote again:
"As a refinement of previous analysis, we introduce here a generalization in which we add energy Fs (per unit height) consumed by comminution [pulverization] of concrete floor slabs, energy Fa required to expel air from the tower, and energy Fe required to accelerate the mass of dust and larger fragments ejected from the tower during the impact of upper part; Furthermore, in contrast to previous studies, the compaction ratio will not be assumed as a constant but will be more accurately calculated as _(z) = (1−kout)μ(z)/μc, and kout = mass outside tower perimeter before the end of crush-down (not afterwards). shedding fraction = fraction of mass that escapes"
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Dave, I think you need to go back and read Bazant's paper. Are you saying that if the upper block eases down onto the lower block without an impact, that the lower building that has held that weight since inception would still obliterate?
That's crazyspeak, my man.
That's crazyspeak, my man.
332nd
Penultimate Amazing
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I'm asking you.
I sincerely hope that you don't have to google it since you brought it up.
Dave Rogers
Bandaged ice that stampedes inexpensively through
Having just looked at it, they've changed the submission date, put an asterisk by it, and added a note at the bottom of the paper.
In effect this fixes the mathematical error, but doesn't affect the underlying fallacy of the paper.
Dave
Dave Rogers
Bandaged ice that stampedes inexpensively through
Why do you imagine I think that?
If you want to discuss the BLBG paper, can I suggest you join Gregory Urich's 9/11 forum at http://the911forum.freeforums.org/, where two of the authors are regular contributors? I'm sure David Benson and Frank Greening will be happy to explain the effect of mass shedding on their collapse calculations, so long as you ask them politely.
Dave
If the USGS showed NIST, they must not have been 'in on it' right? So what did they have to say about them?
Also have you decided to ignore my post, or decided you know the results of the experiment I proposed? I am most interested to find out.
Dave Rogers
Bandaged ice that stampedes inexpensively through
And this, too, is a classic example of the strawman fallacy. I'm saying that if, for example, the upper block hits corner-first because it's rotated as it fell, the lower block is even less able to resist the collapse. This is a fairly simple concept, and most honest and intelligent people seem able to understand it.
And look whose keyboard it's coming from.
Dave
If by fallacy you mean that Bazant does not require an impact of some measurement to proceed with a close model global collapse, I would have to disagree. NIST adheres to a three part block/gap/block model requiring a substantial impact to produce the obliteration phenomenon witnessed.
If by a slow bending of supports, or an easement of mass ONTO the lower mass is what occurs (and by the sudden onslaught it appears not), then the impact would indeed be negligible and the collapse would be arrested. If the supports ALL break simultaneously, and the top block drops 10-15 feet, then a JOLT would indeed be expected, and for NIST highly desired. Without a pop it fizzles.
If by a slow bending of supports, or an easement of mass ONTO the lower mass is what occurs (and by the sudden onslaught it appears not), then the impact would indeed be negligible and the collapse would be arrested. If the supports ALL break simultaneously, and the top block drops 10-15 feet, then a JOLT would indeed be expected, and for NIST highly desired. Without a pop it fizzles.
e^n - no USGS was not 'in on it'. They gave their initial analysis of the dust/debris to NIST. There is more information on the USGS website, along with slides/pics etc...
Sorry if I was seeming to ignore you, that's what I get for posting in multiple threads at once.
If memory serves, the towers were given an upgrade of fireproofing prior to 9/11. I can't recall the exact dates.
Experiment? I don't recall you putting one forth, but again, I apologize for bouncing back and forth. Tomorrow I'll scour back and address it.
Sorry if I was seeming to ignore you, that's what I get for posting in multiple threads at once.
If memory serves, the towers were given an upgrade of fireproofing prior to 9/11. I can't recall the exact dates.
Experiment? I don't recall you putting one forth, but again, I apologize for bouncing back and forth. Tomorrow I'll scour back and address it.
Indeed they did, and they also mention that such iron rich microspheres are an expected product of a building collapse. Evidence has been collected that these spheres are in fact widely produced in various processes which are eventually aggregated into building materials such as concrete. The widescale concrete destruction at the WTC would liberate these particles.
What Dr Jones has done is to look at these particles and note that they contain elements common to thermite or aluminothermic (or similar word!) compounds. Unfortunately these common elements are probably the three most prevalent elements in the buildings. Iron, Aluminium, and Sulphur.
Of course it is possible that these particles are sourced from thermite rather than other more mundane sources, but as far as I am aware Dr Jones has done no satisfactory work in eliminating these other sources, preferring to speculate rather than to investigate.
No problem, I would offer some advice though. You are (intentionally or unintentionally) repeating claims we have heard literally hundreds of times before, in many different forms, from many different truthers. It is obvious that you believe in a particular theory, but I would recommend that you take a single element and discuss it slowly so we can have a chance to illustrate where you might be wrong (or equally so, you may illustrate us on where we are wrong).
This is true but these upgrades only covered a limited number of floors, certainly not enough to guarantee that a plane would impact said floor, and I don't believe they covered the collapse initiation floors in either building. I can check up on this if needed though.
I will quote myself to make things easier:
e^n said:
To elaborate a bit. I'm sure you're aware that gravity accelerates all objects equally (in the simplified equation we use on earth). For this reason, a simple experiment as I have proposed should reasonably show you that static and dynamic loads are quite different, and even a factor of safety of 3 with regards to dead load will do little to prevent failure when applied as live load.
I look forward to your response.
Dave Rogers
Bandaged ice that stampedes inexpensively through
No, that's not what I mean, and it's perfectly clear that it's not what I mean. Bazant requires simultaneous impacts between upper and lower support members for his most optimistic scenario. Less optimistic scenarios do not require the impacts between specific upper and lower members to be simultaneous, and indeed, given the rotation of the upper block as it fell, it is impossible that they could have been simultaneous. Therefore, rather than a single enormous jolt, we expect a series of very much smaller jolts over a period of time, which will not be individually visible but will average out to an overall reduction in the downward acceleration due to gravity. I'll repeat that for simplicity: there wasn't one big jolt that could be seen, there were lots of little ones that couldn't be seen.
False dilemma fallacy. Slow deformation and perfectly simultaneous failure are not the only possibilities, and in fact observation makes it clear that neither occurred.
Dave
Gents, let me remind you that this thread is about my statement Steel structures cannot globally collapse due to gravity alone.
I would like to improve on it: Steel structures cannot be crushed down into small pieces by a top piece of itself due to gravity alone!
So we have a steel structure, part A, with a smaller piece of similar steel structure on top, part C. Part A has carried part C for thirty years. Reason is that part C, due to gravity, applies a force on part A and that part A applies an equal, but opposite, force on part C (as explained by Newton). These forces result in known stresses in the steel structure, which we know are low. The Factor of Safety is at least three.
Now a practical question. How are we going to do to try crushing part A with part C? That's easy! First we disconnect part C from part A; part C then just rests on part A, again by gravity. Then we use a crane and lift part C a bit above part A ... and then we drop part C on part A. Note that when we lift part C, part A becomes unloaded at the top. Stresses in the top of part A become zero. Same happen to part C. Stresses are zero in the bottom part of part C.
Question? Will part A now be crushed, while part C remains intact after collision? Remember that part A is similar in structure as part C. Steel structures! Columns and beams! And plenty of air in between!
It is quite easy to test! My experience due misfortune to drop a part C on a part A as described above is that first there is a big BANG at contact and then that both parts suffer local structural failures in the contact area due to contact forces developing there. And that's all. Part C cannot crush bigger part A because part A, bigger than part C, crushes part C into small pieces before that.
And small pieces of part C will then not affect part A. So the destruction will be arrested latest when part C is in pieces. Normally the local destructions are arrested before that due to the fact that both structures can absorb plenty of elastic and plastic strain energy before local failures develop that also absorbs energy. And then there is friction, etc. The only available energy is the potential energy applied by the drop (mass of part C times drop height times gravity acceleration) and it is very small compared to the total strain energy that can be absorbed by the structures, not forgetting friction of course.
It is quite basic, actually. No need to write pseudo-scientific papers trying to prove the opposite, e.g. that part C creates a rubble layer - part B - of the top part of part A, that part C remains intact, while part A becomes rubble, etc, etc. Try yourself - do a test.
BTW - it doesn't matter if you put in concrete floors in the steel structure. Actually it just adds more strain energy (strength) and objects that will be subject to friction after a drop so arrest will occur much quicker.
I would like to improve on it: Steel structures cannot be crushed down into small pieces by a top piece of itself due to gravity alone!
So we have a steel structure, part A, with a smaller piece of similar steel structure on top, part C. Part A has carried part C for thirty years. Reason is that part C, due to gravity, applies a force on part A and that part A applies an equal, but opposite, force on part C (as explained by Newton). These forces result in known stresses in the steel structure, which we know are low. The Factor of Safety is at least three.
Now a practical question. How are we going to do to try crushing part A with part C? That's easy! First we disconnect part C from part A; part C then just rests on part A, again by gravity. Then we use a crane and lift part C a bit above part A ... and then we drop part C on part A. Note that when we lift part C, part A becomes unloaded at the top. Stresses in the top of part A become zero. Same happen to part C. Stresses are zero in the bottom part of part C.
Question? Will part A now be crushed, while part C remains intact after collision? Remember that part A is similar in structure as part C. Steel structures! Columns and beams! And plenty of air in between!
It is quite easy to test! My experience due misfortune to drop a part C on a part A as described above is that first there is a big BANG at contact and then that both parts suffer local structural failures in the contact area due to contact forces developing there. And that's all. Part C cannot crush bigger part A because part A, bigger than part C, crushes part C into small pieces before that.
And small pieces of part C will then not affect part A. So the destruction will be arrested latest when part C is in pieces. Normally the local destructions are arrested before that due to the fact that both structures can absorb plenty of elastic and plastic strain energy before local failures develop that also absorbs energy. And then there is friction, etc. The only available energy is the potential energy applied by the drop (mass of part C times drop height times gravity acceleration) and it is very small compared to the total strain energy that can be absorbed by the structures, not forgetting friction of course.
It is quite basic, actually. No need to write pseudo-scientific papers trying to prove the opposite, e.g. that part C creates a rubble layer - part B - of the top part of part A, that part C remains intact, while part A becomes rubble, etc, etc. Try yourself - do a test.
BTW - it doesn't matter if you put in concrete floors in the steel structure. Actually it just adds more strain energy (strength) and objects that will be subject to friction after a drop so arrest will occur much quicker.
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Does this mean you now accept that global collapse is possible, but that the pieces are bound to be large?
If not then, as far as I can see, you are merely repeating yourself.
What do you mean with global collapse? That parts A and C just disintegrate by themselves ... due to gravity?
As already explained gravity does only produce forces inside the structures stressing them a little, Factor of Safety >3, which means that local forces can be three times greater than design stresses before the sub-part starts to deform! And even then there will be no global collapse! Just local failure!
Let's take WTC 7 as an example. NIST suggests that by removing column 79 (built with Factor of Safety >3) between floors 11/13, the whole WTC 7 structure then globally collapses first horizontally (?) and then vertically, e.g. that the complete visible structure above floor 16 free falls for 2.25 seconds. I have analysed* that scenario and only found that stresses in adjacent primary structure only increase a little and nothing at all happens to the global strength. Evidently the floors above floor 13 above the locally removed column 79 will sag, but that's all. Stresses in the floors are still quite low. * http://heiwaco.tripod.com/nist7.htm .
Checking the NIST web site I see they do not advertise any expertize at all for structural design or structural damage analysis. NIST seems to have plenty of experience of heat/smoke distribution due fires but structural analysis? None!
(bolding mine)
Heiwa, if all load carrying elements have suffered a local structural failure over a two floor section of the towers, what would then restrain the upper section from being accelerated by gravity downwards? Surely columns can't both fail and also carry load?