How Does Aluminum Cut Steel?

Originally posted by OrionStars
Meaning that the most the plane could have traveled, after tearing out an outside wall of steel and concrete

Just steel. There was no concrete in the outer walls of the WTC.

plus, tearing out the internal steel and concrete internal walls

There was no concrete between the outer walls and the core. The walls were made of plasterboard.

Now either any plane, with heavily lost velocity and momentum, had to either fold like an accordion, slowly enough for the back half of the plane to move forward, and end up entirely in the building. Or, approximately 79', or some footage thereof, of commercial jetliner was going to be extending on the outside of the impact hole, if not folding at all or folding at some footage between 0 and 79‘.

The planes that struck the towers were a 218,000lb mass, moving in unison as a single body. until the point that they lost their structural integrity at which point the individual objects would still be moving forward at considerable speed until such time as they lost inertia or were bought to rest.

The center cores were specifically designed to take the impact of the 707, which was the largest commercial jetliner of its day. There is little difference between 707 and 767 to quibble over minor details of comparison. In other words, no plane compromised the center core beams, due to designing and constructing it to take a 707 impact.. It was planned that way directly due to the history of the EBS and no other reason at the time.

The outer walls were load bearing, and clearly compromised. The structure started to move around its own axis - that is to say that the places where the integiry of the structure were compromised suddenly had no support, this would have caused rapid failure at other joints, welds, bolts etc. Considering that there was actually very little resistance between the steel outer wall and the central core, its entirely possible that large parts of the plane passsing through the structure could have damaged them sufficiently to expose the steel cores.

When academics have never spent a great deal time at working in the field areas of their degrees, they become dependent on the books and articles of those who do, in order to teach what other people experienced long term in a field of employment.

Kind of patronising that really - what you are trying to do is negate the argument put forward by academics because they've not worked in the industry. I'm a civil engineer with structural qualifications. How about you?

Originally posted by neformore


Just steel. There was no concrete in the outer walls of the WTC.

The following says there was.

911review.org...

“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%.

Steel, no matter what temper, no matter what bracing is used, ends up with an overall flexation that exceeds design parameters for deformations and failures occur. These were fact I learned from a documentary in 1990 about the construction of the north tower. Yamsaki's decision making process was outlined and rejected core designs identified.

Both the WTC 1 & WTC 2 towers had a rectangular cast concrete core structure formed into rectangular cells that had elevators and stairways in them.”

So as not to be misled by the last sentence above, the central core steel beams were coated in concrete to avoid the problems being described above.

There was no concrete between the outer walls and the core. The walls were made of plasterboard.

lease see the website above with your repeated no concrete contention.

Exactly what did they attach the plasterboard to in order to make secure walls? What about doors? To what did they frame in and attach them? How did they divide the office space with plasterboard attached to nothing?

The planes that struck the towers were a 218,000lb mass, moving in unison as a single body. until the point that they lost their structural integrity at which point the individual objects would still be moving forward at considerable speed until such time as they lost inertia or were bought to rest.

I could care less if they were 2,180,000 lb masses. How else would an entire intact plane move but in unison as one entire intact plane constructed of various parts?

When a moving object meets a stationary object, and has to slice through materials such as concrete and steel,, the moving object is going to lose a great deal of velocity and momentum on impact, and even more being forced to slice through anything. That is a law of physics given.

The outer walls were load bearing, and clearly compromised. The structure started to move around its own axis - that is to say that the places where the integiry of the structure were compromised suddenly had no support, this would have caused rapid failure at other joints, welds, bolts etc. Considering that there was actually very little resistance between the steel outer wall and the central core, its entirely possible that large parts of the plane passing through the structure could have damaged them sufficiently to expose the steel cores.

Could you qualify further what you mean by this: “The structure started to move around its own axis - …” Exactly where on the building are you placing a hypothesized axis?

You know for a fact the outer wall load bearing walls were obviously compromised? How do you know that for a fact? With the exception of the south tower lean, I haven’t seen one picture or video obviously indicating load bearing compromise on any of the walls. No sagging , no nothing, apart from the obvious severe compromise of the upper floors of the south tower.

I know the exterior walls were load bearing, and were assisted by the concrete slabs of flooring. If the floors were compromised that did not follow the center cores were, and cannot be assumed to be so. If any of the floors had actually collapsed, they still would not have taken the center core with them. There is no actual proof /validation any floor, truss, or load bearer was compromised . That has been entirely speculation to meet the demand of the Bush administration’s “official” report. One truss break is not going to collapse a floor.

Since there is no living witness to any alleged single truss break being responsible for bringing down the twin towers in their own footprints, all we have left is after-the-fact investigation by experts not interested in following any political party line, and proceeding by using every tool science has to offer, for the most viable explanation of what did happen, to drop three WTC buildings in their own footprints. Nothing prior to WTC has ever done the actual collapse effects but controlled demolition implosion.

Kind of patronising that really - what you are trying to do is negate the argument put forward by academics because they've not worked in the industry. I'm a civil engineer with structural qualifications. How about you?

How so? That is what happens in the academic world. If people have little to no field experience in their fields, they are dependant on information from those experts who do. Acquiring knowledgeable expertise is not simply teaching or reading what anyone else relates. Knowledge expertise results from applying, testing, and experiencing what one has studied in books related by others.

Originally posted by OrionStars
The following says there was.

Now, excuse me here. I'm going to bold something in what you quoted. You see, I was referring to the outer walls of the WTC and to refute that you quoted this....

911review.org...

“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.

Which does not refer to the outer walls at all, it refers to the core. And in my post I said

There was no concrete between the outer walls and the core. The walls were made of plasterboard.

See...theres a world of difference if you actually read it properly. Granted, the floors were concrete, but the concrete was only 10cm thick

Please see the website above with your repeated no concrete contention.

Please read what I've written properly.

Exactly what did they attach the plasterboard to in order to make secure walls? What about doors? To what did they frame in and attach them? How did they divide the office space with plasterboard attached to nothing?

Dear me. Do you really not know what drywall construction is and how its done? Really? Have you no experience of construction at all and if not, why are you even trying to argue this stuff?

Maybe I should have said "sheetrock" - here.

Drywall

When a moving object meets a stationary object, and has to slice through materials such as concrete and steel

No concrete in the outer walls, remember

the moving object is going to lose a great deal of velocity and momentum on impact, and even more being forced to slice through anything. That is a law of physics given.

Sure is (hey we agree here!). However the intertia being carried here was huge, and the most dense thing the plane could have hit when it penetrated the outer wall was the core

Could you qualify further what you mean by this: “The structure started to move around its own axis - …” Exactly where on the building are you placing a hypothesized axis?

Suppose you have a beam thats fixed at both ends. If you take away one of the supports the beam is then free, at that point to move. Thats what I am referring to. In the case of the outer walls the contiguous structural support was breached. What that means is that the floors above those points had no support, and the weight was redistributed. At that point any damage at all to the core becomes a BIG factor.

You know for a fact the outer wall load bearing walls were obviously compromised? How do you know that for a fact?

Because a bloody great big 767 jet punched a hole in them and its clear to see from video's of the event.

With the exception of the south tower lean, I haven’t seen one picture or video obviously indicating load bearing compromise on any of the walls. No sagging , no nothing, apart from the obvious severe compromise of the upper floors of the south tower.

Hold on, you just asked me how I knew the towers were compromised and here you are telling me they were. Whats with that?

How so? That is what happens in the academic world. If people have little to no field experience in their fields, they are dependant on information from those experts who do. Acquiring knowledgeable expertise is not simply teaching or reading what anyone else relates. Knowledge expertise results from applying, testing, and experiencing what one has studied in books related by others.

I see...so, as I asked before, how are you an authority on such matters?

Originally posted by neformore
Originally posted by OrionStars
The following says there was.

Now, excuse me here. I'm going to bold something in what you quoted. You see, I was referring to the outer walls of the WTC and to refute that you quoted this

911review.org...

“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.

Which does not refer to the outer walls at all, it refers to the core. And in my post I said

The tube in tube construction were the outer walls. The perimeter refers to all sides of the outside edge of buildings aka exterior wall areas.

There was no concrete between the outer walls and the core. The walls were made of plasterboard.

What was the plasterboard/drywall/sheetrock attached to? They certainly did not simply set interior facade in place, and expect it to remain in place with nothing hold it there, did they? I am well aware of what drywall sheets look like, and how they have to be attached to something to remain securely in place. Drywall is always an interior covering over wall framing in any building.


See...theres a world of difference if you actually read it properly. Granted, the floors were concrete, but the concrete was only 10cm thick

You jumped from outer walls to drywall covering to floors. Therefore, I have no idea exactly what your points are.

Please read what I've written properly.

Are you saying you did not state there was no concrete in the outer walls? If so, it is why I pointed out there definitely was. It was inside the tube-in-tube exterior/perimeter wall frames. Walls are not merely drywall or sheetrock. Without something to attach either to, there will be no walls at all. Framing and covering are all part of what is called a wall on any building.

Dear me. Do you really not know what drywall construction is and how its done? Really? Have you no experience of construction at all and if not, why are you even trying to argue this stuff? Maybe I should have said "sheetrock" - here.

I do, but do you? Can you not answer a very simple question,? To what is dtyway/sheetrock/plasterboard attached to keep it securely in place. I already gave you the answer above.

You don’t have to tell me what drywall or sheetrock is nor show me a picture. I already told you above and in another post what has to happen to make the drywall/sheetrock/plasterboard stay securely in place. Then there are the doors with frames that have to be attached to something to remain securely in place.

No concrete in the outer walls, remember

You can keep repeating that into infinity, and you will still be wrong.

Sure is (hey we agree here!). However the intertia being carried here was huge, and the most dense thing the plane could have hit when it penetrated the outer wall was the core

The core was indeed the densest part of the structure.

Could you qualify further what you mean by this: “The structure started to move around its own axis - …” Exactly where on the building are you placing a hypothesized axis?

Suppose you have a beam thats fixed at both ends. If you take away one of the supports the beam is then free, at that point to move. Thats what I am referring to. In the case of the outer walls the contiguous structural support was breached. What that means is that the floors above those points had no support, and the weight was redistributed. At that point any damage at all to the core becomes a BIG factor.

The floors’ supports were attached on the core side with bolts. The bolts would have sheered off leaving no damage to the core.

If the floors along the exterior/perimeter wall above the impact point had no support, why didn’t they immediately fall if all support was gone? It did not happen but why not when it should have? It is obvious to me if the floors did not fall, they obviously still had enough support.

Because a bloody great big 767 jet punched a hole in them and its clear to see from video's of the event.

Well, the building obviously wasn’t that compromised, or floors would have started to fall very soon at the impact areas. That never happened until the two towers dropped straight down into their own footprints.

Hold on, you just asked me how I knew the towers were compromised and here you are telling me they were. Whats with that?

But you are only going by the impact. Obviously, the building, including impact area, wasn’t that compromised. All the floors were still standing for a relatively long period of time before both buildings imploded. Imploded means pull inward as opposed to explode/push outward. Implosion definitely causes collapse since that is what an implosion is.





[edit on 16-12-2007 by asala]

Um... DEAR GOD, man... learn how to use the quote system!

It's simple. for every [ quote ] you have an [ /quote ] (without the spaces, of course.

For example to get:

What Someone else posted.

what they quoted

and what they said about it

You use:

[ quote ] What Someone else posted.
[ quote ] what they quoted [ /quote ]
and what they said about it[ /quote ]

It's simple, and makes it so we can understand who is saying what.

Now... no, there was no concrete around the outer structural steel. None. Nada. Zip. Zero. Too much concrete would have been too rigid and not allowed the tower to sway slightly in the wind (yes, it's actually better for it to sway, slightly... well... assuming it were a welded design....)

As for your confusion about the drywall comment - you were saying that you could not set up interior walls without some crazy support system you came up with - the link was a counter to that, detailing how interior walls are set up inside of the WTC (which is mostly empty space - why the design was so important and revolutionary, it consolidated all of the vertical supports in the interior and exterior - leaving the rest open and free for use by people as they needed to (no maneuvering around poles dotted all over the place)).

I am not sure if you are genuinely confused, or just acting like it - but I hope this aids in clarifying things for you.

Originally posted by OrionStars
The following says there was.

911review.org...

“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%

^This is so wrong...

Also unique to the engineering design were its core and elevator system. The twin towers were the first supertall buildings designed without any masonry. Worried that the intense air pressure created by the buildingsâ high speed elevators might buckle conventional shafts, engineers designed a solution using a drywall system fixed to the reinforced steel core. For the elevators, to serve 110 stories with a traditional configuration would have required half the area of the lower stories be used for shaftways. Otis Elevators developed an express and local system, whereby passengers would change at "sky lobbies" on the 44th and 78th floors, halving the number of shaftways.

Source

No concrete in the core or the outer mesh...’Cast concrete interior tube’? Where did they get that from? There was NO concrete in the central core.
They’ve got the load distribution backwards, the central core carried the majority of the vertical load and the outer structure carried some of the vertical load but mostly lateral loads (80x20 ratio I believe?). There was no 3rd load bearing core either, The ‘interior core columns’ and the ‘core’ that they mention are the same thing, the inner core structure of 47 steel columns that tapered as they went up from 70ft in the ground to the roof. Built in 3 parts and joined at the sky lobbies, that’s what the sky lobbies were built for.

That must have been written to either purposefully confuse people, or written by someone who was just clueless… Sorry mate!

OK.

So, I think we can conclude there was no concrete in the outer walls of the WTC.

How was the drywall fixed? Off Running frames bolted into the ceiling and floor. That's a standard construction technique.

Now. I poked about a bit and I found an interesting video of a section of WTC outer wall being lifted into place. Its not on Google or Youtube so I'll put the link to it;

Outer section being lifted in

Now I would suggest anyone who thinks that a Boeing 767 travelling at 466mph couldn't have punched a hole into the WTC to have a very good look at that video. Maybe replay it a couple of times, then look at it again.

Why? Well it suprised me and I believed it was possible anyway.

When people refer to lightweight WTC construction its hard to get a picture of it in mind - that video puts it all into context. You can see how slender the outer columns were, and that they were hollow. The video is one of the only things I've ever seen on the WTC that gives you a sense of actual scale, because it shows the construction workers handling the sections.

Its not a "smoking gun" by a long shot, but maybe it will ease some of the ignorance about the structure.

Originally posted by neformore
OK.

So, I think we can conclude there was no concrete in the outer walls of the WTC.

You can believe anything you wish but you are still going to be wrong.

How was the drywall fixed? Off Running frames bolted into the ceiling and floor. That's a standard construction technique.

Finally. Why didn't you just give that answer when I asked two posts ago?

Now I would suggest anyone who thinks that a Boeing 767 travelling at 466mph couldn't have punched a hole into the WTC to have a very good look at that video. Maybe replay it a couple of times, then look at it again.

I do not recall seeing anyone state a plane impacting a building will not cause damage. It will. The issue is how much damage not if it can cause damage. Please understand, a portion of a building may be compromised, but that does not mean the entire building is compromised. It also doesn't mean complete loading support is gone either.

When people refer to lightweight WTC construction its hard to get a picture of it in mind - that video puts it all into context. You can see how slender the outer columns were, and that they were hollow. The video is one of the only things I've ever seen on the WTC that gives you a sense of actual scale, because it shows the construction workers handling the sections.

When they refer to light weight, it is a reference to placing reinforced concrete in lighter weight but high strength steel tubing, and covering that with more but denser steel exterior(part of the redundant design). There was at least one exterior steel wall (tube in a tube loading bearing support) holding reinforced concrete at the center of the tubing of the exterior support walls, and the steel facade. Reinforced concrete has steel rods in the concrete for reinforcement. That makes three layers of steel exterior the loading bearing walls, and, at the very least steel in the exterior façade. That is four layers of steel and one layer of tube shaped reinforced concrete on the exterior walls.. Then there is the massive H beam core structure to carefully consider.

If concrete had not been placed in the tubes, they would have had to use much more and heavier reinforced concrete, as was done at the Pentagon (steel rationed during WWII) and EBS, plus, many more and much heavier steel beams, particularly at the 4 exterior supporting corners. The concrete had to be placed in the tubes to prevent the steel from losing shape over the years from use, ground settling, street traffic (shakes the ground) earthquakes, high winds (particularly at the upper level) etc. The underground base supporting construction is another study well worth doing.

If people think the exterior was nothing but hollow thin steel tubing, it wasn't, because the weight never would have been supported, particularly over time and with use. Either concrete columns and steel beams go into commercial buildings. Or they are built the same way as the WTC, particularly the twin towers.

Its not a "smoking gun" by a long shot, but maybe it will ease some of the ignorance about the structure.

"Smoking gun"? You do not appear to understand the structure. Which is why you do not appear to understand why the WTC 1, 2, and 7 could not possibly have collapsed because of a plane and burning fuel.

The twin towers were specifically built to take the impact of a 707 - the largest plane of its day. That includes considering any and all fuel fires. The planners were not so stupid they forgot planes can carry tons of fuel, and fuel can ignite. They also did not forget the building would be occupied and many flammable materials would be in occupied buildings. Designed the twin towers with that in mind. They were well aware of the fault line running under NYC.

The twin towers were also designed to take the impact of high winds (particularly at the higher levels) and at least a 5.5 Richter scale earthquake (highest scale NYC has recorded), while still remaining standing. There is a fault line running under NYC. The fault line is centered under the New York harbor.

If people more fully understand the structure and considerations going into planning and constructing the WTC, it might possibly give them new food for thoughts if they decide to ponder on 9/11/2001.

reply to post by OrionStars



Follow the link int he post above. For ease of use I will give you the link again. As far as I know it was not in PM.

International Journal of Impact Engineering
How the airplane wing cut through the exterior columns of the World Trade Center
Volume 28, Issue 6, July 2003, Pages 601-625
Department of Ocean Engineering, Impact & Crashworthiness Laboratory, Massachusetts Institute of Technology, Room 5-218 77 Massachusetts Avenue, Cambridge, MA 02139-4307, USA
Here ya go

*shakes head* ..... wow. And I'm told I have quite the hard head....

While true the entire structural support was not compromised when the plane impacted the structure, you must realize that this forced more pressure onto surviving (and damaged) supports. This, combined with the heating of the structure, is not a good thing.

And, if you would have taken the time to read what information was provided to you about drywall construction, then you would have not made yourself look foolish. Orion... you need to help yourself, sometimes, man....

Edit to improve clarity.

[edit on 16-12-2007 by Aim64C]

reply to post by OrionStars

Exactly what did they attach the plasterboard to in order to make secure walls? What about doors? To what did they frame in and attach them? How did they divide the office space with plasterboard attached to nothing?

The typical framework for doors, walls, office space in general is either 2" x 4" pine or 2" x 4" aluminum/steel studs typically spaced either 16" or 24" apart and secured to the floor and typically metal framework at the ceiling level then either gypsum drywall or prefab panels are attached to finish the walls. The walls won't be weight bearing. This type of framework can be easily damaged and would create almost no resistance for a 767 hitting it.

Originally posted by OrionStars

If people think the exterior was nothing but hollow thin steel tubing, it wasn't, because the weight never would have been supported, particularly over time and with use. Either concrete columns and steel beams go into commercial buildings. Or they are built the same way as the WTC, particularly the twin towers.

Takes a deep breath.....

There was NO concrete in the WTC outer walls. None. Nil. Nada. Zip. Nothing, Nowt. I've told you. Aim's told you, Anoks told you, Fred's tried as well... Whats so hard to understand about that?

If people more fully understand the structure and considerations going into planning and constructing the WTC, it might possibly give them new food for thoughts if they decide to ponder on 9/11/2001.

I'm sorry, but you have no right to type that, considering your continued refusal to accept what we've been telling you.

[edit on 16/1207/07 by neformore]

Originally posted by neformore

Takes a deep breath.....

There was NO concrete in the WTC outer walls. None. Nil. Nada. Zip. Nothing, Nowt. I've told you. Aim's told you, Anoks told you, Fred's tried as well... Whats so hard to understand about that?

I have already provided solid substantiation regarding the manufacturing of the WTC exterior walls, which prove your hardset opposition opinion is wrong. Unless you can prove my substantiation incorrect with valid substantiation of you own, you have no reasonable choice but to back off on this. You don't have to accept any valid substantiation. That is your perogative. However, you have no entitlement to promote disinformation, particularly when valid substantiation is readily available and has been presented to this forum specifically for your perusal.

At this point, I am going to agree to disagree with your highly incorrect opinion, regarding the exterior walls of the WTC buildings.

The towers' perimeter walls comprised dense grids of vertical steel columns and horizontal spandrel plates. These, along with the core structures, supported the towers. In addition to supporting gravity loads, the perimeter walls stiffened the Towers against lateral loads, particularly those due to winds. The fact that these structures were on the exterior of the Towers made them particularly efficient at carrying lateral loads. Richard Roth, speaking on behlf of the architectural firm that designed the Towers, described each of the perimeter walls as essentially "a steel beam 209' deep." 1 Regardless, it is clear that the core structures were designed to support several times the weight of each tower by themselves.

As the diagram and photograph illustrate, the perimeter wall structures were assembled from pre-fabricated units consisting of 3 column sections and 3 spandrel plate sections welded together. Adjacent units were bolted together: column sections were bolted to adjacent columns above and below, and spandrel plate sections were mated with adjacent sections on either side with numerous bolts.

911research.wtc7.net...

Funny, not one mention of concrete anywhere. The perimeter walls were ONLY steel, without any concrete reinforcement.

Originally posted by jfj123
reply to post by OrionStars

 

The typical framework for doors, walls, office space in general is either 2" x 4" pine or 2" x 4" aluminum/steel studs typically spaced either 16" or 24" apart and secured to the floor and typically metal framework at the ceiling level then either gypsum drywall or prefab panels are attached to finish the walls. The walls won't be weight bearing. This type of framework can be easily damaged and would create almost no resistance for a 767 hitting it.

Part of your response was probably very helpful to those who did not know what you related. My question was not because I did not know. It was because my opponent stubbornly refused to answer a simple questition until making a third post responding to mine.

Yes, the exterior WTC walls were primary load bearing walls. In fact, the design was biased for loading bearing to the exterior walls. I have already presented that construction substantiation to this forum. I also presented the manufacturing information for the load bearing exterior walls and facade.

The load bearing exterior walls were indeed loaded with tube shaped reinforced concrete, covered in tube shaped steel, and then covered again with a denser steel enclosure. The facade and the perimeter of the floors, were also to additionally assist in load bearing. The reinforced concrete, containing steel rods, was partially for the purpose of necessarily and permanently holding the shape of the steel, and partially for primary load bearing capability.

The exterior walls of the WTC buildings were the primary load bearers. All other wall frame were secondary load bearers. As opposed to private homes where the internal walls are the primary load bearers, and the exterior walls are the secondary load bearers.

Surely, people do not think that hollow steel has any major load bearing capacity, do they? Steel can eventual begin to lose supporting load bearing strength, particularly when hollow. Something my substantiation specifically pointed out. How many construction I and H beams has anyone seen that are hollow and yet rated as load bearing? Any? Because I would not expect anyone to find any. The answer should be obvious as to why.

Its pretty clear based on the evidence and actuall construction pictures etc, that the WTC pretty much only had concrete in the floors.

Some people seem to be hell bent on redoing physics here.

First off detailed study that I linked above showed that the energy required to bust through the outer shell of the building was only about 7 percent of what the aircraft had when hit.

The outershell of the building was desinged to deal with wind loads etc.

The floors of the WTC were open thus between the outer shell and core there was basically soft office equipment and cubicle walls

Ofter first hitting the outside shell the aircraft still had about 93 percent of its total energy to bleed off as it continued through the structure.

Is it that hard to get

Originally posted by Zaphod58

Funny, not one mention of concrete anywhere. The perimeter walls were ONLY steel, without any concrete reinforcement.

Then perhaps you missed the following when I posted it the first time?

911review.org...

"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%.

Steel, no matter what temper, no matter what bracing is used, ends up with an overall flexation that exceeds design parameters for deformations and failures occur. These were fact I learned from a documentary in 1990 about the construction of the north tower. Yamsaki's decision making process was outlined and rejected core designs identified."

reply to post by OrionStars


Im at a loss as to where you are getting your information about how the load bearing structure of the WTC was set up

"The structural system, deriving from the I.B.M. Building in Seattle, is impressively simple. The 208-foot wide facade is, in effect, a prefabricated steel lattice, with columns on 39-inch centers acting as wind bracing to resist all overturning forces; the central core takes only the gravity loads of the building. A very light, economical structure results by keeping the wind bracing in the most efficient place, the outside surface of the building, thus not transferring the forces through the floor membrane to the core, as in most curtain-wall structures. Office spaces will have no interior columns. www.greatbuildings.com...

The exterior walls served ONLY to take lateral wind loads NOT the gravity loads.

Faced with the difficulties of building to unprecedented heights, the engineers employed an innovative structural model: a rigid "hollow tube" of closely spaced steel columns with floor trusses extended across to a central core. The columns, finished with a silver-colored aluminum alloy, were 18 3/4" wide and set only 22" apart, making the towers appear from afar to have no windows at all.
www.skyscraper.org...

Also as someone has already pointed out:

The twin towers were the first supertall buildings designed without any masonry. Worried that the intense air pressure created by the buildingsâ high speed elevators might buckle conventional shafts, engineers designed a solution using a drywall system fixed to the reinforced steel core.www.skyscraper.org...

Please show me where exactly the concrete was here?

[edit on 12/16/07 by FredT]

reply to post by OrionStars


Do you even understand what that says? It says that the INTERIOR core was concrete reinforced, surrounded by a STEEL STRUCTURE. It does NOT say that the perimeter walls were steel reinforced with concrete.

Originally posted by FredT
Its pretty clear based on the evidence and actuall construction pictures etc, that the WTC pretty much only had concrete in the floors.

Some people seem to be hell bent on redoing physics here.[/quote]

Physics? Or do you mean describing the materials actually used in the manufacturing of the exterior walls? I just posted again what materials were used in the exterior/perimeter walls and why.

Since physics were brought up, don't people believe they need to know what was used in the manufacturing of each object impacting, in order to know how to correctly assess how much energy was used on which job alleged planes were doing at impact?

Physics pertaining to kinetic energy - Impacting is a job requiring a great deal of energy. Velocity and momentum being another job requiring a great deal of energy. Slicing through (pushing through resistance) also requires a great deal of energy provided by weight, mass, velocity, and momentum. Energy can not stay at peak performance trying to expend energy on two or more jobs at the same time. Resistance automatically retards velocity and momentum, regardless of weight and mass. Trying to do more than one job at a time, is going to cut energy expended on both.

Can people do more than one job at peak energy on more than one job? People have always expended their energy based on the laws of physics. So does every other physical item existing on earth.