Rick Ensminger
9-11 - Re: WTC Exterior wall plans
Sun Aug 8, 2004 15:22
64.140.158.66

-------- Original Message --------
Subject: Re: WTC Exterior wall plans
Date: Sun, 8 Aug 2004 10:55:39 -0700 (PDT)
From: Rick Ensminger aristos3@yahoo.com
To: Jean Gordon jgordon@igc.org,  F

Tom,
I've been busy and haven't had much time to research the questions of the exterior wall strength of wtc towers 1 & 2. I'm not an expect on construction by any means and some of the technical construction jargon goes by me. But I do have a few questions after having dug around a bit on the subject because what I'm seeing conflicts with what you seem to be saying.

You've maintained that all exterior support colums were made of aluminum. Even said that "There is NO STEEL in the vertical domain, anywhere on the outer wall." Correct me if I'm wrong but your position seems to be that the perimeter wall was so light and flimsy that the 767 had no problem whatsoever achieving deep penetration....that the penetration was so easy that the plane appeared to melt into the building with such meager and flimsy reistance.

I'm wondering how such flimsy construction could have even withstood the considerable lateral forces of wind that all such high rises face?

I may be wrong but from what I have seen in my readings, the only aluminum on the exterior wall was part of the fascade, not the support structure. I'm seeing that the exterior frame was indeed all steel, both the columns and the spandrel plates. Here is part of what I am seeing:

http://www.wcsscience.com/wtc/page3.html

The World Trade Center towers were an unusual design, at least at the time they were built. Their support structure is called a 'bundled tube', or in engineering terms, a glass curtain wall structure.

What this means is that the buildings are tubes, made rigid by a lattice of steel beams on the outside walls.

These vertical columns are strengthened by horizontal beams, and this design is what helps support the building, and keep it stable in high winds. An inner concrete core houses the elevators, and provides additional vertical load support.

The towers had an outer facade of aluminum and glass, and its floors were reinforced concrete. Surprisingly, the many office windows were quite small, designed that way because the architect had a fear of heights!

Apparently this design, which provides support through its load-bearing walls, was one factor which prevented one of the towers from collapsing after the 1993 WTC parking garage bombing

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http://www.unc.edu/courses/2001fall/plan/006e/001/engineering/

Most buildings before the 1970's would use heavy interior bracing and heavy exterior masonry. In addition to this, most of the buildings in New York used interior "X" bracing frames for support against wind. The World Trade Center was different. It used light materials on the outside, and heavy materials on the inside. Yamasaki decided to make his frame a cantilever up (meaning the support came from vertical beams) from the foundation. To use a cantilever up system, though, Yamasaki had to make the frame strong enough to withstand the winds from Caribbean hurricanes that travel up the East Coast (Yamasaki, 116). After much research, engineers were able to conclude that the best way to apply the cantilever up was by using the exterior walls as the main frame. This was the most technological and efficient way, because it used the entire perimeter of the building for support rather than just the interior core. Building's of this structure are often referred to as "tube buildings". The building's 208 foot wide face was threaded by steel columns, 61 on each side (Building Big). Every one of the 61 columns was eighteen inches wide, and there was twenty-two inches between each of them for a window. To save energy on cooling and heating Yamasaki had the columns go twelve inches deep from the outer aluminum face of glass.

The floors acted as a diaphragm that stiffened the outside walls against lateral buckling forces from wind-load pressures (Great Buildings). In a one-hundred mile per hour wind, the towers would move only eight inches, which is nothing in comparison to the building's size (Yamasaki, 116) The floors construction was a networks of steel trusses[note that this is disputed by some; that the horizontal floor supports were actually steel girders] that ran between each column to the building's core 60 feet in, where the elevators were located. These steel trusses held up each of the concrete floors that strengthened the building.

95% of the building's frame was steel. Yamasaki discovered that steel was much stronger than it had been in the past. He knew it would be able to support the building for a longer period of time. By using steel, the tower floors were free of interior columns (With the exception of the core), making for more internal space.

The exterior was made up of a silver aluminum. Aluminum had to be used because any heavy materials would put to much stress on the building.

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http://graybeards.home.att.net/wtc.html

To handle these immense forces, the engineers "designed the World Trade Center essentially as a large beam section," explained another panel member, Robert McNamara, president of the engineering firm McNamara and Salvia. Called structural tubes in the business, each twin tower was strongly framed in structural steel. The frame comprised inner and outer rectangular box tubes consisting of closely spaced steel box columns connected by steel spandrel members or truss beams that supported 40,000-square-foot cross-braced floors, each nearly an acre in area, the empaneled engineers said. This configuration created a complete exterior tube around the building and a center tube down the middle.

The outer perimeter tube, a tight prefabricated latticework with 61 14-inch steel box columns (spaced 39 inches on center) on each building face, provided all the bracing resistance against lateral and twisting forces from wind and seismic action. This exterior grid served as a moment frame, providing a large moment arm (of torque) against overturning and deflection forces. The outer tube bore part of the gravity-induced downward load as well as, they noted.

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And the investigation of the wtc debris shows many pictures of these perimeter steel columns and spandrel plates and I did not see the mention of aluminum in any of the reports when they referred to the exterior colums and spandrel plates. here is an example. Note pictures D-5 and D-8. No reference to aluminum, just steel. http://members.fortunecity.com/911/wtc/WTC_apndxD.htm

As mentioned above, it was the strength of the steel colums that supported the load-bearing walls that kept the building from collapsing after the 1993 bombing. It appears the steel columns were 18 inches wide, went 12 inches deep and were spaced 39 inches from center of each column. That might provide not only some strong lateral resistance to wind and earthquake but to a 767 also. Especially when one considers the reinforcement of the steel reinforced concrete floors and the steel girders under them that connected the inner core to the exterior steel frame.

I remember reading about the official story in which it was explained that each floor was only supported by thin steel trusses and that is what made the collapse and pancaking possible. There are those who disagree and argue that there is no way trusses could have held up against just the wind pressure, much less a 767. Here's one point of view on that: http://vancouver.indymedia.org/print.php?id=40462

The following is taken from the M.I.T., Rotch Visual Collections article Sixty State Street - A Case Study. This teaching resource was available on the internet for years until the 9-11 cover-up required its withdrawal from the public domain. If one desires additional evidence pointing to the group behind the September 11 disaster, all one has to do is to endeavor to find pre-9-11 technical information concerning the World Trade Center (or in fact any other similarly built skyscraper). What one will find is that the internet has been swept clean of such information. Neither Al Qaeda, nor the Arabs, or any other group of Islamics, have the capability to do this. September 11, was clearly an inside job.

[What he seems to be saying, if I am interpreting him correctly, is that if a 39 story building in Boston, The Sixty State Street Bldg., required heavy steel girders(beams) under each floor to fortify the exterior wall from lateral forces, then how could they reduce the requirements of protection and strength for a 110 story building which would be subject to a much higher and stronger lateral force from wind.]

"At 110 stories of the World Trade Center towers were considerably taller than the 39 story Sixty State Street. Thus the wind loading (the horizontal force due to the wind) on Sixty State Street was significantly less than that experienced by the towers. Nevertheless, these lateral forces were still sufficient to necessitate the same heavily reinforced perimeter wall and composite flooring system that was used in the construction of the towers. Without its specially designed perimeter wall and flooring system, Sixty State Street would have simply blown down in high winds."

He's saying that both the exterior wall and the floor beam supports which connected the exterior frame to the inner core frame had to be of a strength way beyond flimsy trusses in order to even prevent the buildings from blowing over.

He gives a link which provides some visual support for the steel floor girders:

http://www.911review.org/Wget/www.nerdcities.com/guardian/wtc/they-lied-about-trusses.htm

The truss theory is the absurd belief that the only support (between the central core and the perimeter wall of the World Trade Center) for the concrete floor slabs, was lightweight trusses. It was invented to explain away what were obviously demolitions and has become the "official" dogma. The central core, perimeter wall and the mythical trusses are all introduced in the article: The World Trade Center Demolition. There you will find out their dimensions, their numbers and their supposed usage. The following illustration describes one of the mythical trusses.

The fact that the tubular structure of the walls is very rigid, does not stop the central core from needing to bend when the walls bend. This means that the walls have to transmit the full force of the wind to the core, so that the core will flex to the same extent as the walls (this is obvious, otherwise if the walls flex while the core does not, the floor slabs would, by definition, be crushed). Again, it is important to note that the rigidity of the walls does not protect the central core from the full force of the wind, what it does, is it limits the distance that the walls (and hence the whole structure) can bend. The more rigid the design the less it tilts in the wind.

In strong winds the midsection of the windward wall will be pushed several feet towards the core. In a typical steel framed building of WTC type design, heavy steel beams transmit the wind loading to the core, which then bends together with the walls. However, in the WTC (as described in the "truss theory") the trusses and floor slabs are too weak to transmit this force to the core without buckling, so the core will stay in its original position as the wall advances to it. This will crush the trusses and floor slabs, leading to the collapse of many floors. Since this did not occur during the 30 years in which the buildings stood, we must assume that the "official" story is false. To see how utterly ridiculous the "official" story is, lets calculate the lateral loading (wind loading) that each one of these trusses was expected to resist. Consider, a one floor segment. Here, we have 30 trusses and a slab of concrete supporting 56 tons. That is about 2 tons per truss and piece of slab. If you balanced a 2 ton block of steel on top of one of these flimsy 60 foot long trusses and (a 60 foot long by 6 foot 8 inches wide by 4 inches thick) slab of concrete, we all know what would happen - the truss and slab would buckle and collapse.

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It appears that a very strong perimeter steel column and steel spandrel frame and a very strong steel floor girder support system was needed just in order to keep the wtc towers from blowing over. Note that the floors were also steel reinforced concrete, each being 4 inches thick and poured on top of a steel deck which was 1 1/2 inches thick itself. And there were the steel girders underneath that. They were all connected in such as way as to make the entire floor function as one unit so as to transfer the lateral forces effectively between the inner and outer frames.

The fact that there was no vertical column support between the inner core and the exterior wall would seem to require that the floors and exterior walls be even stronger to compensate for that loss of support. And from what i have read so far, it appears that both wtc #1 and #2 were built with additional exterior strength and horizontal floor strength to compensate for the lack of vertical columns between. If they had not, then either the 93 bombing or the winds would probably have collapsed those buildings long ago, it would seem.

If the entire exterior frame was solid steel, and it appears it was, and the floors were heavy steel reinforced and supported by steel girders, then it appears a 767 would encounter some pretty strong resistance if it came slamming into that kind of structure.

I see that Brad had posed the question before of why the plane did not show any reaction of hitting any of the steel and concrete floors. I reread your reply but am still confused by your answer. It doesn't seem to address his question.

If a 767 hit one of those steel and concrete floors with the steel girder supports, then why did we not see a shearing effect on the plane? Especially if it had to go thru a steel column and steel spandrel barrier first? What's a "bullet into gelatin" got to do with that?

From what I saw on the videos, it doesn't appear that the "plane" met any resistance whatsoever. yet, it sure appears there was a lot of steel and concrete resistance there to meet it.

If I am misinterpreting the above or leaving out pertinent info, please let me know.

Rick





Jean Gordon wrote:

That's right. Each of the exterior collums are made of cast aluminum. Check out Architectrual Record. I'm just going based on: What I have read, What I have touched, and What information I had given to my Dad, when I asked him to help me solve this riddle, back in 1989, or 90.

He's the one who told me that the 'electrolytic' reaction [in this specific application] would most certainly be profound. That's all he did for Alcoa; bond/reaction work. We had samples of each type they made , plus manganites, silicas and lead. I was raised on pre-cast.

Anyway, If the exterior were Iron, or Steel????

What in the ____ can you people be thinking? It would be utterly impossible for either plane to penertate. No 'professional' architect would have bought it for a second. Webfairy would be President and Bush would be in Git'mo where he belongs!

Since you weren't reading AR, ID, or Metropolis all these years, you probably missed the comparative, side-by-side structural diagrams of all the tall buildings in the world. You will discover this is the only one of its type. Hancock Tower (and the New WTC for that matter,) all have cross-bracing just inside the glass. Where you may get confused is when the same cross-bracing design is used on the exterior, called an exoskelital structure. WTC was a ribbon-flow, multi-lattice affair. It truly 'wiggled' while the Empire State Swwwwayyyyed!

Anyway, "the steel" you're worried about (in the few surviving rooftop photos) is just inside all the verticals you show. It's on about a 26' center, not smaller, if I remember. Each plane would have collided with fewer than