I'm curious how the pancake model for the WTC collapse deals with the very

[spooked911]

large center core structure?




When the WTC collapsed, this large central core structure that had most of the load bearing columns for the WTC also collapsed.

Why didn't the floors collapse around this structure and leave it standing? What made the core collapse?

[Bolo Boffin]

1. Do the math.

Calculate one quarter to one third of the mass of a single tower.

Then calculate the force it would possess after having fallen a single story (10 feet).

There is little that could have withstood that force - certainly not the center core.

[spooked911]

5. How did the core drop? I can see the floors dropping.

How did the core drop?

The pancake model only says the floors came loose from their supports and dropped sequentially.

The pancake model does not explain how the massive core structure collapsed.

[number6]

27. show us your equations bolo

???

[Bolo Boffin]

30. Gladly

p=mv

P is the force
M is the mass
V is the acceleration

[AZCat]

37. It's a bit more complicated than that

The problem is that the collision is an inelastic one, and calculating the force acting on the floor is difficult without a good understanding of how the floor and the falling building segment deform.

We can calculate the momentum of the building segment, but it takes a little work. First we have to determine how long it takes to fall ten feet:

distance=(1/2)*acceleration*(duration of the fall)^2
or
duration=square_root(2*distance/acceleration)
so
duration=square_root(2*10/32.2)=0.788 seconds


Now we can calculate the velocity of the building segment at the end of the ten-foot fall:

velocity=acceleration*duration
so
velocity=32.2*0.788=25.4 ft/sec

We now need an estimate of building mass so we can calculate the momentum of the segment:

I don't know of a good estimate of the mass of the building segment (I've seen wildly differing estimates), so I'll just use "M" as a place holder - this way you can use your own estimates.

momentum=mass*velocity
so
momentum=M*25.4=? lbm*ft/sec


Now once we have this value for momentum, it is important to understand that we are only partly done with our calculations. In an inelastic collision, the momentum of the system is conserved but the kinetic energy is not (some or all of it transfers into other forms of energy). We still need to estimate the mass of the second segment in our collision, but do we select a single floor or do we use the mass of the whole building? After deciding which to use, we need to determine how the collision progresses. We need to understand how the floor is connected to the rest of the building and by what means so we can calculate the stresses caused by the collision and determine whether or not they cause deformation or failure of the structural members.

This is partly why the analysis is tricky. If we were able to model it more exactly we might be able to avoid this, hence the NIST's attempt to exactly that.

[Last Lemming]

2. Speed

I think the second tower went down in about 8 seconds (posted this question on another thread.) If so--then no amount of parsing possibilities, like pancaking or core collapsing or whatever, can explain this away. Things don't fall faster than gravity without some assistance.

[hack89]

13. Short of rockets...

How the hell do explosives make the building fall faster than gravity. Correct me if I am wrong, but isn't the concept behind control demolition that the explosives sever the supports and gravity brings the building down? The charges cut horizontally through the supports - where is the vertical force coming from?

[Old and In the Way]

24. I think it's a red herring to say it collapsed faster than an object can

fall in a vacuum. The videos I've seen show a total collapse time of about 15 seconds. The nominal time for the roof of the WTC to hit the ground would be about 9 seconds....without factoring internal resistance. Divide 6 seconds into 110 floors. That's the average time each floor withstood the collapse event.

I find it very hard to belive a core would not, at least temporarilly, remain standing. Or why large sections of the core were not evident in the collapse. Unless the base of the core was destroyed at the initial start of the collapse.

[LARED]

3. The central core did not

have most of the load bearing columns. The structure is far more complicated that that notion.

Are you of the opinion that the core structure is capable of being a free standing structure? I seriously doubt it was capable of doing that. If you are that may explain your confusion.

[spooked911]

4. did you look at the picture? The core is massive with thick steel beams

I see nothing comparable around the facia of the structure.

Of course the load was carried by the core-- that's where all the strength was.

Are you saying that flimsy outer lattice structure was important for holding up the WTC?

[LARED]

6. If it is safe to assume

you believe the core was capable of being a free standing structure and the perimeter columns had little to do with holding up the structure; frankly, you're clueless.

Really, you are. I'm not trying to be mean or snarky, but if you really believe that, and are not willing to listen and learn something you have no business discussing the issue.

[spooked911]

8. Sorry, that's not what I meant to say.

Of course the outer structure was important.

But I interpreted what you said as that the central core was not as important as the outer structure in terms of load-bearing.

That doesn't seem right to me.

Also, do you know for a fact that the central core couldn't be a free-standing structure? If so, could you clue me in how you know this?

Thanks.

[LARED]

16. re:

Both the core and the perimeter columns are important. The building can not function without both of them remaining intact. Each floor joist is connected to both. The floor loads are then distributed to each side; the core columns and the perimeter columns. It is safe to say it was roughly a split. Was it 40/60, 50/50. 60/40? I'm not sure. But just a crude free body diagram tells you the loads have to be distributed at the core columns and perimeter column at roughly equal loads. That is a gross simplification of course.

The perimeter columns were designed to take up the wind loads. (very significant loads)

"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. (this does not mean it takes ALL the gravity load) 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. In the upper floors there is as much as 40,000 square feet of office space per floor. The floor construction is of prefabricated trussed steel, only 33 inches in depth, that spans the full 60 feet to the core, and also acts as a diaphragm to stiffen the outside wall against lateral buckling forces from wind-load pressures.

http://www.greatbuildings.com/buildings/World_Trade_Center.html

One way to look at this is that the perimeter column structure was STRONGER than the core structure as it had to take the wind loading plus gravity loads.


As for the standing core I cannot tell you I know for sure it would not free stand. But based on the fact that the perimeter columns were designed to take the wind loading; and the image you provided shows only minor lateral supports without the floors, and the free standing core would only be 80 feet wide by 1350+ feet tall, all adds up to a near impossibility for it to stand on it own.

[AZCat]

18. The NIST report details the load distribution

In the June 2004 Interim Report, Appendix D covers the Preliminary Stability Analysis for the WTC Towers. If you download it, check out table D-8 - it shows the load distribution between core and exterior columns for the various sections of the WTC and what happened (theoretically) after the impact and fire damage.

[LARED]

19. Thanks

Link for those that want to read the report

http://wtc.nist.gov/progress_report_june04/appendixd.pdf

For those not inclined to read it, it basically says for the final construction stage the loads between core and perimeter columns is split evenly.

[spooked911]

22. I appreciate your thoughtful replies.

But I guess the question is-- can we really trust their analysis? Certainly it serves their version to have so much weight on the perimeter.

What I do know for sure is if you look in the image I started this thread with, the core of the structure is extremely large and substantial, with thick steel beams, whereas the outer framework appears flimsy in comparison. Granted, that at one particular point on the structure the outer framework may not be very strong but that the combined total of the perimeter could add up to a very strong weight-bearing entity.

The point is that I can see how the outside structure could break apart during a collapse, but I don't see how the central core will fall apart so readily. In any case, doesn't the pancake model say that the floors rip away from their supporting trusses, and shouldn't this leave the center more or less intact? Granted if enough floors collapse, this could put enough strain on the core for it to eventually topple over or cave in, but this doesn't seem to be the pattern of collapse that happened-- rather everything apparently went at once (in the south tower).

In the north tower, before the tower collapsed, the top antenna actually caved in before the floors starting collapsing-- suggesting that the core was giving way first. How could this be?

[LARED]

25. It's very frustrating to continually

question the NIST reports. Putting aside for the moment that common sense tells you that the load should be evenly distributed between the core columns and the perimeter column based on the design, what evidence is there that the reports are tainted. The NIST is not a political arm of anyone. They have been around for a looooong time.

What I do know for sure is if you look in the image I started this thread with, the core of the structure is extremely large and substantial, with thick steel beams, whereas the outer framework appears flimsy in comparison. Granted, that at one particular point on the structure the outer framework may not be very strong but that the combined total of the perimeter could add up to a very strong weight-bearing entity.

First you need to mentally remove the structures that the cranes sit on, as they do not stay in place. The core is in reality not very large and substantial given the size of the WTC. There are something like 47 column spread out over about 10,000 sqft. You need to know that the outer framework was incredibly strong when taken as a whole. (All four sides) It is designed to take the wind loads of at least 100 hundred miles per hour over the surface of the building. This is a huge load, that makes the gravity load look tiny in comparison.

The point is that I can see how the outside structure could break apart during a collapse, but I don't see how the central core will fall apart so readily. In any case, doesn't the pancake model say that the floors rip away from their supporting trusses, and shouldn't this leave the center more or less intact? Granted if enough floors collapse, this could put enough strain on the core for it to eventually topple over or cave in, but this doesn't seem to be the pattern of collapse that happened-- rather everything apparently went at once (in the south tower).

The core had floors, They were slightly thicker than the open area floors. The floors were constructed in a similar fashion. Concrete over joists. The cores was also badly damaged from the impact and fires. One thing you need to consider is when the floors pancake they remove the lateral support of the core columns. Lateral supports are critical for column to remain stable. Without those the column will buckle quickly. As an intact structure the WTC was very strong. The core was, the perimeter was. Once you start removing supports that stiffen the structure it's all over.

[spooked911]

26. Okay thanks. That makes sense-- I have only one quibble:

"The cores was also badly damaged from the impact and fires."

In fact, we don't really know how badly the core was damaged. We can assume some damage-- particularly in the north tower where the plane must have smacked into the core after slicing through the outer wall. The south tower core should have had very little damage-- I even looked at the NIST report for this. I think they said only one or two columns were damaged.

[LARED]

29. This might be of interest

http://wtc.nist.gov/media/P2BaselineStrucPerf&AircraftImpact.pdf

http://www.arasvo.com/NIST_WTC.htm

[AZCat]

7. Yes that "flimsy outer lattice structure"...

was important for "holding up" the WTC.

I think we need some sort of a primer - a Mechanics of Materials 101 - because there are a lot of posters with questions that can't be answered without some background in the subject.

[spooked911]

9. Yes-- do you know where we copuld get a copy of the WTC blueprints?

I wonder why they are so hard to find????

I wonder...

[Last Lemming]

10. I think there is mention

in a footnote in the 9/11 commission report that the outer walls were the main structural supports. And since the committe said it--it must be true. They reference some plans but I can't give anymore specifics. Is the report on line and searchable?

I think the question has been explored by others. . .

[Bolo Boffin]

11. The original blueprints were in the towers.

They're gone.

[demodewd]

12. copies?

Certainly there must be copies.

[spooked911]

14. well isn't that conveeenient.

I can't believe there were no copies.

[Bolo Boffin]

15. According to the NIST interim report

By December 2002, the team had received or inspected the following:

The original design drawings (structural, architectural, mechanical, electrical, plumbing) and the original fabrication and construction drawings for the WTC towers

Tenant alteration application reports, including drawings and specifications, for the WTC towers and WTC 7, and associated construction audit reports

By March 2003:

Documents, videos, and photographs related to the fireproofing of the WTC tower structures

WTC floor plan for the fire alarm system and drawings of WTC subgrade plumbing and city water main

By August 2003:

Design and structural calculations from Leslie E. Robertson Associates (LERA) for the WTC towers, including TV antenna, beams, and beam girders, as well as wind analysis and calculations

Laclede floor truss shop drawings (1,364 sheets) and other documents on steel and joints

List of WTC drawings in possession of Yamasaki and Associates

By May 2004:

Photographs of WTC 7 construction project

Architectural and HVAC drawings for WTC 7, including modifications


The report continues:

The few NIST requests for materials that are lost, currently pending, or not yet located include:

• Original contract specifications for WTC towers (lost in the collapse of the buildings)
• Construction and maintenance logs for WTC 1, 2, and 7 (lost in the collapse of the buildings)
• Calculations and analyses that supported the original aircraft impact studies (lost in the collapse of the buildings)
• Descriptions of partitions and furnishings in most of the tenant spaces of WTC 2 and WTC 7 in the fire and impact zones
• Shop drawings showing connection details of WTC 7

So they do have information on the structure of the building. They just don't have all the source information because it was lost in the collapse.

[Christophera]

48. Giuliani Took WTC Documents, Courts Won't Force Return

http://www.nyclu.org/g_archive020602.html

...."Our concern is based on the following facts, as we understand them. On or about December 24, 2001, Commissioner George Rios, on behalf of the City of New York and/or the Department of Records and Information Services of the City of New York, entered into a contract with the Rudolph W. Giuliani Center for Urban Affairs Inc., signed by Saul Cohen, President, concerning the records of the mayoralty of Rudolph Giuliani. The records are said to include appointment books, cabinet meeting audiotapes, e-mails, telephone logs, advance and briefing memos, correspondence, transition materials, and private schedules, as well as Mr. Giuliani’s departmental, travel, event, subject, and Gracie Mansion files. Giuliani's "World Trade Center files" and "Millennium Project files," together with 6000 files of photographs, 1000 audiotapes, and 15,000 videotapes, are also reported to be a part of the records covered by the contract. In addition, the records include those of his chief of staff and every deputy mayor, together with their chiefs of staff. Finally, gifts such as plaques, awards, personalized clothing, and other items presented to the mayor and deputy mayors, as well as World Trade Center-related materials are alleged to be included as part of the records. All of these items were reported to have been delivered from the control of the City to a warehouse storage facility in Long Island City at the end of December 2001."



The British Knights
Who "Cleaned Up" 911

By Christopher Bollyn
American Free Press
15th August 2002
PAGE URL
http://www.gulufuture.com/future/knights_z.htm

  A foreign company - headed by a Knight of the British Empire - managed the controversial clean-up of the rubble at the World Trade Center and the Pentagon.

Although the terror attacks of September 11 were clearly criminal acts of mass murder, no effort was made to preserve the integrity of the crime scenes and the essential evidence was disposed of like garbage.

Former New York City Mayor Rudolph Giuliani was made a Knight of the British Empire - after he hired two large British construction management firms - both headed by Knights of the British Empire, to oversee what many experts consider to be massive criminal destruction of evidence.

[Bolo Boffin]

56. You're posting crap from Christopher Bollyn?

That really says it all, doesn't it?

[AZCat]

17. Even if you get your hands on a copy...

good luck understanding and interpreting them. Here's the list of everything included (from the June 2004 Interim Report, Appendix B):

B.2.1 Description of WTC Structural Documents

The WTC structural drawings were issued in two main formats: large-size sheets containing plan and elevation information and smaller book-sized drawings containing details and tabulated information.
Throughout the WTC drawings, Tower A or WTCA denotes WTC 1 (north tower) and Tower B or WTCB denotes WTC 2 (south tower). The large size drawings always make reference to the structural drawing books through their notes, sections, and detail references. The structural drawing books for WTC 1 and WTC 2 include the following:

Book 1 contains exterior wall information to elevation 363 ft. (Dates: 02/1967 to 12/1968, Approx. 213 pages).

Book 2 contains exterior wall information elevation 363 ft to floor 9. (Dates: 04/1967 to 12/1967, Approx. 62 pages).

Book 3 contains core column information. (Dates: 03/1967 to 09/1969, Approx. 137 pages).

Book 4 contains exterior wall information floor 9 to floor 110. (Dates: 04/1967 to 10/1972, Approx. 1,080 pages).

Book 5 contains the beam schedule. (Dates: 05/1967 to 08/1969, Approx. 292 pages).

Book 6 contains connection details and core bracing. (Dates: 08/1967 to 05/1969, Approx. 1,060 pages).

Book 7 contains truss floor panel information. (Dates: 10/1967 to 07/1969, Approx. 345 pages).

Book 8 contains concrete notes and details. (Dates: 03/1968 to 07/1974, Approx. 926 pages).

Book 9 contains roof area column splice details. (Dates: 05/1970 to 04/1971, Approx. 440 pages).

Book 18 contains strap anchor and core truss seat information. (Dates: 10/1968 to 11/1969, Approx. 219 pages).

Book 19 contains revisions after fabrication. (Dates: 08/1968 to 05/1975, Approx. 374 pages).

Book 20 contains structural steel details. (Dates: 07/1968 to 03/1971, Approx. 41 pages).

Book D contains damper details. (Dates: 03/1969 to 09/1971, Approx. 43 pages).

The remaining number books (Books 10, 11, 12, and 13) contain information about the sub-grade structure. Books 14, 15, 16, and 17 were never used.


Until fabrication was begun, the above drawings and drawing books (with the exception of Book 19) for the project were modified in keeping with the requests for changes by contractor(s) and early tenant modifications. The drawings were modified up until such time as the fabrication of elements commenced. At that time, Book 19 was introduced. It contained the information regarding ‘revisions
after fabrication’.

LERA believes that the original structural drawings represent significantly accurate ‘as-built’ drawings for the towers. As tenant modification requests became large in scope, they became separate projects (e.g., the Fiduciary Trust Vault Project, see Section B.2.4). Tenant structural modifications designed by LERA were then documented in a single book of quarter-size plans referred to as the ‘WTC Tenant Structural Modifications Book’. Later tenant modifications were mostly archived on a job-by-job basis without a central accounting for all the changes. NIST has in its possession complete copies of all the drawings, drawing books, and modifications to the towers performed by LERA. In some instances modifications were made by the Port Authority of New York and New Jersey (PANYNJ) Engineering, such as additions to the mechanical levels. In other instances, tenant modifications were performed by other engineers. For these instances, LERA does not have record of the work completed. According to the PANYNJ, no record of structural work could be found so far for the additions to the mechanical floors made by the PANYNJ Engineering, and it is likely that they were lost with the collapse of the towers. Modifications made by other engineering firms include openings or closings of floor slabs and local reinforcement of floor segments to accommodate new loads. For these modifications, NIST has access to the documents related to the work.
</snip>


Needless to say, this is a lot of information. Without a team of people skilled at reading blueprints and translating them to some sort of a CAD format, it would be difficult (if not impossible) to test out any sort of collapse theory on your own.

[spooked911]

20. Yes, you're right. I'm not saying I could interpret them.

But I have read other people say they would like to see the blueprints.

Certainly, professionals who want to understand why the towers collapsed would like to see them.

[AZCat]

21. I don't know if there are plans to place them in the public domain

I think they might be the property of the original architectural firm and I don't know how that affects the release, but it would be nice if copies were available (for a fee) or if the completed NIST report included some sort of a limited release along with the rest of the information.

I know blueprints to some degree have to be public domain but I don't know how this would apply here.

[k-robjoe]

23. I saw this being discussed

on another discussion board.

And there was a guy there that argued that we can tell from the pics below, that the lower part of the core structure of WTC2 did in fact stay up for a second or two, after the outer parts of the tower had collapsed around it.

[spooked911]

28. Nice pictures! I had seen a video of this but not these nice shots.

Yes, it does sort of look like the core remained up for a while. I wonder why it didn't stay up longer?

Really though, we can argue physical evidence all day and not get anywhere.

The key thing for me is that people heard and saw bombs on 9/11 and now there is clearly a cover-up on the part of the NYFD and the media not to talk about the bombs.

[vincent_vega_lives]

31. The core was stronger as it got closer to the ground floor.

There is not "clearly a cover-up" in the FDNY. And I discussed the "people heard and saw bombs"

In the context of the attacks it is understandable that any loud bangs would be interpreted as "bombs". If you have a truck backfire on your street do you immediately assume it is a bomb? No, but imagine if a house on your street was bombed a few hours prior.

[spooked911]

34. Why is there not a cover-up in the FDNY? And when did you discuss

the people who saw and heard bombs?

Sure, some of them may have heard something else, but there were so many reports of bombs initially it is hard to discount all of them.

[vincent_vega_lives]

38. The thing is, during an investigation you don't

discount anything. You take everything together and then look for corresponding evidence. Is there any? There were plenty of things going on that could have had the signature of "bombs going off". Gas lines, structural failure before the collapse...all could have been mistaken as explosions. And without collaborating evidence, that's all the reports are, one event mistaken for another.

[seatnineb]

39. I'll let the words............

.........of one Professor Abolhassan Astaneh-Asl of the University Of California at Berkeley do the explainin'.....

Narrator:
Professor Astaneh was one of the few scientists to examine the steel in the New Jersey Yard before it was sold abroad for scrap....

Professor Astaneh Asl:
"This is the inside face of back columns....so plane went in ...exploded right here(points to column lying flat in yard) and the explosion hit this surface....what you see here is first of all a bend that is due to explosion but more importantly this here is a signature of explosion(points to a small "crater" with black residue within the colmn)...this has happened due to explosive material hitting this column and making that bulge.........so this is the floor where explosion happened.....
and the windows are blown away........everything is burnt ....even fireproofing is burnt"

From the Documentary.
How The Twin Towers Collapsed.
Channel 4
U.K(2002)

Now what was that you were sayin' about not discounting anything in an investigation....

[vincent_vega_lives]

40. Not discounting says nothing about suspending reason.

1. An AIRLINER hit the building.
2. The AIRLINER, laden with fuel, exploded.
3. This event WILL leave a large impact on the environment.
4. Demolition explosives do NOT bend, or burn girders, they cut them. That is what they are designed to do. Low order fuel explosions, however will.
5. Each girder has a code, that code can tell investigators exactly where the piece was located in the building.
6. One would expect pieces that were located at the site the airliner hit to building to exhibit damage as described.

[spooked911]

41. Of course-- you're right. But by the same token,

you can't rule out planted explosives either.

And you didn't really say why there wasn't a cover-up in the FDNY.

If it was just gas-lines blowing, why would they care about firemen talking about it?

[vincent_vega_lives]

44. No early on you can't "rule out" anything

when you start an investigation. Of course it is important to keep an open mind. But the whole point of an investigation is to "rule out". What's left is the facts.

I don't profess to know what rumors are murmured in fire houses in NYC. I'm sure some firemen are certain that "bombs" were going off in the WTC. I also don't doubt that fire officials would try to squelch those, at this point, unsubstantiated claims, that may embarrass the FDNY. We know gas lines were popping, so until there is evidence of explosives (we're talking 3+ years now) they are just rumors.

[k-robjoe]

32. yes

> "I wonder why it didn't stay up longer?"

Me too.

By the way. Have you seen this pic.

[spooked911]

33. Yes! Exactly! That's what I have wondered about too!

[k-robjoe]

36. I edited my post

and took away the comment that apparntly the pancake model doesn´t work every time.

But you´re post seems to be answering to that, so I´m putting it back in, for context.

( Ofcourse the building is not identical. That must be taken into consideration. )

[gbwarming]

35. That was Bill Biggart's last photo. WTC3 about a minute before WTC1 fell.

There's a nice tribute here and a gallery of his last photos.
http://digitaljournalist.org/issue0111/biggart_intro.htm

[ryan_cats]

45. Wow!

That was the hotel wasn't it. I've never seen tha picture before, do you have a link to more?

[spooked911]

42. Here's something similar and weird from the north tower collapse

The overall sequence is amazing-- seen here:
http://plaguepuppy.net/public_html/video%20archive/ne-spire.htm

(they won't let me post the jpg files, but it is well worth a look)

What on earth created such a delicate structure that then simply disintegrated into smoke, seemingly?

[AZCat]

43. I think what you are seeing...

is the dust that has settled on that bit of structure being thrown up in the air as that last section collapses.

It's hard to tell with the sequence of images, but it looks like in image #6 (from the top) that that structure is descending vertically, which would disturb any dust that had landed on it after the first collapse.

Just my opinion, though. Take it for what it's worth.

[Christophera]

46. The Concrete Core Was Cast Inside Advancing Steel Frame

What we see in the helicopter photo of the top of a tower are the heavy box columns that surrounded the cast concrete core. Just inside that is a trussed framework that supports the kangaroo cranes in each corner. It is raised up on fasteners that anchor it to the inside of the outer steel framework that comprises the exterior tube of the "tube in a tube" construction that made the tower able to stand 140 MPH winds.

Other designs having steel core columns failed in a 65 MPH wind because the building starts to "fly" in the wind and twist because of it. The resulting deformations would cause failures.

For that reason, Yamasakis "tube in a tube" having a rigid, steel reinforced, cast concrete inner tube, was selected for construction.

The inner forms were breakdown steel forms that the kangaroo cranes would advance up , 40 feet per pour, on the inside of the core that had parallel faces. The outer forms were constructed of wood and supported off the inner faces of the heavy interior box columns that were carefully bolted to the concrete as the tower advanced upward in order to get the full benefit of the anti torsion aspect of the concrete core. The core was tapered on the outside 17 feet thick at the bottom and 2 feet thick at the top.

FEMA has deceived us about the towers design in order to make the fire explanation more plausible. What is often referred to as "core columns" are actually the elevator guide rails. They were only seen in place before the core got off the ground or being lowered into the core for placement before the inner forms were advanced another 40 feet.

[OneMind]

47. And the steel columns were heavily cross-braced.

You could run jets into those towers all day long and the cores would remain standing. But on 9/11, one strike and the cores were completely obliterated.

[NecessaryOnslaught]

49. That pesky cross-bracing

Have to blast that out so the core columns can fall independently

[LARED]

50. That so called pesky cross bracing

was to support the cranes. It is removed after the cranes were removed.

[OneMind]

51. No.

Cross-Bracing

Construction photographs show that each group of four adjacent columns on the core's four corners were stitched together with numerous cross beams and diagonal trusses. In addition, they show large cross beams linking the other columns at every floor. The debris photograph below shows what appears to be a core column surrounded by perpendicular I-beams approximately three feet deep.

http://911research.wtc7.net/wtc/arch/core.html

[LARED]

52. Are you referring to the

beam connecting the columns or the cross bracing seen on the crane supports?

[Christophera]

54. Interior Box Column With Floor Beam Intersection

That was a 14"x14" box column the torch worker is "de-limbing" of the floor beams at the intersection. Near the top the box columns were 1" thick and nearly solid steel at ground level.

The presence of the horizontal joint marks it as an exterior box column.

In the below photo a spire is formed by an interior box column near a corner of the concrete core where its walls still support the steel surrounding it somewhat, enabling the spire. The horizontal floor beams connected to the box columns can be seen,

If the heavy concrete core columns existed, they would be seen in this photo.

[LARED]

57. heavy concrete core columns?

To my knowledge there were no such animals in the WTC

[Christophera]

53. No Cross Bracing There, Elevator Guide Rails

The core column, if they were to exist are VERY long.

Precision elevator guide rails were installed an fastened to the interior of the concrete core. The concrete core with its rigidity gave the very best structure for the elevators. The reason there was an elevator swap in the middle of the building was because long elements of steel turn to spaghetti unless it is cross braced constantly in truss members.

Of course elevator guide rails cannot do that. At the 48th floor there was a 2 floor base for the second level elevator, some of the fastest in the world, because the concrete core was so precise the guide rails were always uniform in dimension.

Those are the same rails seen sticking out of the top of the farmework before it is more than 1-2 floors off the ground. rectangular in shape. The guide rails had to be set starting from the basement. The new core section was always being cast 2-3 floors over the tallest set of guide rails and employees/contractors depended on the elevators throughout the tower construction. Steel workers I've talked to said that had to climb as far as ten floors of temporary stairs from the top elevator position to work on the advancing exterior steel framework.

[Name removed]

55. Deleted message

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[LARED]

58. interior of the concrete core?

What concrete core?

[NecessaryOnslaught]

59. What?

Elevator guide rails in the concrete core? Sorry but you are misinformed. The elevator shafts were interspersed between the heavy box STEEL core columns. As for the structual core being composed of concrete...:crazy: :crazy:

[Christophera]

60. Concrete Core Standing;No Frame, No Box Columns

The steel exterior tube framework of WTC 2 has fallen completely away and the tubular concrete core stands with a smooth rounded top. Where are the "heavy box STEEL core columns"?



Oh, that is not a building behind the tower atfer it is fallen, here the core has detonated a few more 40 foot sections off.



Where are the "heavy box STEEL core columns"?