Let's look at the trusses

[DoYouEverWonder]

Here's a good pic of them during construction.





Here's another shot that also shows a section of the core construction and with one of the trusses in place. The steel columns in each corner of the core were massive. So was the steel in the rest of the core. The trusses are flimsy in comparision.





The core itself took up about a third of the square footage on each floor. Inside the core were the elevators, utilities, storage, etc.

Typical Floor Plan of the World Trade Center: A perimeter of closely spaced columns, with an internal lift core. The floors were supported by a series of light trusses on rubber pads, which spanned between the outer columns and the lift core. http://www.ussartf.org/world_trade_center_disaster.htm

See the trusses in the first picture? They only attach at a couple of points and are not integral to the core. The design is similar to putting a wrap around porch on a house. Even if the porch fails, the house would probably remain. However, if the house failed, the porch doesn't stand a chance. Wouldn't the same be true for the WTC? Even if large sections of the outer wall and trusses failed, which they did as soon as the plane went through them, the core and the base should be and was able to withstand the damage and they did.

Yes, there was plenty of fire but little, if any of it, was below the 50th floor, so even if the top 50 collapsed, large chunks of the bottom 50 should have been left standing.

It is apparent that the OCT version doesn't make much sense. So tell me, how do two passenger jets cause the catastrophic failure of two steel towers? Two steel towers turned into a piles of dust and steel toothpicks? Two steel towers totally destroyed in under 2 hours? Buildings don't spontaneously combust. That requires a lot of energy and there has to be a source for that energy. When we figure that part out, then maybe we can begin to understand what happened that day.

[HamdenRice]

1. What my bathroom renovations taught me about the trusses

Thanks, DYEW, for those great pictures. I was thinking about the trusses myself because of something that happened to me recently while renovating my bathroom. I live in a very old house that I have been slowly renovating myself for the last few years.

One project was to replace a shower stall pan that was leaking into the kitchen below. I had to break out the bottom of this old tiled shower to replace the old lead pan, which catches water that leaches through the tile and cement base. When I got down to the floor beams, I was horrified to discover that years of water leakage had rotted one of the floor beams. What surprised me is that no part of the bathroom floor was sagging.

I have lived in a few very old apartments before that had bad beams that tend to make the floor slope or sag into the bad sections, and I was puzzled that the bathroom floor never sagged despite the damage. Then I had my eureka moment: the entire tile floor, including the shower and the rest of the bathroom, was a rigid concrete slab, so unlike with wood floors, if a beam sags, the rigid slab keeps the rest of the floor level and even. The rigid slab transfers the load to the other undamaged beams.

This made me think about the WTC. In animations, we always see the trusses, weakened by fire, begin to fall away from the rigid slab that they support. But this would not happen if my bathroom model is correct. If you look at the truss in your first picture, and imagine it supporting a rigid concrent slab (the slab was poured over the thin metal form covering the trusses in the picture), if that truss was weakened by fire temperatures, the floor would not sag or collapse over it, because the slab would transfer the load to the undamaged trusses.

All the trusses would have to collapse at the same time, when the weight of the entire slab was greater than the bearing capacity of all the trusses.

This does not necessarily disprove the weakened truss theory, but it means that the animation that is usually used is clearly wrong. Individual trusses under a concrete slab would not fall away individually as they or their attachments to the outer walls of the WTC failed.

[spooked911]

2. excellent point, HR

in any case, even if one floor drops, it can never explain why the core collapsed along with it-- why the core completely failed in both towers at the start of the collapses

[DoYouEverWonder]

3. The slabs in the WTC were not just concrete

They put steel pans underneath and then poured the concrete into the pans, so the floors would have been even stronger.

In other words, the WTC towers were built like steel shithouses.

[vincent_vega_lives]

24. Well then

That certainly qualifies you in structural analysis! Thank christ we have you here to shed light on this conundrum.

Too bad that eureka moment only goes so far. Quite of the trusses already lost one of they're anchors in the aircraft strike, so they were no longer supporting the floor. Then the fires weakened many more, allowing the weight of the floor to pull on the outer perimeter columns, compromising them, and transferring MORE of the load to other trusses and other columns. Until enough trusses and perimeter columns had failed so the remaining could not hold the weight. Hence "progressive" collapse.

ps: I left an error for you to sniff out.

[William Seger]

29. That's the "zipper theory" that petgoat loves to mention every other post

AKA the "pancake theory." But you need to read the NIST report more closely; after a careful analysis they found a better explanation. The sagging floors pulled the perimeter columns inward and -- the very topic of most of the posts in this thread -- a column that is no longer held vertical can no longer hold its full design load.

[petgoat]

102. FEMA said the perimeter columns buckled outward, NIST

said they buckled inward, but neither one of them has the steel
samples that could have told the tale, because Tomasetti ordered
all the steel destroyed.

[William Seger]

117. Baloney

You KNOW the columns buckled inward because you've seen it clearly here:
http://video.google.com/videoplay?docid=-5405555553528290546&q=wtc+collapse+church

I seriously wonder if you have enough intellectual integrity to try to explain to yourself why you're pretending that you don't know that.

[petgoat]

131. And how did NIST allow for refractive distortion in making that

analysis? And why won't they release the photos and videos?

And so what if the columns buckled on one side? Tensile restraint
on the other would have held the building up.

And what brought down the core?

[Bolo Boffin]

128. You know the perimeters buckled inward

I have shown you this picture before:



The trusses are pulling the perimeter columns into the building. Some are being displaced as much as five feet.

[DoYouEverWonder]

129. Do you happen to have

a copy of that image without the Photoshop treatment?

It would be nice to compare apples with apples. Thanks.

BTW: NYPD or whoever made that image needs to drop the copywrite. Images from government organizations are not subject to copywrite since their funds come from taxpayer dollars.

[Bolo Boffin]

136. These mental games you play with yourself

so that you don't have deal with the reality of things like that picture...

...these games are hurting you.

[DoYouEverWonder]

140. I'll take that

has a no, then. Thank you.

[petgoat]

141. Why won't NIST release the 7000 photos and 7000 videos of the WTC? nt

[mirandapriestly]

4. Thanks for posting that, I never really thought about the

trusses that much. I think one of the reasons they chose to blame the trusses is because they are so relatively thin that it is more believable that fire could soften them. But what makes no sense is that the entire building would fall to the bottom, particularly, as you say, below the 50th floor. There is no explanation for that except CD. It seems as though they would not rely on those flimsy trusses to support the entire building to me, in any case, I can't imagine they were so crucial that the building would fall THAT FAST, and in it's entirety.

[Old and In the Way]

5. It's never made any sense to me either.

If the trusses failed as we are told, I could see a floor pancaking scenario, but I'd also expect to have seen a core standing, once the dust had cleared. It makes no sense to me why they disappeared along ith the floors. That core was tied together and directly to the bedrock.

I'd be interested in how they planned to dismantle the WTC at the end off life. I suspect that they'd have collapsed the floors using the core as a guide post.....

[DoYouEverWonder]

6. Another thing that doesn't make sense if the floors pancaked

why did one side of the outer wall from both buildings remain standing?

[mirandapriestly]

7. Just came across this while searching for something else

It looks like the trusses hold up the floors, but not much else...

[dailykoff]

8. With the assistance of beams,

like the one the guy in the middle has his foot on:



Funny how the MIT articles and governmnet reports never say much about the beams.

[vincent_vega_lives]

13. Thats because they just REMOVED IT!!!

It is a temporary structural brace that is there to keep the core ABOVE the floor trusses rigid!

The FLOOR trusses tie the perimeter columns to the core.

[dailykoff]

15. I forgot, construction is all about removing steel from the frame.

Roger that.

:crazy:

[vincent_vega_lives]

16. Any other smart Ideas?

http://www.democraticunderground.com/discuss/duboard.php?az=show_mesg&forum=125&topic_id=129006&mesg_id=129386

[dailykoff]

17. Waiting for your answer here:

http://www.democraticunderground.com/discuss/duboard.php?az=show_mesg&forum=125&topic_id=127965&mesg_id=130603

[quickesst]

9. Bingo...

According to the oct, the only damage by outside forces resulted from the impact of the jets on the buildings. The areas below the impact are the key. I've always said this, and still think it is one area the oct cannot defend with any logic. Don't rely only on engineers, physicists, etc. completely. I'd suggest talking to the man on the job who's responsibility is to translate what the architects and engineers draw on paper to practical application. There lies the knowledge of construction and how it is applied. You may be surprised at the surprise shown when some of these people are confronted with the issue. Laughing at the oct is part of the reaction, but admitttedly, not useful in proving anything but the obvious. Thanks.
quickesst

[vincent_vega_lives]

10. The trusses were a key component to the structure

They did more than just hold up the floors, which collectively was a massive role in in itself, they tied the outer columns to the core. Neither the outer columns nor the core ALONE could safely support the full load of the building.

You forget parts of the floor trusses, and outer columns were taken out by the aircraft. That transfered their loads to the other trusses and the core, which was likely damaged as well. Trusses that sagged due to fire compromised the outer columns they were attached to, which then negated their load bearing ability.

You cant look at the trusses, core or the outer columns as a single isolated component. All three were tied to the other.

[DoYouEverWonder]

11. The massive core structure of the towers

has enough steel and strength to stand on their own. Keeping them up may have been a different issue, let's say in the event of a hurricane, where they may not have had the stability to stay upright under extreme wind conditions. The perimeter curtain walls also had enough strength to stand on their own up to a point has is evidenced by the pictures of Ground Zero where sections up to over 20 stories tall remained standing on their own, despite the rest of the building falling down on them. The trusses tied the perimeter walls to the core and gave the curtain walls stability but they did not hold the core up.

[vincent_vega_lives]

12. Again. See this post

http://www.democraticunderground.com/discuss/duboard.php?az=show_mesg&forum=125&topic_id=94447&mesg_id=130588

[DoYouEverWonder]

14. I think the key word in your post is 'safely' support

Of course, the core could not support the weight of the floors that went from the core to the perimeter walls by themselves. But the core could do just fine without the floors and the curtain wall. The curtain wall and the trusses gave the core stability but the certainly didn't bear any of the load from the core.

[vincent_vega_lives]

18. Your point is irrelevant

Lets say...for sake of argument...that the core could support itself and remain standing if all the floors and perimeter columns were deliberately dismantled and carted off (it couldn't as the slightest breeze would be a serious problem with NO lateral rigidity, as it was never meant to stand alone. Hence the temporary lateral beams during construction).

Back to your point...even if it could support itself, the core could NEVER support the impulse force of one full story collapsing on another. A full 20% of the buildings mass at accelleration. Ive done the math here many times before. I'm sure you can figure it out in terms of MJ for yourself.

[petgoat]

23. No lateral rigidity? That's ridiculous.

There is no way that a structure 140 feet X 90 feet with massive box columns every twenty
feet connected by rigid overbuilt floor girders and 5" concrete floors could have
no lateral rigidity.

Your assumption that the diagonal braces are temporaries necessary to strengthen a fragile
core structure during construction is just circular reasoning. Those massive diagonals
in the low level construction photos are far stronger than would be needed for temporary
bracing of any sort.

I do think that a core lacking supplemental support would, if over fifty stories tall, tend
to topple in its narrow axis. Which is, IMHO what should have happened in a natural collapse.
The birds nest of chaotic debris would have been resisted by the fence post core, shoving the
debris aside and leaving a fifty-story core standing, which would then have toppled in the case
of WTC2 onto One Liberty Plaza or the WFC. In the case of WTC1 the core would have toppled into
WTC2 or into the Verizon Building and WTC7.

the core could NEVER support the impulse force of one full story

The view of the entire top of the building as a piledriver is absurd. If was more like
a rake hitting a rake. The degree to which the lower part of the interface was damaged,
to that degree the upper block would be damaged. While the lower block was losing two
floors, the upper block was losing two floors. Your pile-driver upper block could not hit
very effectively when hitting through the cushion of a disorganized mass of debris from
four floors. And it wasn't a piledriver. The interaction was more like hitting a rake with
another rake.

[vincent_vega_lives]

26. Vs WIND LOADING?

None. Core + truss/floor + perimeter = lateral rigidity.

The view of the entire top of the building as a piledriver is absurd.

In terms of mass? Not at all.

While the lower block was losing two floors, the upper block was losing two floors.

I agree with that.

Your pile-driver upper block could not hit
very effectively when hitting through the cushion of a disorganized mass of debris from
four floors. And it wasn't a pile driver. The interaction was more like hitting a rake with
another rake.

Here your analogy falls COMPLETELY apart. Cushion??? We are talking accelerating 50,000 tons here. I suppose you think the carpeting and desks would cushion the blow? Having difficulty what your "rake on a rake" analogy is supposed to mean.

Pile diver? No, that would imply it was a homogeneous mass that would remain intact during the decent. Mass was lost during the mutually grinding collapse in the form of debris. But it didn't matter. There was plenty of mass in the upper floors to completely crush the structure below. In relative terms of the FORCE applied in the collapse the WTC each tower was a house of cards.

[petgoat]

31. The perimeter and the floors were a house of cards.

The core was a brick shithouse, built to take the entire weight of the structure,
multiplied by a safety factor (usually five). Kevin Ryan says the building was
twice as strong as it would have been built in Chicago, to add for hurricane
resistance.

Built to hold up the entire structure X 10, the core was subject to attack only by
core debris--not by the entire mass of the top of the tower.

Invoking a "piledriver in terms of mass" is missing the point. Five pounds of
hammer will break a plate. Five pounds of toothpicks won't. Toothpicks are
not a piledriver, regardless of mass.

The structure of the core more resembled a rake or a fork than a piledriver.
Getting a direct blow on broken columns would have been hit-and-miss, and mostly
miss. The force would have mostly been applied to the girders and the floors.
Horizontal debris would soon have bridged across multiple girders, and jammed in
elevator shafts, slowing collapse. The core should have collapsed more slowly
than the floors, soon standing above the zone of collapsing debris.

[vincent_vega_lives]

36. So based on your expertise...

you susbscribe to the explosives required on EVERY floor theory? And NOT just required for collapse initiation correct?

[petgoat]

145. I don't know. nt

[William Seger]

21. What you need to look at is...

... what happened in the first few seconds of the collapse. If just the floors had fallen away, then it's possible that a fairly considerable height of the core could have stood on it's own, but that's simply not what happened. The perimeter columns failed on one wall first in the north tower and on two walls in the south tower. In both cases, that asymmetric beginning of the collapse caused the tops of the towers to tilt over -- more so in the south tower but also in the north -- because the hat trusses at the tops of the buildings were still holding the top sections fairly rigid. That tilting had two effects: (1) the center of mass of the top sections moved toward the core columns nearest the failed wall, putting most of the weight of the top section on just those columns, and (2) the motion of the tops to one side caused and equal-but-opposite lateral force in the opposite direction on the columns holding up the top (in accordance with Newtonian physics). That lateral force pushed the columns sideways, which meant that they could no longer hold their full design load, much less that redistributed load. The core columns nearest the failed walls would have failed next, redistributing their loads to the remaining columns, which quickly failed. (It was that final failure that halted the continuation of the tilting, since there was so solid point for the tops to pivot on.) Now, with the tops falling as a block, the hat trusses continued to redistribute a lot of the forces from the top section to the core columns in the top section, so the core of the top section battered away at the core of the bottom. Once there was enough mass in motion over the cores, it didn't need the redistribution of load from the rest of the building to continue.

[William Seger]

19. "When we figure that part out..."

> ... "then maybe we can begin to understand what happened that day."

One can only hope. Almost all the people in the world who have the knowledge necessary to understand it already have.

Why were the core columns so massive? Because they needed to carry a lot of weight, and they already were when the collapse started. You don't need to be an engineer to understand that a lot of weight, moving = a lot of energy. Think about common examples of how much force things hit with if they fall from the height of one WTC floor, 12 feet. The easiest way to understand just how much gravitational energy was available in the towers is to recognize that it was approximately equal to the energy that it would take to lift a tower about half its own height. (More precisely, it would be the energy it would take to lift a tower to its standing center of mass, which would be a little less than half-way because the bottom structure was heavier than the top. But that would still be the energy it would take to lift almost a half-million tons perhaps about 600 feet in the air.)

I believe the two important factors to understand about the collapse are that while the core was designed to carry that massive weight plus a safety factor, (1) the kinetic energy of that much weight falling exceeded the carrying capacity (which has been extensively analyzed by many people including Dr. Greening), but perhaps just as important (2) the design load limits could only be met if the force was applied strictly vertical, but the collapse simultaneously destroyed the structural components designed to hold the columns vertical while putting lateral loads on the column to push them aside. Columns that were no longer vertical could no longer carry the weight they were already carrying, much less the force of that hugh falling mass.

If you really want to understand the collapse, then you should start by understanding why essentially no structural engineers agree with your baseless suppositions about what the towers should have withstood: Even without doing a precise analysis, structural engineers know that buildings are simply not designed to survive that kind of failure. I really don't understand why some people insist that it's just "common sense" to think the towers should have stood; to me, it's anything but sensical.

[dailykoff]

20. Um, don't you mean "crane scaffolding"?

Mighty big cranes!



:rofl:

[William Seger]

22. Please

I sorta like that smiley, and you're trying to redefine it to mean, "I'm an idiot." Yes, that's a crane tower in the photo.

[dailykoff]

43. Well, you're half right.

The part about the smiley.

:rofl:

[vincent_vega_lives]

48. I take that to mean you don't think that is a temporary structure in the core?

Compare this picture to the B&W pics of the WTC under construction. Note the crane. Obviously the WTC would be too tall and widd to effectively use an external crane, so they had to use four internal ones.



some poor quality cips available here.
http://www.nysm.nysed.gov/wtc/new_media/movie_index.html



Here is an interesting paper detailing the physics involved

http://911myths.com/WTCREPORT.pdf

[dailykoff]

50. No, they are permanent parts of the core

although they do resemble the temporary crane towers in your photo. Here's a larger view:

[vincent_vega_lives]

51. Seen it

So what's their purpose exactly?

[dailykoff]

52. To resist lateral loads

transferred to the cores from the perimeter walls. Apparently they also served as crane towers, eliminating the need for temporary construction. Clever! :)

[vincent_vega_lives]

53. I don't think so

I read somewhere the elevator shafts were intergrated with the crane towers. The large core columns took the loads transfered from the peremeter walls.

[dailykoff]

54. That IS a large core column.

It looks like the core column is on the left side, and the diagonal bracing on the right is basically a shear wall.

[DoYouEverWonder]

55. Here's the best pic I've seen of what the core looked like

?sdfe

It looks like the structure used to hold up the cranes during construction then became the corners of the core. Very clever system.

Keep in mind that WTC2 was oriented perpendicular to WTC1. The plane that hit WTC2 had to go through the thickest part of the core, which is probably why more of it came out the side of the building.

[vincent_vega_lives]

56. No those ARE crane towers.

And have nothing to do with the core. You can see the corner column in front of the nearest crane derick.



Note the cranes in this pic. One is an A fram. the other a Z shaped brace. Also note that in the Top B&W picture the towers have the A frame.



In this picture note the Z shaped frame. Wheres the A frame?

[DoYouEverWonder]

57. Yes, they are crane towers

the question is that in the case of the WTC were they removed after the floor was finished or were they incorporated into the rest of the structure?

[vincent_vega_lives]

59. Elevator shafts

The engineering was incredible, and the building could not have been built without technologies developed in other countries. The "Kangaroo" cranes that hoisted themselves up the elevator shafts were developed in Australia. Nothing like them was available in the United States. They were needed to raise the very heavy steel columns that were the load- bearing walls, another unique design feature of the

http://www.amazon.com/Twin-Towers-Citys-World-Center/dp/0813527422

http://web.mit.edu/civenv/wtc/PDFfiles/Chapter%20I%20History.pdf

[DoYouEverWonder]

60. Therefore, they were part of the core

The inner steel frame housed the elevator cab shafts, mechanical shafts and other support spaces necessary on each floor. The outer tube served as the framework for the exterior wall and was made by bolting together hundreds of premanufactured 3-story tall rigid steel frames. These rigid frames carried both the internal dead and live loads from the floor plates as well as in-plane stresses. The designers were careful to alternate the height of adjacent rigid frames so that they avoided creating a continuous joint around the circumference of the tube. The elevator shafts were recruited during construction to serve double duty by being incorporated into the hydraulic lift system that secured and lifted the construction cranes.

Another interesting point is that they also mention staggering the 3-story tall rigid steel frames to avoid creating a continuous joint around the circumference of the tube. It is important to note that on the mechanical floors, the frames were not staggered. They frames were even with each other. If you blew some of these seams on the mechanical floors, I bet you could take down the building.

[vincent_vega_lives]

61. They were lifted hydraulically

So how on earth could they be permanent parts of the structure???

and this part you bolded: outer tube served as the framework for the exterior wall and was made by bolting together hundreds of premanufactured 3-story tall rigid steel frames.

They are referring to the outer perimeter columns.

[DoYouEverWonder]

62. It was a new point

that I happened to notice, when I read the above passage. I wanted to bring attention to it because I believe that this is a significant bit of information to understand, if you want to understand how the building was put together and how it was taken apart.

[William Seger]

76. Kangaroo crane towers are removed after construction

I haven't been able to find a complete description of how the crane towers worked at WTC, but those cross-braced sections would certainly be removed after construction. (If you look at the picture, you'll notice that if you put an elevator in that shaft without removing the cross-braced tower, getting in and out the elevator door would be a little awkward.)

[DoYouEverWonder]

85. They would only need to remove the cross braces

from one side. Since the passenger elevators opened toward the inside of the building, I don't see why they would bother removing the the bracing on the other 3 sides.

It would be interesting to find out what they actually did.

[William Seger]

86. Looking at the picture some more...

... it appears to me that the cross-braced part we're seeing is just the "kangaroo" part -- the section that could be raised. In a typical kanagaroo crane, the tower below would look similar (but slightly smaller because it would be just inside that moving section), and it would be installed in fairly short sections directly under the crane head as it was raised. All of that tower would then be removed when the building was finished. After thinking some more about what little I've found about the cranes at WTC, it actually sounds like they may have used the kanagroo crane head but somehow had it riding up on core columns instead of the typical prefabricated tower sections. So, there's no way to tell from those photos how much cross-bracing there was below. If the floors were in place to brace the core columns, then little or none would be needed.

But anyway, the general proof that the core couldn't have been fully cross-braced like a truss tower is that there were hallways and doors throughout the core, which would have prevented it.

[William Seger]

90. Hmmm.. look at this

This picture shows the kangaroo crane heads sitting atop core columns that don't appear to be cross-braced like the movable sections immediatetly below the crane.

[dailykoff]

87. The cranes were removed, the elevator shafts were not.

On account of the holidays, I will refrain from saying "duh."

[DoYouEverWonder]

88. Be nice now

We've been having a lovely conversation today and it's been quite civil.

;-)

[William Seger]

89. It wouldn't kill you to do a little research before posting

I'm sure you can find info about kangaroo cranes on Google, so I'm not going to look that up for you, but here's about the most I've found about the WTC cranes, from a PBS documentary transcript:

"In August, 1968 actual steel construction began. Kangaroo cranes imported from Australia were used for the first time in the United States. The cranes were assembled on top of the core columns. Each could lift 60 tons at a time. They would be the driving force behind the towers' construction. The cranes had the ability to jack themselves up 36 feet at a jump. As the walls grew to the height of a crane, the crane would hoist itself up, a neighboring crane would swing core columns into place beneath it, and construction would continue."

And.... :banghead:

[William Seger]

75. Very candid of you to admit that...

... but I'm also right about that being a crane tower.

(P.S. This is my "Yes, you are" smiley: :banghead: )

[petgoat]

25. "why essentially no structural engineers agree with your baseless suppositions "

Because they very wisely avoid having opinions about stuff that is
outside of their areas of expertise when they don't have the information
they need or the time the develop an opinion.

When Dr. Eagar's absurd zipper theory was the current dogma, not one
structural engineer uttered a peep about it. Not one structural engineer
uttered a peep about the destruction of the steel. When NIST tossed the
zipper theory aside, not one structural engineer would defend it.

Your supposition that silence is consent is unreasonable.

Neither FEMA nor NIST explained why the core fell down to the ground.
They didn't because they can't.

[vincent_vega_lives]

27. Resonable explanations are a dime a doz

If you just look around...this from the very DAY of the collapse

http://www.civil.usyd.edu.au/wtc.shtml

The structural integrity of the World Trade Center depends on the closely spaced columns around the perimeter. Lightweight steel trusses span between the central elevator core and the perimeter columns on each floor. These trusses support the concrete slab of each floor and tie the perimeter columns to the core, preventing the columns from buckling outwards.

After the initial plane impacts, it appeared to most observers that the structures had been severely damaged, but not necessarily fatally.

It appears likely that the impact of the plane crash destroyed a significant number of perimeter columns on several floors of the building, severely weakening the entire system. Initially this was not enough to cause collapse.

However, as fire raged in the upper floors, the heat would have been gradually affecting the behaviour of the remaining material. As the planes had only recently taken off, the fire would have been initially fuelled by large volumes of jet fuel, which then ignited any combustible material in the building. While the fire would not have been hot enough to melt any of the steel, the strength of the steel drops markedly with prolonged exposure to fire, while the elastic modulus of the steel reduces (stiffness drops), increasing deflections.

Modern structures are designed to resist fire for a specific length of time. Safety features such as fire retarding materials and sprinkler systems help to contain fires, help extinguish flames, or prevent steel from being exposed to excessively high temperatures. This gives occupants time to escape and allow fire fighters to extinguish blazes, before the building is catastrophically damaged.

It is possible that the blaze, started by jet fuel and then engulfing the contents of the offices, in a highly confined area, generated fire conditions significantly more severe than those anticipated in a typical office fire. These conditions may have overcome the building's fire defences considerably faster than expected. It is likely that the water pipes that supplied the fire sprinklers were severed by the plane impact, and much of the fire protective material, designed to stop the steel from being heated and losing strength, was blown off by the blast at impact.

Eventually, the loss of strength and stiffness of the materials resulting from the fire, combined with the initial impact damage, would have caused a failure of the truss system supporting a floor, or the remaining perimeter columns, or even the internal core, or some combination. Failure of the flooring system would have subsequently allowed the perimeter columns to buckle outwards. Regardless of which of these possibilities actually occurred, it would have resulted in the complete collapse of at least one complete storey at the level of impact.

Once one storey collapsed all floors above would have begun to fall. The huge mass of falling structure would gain momentum, crushing the structurally intact floors below, resulting in catastrophic failure of the entire structure. While the columns at say level 50 were designed to carry the static load of 50 floors above, once one floor collapsed and the floors above started to fall, the dynamic load of 50 storeys above is very much greater, and the columns were almost instantly destroyed as each floor progressively "pancaked" to the ground.

While the ways the two towers fell were slightly different, the basic cause is similar for both - a large number of columns were destroyed on impact, and the remaining structure was gradually weakened by the heat of the fire. Not much significance should be taken from the fact that one tower fell in 45 minutes and the other in 90 minutes.

The gigantic dynamic impact forces caused by the huge mass of the falling structure landing on the floors below is very much greater than the static load they were designed to resist.


and then added this on 14 January 2006...in response to...well you know. :eyes:

This website generates many queries from people in response to some of the other theories that are put forward relating to the collapse - namely that it was a controlled explosion.

The initial impact/further weakening by fire reasoning is based on uncontestable knowledge about the behaviour of structures in general, and the weakening of steel under fire conditions, plus video footage of the events and examination of the steel afterwards. The official FEMA report written by engineering experts came to this conclusion based on the evidence.

However, should additional evidence come to light that supports a different theory, the author is willing to reassess his views.

The fire wasn't hot enough to melt the steel
There has never been a claim that the steel melted in the fire before the buildings collapsed, however the fire would have been very hot. Even though the steel didnt melt, the type of temperatures in the fire would have roughly halved its strength.

There would have been variations in the distribution of the temperature both in place in time. There are photos that show people in the areas opened up by the impact, so it obviously wasnt too hot when those photos were taken, but this is not to say that other parts of the building, further inside were not hotter. In addition, to make a reasonable conclusion from these photos, it would be important to know when they were taken. It might be possible that just after the impact the area wasnt very hot, but as the fire took hold the area got hotter.

The way the building collapsed must have been caused by explosions
One demolition expert on the day of the collapse said it looked like implosion but this is not very strong evidence. Implosion firstly requires a lot of explosives placed in strategic areas all around the building. When and how was this explosive placed in the building without anyone knowing about it. Second, implosion required more than just explosives. Demolition experts spend weeks inside a derelict building planning an event. Many of the beams are cut through by about 90% so that the explosion only has to break a small bit of steel. In this state the building is highly dangerous, and there is no way such a prepared building could still be running day to day like WTC was.

Why did the building fall so quickly?
The buildings did fall quickly - almost (but not exactly) at the same speed as if there was no resistance. Shouldn't the floors below have slowed it down? The huge dynamic loads due to the very large momentum of the upper floors falling were so great that they smashed through the lower floors very quickly. The columns were not designed to carry these huge loads and they provided little resistance.

What about World Trade Center 7?
I have not studied WTC in any great detail and cannot offer any theories on its collapse mechanism. In the chaos of the day, little attention was paid to WTC7, so there is less evidence available on the damage it sustained before it collapsed. However, some questions that you may want to ponder ...
* While it did not receive any direct impact form the planes, how much debris hit at as the main towers collapsed and what damage did it cause?
* To what extent (if any) did the shock or vibrations caused by the collapse of WTC1 & 2 affect the integrity of WTC7?
* Did any unseen damage to the WTC7 foundations occur in the collapse of WTC 1 & 2?
* Did any of the fire suppression systems in WTC7 function?


The author respect people's right to question theories, but at the present time the author does not believe there is enough evidence for him to change his views on this incident.

[petgoat]

30. That's all they're worth.

The glaring deficiencies in the $20 million NIST and $600,000 FEMA
reports speak far more eloquently than do the hasty hand-waving of
the instant-rationalizers.

Nobody explains why the core did not resist the collapse. For a
disorganized mass of debris to take the core down is like a bird's
nest taking down a fence post.

[William Seger]

32. Write up your "bird nest" theory...

... and post it on the JREF Conspiracies board. There are several structural engineers there.

[petgoat]

34. It's not a theory, it's a fact, unless you're going to suppose

that the magic twenty top stories of the building somehow retained their
integrity all the way down, breaking down 90 stories of building and
then disintegrating when they hit the ground.

There is no way the debris mass was anything but a bird nest by the time
it reached the sixtieth floor. And by that point the core should have
been fighting back.

[Bolo Boffin]

35. You wouldn't want to, like, take pictures of yourself throwing a bird's nest

at a fence post, would you?

I ask merely out of professional scientific curiosity. :popcorn:

[William Seger]

39. In other words

... you're afraid of the ridicule you would get from a structural engineer. I don't blame you one bit: Willful ignorance is the only thing that can save your "bird nest" theory from collapsing, and we wouldn't want that to happen.

But no, for the record, all I'm "supposing" is that mass in motion has kinetic energy. Where's the "integrity" term in the equation F = ma ?

[petgoat]

40. Mass in motion has kinetic energy, but the effective

transmission of that kinetic energy to some other body
depends on the degree of organization of the mass.

Swing a bag of sand in my face and you might knock me out.

Empty a bag of sand on my head and you won't.

It's illegitimate to apply all the kinetic energy of the
top part of the tower to the problem of deconstructing the
core. Only a part of that energy was available to attack the
core. Much of the kinetic energy of a disorganized debris pile
is expended in churning the pile around non-productively.

[vincent_vega_lives]

47. Good point

Cohesion is key. You mean like a mass of steel girders, bound to concrete floors? The disintergration of the building occured two stories at a time. That means 40 stories would be collapsed by the time the top floor was collapsed. Mass would have been loss in the form of debris but the momentum (p) from some 50,000 tons (M) accelerating (v) downward would still be more than enough to collapse the rest of the building...as I am sure you recall that once an object is in motion it takes an equal amount of force (in the form of friction) to stop it.

[William Seger]

77. Your imagination doesn't always match reality

First, you seem to be imagining that the tower somehow turned into "sand" before it fell. Very imaginative, but not very realistic; the concrete and gypsum were obviously crushed after impact. Second, as I mentioned to you before, almost all of the pulverized material was trapped between the steel decking, held in place by the debris above, not floating around like sand poured out of a bag -- your sand IS in a "bag," a steel one -- and only stuff near the edges of the building could escape out the sides. Third, there's no reason to think that the concrete was completely pulverized even after the debris hit the ground, much less in the initial impact of the falling debris. And of course, none of the 200,000 tons of steel was not pulverized at all.

[petgoat]

146. Your literal interpretation of a general metaphor obscures the point

I am not imagining that the tower turned to sand. I was making a general point about
the efficiency of transfer of kinetic energy.

almost all of the pulverized material was trapped between the steel decking, held in
place by the debris above, not floating around like sand

Right, which is what maked the mushroom cloud pictures so puzzling. How did all that dust
get pushed out? It should have been retained between the steel decks, restrained by vinyl
flooring and nylon carpet.

your sand IS in a "bag," a steel one

Right, but those particular sand bags were applied only to the destruction of the floors and
the perimeter columns. So what took down the core columns?

there's no reason to think that the concrete was completely pulverized even after the
debris hit the ground

Show me a picture of concrete floor slabs. There should have been a hundred of them stacked
up like a stack of broken plates. There's only dust.

[G Hawes]

82. That's a great suggestion.

http://forums.randi.org/forumdisplay.php?f=64

It would be a great place for petgoat to test his theories if he has the courage of his convictions, and it would be a great place for him to learn from actual professionals in relevant fields in the process.

[William Seger]

28. Argh! How many times are you going to make that same faulty argument?

> Because they very wisely avoid having opinions about stuff that is
outside of their areas of expertise when they don't have the information
they need or the time the develop an opinion.

Yeah, such as the common-sense "design concept" necessity of erecting building with built-in demolition explosives, just in case someone decides they need to bring the building down in a hurry?
http://www.democraticunderground.com/discuss/duboard.php?az=view_all&address=125x127965#128404

> When Dr. Eagar's absurd zipper theory was the current dogma...

Last time for this: Without knowing the details of the connections and without doing a detailed analysis, there was nothing "absurd" about the "zipper theory." What was "absurd" was calling it "absurd" before doing that analysis, which CTers did, while NIST didn't. You conveniently ingnore the fact that it was primarily based on several photos that did show large sections of floor broken away from the perimeter and sagging in one piece. Spin it anyway you like, those collapsed and sagging floors proves that the "zipper theory" was not at all absurd; NIST simply decided, after a careful analysis, that it was not the best explanation. Now, the next time you mention the "absurd zipper theory" I promise you I won't respond at all -- but just imagine me thinking to myself "WTF is wrong with that guy!"

> Neither FEMA nor NIST explained why the core fell down to the ground. They didn't because they can't.

Wrong, they didn't because they didn't see any need to: People who understand these things don't have a problem understanding why the building could not withstand that initial collapse. Now, you might argue that they should have included that anyway, just for the benefit of people who don't understand it, and I might agree. But I'm sure you know -- and therefore you are simply being disingenuous -- that other people such as Dr. Greening have filled in (some) of the details, and that CTers like Gordon Ross haven't been successful at refuting that analysis. But even Dr. Greening's analysis was an over-simplification in that it didn't take into account the chaotic displacement of the columns and the resultant loss of carrying capacity (which would be extremely difficult to model accurately). But there isn't any need to do that level of detail since calculations show that even if the collapse forces had been applied uniformly and straight down, it was more than the structure could handle.

[petgoat]

33. I have many times explained to you what is absurd about the

zipper theory on its face--no analysis needed. It claims that the perimeter clips
were so flimsy the floors unzipped, but the core clips were so strong that the
floors tore the core down. That's absurd.

the common-sense "design concept" necessity of erecting building with built-in
demolition explosives, just in case someone decides they need to bring the building
down in a hurry?

All right, smart guy, what do YOU do with a 1300 foot tower that's been kinked by
a thousand-year hurricane and threatens to topple? Call in the Air Force? Do you
think such contingency planning was not part of putting the structure up?

I'm not saying explosives were or were not installed. I don't know. I'm confident
that if they were, their presence would have been a closely guarded secret. I don't
see how it's unreasonable to think they might have been.

even if the collapse forces had been applied uniformly and straight down, it was
more than the structure could handle.

You're arguing what NIST argues--since the building fell down, that proves it couldn't
handle the stress, therefore we know why it fell down.

The collapse forces were NOT applied uniformly. The core was built to take five to ten
times the weight of the entire structure and was subject only to the weight of the core
debris. This debris would have seen been tangled up into a ball that would have impaled
itself on the core columns like a meatball on a fork. The floors peeling off the core
would have caused minimal damage to the core because the floor pinnings were designed
only to hold up one floor while the core was designed to hold up the entire building.

But you guys want us to think the core was so flimsy it had to be braced during
construction!

[Bolo Boffin]

37. Ooo, meatball on a fork!

Pictures of that too, please.

But really you have almost a shred of a point. I remember a spire standing a few moments after most of the rest of the building collapsed. I would hazard a guess that at about that point in the collapse, the upper floors had been completely torn apart.

Little good it did.

But, yes, please, pictures of you (you can hide your face and identifying features) tossing a meatball onto a fork. It's in the interests of science.

[petgoat]

41. Meatball on a fork

That's what should have happened. Then we'd be left with six hundred feet
of top-heavy naked core that would have fallen over on One Liberty Plaza
or WFC.

[Bolo Boffin]

44. Thank you.

Tell me something: if an ant was one hundred times larger than it is, could it carry one hundred times more than it could carry at regular size?

This has everything to do with your hypothesis.

[petgoat]

45. Ah, so now the core is ant-sized and the top of the tower is

a hundred times larger?

[Bolo Boffin]

49. Afraid of the question? Answer it. n/t

[petgoat]

63. I'm not going to indulge dimestore socratism. I see no

relevance in the issue.

The towers were scaled to hold themselves up.

Your point would appear to be a variation on the "The towers were too big to
fall anywhere but straight down" theme. Which is absurd. The Queen Mary wasn't
too big to steer.

[Bolo Boffin]

65. You can resist reality all you like, but you still have to live in the real world.

And if you're going to talk about these things, then expect reality to be presented to you constantly.

The answer is, if an ant were the size of a human, it wouldn't be able to stand up.

4.7 Why can ants/insects carry so much?

The reason is because lifting power scales in proportion to the
cross-sectional area of the muscle -- while mass scales with the
volume. This is the complicated explanation. Imagine a human
which could lift his/her own weight were shrunk down to 1/100th
of his/her original size. Accordingly, they should be able to
lift 1000 times his/her own weight. In terms of muscle power,
humans are roughly 20 times stronger than ants. If ants were
enlarged to our size, they probably wouldn't be able to lift
themselves off the ground. --Mr. Ant

A goat can learn a lot from an ant, especially constructing VALID illustrations and not PROPAGANDISTIC ones. Your exaggerations of scale are NOT adequate to explain the towers - they serve only to cloud your mind as to the actual forces involved in the collapse of the towers. Your bag of sand model, your bird nest model, your meatball model (particularly callous), your Queen Mary through water model, and spooked911's rabbit cage experiments all fail on a physical level of scale to explain the forces involved in the tower collapses.

You are doing yourself no favor with these examples, not if you're looking for truth, and you are spreading your nonsense around. Try steering the Queen Mary through an iceberg field.

[vincent_vega_lives]

70. Yes I tried to explain scaling using a matchbox car

a while ago. You can't replicate the effect of dropping a car from 100' by dropping a matchbox car from 20", but that is what some of the analogies here are trying to do.

[petgoat]

79. Nobody is proposing a giant meatball on a giant fork.

What is proposed is that the giant core structure of the WTC, built
to carry 10X the weight of the entire tower above, should have
captured the disorganized wreckage of the WTC wreckage that was
disintegrated core above it, rather than collapsing under this
relatively small amount of wreckage.

Meatball on a fork is a metaphor. I don't think that you lectured
Dr. Eagar to the effect that zippers were not scalable to the
magnitude of one acre floor slabs.

[William Seger]

83. "the giant core structure of the WTC..."

"...built to carry 10X the weight of the entire tower above..."

That's a lie. Please stop lying; it makes the "truth movement" look bad.

[Name removed]

91. Deleted message

Message removed by moderator. Click here to review the message board rules.

[vincent_vega_lives]

92. There is a big difference between

the types of loads you are referring to. The perimeter column - truss - core system is what gave it great strenght agianst wind loading, not 'overbuilding'. The x4 safety factor was against construction and design flaws, NOT against compromise of key structual components.

[William Seger]

93. Credibility?

> I see no evidence that you have any interest whatsoever in maintaining the credibility of the truth movement.

In case you hadn't noticed, I do happen to take an interest in the fact that the "truth movement" spreads a lot of lies, and I couldn't care less what you perceive my motivations to be.

> Building structures are commonly overbuilt by 5X for safety.

Bullshit. Just because that's a common myth in the "truth movement" doesn't make it true. For gravity loads, structures are commonly built with up to a 2x safety factor, and the NY City code at the time required only a 1.67 factor. Furthermore, you claimed the core alone was "built to carry 10X the weight of the entire tower above." The core was built to carry only 60% of the weight of the tower, so even if you assume they were actually built with a full 2x safety factor, that's 120% of the "entire tower above," not 1000%. Your false claim is exactly equivalent to claiming that the core cost 8 to 10 times more than it needed to, and if you'll investigate the history of the towers, you'll see that one of criteria behind the unique design was to keep the cost down.

> According to Kevin Ryan, WTC was built twice as strong as it would have been built in Chicago, because it had to resist hurricane winds.

Why does the "truth movement" depend on water testers and theologians for information about structures? Answer: Because structural engineers won't tell them what they want to hear. The core was not designed to carry any wind loading at all. The perimeter columns were designed as a "tube," held rigid by the floor diaphragms, to withstand wind loading. Unfortunately, the collapse was initiated when the perimeter columns on one side were pulled inward by the floors, so the tube became crimped like a buckling straw. If the towers had remained vertical when that happened and somehow redistributed the loads uniformly across all of the remaining structure, then it's possible that the structure might have held, even with some of the columns destroyed or damaged by the plane crash. But that's not what happened. The towers began to lean toward the failed walls, which put a disproportionate percentage of the load on the core columns nearest the perimeter failure, and it also caused those columns to begin to bend, which immediately made them much more susceptible to buckling, so they could no longer carry even their design load. That rotation of the top sections also put lateral forces on the columns in the opposite direction of the leaning, which also decreased the resistance to buckling. That combination of overloading, bending, and lateral forces caused those core columns closest to the failed perimeter to fail next, and then there was nothing left that could possibly stop that level from completely failing. Then, when the top block hit the floor below at more than 8 meters per second, according to people who best understand these things, there was no way for the building to stop the collapse, because the forces involved were simply larger than the safty factors. No "bird nest on a fence post" or "meatball on a fork" about it.

Okay, I'll take your word for it that you were not intentionally lying, that you were simply mislead by the disinformation you got on some "truth" site. But can I expect to not see that "10X the weight of the entire tower above" claim again? Given your past record, I seriously doubt it.

[dailykoff]

96. Speaking of which, you left out a few things

as usual. For example, what kept the "tube" rigid? The tube in the tube, i.e., the core, and what kept it rigid was the bracing.



Try building a house without shear walls some time and see what happens.

[William Seger]

99. Wrong again

The structural design of the WTC towers is discussed on many, many sites by now, dailykoff -- there is no reason for you to substitute your imagination and very limited knowledge and understanding -- so please do some research. The exterior walls were the shear walls (that was the main purpose of the deep spandrel plates), and the floor diaphragms held the exterior walls in that tube shape. With that tube shape maintained by the floors, bending due to wind loading was transferred through both the floor diaphragms and the spandrel plates (the stiffness of which made the side walls act like webs of a beam), so the lateral wind forces were absorbed completely by the perimeter columns -- primarily by compression on the leeward side -- and the core played no part in that. That's why the perimeter columns were "over-designed" with respect to gravity loads alone. The core was not in any way designed as a shear wall -- there was no need, with all 4 exterior walls serving that purpose -- it simply carried the floor gravity loads.

And, since you (intentionally?) missed it, I think we've solved the "mystery" of the crane towers: That tower in your photo is just the "kangaroo" section that lifted itself up through the elevator shaft as the building went up. Want me to prove it again? Fine:



See those crane towers at the top of the building on the left? Those are the cross-braced towers of the moving section, which is what we see in your photo. See how they extend down into the building for a way, but then there are core columns below that? Those are the elevator shafts that the crane climbed, and those are what was left when the crane towers were removed.

:banghead:

[dailykoff]

100. Oh please. Build a model without a braced core and blow on it.

You've been watching too many cartoons.

[dailykoff]

101. p.s. shear walls don't have hinges.

:rofl:

[William Seger]

115. Really? How would you know when you don't understand either concept?

:banghead:

[dailykoff]

118. I don't see you disagreeing here:

http://www.democraticunderground.com/discuss/duboard.php?az=show_mesg&forum=125&topic_id=127965&mesg_id=131086

p.s. glad I was able to clear things up for you. :hi:

[William Seger]

119. How many times should I try to explain something that simple?

If you don't yet understand that those columns will buckle in the weakest direction -- which would be in the direction that the joist seats allow them to rotate -- then I think it's safe to say you never will. And as long as you don't understand it, then obviously you'll never understand why Taxloss' photo shows exactly the type of buckling that should be expected by someone who does understand it. But fortunately for me, your inability to understand simple mechanics is not my problem. Just like your inability to understand something as simple as stereo photography when I first started posting on this subforum, and just like your inability to understand why a torch cut doesn't look like a mythical thermite cut, and just like your inability to understand the principle of a kangaroo crane -- there is some limit to how many times I'm willing to try to explain the same thing over and over to a brick wall.

[dailykoff]

120. As I said, you're wise to let it go. (n/t)

[William Seger]

121. Oh, I didn't say I was going to "let it go"

All I said was there's a limit to how many times I'll try to explain the same simple things over and over. Ridiculing you mercilessly is still on the option list.

[dailykoff]

122. Then I'll look forward to your answer here:

http://www.democraticunderground.com/discuss/duboard.php?az=show_mesg&forum=125&topic_id=127965&mesg_id=131086

p.s. but I won't count on it.

:rofl:

[William Seger]

123. Why? The answer is already there, right above it, several times

You're the one who owes me an answer: I asked you to directly answer, yes or no, if you think those 14" square columns would buckle like your top photo before those joist seats would bend or break off. Your answer to that question would either force you to understand the thing or demonstrate your impenetrable denseness -- your choice -- and I assume that's why you ducked it.

:banghead:

[dailykoff]

124. A wise retreat into irrelevance. (n/t)

[William Seger]

125. Answer the damn question

[dailykoff]

126. Answered, right here:

http://www.democraticunderground.com/discuss/duboard.php?az=show_mesg&forum=125&topic_id=127965&mesg_id=131086

And with that I bid you good night, as I have no wish to embarrass you further. :hi:

[Name removed]

127. Deleted message

Message removed by moderator. Click here to review the message board rules.

[William Seger]

139. Well, apparently telling you what I think of your answer is against the rules

So, I'll just ask the question again: Do you or do you not think that those 14" square columns would buckle like your top photo before the angle clip joist seats either bent or broke off? Please answer yes or no.

[petgoat]

103. What's with all the unsourced assertions?

You've got no source or are you ashamed of your sources?


Steel structures are commonly overbuilt by a factor of five. Ryan said
the WTC was overbuilt for hurricane forces by an additional factor of 2.


The core was not designed to carry any wind loading at all.

The core was an essential part of the system. Without the core, the
hat truss could not do its job.

The wind design defeats your scenario. Buckled perimeter columns (assuming
there were some) can not carry compressive loads, you're right. But the
wind design provides for the forces to be taken by the tensile restraint,
mediated by the hat trusses, of the perimeter columns on the other side.

Those perimeter columns were rated at 2000% of the live load, which was equal
to the dead load. That's 20X. Again, this comes from Ryan.

[William Seger]

112. You want sources to refute a water tester?

And why would you think that I'd be afraid to put the American Institute of Steel Construction (AISC) up against your water tester? Their Manual of Steel Construction is used as the basis for most of the steel building codes in the country. You can Google for "AISC column safety factor" and verify that they recommend factors of safety ranging from 1.67 up to 1.92, depending on the column's slenderness ratio and restraint conditions:

http://www.google.com/search?hl=en&lr=&client=firefox-a&rls=org.mozilla%3Aen-US%3Aofficial&hs=8Lr&q=aisc+column+safety+factor&btnG=Search

In a preliminary report, NIST reported that the original design criteria included a factor of safety of 1.67 for the core columns. But after NIST did their computer model, we no longer have to guess about that: That model effectively reverse-engineered the "as built" core columns. They found that the actual factors of safety for individual columns ranged from about 1.6 up to about 2.8. (The numerical average would be 2.1 if we gave each column equal weight, but in fact it was generally the smaller columns that had the larger numbers -- probably because of rounding up to standard steel sizes -- so the total effective factor of safety for the entire core was definitely less than 2.) The results are in NIST NCSTAR 6D on page 232 (but note that their diagram shows "demand-to-capacity" ratios, which is the inverse of the factor of safety -- divide those numbers into 1 to get the FoS):

http://wtc.nist.gov/NISTNCSTAR1-6D.pdf

So, yes indeed, I'll take AISC Standards and computer analysis of the actual columns over your water tester's hyperbole multiplied by your misremembered or misunderstood lecture added to your misunderstanding Eagar's comment to mean that the core was designed to carry the whole tower -- any day.

> > The core was not designed to carry any wind loading at all.

> The core was an essential part of the system. Without the core, the
hat truss could not do its job.

The wind design defeats your scenario. Buckled perimeter columns (assuming
there were some) can not carry compressive loads, you're right. But the
wind design provides for the forces to be taken by the tensile restraint,
mediated by the hat trusses, of the perimeter columns on the other side.

Sheesh, you're getting as bad as dailykoff. No, that's total gibberish; the hat trusses had nothing to do with the wind loading; they were for redistributing vertical gravity loads. The floor diaphragms and the spandrel plates made the perimeter walls a rigid tube, which was all that was necessary to redistribute lateral wind loads.

And what do you mean by "buckled perimeter columns (assuming there were some)." After all the direct, unambiguous proof you've been shown in the form of videos and pictures, I suppose I should be glad you're now willing to "assume there were some," but still... that's simply annoying as hell.

> Those perimeter columns were rated at 2000% of the live load, which was equal
to the dead load. That's 20X. Again, this comes from Ryan.

Well then, again, it appears that Ryan is full of shit. Perhaps, like you, he got carried away with multiplying exaggerations by his own misunderstandings. You're changing the subject away from the core, but because the perimeter columns were also used to handle the wind loads, they had about 5x (500%) the capacity they would have needed to carry just the gravity loads alone, which is likely where your original 5x number came from before you misapplied it to the core columns. But that number is irrelevant since we know from the videos that perimeter columns buckled inward at the beginning of the collapse -- hard to do with explosives! -- and we also know that as the collapse progressed, the perimeter column sections were literally ripped away from the building well before they could reach their compressive limits. Which takes us right back to an important principle that I can assure you (from working with them for 5 years) that structural engineers understand very well, whether or not certain water testers and other CTers do: ALL of the theoretical load-carrying capacities of structural members assume that structural integrity is maintained. Destroy the structural integrity, and the maximum limits under ideal conditions are totally meaningless. And that, my friend, is the real story of the towers' complete collapse in a nutshell, and that's why structural engineers aren't impressed with CTer's hand-waving pseudo-analysis.

[petgoat]

143. "actual factors of safety for individual columns ranged from about 1.6 up to about 2.8"

Right. And then you have a highly redundant design.

So assuming the individual columns have a safety factor of two,
and you use 2-1/2 times as many columns as you need, you then
have a safety factor of five.

the hat trusses had nothing to do with the wind loading; they were for
redistributing vertical gravity loads.

Wind loading has everything to do with redistributing vertical loads.
The windward side of the building is put under tension, the lee side
under compression. The hat truss ties these two sides together, and its
fulcrum is the core.

And what do you mean by "buckled perimeter columns (assuming there were some)"

I mean I've seen no "direct, unambiguous proof." I've seen some photos that might show
column bending or might show refractive distortions of light from heat. I've seen
no photos of buckled columns, and no samples of buckled columns were preserved.

ALL of the theoretical load-carrying capacities of structural members assume that
structural integrity is maintained.

Right. "The towers fell, therefore there must have been buckling." FEMA said the
columns buckled outward. NIST said they buckled inward. Neither has produced any
buckled columns, and I've never seen any pictures of buckled columns.

The fable is that ALL the kinetic energy of the upper block was applied in a coherent
and effective way to the destruction of the lower part of the towers.

The fact that the floors could be easily overwhelmed by falling debris is used to
cover over the fact that the core could NOT be easily overwhelmed by falling debris.

Who has calculated the energy necessary to disintegrate the upper block and twenty
floors under it? That energy must be subtracted from the kinetic energy available
to attack the lower towers.

NIST claims that the collapse is too complicated to model. I think that's "coverup-speak"
for "We can't get the core to collapse, so therefore it's too complicated for our software
to explain."

[William Seger]

144. Again (and again)

> Right. And then you have a highly redundant design. So assuming the individual columns have a safety factor of two, and you use 2-1/2 times as many columns as you need, you then have a safety factor of five.

Total bullshit. I just told you the NIST study effectively reverse-engineered the core columns and found that the factor of safety was less than 2 -- that's for all the columns together, not half of them.

> Wind loading has everything to do with redistributing vertical loads. The windward side of the building is put under tension, the lee side under compression. The hat truss ties these two sides together, and its fulcrum is the core.

Total bullshit. A tube (square or round) will transmit the bending moment of lateral wind loading without any hat truss at the top to distribute vertical loads. All the towers needed to redistribute wind loads was the stiffness of the spandrel plates and the floors to hold the square shape. Again, the design of the towers is discussed on many websites, and your imagination is a poor substitute for the engineering principles that went into it. I dare you to find any description that says the hat trusses played any role in redistributing wind loads.

> Right. "The towers fell, therefore there must have been buckling." FEMA said the columns buckled outward. NIST said they buckled inward. Neither has produced any buckled columns, and I've never seen any pictures of buckled columns.

Wrong, three times actually, since two of your assertions are wrong and you didn't address my point at all. Buckling was directly observed in the perimeter columns, not deduced by the reasoning you imagine, and there are numerous pictures of that fact and of buckled columns in the debris, whether or not you refuse to see them. But the point I made that you pretended to be addressing was about "structural integrity," not buckling. What I mean by that is the connections that held the columns and floors in place as a solid unit. Break out the floors, and both the perimeter and core columns are no longer supported laterally, so they can be knocked over to the side long before reaching their buckling loads.

> The fable is that ALL the kinetic energy of the upper block was applied in a coherent and effective way to the destruction of the lower part of the towers.

Wrong, Greening included a factor in his calculations for the debris that fell over the sides.

> The fact that the floors could be easily overwhelmed by falling debris is used to cover over the fact that the core could NOT be easily overwhelmed by falling debris.

Wrong, for the reason I stated above: Knock out the floors and the core columns have no lateral stability, regardless of how much load they could carry when they had stability. The idea that only the floor outside the core failed is illogical, since that top block started pounding on everything below it, not just the outside floors.

> Who has calculated the energy necessary to disintegrate the upper block and twenty floors under it? That energy must be subtracted from the kinetic energy available to attack the lower towers.

Greening, among others. At each floor, there was some loss of energy destroying that floor, but there was an even greater gain in both mass and velocity as the debris fell another 12 feet.

> NIST claims that the collapse is too complicated to model.

No, I claimed that, because of all the factors you would need to take into consideration in that kind of chaos. Just modeling the fires and the structural changes that initiated the collapse was by far the largest and most complicated computer modeling of a building failure ever attempted. However, I have read that several people have made simplified computer models of the collapse (using a model similar to Greening's but modeling individual floors and columns instead of an aggregate) and they didn't have any trouble getting the core to collapse. So, of course you'll dismiss those as being obviously too simple, even though the actual situation with the loss of structural integirty would have made collapse even easier.

> I think that's "coverup-speak" for "We can't get the core to collapse, so therefore it's too complicated for our software to explain."

Well, at least you're now saying "I think that" instead of stating it as a fact.

[DoYouEverWonder]

94. If he is wrong

then he makes himself look bad.

If you have proof he is wrong present it. Hold it up for DU's peer review and then the rest of us can decide whose 'facts' are more correct. I don't want to continue to passing along incorrect information, once I find out it's wrong.

[LARED]

95. There is really no question about it

PG is wrong. There is no way the WTC core was designed to to carry 10X the weight of the entire tower.

I'm not sure what kind of proof you're looking for, but it was simply not designed that way. There is no reason to design it that way, it would be too costly, and provide no benefit. Safety factors and design criteria have has been explained to PG many times, to no avail. Also the source of the 10X nonsense is Kevin Ryan, a person with no credentials to make that statement. This misinformation is not surprising either in that Ryan lost his job because he publicly commented about stuff he does not understand putting his employer, UL in a bad situation.

[dailykoff]

97. The fact that Ryan was targeted speaks to his credibility.

And to Jones's, and to all the other 9/11 whistleblowers who find themselves out of a job.

[LARED]

105. Why is it being a so called "whistle blower" bestows

instant credibility no matter what subject matter the "whistle blower" addresses?

Ryan was a "water guy" at UL. He does not have any authority to speck about design criteria for steel building.

[petgoat]

106. "He does not have any authority to speck about design criteria for steel building."

He knows junk science when he sees it, and Bush science is junk science.

[William Seger]

114. You're delusional

"Junk science" is what the Scholars for Truth is all about. And there's no mystery about why CTers prefer junk science, either: That's just the thing you need to tell yourself you were right all along. It's just mind-boggling that you are so in love with your conspriracy theories that you can convince yourself all of the FEMA and NIST investigators and all of the structural engineers who have looked at the WTC collapse before and since those investigations -- people all around the world -- are pro-Bush and pro-mass-murder, but Ryan "knows junk science when he sees it." It's really pretty pathetic, actually.

[petgoat]

133. "all of the FEMA and NIST investigators and all of the structural engineers "

Ah the Great Silent Majority Speaks (not).

Most of the NIST and FEMA investigators worked on narrow compartmentalized
specialities, and can not be assumed to endorse elements of the report
on which they did not participate.

Not one structural engineer would criticize the ludicrous zipper-pancake
theory, so your assumption that the engineering community has studied the
NIST report and the collapses and concurs oin any informed way with the
report is absurd.

You appear not to understand about professionals: For them to engage in
controversy is a betrayal of their partners, clients, and business associates.

[William Seger]

137. Bullshit

> You appear not to understand about professionals: For them to engage in controversy is a betrayal of their partners, clients, and business associates.

And you appear to not have the first foggy clue about a very significant percentage of the professionals I'm accustomed to working with. But you really don't care who you slander to keep your delusions intact, do you.

[petgoat]

142. "you appear to not have the first foggy clue "

I see. So a significant number of the professionals you work with would challenge
official findings even though they never had access to secret blueprints, they
don't have time to do a proper analysis, and nobody asked them to do so?

No? But you think they show integrity when they validate the official findings
in spite of the fact that they never had access to secret blueprints, don't have
time for a proper analysis, and nobody asked them to do so?

[dailykoff]

116. Because in Bushworld, "incompetence" is rewarded,

and truth-tellers are demoted, fired, ridiculed, anthraxed, small-planed, and/or suicided.

[DoYouEverWonder]

98. Proof?

Even if PG is wrong, you still haven't proven that you are right. How much load was the core designed to carry? Can you provide a citation or a link, or are we all just supposed to believe you and no one else?

[LARED]

107. Go to page 33

to get some insight into the design

http://www.house.gov/science/hot/wtc/wtc-report/WTC_ch2.pdf

[William Seger]

113. Yup, Proof

My reply to petgoat: http://www.democraticunderground.com/discuss/duboard.php?az=show_mesg&forum=125&topic_id=94447&mesg_id=131272

[DoYouEverWonder]

130. So where is the specific reference in the NIST report

that states what the numbers were for the WTC. Out of 480 pages, how am I to know what section you are referring to?

BTW: Does the calculator at the other link take into account designing for a hurricane zone? There's a big difference between buildings designed for hurricane zones and buildings that are not.

[petgoat]

132. Re: Hurricane Design, Kevin Ryan says the WTC was built

twice as strong as it would have been built in Chicago.

[DoYouEverWonder]

134. That wouldn't surprise me

I'm in the process of redesiging the roof on my house and I'm in a hurricane zone. My guess it will add anywhere 25% to the cost in order to comply with the windload requirements. The only good thing, is that the damn roof better not go anywhere when we're done. Unless of course, one of the 90 foot tall pine trees in the front yards comes down. Then I just hope no one's home.

[William Seger]

138. Which just goes to show...

... that (1) Ryan is a "junk scientist" and (2) that's the kind of "science" you prefer when it comes to conspiracies at least.

[William Seger]

135. It's on p. 232

(I referenced that page in the text or my reply; sorry you missed it.)

First, that calculator has nothing to do with anything. It's just one of the many references that would tell you that the AISC recommended safety factors range between 1.67 and 1.92. I gave the Google search because the AISC Manual of Steel Construction isn't available online -- you have to buy it -- and I was too lazy to search through all those links to find a good reference because (1) the only point was to disprove petgoat's "5X is commonly used" claim, and (2) we already have the actual reverse-engineered numbers for the towers.

And second, as we've already discussed -- over and over -- the core was not designed to carry any of the wind loading. But anyway, for the perimeter columns, no, the wind loading would be calculated separately and included in the total column loading before applying the safety factor we're talking about. The "factor of safety" (which is the more correct term) is not intended to cover anything but possible flaws in materials and construction (or possible errors in the engineering itself if there were calculation errors or any unanticipated conditions that were unaccounted for -- but engineers don't like to talk about those). (The term "safety factor" actually has a slightly different meaning, in that safety factors would be included directly in the calculation of such things as the wind loads and floor live loads from people and furniture, which are really only estimates of maximum loading, before applying the "factor of safety" to the calculated loading.) We know from the reverse-engineering that the perimeter columns had about a 20% demand-to-capacity rating at the time of the collapse, with no significant wind loading present, which means that those columns had about 5x the minimum capacity they would need to carry just the gravity loads. That would be because of both the anticipated wind loading of a hurricane and the factor of safety.

[petgoat]

104. "Ryan lost his job because he publicly commented about stuff he does not understand"

Ryan understands it fine. He was fired for violating protocol and/or
shining a spotlight on the truth.

It appears he thought he had a green light from the top to keep tabs
on UL's interest in their steel ratings. It appears he was wrong
about that or that the top changed its mind after Ryan's letter was
published.

Ryan was the source of the 2X overbuilding for hurricane conditions.
My source for the 5X overbuilding convention was a statement by an engineer
in a lecture I attended in college.

My understanding that the core was designed to carry all the gravity loads
probably comes from Eagar and Musso:

The building is a huge sail that must resist a 225 km/h hurricane. It was designed to resist a wind load of 2 kPa—a total of lateral load of 5,000 t.

In order to make each tower capable of withstanding this wind load, the architects selected a lightweight “perimeter tube” design consisting of 244 exterior columns of 36 cm square steel box section on 100 cm centers (see Figure 3). This permitted windows more than one-half meter wide. Inside this outer tube there was a 27 m × 40 m core, which was designed to support the weight of the tower. It also housed the elevators, the stairwells, and the mechanical risers and utilities.

http://www.tms.org/pubs/journals/JOM/0112/Eagar/Eagar-0112.html

[LARED]

108. What does

overbuilding mean? Never heard of it.

[DoYouEverWonder]

109. Overbuilding

is what the guy did, who built the bathrooms in the warehouse my husband & I bought.

All the interior bathrooms had cinder block walls, with rebar and concrete poured into all the openings in the cinderblocks. Taking out some of those walls was loads of fun. Especially when wood frames with drywall would have been just fine.

[petgoat]

110. "To prevent safety and structural problems, many hacks are deliberately 'overbuilt.'"

I guess you hang with the wrong crowd.

http://hacks.mit.edu/Hacks/articles/engineering_in_action.html

[LARED]

111. Translation

I don't know what I mean by overbuilding. It sounded good when I wrote it.

[vincent_vega_lives]

66. I know meatballs

THAT does NOT look like any meatball I've ever seen! :yoiks:

[DoYouEverWonder]

68. I have to admit

it does look more like the flying spagetti monster of death.

[vincent_vega_lives]

73. Perhaps its

The Flying Spaghetti Monster At Christmas


Flying Spaghetti Monster,
Parent of Christ,
With its noodly appendage,
It gave to him life.
Put upon the earth,
To do its pasta-ry work-y,
And born in a stable,
Right next to a turkey
(Which didn't feature,
In the novelisation,
They ate it later,
'Twas a taste sensation).

[vincent_vega_lives]

38. I would LOVE to see you test this analogy

This debris would have seen been tangled up into a ball that would have impaled
itself on the core columns like a meatball on a fork. :rofl:

And this just proves how clueless you really are on the subject goat...

All right, smart guy, what do YOU do with a 1300 foot tower that's been kinked by
a thousand-year hurricane and threatens to topple? :eyes:

I'm not saying explosives were or were not installed. I don't know. I'm confident
that if they were, their presence would have been a closely guarded secret.

And just whom whould've been the 'guardians' of this little secret?

The core was built to take five to ten times the weight of the entire structure and was subject only to the weight of the core debris.

You really don't understand the forces involved.

[petgoat]

42. All I see is baseless attacks on my competence.

Who would have been the guardians? I suppose the people who would have been responsible
for the decision to bring down the towers if an emergency necessitated it. Also the people
who designed and supervised the installation of the system.

[vincent_vega_lives]

46. Not competence Goat

I have no Idea how competent you are. I only have your posts to go on regarding this particular subject and IMHO the critiques are not baseless.

What about the firm that sold the explosives to the contractor who installed them and the construction workers who worked with them, and the city planner who aproved the plans, and the safety inspector who inspected the work, and the fire marshall who OF COURSE saw no problem with stuffing hunderds if not thousands of pounds of explosives in an office building in one of the most densely populated places on earth that it self has thousands of people working in it every day. They held the SECRET too?

[mirandapriestly]

58. that's not the point

the point is why can't NIST tell us what happened?

[petgoat]

64. Back in the day, closeted gays were frequently chosen for

discreet assignments. I'm told that law firms prized such people highly.

[Bolo Boffin]

67. How special.

I'm glad I don't have to insinuate homophobia here, because no one would EVER be tossing out CTs based on homophobia HERE.

[petgoat]

80. Not homophobia, just an historical fact. nt

[vincent_vega_lives]

69. OK

:wtf: are you talking about?

[William Seger]

78. Well, guess I have to break my promise

> It claims that the perimeter clips were so flimsy the floors unzipped, but the core clips were so strong that the floors tore the core down.

After pointing out to you several times that you were misstating the theory, I gave you a link to Eagar's original paper, which you surely know by now says nothing whatsoever about "the floors tore the core down." Yet, even knowing that now, you keep saying it. Knowingly saying things that aren't true is called "lying." Okay, so this is the last thing I'll say to you about the "zipper theory": stop lying, and please spare me your rationalizations about why you're lying. Just stop it.

> Do you think such contingency planning was not part of putting the structure up?

I thought we covered this: I think that any engineer, architect, or builder who thinks that loading a building with explosives is good "contingency planning" is bug-fucking insane. What happens if, say, a lightning strike sets off the explosives and thousands of people get killed? Are you going to say, "Well, it seemed like a good idea at the time?"

> > even if the collapse forces had been applied uniformly and straight down, it was
more than the structure could handle.

> You're arguing what NIST argues--since the building fell down, that proves it couldn't
handle the stress, therefore we know why it fell down.

Bullshit. Read it again. I'm arguing that calculations of the forces involved would predict total collapse.

> But you guys want us to think the core was so flimsy it had to be braced during
construction!

What you can't seem to get your head around is that the towers -- like virtually all structures except those designed to withstand weapons attacks -- were designed to support themselves plus a safety factor, but the progressive collapse of a single floor exceeded that safety factor. This is an extremely simple concept. Some people who are weak in mechanical aptitude may be having a hard time imagining how much force was involved in that collapse, but a lot of CTers seem to be very, very intent on simply refusing to understand it, apparently in the mistaken belief that if they continue to insist they don't understand it then it couldn't happen.

[petgoat]

81. ..

I gave you a link to Eagar's original paper, which you surely know by now says nothing whatsoever about "the floors tore the core down."

My point exactly. Eagar/FEMA and NIST both decline to explain what brought the core down.
But the core did come down. Therefore if unzipping and pancaking floors caused the
towers to collapse, the floors must have torn the core down. Which is absurd. Thus
the zipper theory is absurd.

What happens if, say, a lightning strike sets off the explosives

I'm no expert on explosives, but I understand that many forms are inert unless properly
detonated.

calculations of the forces involved would predict total collapse.

Calculations of the total forces on the total tower maybe. Splitting out the
non-core insults from the core insults shows the impossibility of core collapse.

the progressive collapse of a single floor exceeded that safety factor.

But not in the core. The collapsing single floor in the core was manifested not
as a steel fist but as a rake.



Rake meets rake. Upper rake at best tears itself to pieces while tearing an equivalent
number of lower rake floors (20 or so) to pieces.

That leaves seventy stories of core standing until it topples over onto the WFC.

[vincent_vega_lives]

84. Inert means that it wont detonate

if you drop it or burn it. Explosive DO BURN nicely (as they are stored energy) and will detonate if burned in a contained space, or if subjected to percussive shock or electric discharge.

And lets not even get in to detonators.

[bushatbooker]

71. I like the 'Jenga block' theory myself

:crazy:

[DoYouEverWonder]

72. Except steel skyscrapers

aren't Jenga blocks.

[vincent_vega_lives]

74. Good thing

They'd be fun at parties thou. :party: