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"The towers couldn't have fallen that way..."

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posted on Oct, 20 2011 @ 02:51 PM
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Originally posted by ANOK

Originally posted by psikeyhackr
The welding could weaken the alloy. I don't know whether it does or not. But if you are going to bring it up get it right. You undermine yourself with a lot of the nonsense you talk.

psik


What nonsense? Get what right? An alloy does not make steel not be a metal, and as I have already said the welding can weaken the steel around the joint, but it is not a huge problem if the welds are done correctly by a professional welder.


What did you say about welds at every floor along the columns?

1. Abbr. M Any of a category of electropositive elements that usually have a shiny surface, are generally good conductors of heat and electricity, and can be melted or fused, hammered into thin sheets, or drawn into wires. Typical metals form salts with nonmetals, basic oxides with oxygen, and alloys with one another.
2. An alloy of two or more metallic elements.
www.thefreedictionary.com...

Steel is not an element and carbon is not a metal. Therefore if it is only iron and carbon...

What was that business about potential energy and force?

psik




posted on Oct, 20 2011 @ 03:16 PM
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Originally posted by Varemia
Compression would certainly halt the collapse, but that was not the force at work.


Just wondering, on what exactly do you base that? In fact, the model by Bazant (and the one you linked earlier) actually assumes compression as primary failure mode. And his conclusion was that the collapse would not arrest.



posted on Oct, 20 2011 @ 04:06 PM
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Originally posted by -PLB-

Originally posted by Varemia
Compression would certainly halt the collapse, but that was not the force at work.


Just wondering, on what exactly do you base that? In fact, the model by Bazant (and the one you linked earlier) actually assumes compression as primary failure mode. And his conclusion was that the collapse would not arrest.


It's really just my opinion. I was meaning in the manner that psikey models, the compression of vertical columns crushing only upon each other would result in a collapse arrest, because the vertical upon vertical actually are designed for vertical loading.

What psikey fails to acknowledge is that horizontal connections are not designed and almost cannot be designed to take on dynamic, vertical loading hardly any greater than the maximum distributed load of the floor and office stuff. The extreme vertical loading caused by suddenly taking on the weight of a falling 20-30 floors causes the connections to rip away like aluminum foil. (I assume this is what shearing is. I honestly haven't looked it up. Just, based on the context, this seems to be most logical)

I suppose it also depends on the definition of compression you are using when determining what effect it had. I often say I'm not an expert, but many members here seem to expect expert responses. This is why I try to refer to expert opinion, but people like ReptileRipper really don't want to look at anything an expert has to say, unless of course the expert agrees with him, and then suddenly the expert will be speaking the gospel.



posted on Oct, 20 2011 @ 04:15 PM
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Originally posted by psikeyhackr
What did you say about welds at every floor along the columns?


I replied to your correction, I said I wasn't sure, what is your point?

This is what I originally said...

"The 47 main core columns did go from bottom to top in one continuous piece, welded I believe at each floor level."

'I believe' means I am not completely sure. But seeing as it's not that important exactly where they were welded, just that they were, I didn't think it was that important. And then to have a fellow 'truther' pick on it seems pretty odd to me.


1. Abbr. M Any of a category of electropositive elements that usually have a shiny surface, are generally good conductors of heat and electricity, and can be melted or fused, hammered into thin sheets, or drawn into wires. Typical metals form salts with nonmetals, basic oxides with oxygen, and alloys with one another.
2. An alloy of two or more metallic elements.
www.thefreedictionary.com...

Steel is not an element and carbon is not a metal. Therefore if it is only iron and carbon...


Huh? Steel is iron, iron is an element, Fe, it has carbon added to it making it an alloy of iron and carbon, it is still IRON, a metal.


Alloys
Main article: Alloy

An alloy is a mixture of two or more elements in solid solution in which the major component is a metal. Most pure metals are either too soft, brittle or chemically reactive for practical use. Combining different ratios of metals as alloys modifies the properties of pure metals to produce desirable characteristics. The aim of making alloys is generally to make them less brittle, harder, resistant to corrosion, or have a more desirable color and luster. Of all the metallic alloys in use today, the alloys of iron (steel, stainless steel, cast iron, tool steel, alloy steel) make up the largest proportion both by quantity and commercial value.

secure.wikimedia.org...


What was that business about potential energy and force?


What is your beef with me all of a sudden? What business about potential energy and force?

edit on 10/20/2011 by ANOK because: typo



posted on Oct, 20 2011 @ 04:19 PM
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Originally posted by Varemia

Originally posted by ReptileRipper
And what i mean by numbers and squiggly lines mean nothing to me is - i saw them collapse , i have seen it over and over , i know its not a natural collapse , we all know it , even you know it , you actually most probably beleive it was controlled demolition , your just being arkward as usual.


So, by this statement, you're saying it doesn't matter what gets proven. That because YOU personally believe that the collapse wasn't possible, that it had to be demolition. Okay, strike one on the irrational position scale.


Care to share YOUR theory ?


I personally do not have a "theory." I go with what information I can find. I then decide based on my rational judgement which information is accurate and which information is purely speculation. I refuse to become emotional and allow myself to become attached to a single idea. Currently, the buildings appear to have not needed demolition in order to collapse. This is what I try to argue (although, honestly, I don't try to argue that point all that much. I just try to point out the flaws in the demolition argument.)


oh so let me get this straight .... the office fires werent melting the steel ... but ... when the towers collapsed and there was very little fire left from those fires , if any , the steel melted because it was smouldering


Basically. There were broken natural gas lines under the towers which caused massive flames. The pockets of fire then smoldered, causing a very, very slow heating process on very localized steel. When they were exposed to the air, it caused a flash burn, and they became extremely bright and extremely hot with new fire.


I wonder if your science and math can explain why both towers were obliterated into dust too ?

Dont give me links to "official" reports ...... describe how YOU see it.


They weren't obliterated to dust. That should be obvious from the debris pile.

With regard to the "official" reports, does this mean I'm not allowed to use any source that supports the "official story?" How the hell does that make any sense?

From what I can tell, you are simply attempting to propagate ignorance by actively ignoring anything that contradicts your presupposed ideas.

One last thing. The reason that I was "silent" is because this is not my job. I have class and work quite often. I come here because I'm trying to reduce the ignorance that people like you are spreading. So before you post, look at yourself and think for a moment. Are you REALLY being intelligent right now? Are you REALLY looking at all the evidence objectively? Or are you just accepting what fits your worldview and then running with it as if any other evidence doesn't exist?
edit on 20-10-2011 by Varemia because: fixed the quotes


Actually as i have already said .... i have been digging into this for years now , i have seen the official reports and i dont beleive them , i have also said that once you point out why you beleive they are not BS , i will point out why they are BS... something you still have not done .

And yes , they were obliterated into dust , there wasnt as much debri at ground zero as there should have been after a pancake collapse, the dust filled the streets ...

And with regards to the "official" reports ... i mean , based upon YOUR knowladge , your science and math , explain how you see it , and dont quote the so called "experts". You already knew what i meant , but as usual you are dodging any reasonable request.

And as for looking at myself .... tut tut ... is it really getting this low now ?

Once again you are ignoring the fact that i have put forward my theory and am merely asking you for yours ..... how is that accepting what fits into my "worldview" ? Isnt that what discussion is all about ?

I will ask you again ............... why are you even here ?

Plus .... were gas lines in the 911 report ?
edit on 20-10-2011 by ReptileRipper because: (no reason given)



posted on Oct, 20 2011 @ 04:33 PM
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Originally posted by ReptileRipper
Actually as i have already said .... i have been digging into this for years now , i have seen the official reports and i dont beleive them , i have also said that once you point out why you beleive they are not BS , i will point out why they are BS... something you still have not done .


So, you expect me, a layman, to go through every detail of the "official reports," and explain to you why they are not BS? Isn't it easier for you to explain why they are BS? I mean, you're telling me that you deny everything in the "official reports," yet you expect that I'll somehow have an explanation you find satisfactory. Well, I'm not your bitch, so I shall not be doing that, ok?


And yes , they were obliterated into dust , there wasnt as much debri at ground zero as there should have been after a pancake collapse, the dust filled the streets ...


Wrong. Why do I even have to explain how wrong you are here. You say you've been researching for years, yet you don't even know how much debris there was?

I mean, I suppose you think it should have just piled up magically rather than spreading out with the extra energy from the collapse.


The last debris was processed on July 26, 2002, day 321 of the project. At the close of the Staten Island Landfill mission:

• 1,462,000 tons of debris had been received and processed
• 35,000 tons of steel had been removed (165,000 tons were removed directly at Ground Zero)
• 806,000 tons of debris had been screened, an average of 75 tons per hour
• 14,968 workers had been through the PPE process
• 43,600 people (39,795 NYPD, 6,212 non-NYPD) had been through the Site Specific Indoctrination
• Over 1.7 million man hours had been worked
• Over 55,000 discrete pieces of evidence had been recovered
• 4,257 body parts had been recovered
• 209 victims had been positively identified


sites.google.com...

Here's a working archive link of the pdf which contains the data:
web.archive.org...

Now just TRY and tell me that it was mostly converted to dust. Just TRY.


And with regards to the "official" reports ... i mean , based upon YOUR knowladge , your science and math , explain how you see it , and dont quote the so called "experts". You already knew what i meant , but as usual you are dodging any reasonable request.


I'm. not. an. expert. All you'd get from me is my layman understanding. If you won't even accept an expert's explanation, how is mine going to be any better?


why are you even here ?


Because I'm bored, and it's satisfying to learn and help others get past misunderstandings.



posted on Oct, 20 2011 @ 04:41 PM
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Originally posted by psikeyhackr

The south tower was sheared and we have no explanation for the energy that did that.

psik


Are you talking about the truss seats being sheared off? If so, that was because of the collapsing debris and floors.



posted on Oct, 20 2011 @ 04:44 PM
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reply to post by Varemia
 


So let me get this straight .... you simply refuse to tell me what YOU think happened that day ? arent you the one who has this amazing scientific and mathematical knowladge ?
And did i or did i not , say not to use the official reports ?


You do know what a pancake collapse looks like right ? does it look anything like ground zero ?

you didnt answer my question ...... were these gas lines mentioned in the 911 report ?


And is there any need to be copletley ignorant? Why wont you just explain to me your understanding of what happened that day .... its a fair request. Or is it that you dont actually have your own opinion ? and your just accepting what your told like a good little sheep.

Once you have explained to me why you dont think the official reports are BS , i will actually show you why they are BS. Take me up on it ...... i dare ya
edit on 20-10-2011 by ReptileRipper because: (no reason given)



posted on Oct, 20 2011 @ 04:55 PM
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reply to post by ReptileRipper
 


You're ridiculous.

As for the gas lines thing, it's from an eyewitness survival story.

www.bowhunter.com...


At exactly 10:29 a.m., an immense shuddering rumble shook the buried corridor. It was the North Tower was collapsing into itself. .... About then the first fireballs tumbled into the hole, filling his cramped space with searing heat and a radiant flickering light. That was the single moment Will admits that he almost gave up all hope. Please, God, he fervently prayed, don’t let us burn to death!



posted on Oct, 20 2011 @ 04:59 PM
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Originally posted by Varemia
reply to post by ReptileRipper
 


You're ridiculous.

As for the gas lines thing, it's from an eyewitness survival story.

www.bowhunter.com...


At exactly 10:29 a.m., an immense shuddering rumble shook the buried corridor. It was the North Tower was collapsing into itself. .... About then the first fireballs tumbled into the hole, filling his cramped space with searing heat and a radiant flickering light. That was the single moment Will admits that he almost gave up all hope. Please, God, he fervently prayed, don’t let us burn to death!


So in other words ... NO .... it wasnt in the official reports.

And i`m ridiculous ? even though i have come here to discuss the collapse of the towers , and i am ..... you seem to have come here for the same reason , yet wont share your own opinion ..... so please .... tell me how i am being ridiculous ?

Are you going to tell us what YOU think happened , how it all happend , with your science and math ? how many times have i asked you now ? dont use a calculator



posted on Oct, 20 2011 @ 05:03 PM
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Originally posted by GenRadek

Originally posted by psikeyhackr

The south tower was sheared and we have no explanation for the energy that did that.

psik


Are you talking about the truss seats being sheared off? If so, that was because of the collapsing debris and floors.


No, I am talking about the bottom of the 29 story block moving horizontally about 20 feet in less then 2 seconds.





I do not give a damn about truss seats at all. To me it is just part of the floor pancaking crap and explains nothing about how the core could have been destroyed.

psik
edit on 20-10-2011 by psikeyhackr because: (no reason given)



posted on Oct, 20 2011 @ 05:04 PM
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reply to post by ReptileRipper
 


You're telling me that you won't explain what's wrong with the reports unless I give you my opinion on why they're more likely than other theories. This is just ridiculous, and I'm tired of going back and forth with you. I'm done with your trolling.



posted on Oct, 20 2011 @ 05:06 PM
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reply to post by psikeyhackr
 


Look at slides 10-12. They answer your qualm fairly succinctly. If you feel up to it, you can challenge the calculations that are made in the following slides.

www.slideshare.net...



posted on Oct, 20 2011 @ 05:14 PM
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Originally posted by Varemia
reply to post by ReptileRipper
 


You're telling me that you won't explain what's wrong with the reports unless I give you my opinion on why they're more likely than other theories. This is just ridiculous, and I'm tired of going back and forth with you. I'm done with your trolling.


Ok .... go back ..... quote and highlight my trolling please .... as i dont understand why you would say such a thing.

And no , im not telling you i wont explain whats wrong with the reports ..... what i am saying is..

If you know as much as you claim to know .... please explain to me and point out Key parts of the reports that you think completley prove that those two towers collapsed due to burning plastic / carpets / airpreassure ... strucural damage .. what ever it is you actually beleive ... since you have not cleared that up.
Once you have proven to me that you atleast have the slightest idea of what you are talking about , then i will actually SHOW YOU the key mistakes in the official reports.

I have also requested you explain to me in your words , your understanding of what happened .... but your just being childish at the moment.

Seriously ...... why cant you understand what i am writing ? is it coming out in another language ? do you require a translator ?



posted on Oct, 20 2011 @ 05:19 PM
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Originally posted by ReptileRipper
Once you have proven to me that you atleast have the slightest idea of what you are talking about , then i will actually SHOW YOU the key mistakes in the official reports.


This is where you are trolling.

I'm still open to new ideas. I consider demolition to be unlikely, but I don't hold a solid position on any of it. I'd like to see if you have any new information that would be convincing. Thus far, you have not said anything. Every time, you give me this "If and only if" ultimatum. I'm simply not going to play your game, because I know that if I try to explain my basic non-understanding, then you will rip it apart as a strawman to attack. I want to know what you find wrong with the stuff that I linked, because you are adamantly against it. I explain why I am ever against information, or why it is being misinterpreted. That's where I try to stay. A neutral position that attempts to fix misinformation.



posted on Oct, 20 2011 @ 05:28 PM
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reply to post by psikeyhackr
 


What you are seeing is the initiation of the P-Δ effect as a consequence of the viscoplastic buckling of the remaining support columns.

It is well covered in Bažant's Why Did the World Trade Center Collapse?—Simple Analysis



posted on Oct, 20 2011 @ 05:35 PM
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Originally posted by Varemia

Originally posted by ReptileRipper
Once you have proven to me that you atleast have the slightest idea of what you are talking about , then i will actually SHOW YOU the key mistakes in the official reports.


This is where you are trolling.

I'm still open to new ideas. I consider demolition to be unlikely, but I don't hold a solid position on any of it. I'd like to see if you have any new information that would be convincing. Thus far, you have not said anything. Every time, you give me this "If and only if" ultimatum. I'm simply not going to play your game, because I know that if I try to explain my basic non-understanding, then you will rip it apart as a strawman to attack. I want to know what you find wrong with the stuff that I linked, because you are adamantly against it. I explain why I am ever against information, or why it is being misinterpreted. That's where I try to stay. A neutral position that attempts to fix misinformation.


So you see that as "trolling" .... seriously ?


And please .... dont be afraid to explain your "basic non-understanding" .... i am here to hear both sides of the story , but at the moment i sit firmly in the controlled demolition corner ......... i want to know if you can surprise me .... you sit there knocking back anything that points toward controlled demolition , yet will not explain in your own words your reason for doing so. Its frustrating to say the least.

The link you keep throwing up is the same link you have used for pages and pages now .............. isnt THAT considered to be trolling ?


And if you think none of the information i have provided is convincing ...... would you care to point out what you disagree with ? C`mon .... your here to discuss right ? so why the ping pong post game ?



posted on Oct, 20 2011 @ 05:42 PM
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Originally posted by ReptileRipper
.... please explain to me and point out Key parts of the reports that you think completley prove that those two towers collapsed due to burning plastic / carpets / airpreassure ... strucural damage .. what ever it is you actually beleive ... since you have not cleared that up.
Once you have proven to me that you atleast have the slightest idea of what you are talking about , then i will actually SHOW YOU the key mistakes in the official reports.

I have also requested you explain to me in your words , your understanding of what happened .... but your just being childish at the moment.

Seriously ...... why cant you understand what i am writing ? is it coming out in another language ? do you require a translator ?


ReptileRipper, If may quote myself from a recent thread on the identical topic why don't you start here...



post by Drunkenparrot
 

I beg to differ, Bazant describes a satisfactory mechanism that requires neither government ninjas planting demolition charges or Israeli thermonuclear weapons in the basement.


First, let us review the basic argument . After a drop through at least the height h of one story heated by fire (stage 3 in Fig. 2 top), the mass of the upper part of each tower has lost enormous gravitational energy, equal to m0gh. Because the energy dissipation by buckling of the hot columns must have been negligible by comparison, most of this energy must have been converted into kinetic energy K = m0v2/2 of the upper part of tower, moving at velocity v.

Calculation of energy Wc dissipated by the crushing of all columns of the underlying (cold and intact) story showed that, approximately, the kinetic energy of impact K > 8.4 Wc ). It is well known that, in inelastic buckling, the deformation must localize into inelastic hinges. To obtain an upper bound on Wc, the local buckling of flanges and webs, as well as possible steel fracture, was neglected (which means that the ratio K/Wc was at least 8.4).

When the subsequent stories are getting crushed, the loss m0gh of gravitational energy per story exceeds Wc exceeds 8.4 by an ever increasing margin, and so the velocity v of the upper part must increase from one story to the next. This is the basic characteristic of progressive collapse, well known from many previous disasters with causes other than fire (internal or external explosions, earthquake, lapses in quality control)

Merely to get convinced of the inevitability of gravity driven progressive collapse, further analysis is, for a structural engineer, superfluous. Further analysis is nevertheless needed to dispel false myths, and also to acquire full understanding that would allow assessing the danger of progressive collapse in other situations.


Specifically regarding the assertion that

steel will not just crush down upon itself
...


Variation of Mass and Buckling Resistance along the Height Near the top, the specific mass (mass per unit height) μ = 1.02 × 106 kg/m. In view of proportionality to the cross section area of columns, μ = 1.05 × 106 kg/m at the impact level (81st floor) of South Tower.

Although precise data on μ(z) are unavailable, it appears sufficient to use the approximation μ(z) = k0ek2z + k1 (where k0, k1, k2 = constants), with a smooth transition at the 81st floor to a linear variation all the way down. The condition that R H 0 μ(z)dz be equal to the total mass of tower (known to be roughly 500,000 tons) gives μ = 1.46 × 106 kg/m at the base. There are various local complexities whose possible effects were estimated in calculations (e.g., the fact that 16 of 47 core columns at the bottom were much more massive than the rest).

However, they appeared to have no appreciable effect on the overall response, particularly on the diagram of z(t) and the collapse duration. The total energy dissipation per unit height, which represents the resisting force Fc, consists not only of energy Fb dissipated by the inelastic hinges formed during column buckling, but also of energy Fs required for comminuting concrete floor slabs, energy Fa required for expelling air from the tower, and energy Fe required for ejecting particles and fragments.

Based on Fig. 5 and Eq. 8 of Baˇzant and Zhou (2002), we have, for three-hinge column buckling: Fb = Z uf 0 F(u)du h , F(u) = XN i=1 2[Mai(i) +Mbi(0i)] Li sin i , i = arccos  1 − u Li  (6) where F = axial force resultant of all the columns in the story; u = vertical relative displacement between column ends, uf = final u-value; 0i = 2i; i, 0i = hinge rotations at the ends and middle of column i, which are functions of u; Mai,Mbi = bending moments in inelastic hinges at the ends and middle of column i, as functions of i or 0i; and Li = initial clear length of columns i. For plate-type four-hinge buckling, similar simple expressions apply.

Although some core columns were rectangular, their plastic bending moments Mp were nearly proportional to the column cross section areas because, in the weak buckling direction, most core columns had the same width as the perimeter columns. Thus the curve F(u) corresponding to perfect plasticity (Mai = Mbi = Mpi) is not difficult to estimate from the weight of all the columns in a story.

However, three effects doubtless intervened to reduce F(u): 1) multi-story buckling of some columns; 2) softening due to local plastic flange buckling, and 3) fracture of steel in inelastic hinges (the last two likely occurred only at large buckling deflections for which F(u) is small).

The available data are insufficient to make an accurate estimate of these effects, and even the data on the flange thicknesses in the perimeter and core columns of all the stories are missing.

So we simply apply to Fb an empirical correction factor ( 1) which is reasonably expected to lie within the range (0.5, 0.8) for normal structural steel (yield limit 250 MPa), but in the range (0.1, 0.3) for the high-strength steel (yield limit 690 MPa) which was used for perimeter columns in the lower stories.

The high-strength steel has a much lower ductility, which must have caused fractures (with a drop of axial force to zero) very early during buckling, and must have been the cause of formation of large multistory fragments seen to fall from the lower part of tower. Consequently,the energy dissipated (which is equal to the area under the load-displacement curve of column) was probably about the same for high- and normal-strength columns.






What Did and Did not Cause Collapse of WTC Twin Towers in New York



followed by



post by Drunkenparrot
 


In the interest of honest discourse I will withhold further comment until after I have had a chance to follow more of your rebuttal in the thread you linked.

I will say that in 10 years I have yet to read anything more substantial than misinterpretation and innuendo to suggest anything more conspiratorial than gross incompetence to contradict the official story.

For anyone unfamiliar with the conversation, Zdeněk P. Bažant is a well known structural engineer and proponent of the 9-11 OS.

His position is thus..


Previous analysis of progressive collapse showed that gravity alone suffices to explain the overall collapse of the World Trade Center towers.

However, it has not been checked whether the allegations of controlled demolition by planted explosives have any scientific merit.

The present analysis proves that they do not. The video record available for the first few seconds of collapse agrees with the motion history calculated from the differential equation of progressive collapse but disproves the free fall hypothesis (on which the aforementioned allegations rest).

Although, due to absence of experimental crushing data for the lightweight concrete used, the theory of comminution cannot predict the size range of pulverized concrete particles, it is shown that the observed size range (0.01 mm – 0.1 mm) is fully consistent with this theory and is achievable by collapse driven gravity alone, and that only about 7% of the total gravitational energy converted to kinetic energy of impacts would have sufficed to pulverize all the concrete slabs and core walls (while at least 158 tons of TNT per tower, installed into many small holes drilled into each concrete floor slab and core wall, would have been needed to produce the same degree of pulverization).


Regarding the mechanism postulated by Bažant, both direct observation and mathematical prediction seem to be satisfied. The mechanics are clearly defined as described by Bažant in the following...

Differential Equation of Progressive Collapse


The collapse, in which two phases—crush-down followed by crush-up—must be distinguished, is described in each phase by a nonlinear second-order differential equation for the propagation of the crushing front of a compacted block of accreting mass. Expressions for consistent energy potentials are formulated and an exact analytical solution of a special case is given.



The governing differential equations [5] are:





They were derived by continuum homogenization of the energy dissipation per story [5]; t = time, z = vertical (Lagrangian) coordinate = distance of the current crushing front from the initial position of the tower top; the superior dots denote time derivatives; m(z) = cumulative mass of the tower above level z; Fc = resisting force = energy dissipation per unit height,





where Wd = energy dissipation per story due to buckling; Fb = energy per unit height consumed for buckling of steel columns; Fs = energy per unit height consumed by fragmenting (or comminuting) concrete floor slabs and core walls; Fa = energy of expelling air (laden with dust), per unit height (in [5], Fs and Fa were neglected).





Here V0 = initial volume of the tower, V1  volume of the rubble on the ground into which the whole tower mass has been compacted; / (z) = effective compaction ratio = (1/h)× the thickness of the layer of debris to with each story is compacted; kout = fraction of mass that is ejected outside the tower perimeter before it receives significant downward acceleration, and Wd(z) = total energy dissipation up to level z (for the idealized special case of  = Fc = out = 0 and constant μ = dm/dz, Eq. (2) reduces to the differential equation (zz˙)˙ = gz, .

Eq. (2) may be rewritten where Fm = force required to accelerate to velocity z˙ the stationary mass accreting at the crushing front, and ¯μ = d[m(1−)]/dz = non-ejected part of the accreting mass per unit height. This force causes a greater difference from free fall than do forces Fb, Fs and Fa combined.






(repeated from previous post)

Regarding video corroboration of propagation of a crushing front of a compacted block of accreting mass (Crush up/Crush down
)


Some critics believe that the bottom of the advancing dust cloud seen in the video represented
the crushing front. However, this belief cannot be correct because the compressed air exiting
the tower is free to expand in all directions, including the downward direction, which causes
the dust front to move ahead of the crushing front (the only way to prevent the air from jetting
out in all directions would be to shape the exit from each floor as a diverging nozzle of a rocket,
which was obviously not the case).


as well as..

Comparisons of Calculated Motion with Video Record


The main point to note is that the curve identified from the video record grossly disagrees with the free fall curve, for each tower.

The belief that the towers collapsed at the rate of free fall has been the main argument of the critics claiming controlled demolition by planted explosives.

The video record alone suffices to prove this argument false. For the South Tower, the difference between the free fall curve and the curve calculated from Eq. (2) is less pronounced than it is for the North Tower.

The reason is that the initial upper falling mass of the South Tower is nearly twice that of the North Tower, causing the resisting force to be initially a much smaller fraction of the falling weight.


Comparison of Collapse Duration with Seismic Record


Calculations show that the duration of the entire crush-down phase exceeds the free fall duration by 57.6% for the North Tower, and by 41.9% for the South Tower (Fig. 6b). This is a significant difference, which can be checked against seismic records registered at Lamont-Doherty Earth Observatory of Columbia University [23], shown in Fig. 6b. The first tremor, which is weak (and is marked as a), is assumed to represent t = 0, i.e., the moment of impact of the upper part of tower onto the lower part (a correction of 0.07 s is made for the delay due to the travel time of the sound wave along the steel columns to the ground). The sudden displacement increase at instant b (Fig. 6b) is attributed to ejected large structure segments that hit the ground outside the tower perimeter. Their travel durations,9.74 s for the North Tower and 8.4 s for the South Tower, are much shorter than the crushdown
because there is no mass accretion, although they must be a bit longer than a free fall in
vacuum because of air drag (which is, however, relatively small for massive pieces). The free
fall times for ejected mass are 8.61 s and 7.91 s for the North and South towers, respectively
(they are not the same as the free fall times shown in the Fig. 6b, because the ejected mass is
hitting the ground, while the free fall time shown in Fig. 6b corresponds to the upper falling
mass hitting the top of debris pile which is above the ground level).






What Did and Did not Cause Collapse of WTC Twin Towers in New York

Mechanics of Progressive Collapse: Learning from World Trade Center and Building Demolitions





(videos for reference added by current poster)

Zdeněk P. Bažant's academic credentials are honestly impressive, a noticeable contrast to the Architects for 9-11/Truth roster..

Zdeněk P. Bažant's biography on Proceedings of the National Academy of Sciences of the United States of America (PNAS is the official journal of the United States National Academy of Sciences) describes him as...


Engineer Zdeněk P. Bažant is best known as a world leader in scaling research in solid mechanics . His research focuses on the effect of structure size on structural strength as it relates to the failure behavior of the structure. He also has made outstanding advances in structural stability , fracture mechanics, the micromechanics of material damage , concrete creep , and probabilistic mechanics


He is credited with publishing over 400 refereed articles www.civil.northwestern.edu..." target="_blank" class="postlink">PUBLICATIONS OF ZDENˇEK P. BAˇZANT


Born in Prague to a geotechnical engineering professor and a sociology Ph.D., and the grandson of a professor of structural mechanics and former university president, Bažant was the winner of the 1955 Mathematical Olympics.

He studied civil engineering at Czech Technical University (ČVUT), where he was first in his class. He was awarded the C.E. degree with the highest distinction in 1960. While working as a bridge engineer for the state consulting firm Dopravoprojekt in Prague, he studied for his Ph.D. in structural mechanics at the Czech Academy of Sciences, which he received in 1963.

In his dissertation on concrete creep theory, he developed a new method to analyze fracturing and cracking in concrete structures.He went on to earn a postgraduate diploma in theoretical physics from Charles University in 1966 and attained docent (Associate Professor) habilitation in concrete structures from ČVUT in 1967.


Biography of Zdeněk P. Bažant


He is an ISI highly cited researcher in Engineering, which places him among the 250 most cited authors in all engineering fields worldwide. He was elected to the National Academy of Engineering in 1996, the National Academy of Sciences in 2002, Fellow of the American Academy of Arts and Sciences in 2008, and is a registered Structural Engineer in the state of Illinois. He has supervised 60 Ph.D.s in addition to receiving six honorary doctorates of his own (ČVUT 1991, TU Karlsruhe 1997, CU Boulder 2000, Politecnico di Milano 2001, INSA Lyon 2004, and TU Vienna 2005).


Zdeněk Bažant


edit on 20-10-2011 by Drunkenparrot because: (no reason given)



posted on Oct, 20 2011 @ 06:44 PM
link   

Originally posted by Varemia
reply to post by psikeyhackr
 


Look at slides 10-12. They answer your qualm fairly succinctly. If you feel up to it, you can challenge the calculations that are made in the following slides.

www.slideshare.net...


It is not my fault that you regard empty claims as an explanation.

Frank Greening was involved with that. I explained why his 32 page paper was nonsense years ago. He divided the total mass of the building by 110 on page 3. His Potential Energy calculations were nonsense.

forums.randi.org...

psik



posted on Oct, 20 2011 @ 07:08 PM
link   
reply to post by Drunkenparrot
 


Although i agree with alot of things Zdenek Bazant has said , he has openly admitted that he does not have all of the information required to actually go into detail.

And i am still confused as to why so many people beleive this was caused by fire and or structural damage.
The heat from a fire started by kerosene , and burning up various other things like paper plastic wood and fabric, is nowhere near the heat required to even -bend- the steel that was in those towers , there is no way at all did fire bring them down, i remember seeing a documentary back in the 90`s , those things were constructed to withstand everything imaginable.

1 WTC alone sort of swings to the demolition "theory" , during its collapse , it showed no disintegration in the top section as it fell , it was visually solid.

So going by the "truss failure theory" the descending core would have sheared off all bolts connecting trusses to the inner core .... this would have resulted in the failure of all trusses in and around that section of the building, and the perimeter walls would have lost all support.

If the perimiter walls were supposed to be load bearing (which they werent designed to be) .. they would have had no strength without the bracing of trusses, it should have disintegrated as the roof came down.
If fires weakened the core columns of 1 WTC enough for them to fail ( which would have been impossible with kerosene and office equipment ) .... it would have fallen to the side , but it fell straight down where there was obviously least resistance. Sounds like controlled demo to me ... shaped charges on the core columns maybe .

There is no way at all would they have even started construction on those towers if they were as weak as they want you to beleive .......

I can provide a link to the blueprints if anyone is interested and hasnt seen them yet.... just to be nice





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