WTC Collapses

[MacGyver1968]

My source says the following on the subject:
Yamasaki's design for a torsion resistant core structure made from non flexible material, steel reinforced cast concrete, won a competition in strength with several others. All steel towers failed high winds because the steel perimeter columns could take the weight but were prone to flexing and the twisting.

And here lies the problem Scott. Your "source" is a anonymous, poorly constructed, freebie homemade webpage that could have been written by anybody. It's not attributed to anyone, and the data is just put out there for us to believe, with no references to where the data came from. Just because it's on the web, does not necessary make it true. I have seen you time and time again take the word of dubious sources as gospel truth. You have to not only look at the data..but see where it's coming from.

 

[scott3x]

My source says the following on the subject:
Yamasaki's design for a torsion resistant core structure made from non flexible material, steel reinforced cast concrete, won a competition in strength with several others. All steel towers failed high winds because the steel perimeter columns could take the weight but were prone to flexing and the twisting.

there is a lot on that website that doesn't pass the bullshit test, for example what exactly is he communicating here:

Ah, vertical hallways interupting and such . I'll take your word over his. I've never seen the author of that page defend a point; I've definitely seen you do it, however.

 

[scott3x]

This post is in response to Headspin's post 1059 in this thread.

i have not been able to confirm scotts assertion that the box columns was surrounded by concrete. all construction videos i've seen of WTC 1 and 2 shows no such concrete.

I would agree.

Wait, the source didn't say that the box columns were surrounded by concrete, but rather the reverse- that the steel beams surrounded the concrete. Here's a quote:
"The design was a "tube in a tube" construction where the steel reinforced, cast concrete interior tube, was surrounded with a structural steel framework configured as another tube with the load bearing capacity bias towards the perimeter wall with the core acting to reduce deformation of the steel structure maximizing its load bearing capacity. All steel structures with the proportions of the WTC towers have inherent problems with flex and torsion. Distribution of gravity loads was; perimeter walls 50%, interior core columns 30% core 20%."

 

[scott3x]

My source says the following on the subject:
Yamasaki's design for a torsion resistant core structure made from non flexible material, steel reinforced cast concrete, won a competition in strength with several others. All steel towers failed high winds because the steel perimeter columns could take the weight but were prone to flexing and the twisting.

And here lies the problem Scott. Your "source" is an anonymous, poorly constructed, freebie homemade webpage that could have been written by anybody.

I sincerely doubt that. However, as I said, I'll take Headspin's word over this anonymous source.

It's not attributed to anyone, and the data is just put out there for us to believe, with no references to where the data came from.

Well it definitely comes from a truther site, but I agree that references to where the data came from would be very helpful in determining its veracity. Kind of reminds me of the way NIST does many things

Just because it's on the web, does not necessary make it true.

That's true. It just seemed so complex I thought it had to be true. I guess that's how NIST gets a lot of people too...

I have seen you time and time again take the word of dubious sources as gospel truth.

Wait, wait, time and again? As far as I remember there was only the mini nuke thing before this...

You have to not only look at the data..but see where it's coming from.

Well if they'd provided their sources I'd have done just that. But since they didn't and the author seemed to speak in an authorative manner, I felt that it was probably right. As I've mentioned, NIST and the mainstream media employs the same technique and it's certainly managed to persuade many people.

 

[leopold]

. . . with no references to where the data came from.

careful, you start asking questions about "where the data comes from" you might be called a "silly bastard".

 

[scott3x]

The Structure of the World Trade Center, Round 2, Part 2

This post is in response to the 2nd part of shaman_'s post 643 from this thread.

Here is an article which discusses mistake NIST made so you may actually read it. It goes into more detail regarding the distribution of loads on WTC1.

http://www.cool-places.0catch.com/911/loadDistribution_v1.pdf

Can you quote the part where it discusses the mistake(s?) NIST made? Don't want to have to read through the whole thing .

It’s the second paragraph[:]

As will be seen, it appears likely that NIST got the load distributions wrong in favor of survival of the structure. A simple explanation is that the core supported all floor loads within the core plus approximately half of the floor loads outside the core. Further, the DCR for the core is found to be roughly in agreement with Banovic, Foecke, and Luecke [2007] who state “The core columns were designed to carry the building gravity loads and were loaded to approximately 50% of their capacity before the aircraft impact”.

That's one small step for conspiracy theorists but one giant leap for the truth ;-)! Well, perhaps I'm being a little dramatic

Yes. Apparently they believe that the core bore more of the load then the article in 911review.org believed. Still, the difference isn't -that- large. They believe it was 63% and they seem to make no distinction between the core and the steel core columns surrounding it

From what I have read Scott there is no distinction to be made. The steel columns were providing all the support for the core.

Well, since Headspin disagrees with some of that source, if he, Tony or psikey agrees with you on this I'll leave it at that unless I get more evidence.

You honestly think an 18 second video is going to persuade me that the twin towers had no concrete core?

Your own site said so!

I have certainly not seen any evidence of this. Could you please point out where my 'own site' (9/11 research? or 911review.org?) said so?

In fact, comparisons between the Windsor tower and the WTC Towers are limited because of the very different structures of these buildings. The Twin Towers and Building 7 were both 100% steel-framed, with large wide-flange columns and box columns, some measuring over four feet wide and fabricated of steel up to five inches thick. Severe fires in other skyscrapers which, like the WTC Towers, were 100% steel-framed, have not produced even partial collapses.

In contrast to the WTC Towers, the Windsor building was framed primarily in steel-reinforced concrete, with columns of concrete reinforced by thin sections of rebar. 4 The concrete pillars in the Windsor building are clearly visible in the photographs showing the intact core exposed by the collapsed facade. The very light construction of the perimeter, described below, makes it clear that the core was the main load-bearing component of the building.

The framing they are referring to includes the box columns which made up the core.

My base was the source I mentioned before, so again if Headspin/Tony/psikey agrees with you, I'll let it rest.

Except for the one I brought up from 911review.org. I can certainly agree that the whole matter could use further investigation and am very interested in seeing where you believe my 'own site' says that the concrete core wasn't reinforced by steel columns.

Your Madrid Tower article makes no mention of a concrete core at all.

True. Nor does 9/11 Research mention a concrete core in an article dedicated to the design of the twin towers. I certainly trust 9/11 Research more then the other anonymous author from 911review.org.

 

[Buffalo Roam]

The Windsor Tower in Madrid, Round 2, Part 2

The Madrid Windsor Tower was not compromised by a major aircraft strike so it's not the same, parameters.

Plus it didn't use the same construction techniques as the WTC constructions.

The WTC was a litesteel construction, the Windsor Tower was a beam and girder building, with intervening vertical girders between the core and the outer walls.

The WTC floor plan was a open plan with no support for the horizontal floor beams, except at each end, at the Core and outer wall.

So there is no comparison between the two building techniques, and nothing can be gained from the comparison.

 

[Headspin]

The Madrid Windsor Tower was not compromised by a major aircraft strike so it's not the same, parameters.

neither was wtc7

Plus it didn't use the same construction techniques as the WTC constructions.

The WTC was a litesteel construction, the Windsor Tower was a beam and girder building, with intervening vertical girders between the core and the outer walls.

what exactly do you mean by "litesteel" ?

are you still maintaining the towers were supported by the stupid aluminium-like things in your picture?

 

[Tony Szamboti]

careful, you start asking questions about "where the data comes from" you might be called a "silly bastard".

This wasn't the reason I said you seemed to be a silly bastard or were acting like one. You were baiting and then when the data was provided you refused to look at it and used ridiculous excuses.

Even after you did finally look at the data you had the audacity to state that I wasn't qualified to determine the factors of safety of columns with the loads, column cross sectional areas, and the yield strengths known.

 

[scott3x]

Steven Jones debunks some official story claims, Round 2, Part 1

This post is in response to the 1st part of shaman_'s post 648 in this thread.

Indeed I must first apologize for something- I was referring to Steven Jones debunking one of the aforementioned peer reviewed documents as well as some information from NIST, not debunking Abstaneh specifically.

With that in mind, here's an excerpt from the above linked paper:
****************************
My reasons for advancing the explosive-demolition hypothesis while challenging the “official” fire-caused collapse hypothesis are these:
1..2..3..etc..

11. One attendee to the BYU Seminar on 9-11 anomalies suggested I review the paper by Bazant and Zhou, which I did. Quoting:

The 110-story towers of the World Trade Center were designed to withstand as a whole the forces caused by a horizontal impact of a large commercial aircraft. So why did a total collapse occur? (Bazant and Zhou, 2002, p. 2.)

Leslie Robertson:
"We had designed the project for the impact of the largest airplane of its time, the Boeing 707. The 767 that actually hit the WTC was quite another matter again. First of all it was a bit heavier than the 707, not very much heavier, but a bit heavier. But mostly it was flying a lot faster. And the energy that it put into the building is proportional to its square of the velocity, as you double the velocity, four times the energy. Triple the velocity, eight times the energy and so forth. [Sic; actually triple velocity means nine times the kinetic energy.] And then of course with the 707 to the best of my knowledge the fuel load was not considered in the design, and indeed I don't know how it could have been considered. But, and with the 767 the fuel load was enormous compared to that of the 707, it was a fully, fully fuelled airplane compared to the 707 which was a landing aircraft. Uh, just absolutely no comparison between the two. [19]"

I've gone over this before, but perhaps when you wrote this I hadn't yet gone over it (this post is something like 400 posts before present after all). Anyway, basically, the 767 wasn't going fully loaded and the twin towers were definitely designed to handle their impacts, according to John Skilling, who some argue was the true lead designer of the towers (as opposed to Leslie).

Correct — jet collisions did not cause collapses — we can agree on that. MIT’s Thomas Eager also concurs “because the number of columns lost on the initial impact was not large and the loads were shifted to remaining columns in this highly redundant structure” (Eager and Musso, 2001).

We continue with Bazant & Zhou:

The conflagration, caused by the aircraft fuel spilled into the structure, causes the steel of the columns to be exposed to sustained temperatures apparently exceeding 800C… (Bazant and Zhou, 2002, p. 2.)

But here we note from the recent NIST report that: “The initial jet fuel fires themselves lasted at most a few minutes” and office material fires would burn out within about 20 minutes in a given location. (NIST, 2005; p. 179, emphasis added.) Certainly jet fuel burning was not enough to raise steel to sustained temperatures above 800C.

But, as demonstrated, office materials can.

From what I remember, it wasn't demonstrated, but feel free to provide your alleged evidence (once more?) for me to (once again?) debunk it. I also see that you have handily sidestepped the fact that I've proven my point- Steven Jones has just handily debunked some Bazant and Zou's peer reviewed material and you haven't even batted an eye...

But we continue:

Once more than half of the columns in the critical floor.. suffer buckling (stage 3), the weight of the upper part of the structure above this floor can no longer be supported, and so the upper part starts falling down onto the lower part below…”(Bazant and Zhou, 2002, p. 2.)

Bazant & Zhou do not explain how “more than half of the columns in the critical floor [can] suffer buckling” at the same time to precipitate the complete and nearly symmetrical collapse observed.

Describing it as all the columns bucking at the same time can give the impression of something unnatural happening.

Certainly something that couldn't have happened without syncrhonated explosives, yes.

It doesn't quite work like that. There was clear weakening of the support columns leading up to the collapse. Floors were sagging and pulling on the perimeter columns.

Sagging floors in a localized area of the buildings don't create a tower that collapses at near free fall speeds, sorry. I constantly marvel at the fact that you fail to question -why- it is that NIST never modelled the actual collapse of the towers, instead leaving things at 'poised for collapse'.

This is evidence that the conspiracy theorists are unable to account for. When the supports were sufficiently weakened so that a collapse started the remaining ones were not able to hold the extra load so they fail as well. So they didn't fail at exactly the same time.

I'm sure Tony or Headspin could really debunk these arguments. As for myself, I'll simply ask if you can provide evidence that the office fires could have collapsed even 1 floor. If you can manage that, I'll be happy to hear evidence on how it would have caused the collapse of the rest at near free fall speeds.

 

[Tony Szamboti]

The Madrid Windsor Tower was not compromised by a major aircraft strike so it's not the same, parameters.

Plus it didn't use the same construction techniques as the WTC constructions.

The WTC was a litesteel construction, the Windsor Tower was a beam and girder building, with intervening vertical girders between the core and the outer walls.

The WTC floor plan was a open plan with no support for the horizontal floor beams, except at each end, at the Core and outer wall.

So there is no comparison between the two building techniques, and nothing can be gained from the comparison.

You are completely wrong about this litesteel notion. I believe you actually mean lightweight construction. There is a big difference.

The core columns in the towers were either built up box beams, made by welding structural steel plates into the specific shape, or rolled wide flange sections. The perimeter columns were built up box beams, made by welding structural steel plates into the specific shape, joined together by deep spandrel plates welded to them in a horizontal way and creating a moment resisting frame. The perimeter columns had a 5.00 to 1 safety factor for gravity loads and the central core a 3.00 to 1 safety factor for gravity loads.

Most skyscrapers built since the twin towers use a similar construction method to create more open floor space but this does not mean they are weak. The important thing to do in building any structure is to put the material where it needs to be to take the loads while minimizing stress and maintaining stability. Your contention that lightweight construction is what caused the towers to collapse has no basis. What caused the core to collapse? It was not lightweight and could handle three times the load that was on it. There was no deceleration of the upper block so it's load couldn't have been amplified. You need to think seriously about this if you are an honest person.

 

[Tony Szamboti]

I have seen no evidence that the core of the twin towers was concrete. the towers had to flex in the wind, i don't see how a concrete core could survive 50 years of flexing.

There are some very tall structures made from reinforced concrete but the core columns in the twin towers were not concrete. They were mostly built up box beams made from ASTM A36 structural steel and those that weren't box beams were rolled wide flange I sections made from ASTM A36. The cross sections can be seen at http://wtcmodel.wikidot.com/nist-core-column-data. This data was released by the NIST in the summer of 2007.

 

[Tony Szamboti]

Rescue, escape what ever, it was remarkable the the Towers lasted long enough to allow all those people to make it out.

The fact is that in that type of construction, the Outer Walls need the Inner Columns for their structural integrity, and the Inner Columns need the Outer Walls to keep it's structural integrity.

Compromise either one and the system fails and you get a catastrophic collapse, and both outer wall and column in the WTCs were compromised, and the damage spread out from their like dominos causing more and more lose of structural integrity to the wall systems and inner columns, till total catastrophic collapse initiated.

What is really remarkable is that some still support this theory given the fact that there has been no physical evidence provided to substantiate claims of high steel temperatures in the towers and that 99.5% of the steel was never tested and out of the 0.5% that was very little of it was from the fire affected areas.

The central core was self supporting. It isn't true that it needed anything else to support it. Additionally , why would the neighboring perimeter columns simply collapse when a floor section attached to another column allegedly gave way? The perimeter columns did not give way when their neighboring columns were impacted and cut by the aircraft. That would have put a whole lot more stress and strain on them than a nearby floor section.

 

[scott3x]

I have seen no evidence that the core of the twin towers was concrete. the towers had to flex in the wind, i don't see how a concrete core could survive 50 years of flexing.

There are some very tall structures made from reinforced concrete but the core columns in the twin towers were not concrete. They were mostly built up box beams made from ASTM A36 structural steel and those that weren't box beams were rolled wide flange I sections made from ASTM A36. The cross sections can be seen at http://wtcmodel.wikidot.com/nist-core-column-data. This data was released by the NIST in the summer of 2007.

Wait, neither I or the anonymous source ever said that the columns were concrete- the idea was that there was a concrete core surrounded by steel columns. That may be wrong as well, but I just wanted to set the record straight on what I actually said.

 

[Tony Szamboti]

Wait, neither I or the anonymous source ever said that the columns were concrete- the idea was that there was a concrete core surrounded by steel columns. That may be wrong as well, but I just wanted to set the record straight on what I actually said.

They couldn't pour concrete in the rolled wide flange I-section columns and it is unlikely that they filled the box columns. I think there would have been a concern about damaging the welds on the box beams which occurred every three floors. They also didn't need any additional compressive strength as the stress on both the core and perimeter columns from gravity was approximately 11,000 psi and the yield strength of the core columns was 36,000 psi or above. The yield strength of the perimeter columns varied from 36,000 psi to 100,000 psi depending on where they were located. The reason for these higher strengths of some of the perimeter columns was bending resistance to take wind and seismic loads not gravity loading.

 

[leopold]

Even after you did finally look at the data you had the audacity to state that I wasn't qualified to determine the factors of safety of columns with the loads, column cross sectional areas, and the yield strengths known.

and i'll say it again, you do not have the experience nor the expertise to determine safety factors in connection with high rise buildings.
nothing audacious about it.

just because i can run a perfect weld on aluminum by no means says i'm qualified to weld pressure vessels does it?

you know where i'm coming from tony, stop being obtuse about it.

 

[Tony Szamboti]

and i'll say it again, you do not have the experience nor the expertise to determine safety factors in connection with high rise buildings.
nothing audacious about it.

just because i can run a perfect weld on aluminum by no means says i'm qualified to weld pressure vessels does it?

you know where i'm coming from tony, stop being obtuse about it.

Now you are just being straight out inane. Maybe your avatar really suits you literally.

I am plenty qualified to determine what those factors of safety on the tower columns were. I am a structural engineer and it is a simple procedure for gravity loaded columns. I explained the calculations in the paper.

I am curious as to what your criteria would be for someone to be qualified to do it. So why don't you tell us? While you are at it tell me what you think I could have gotten wrong.

The obtuseness is obviously not on my side Leopold.

 

[leopold]

I am curious as to what your criteria would be for someone to be qualified to do it. So why don't you tell us?

i got straight A's in welding school. my teacher even extolled my achievements in a recommendation letter. will NASA let me weld their LOX tanks?


that's why.

 

[Buffalo Roam]

You are completely wrong about this litesteel notion. I believe you actually mean lightweight construction. There is a big difference.

The core columns in the towers were either built up box beams, made by welding structural steel plates into the specific shape, or rolled wide flange sections. The perimeter columns were built up box beams, made by welding structural steel plates into the specific shape, joined together by deep spandrel plates welded to them in a horizontal way and creating a moment resisting frame. The perimeter columns had a 5.00 to 1 safety factor for gravity loads and the central core a 3.00 to 1 safety factor for gravity loads.

Most skyscrapers built since the twin towers use a similar construction method to create more open floor space but this does not mean they are weak. The important thing to do in building any structure is to put the material where it needs to be to take the loads while minimizing stress and maintaining stability. Your contention that lightweight construction is what caused the towers to collapse has no basis. What caused the core to collapse? It was not lightweight and could handle three times the load that was on it. There was no deceleration of the upper block so it's load couldn't have been amplified. You need to think seriously about this if you are an honest person.

Tony I am being honest, and I also have a Brother-in Law, who was the president of one of the largest construction firms on the West Coast, and I spent the afternoon on the phone with him asking questions.

He pointed out that the floors of the WTC were laterally braced, and no vertical bracing at all, they were only connected at each end to the Core Column and the Outer Wall, other than that, there was no vertical bracing of the floor support beams.

So when the collapse came, the only support the lower floor had was at each end, and those end supports basically only were designed for load + 15% that is standard, on occasion it is a safety factor of load + 25%, and even only 10 storys coming down on that is far in excess of load + 15% or even load + 25%, and that is with no damage to the structure.

Hell even load + 100%, means that the receiving floor could hold it's self + the next floor above it, not the other 9+ floors, and with every floor collapse, that weight only increased, and the safety margin still stayed at Load + 15%.

He suggested these as a lead:

http://www.usyd.edu.au/research/opportunities/opportunities/415

Behaviour of LiteSteel Beams (Hollow Flange Channels)
Summary

This project involves the researching the structural behaviour of LiteSteel Beams.


Supervisor(s)
Dr Tim Wilkinson

Research Location
Civil Engineering

Synopsis

Smorgon Steel have developed a new range of cold-formed steel sections using a patented Dual Electric Resistance Weld technique. This allows the production of structural shapes similar to those of traditional hot-rolled steel sections but with hollow flanges - which increase the torsional stiffness of the section. The result is a hollow flange channel section, which has is being marketed as the LiteSteel Beam.

The Department of Civil Engineering and Smorgon Steel were awarded an Australian Research Council Linkage Grant to research the structural behaviour of these new sections. The main aim has been to identify the specific areas in which these sections would behave differently to normal cold-formed sections, and then investigate this behaviour. It was identified that the behaviour under bearing, bending moment and connections would require research. Other structural actions, such as compression, are being researched, in order to take advantage of the higher material strength in the weld.

This research involves experimental investigations and finite element analysis. A team of researchers are examining the various aspects of the behaviour.

Bearing Capacity: Tests on different orientations of joists and girders are assessing the bearing strength of the sections. Complexity is involved in the interaction between flange crushing and web crippling modes. Assessment of some simple stiffening/strengthening menthods is also being carried out.

Connections: Research on the connection behaviour of LSBs has begun. The initial program is to research connection behaviour using traditional connection methods of bolting, with subsequent research to consider connectors such as screws and nails which can be used more easily on the construction site.

Compression: The unique shape of the LSB gives the hollow flange of the section a higher yield stress than the web. Research is being undertaken to capitalise and quantify the strength enhancement that this can provide.

http://www.usyd.edu.au/research/opportunities/opportunities/417

Section Classification & b/t Limits for Hollow Sections
Summary

Most of the current b/t limitations in international steel design standards are based on investigations of hot-rolled I-sections. This project has been examining the behaviour of hollow sections, such as RHS and SHS to examine their classifications.

To date, there have been bending only tests on SHS and RHS, as well as bending and compression tests on SHS and RHS in both the Class 1 and Class 2 range. Finite element simulation has also been performed.


Supervisor(s)
Dr Tim Wilkinson

Research Location
Civil Engineering

Synopsis

When a beam has suitable lateral bracing, its strength is usually governed by local buckling of the individual plate elements that make up the cross-section. A section is classified according to its moment capacity with respect to the fully plastic moment (Mp) and the yield moment (My) and the rotation capacity. A beam cross-section that can resist the plastic moment, and has a sufficiently large rotation capacity to be deemed suitable for plastic design is sometimes call a “Class 1” or “plastic” or “compact” section depending on the terminology of the relevant specification.

Local buckling is primarily a function of the slenderness of the individual plate elements, usually referred to as the b/t ratio. Design standards specify slenderness limits against which the b/t values are compared in order to classify a cross-section. These limits change according to the stress distribution and support conditions experienced by the element under consideration.

Some of the publications related to this research include:

*Wilkinson T. and Hancock G. J., (2002), “Predicting the rotation capacity of cold-formed RHS beams using finite element analysis”, Journal of Constructional Steel Research, Elsevier, Vol 58, No 11, November 2002, pp 1455 - 1471.

*Wilkinson T. and Hancock G. J., (2000), “Tests to examine plastic behavior of knee joints in cold formed RHS”, Journal of Structural Engineering, American Society of Civil Engineers, Vol 126, No 3, March 2000, pp 297 305.

*Wilkinson T., (2003), “Recommendations for Cold-Formed RHS in Bending and Compression”, Tubular Structures X, Proceedings of the 10th International Symposium on Tubular Structures, Madrid Spain, (Balkema, publ.), (Jaurrieta, Alonso & Chica eds.), pp 293 300.

*Wood K. and Wilkinson T., (2003), “Measuring Imperfections in Hollow Sections”, Tubular Structures X, Proceedings of the 10th International Symposium on Tubular Structures, Madrid Spain, (Balkema, publ.), (Jaurrieta, Alonso & Chica eds.), pp 285-292

*Jouaux R & Wilkinson T, (2005), "Tests To Examine The Effect Of Axial Compression On The Rotation Capacity Of Square Hollow Sections", ICASS05, 5th International Conference on Advances in Steel Structures, Shanghai, China

 

[leopold]

He pointed out that the floors of the WTC were laterally braced, and no vertical bracing at all, they were only connected at each end to the Core Column and the Outer Wall, other than that, there was no vertical bracing of the floor support beams.

that was one of the innovative features of the twin towers. each floor was almost an acre of uninterrupted floor space that could be partitioned any way the renter deemed necessary.