Pancaking Buildings-Debunking L'ambiance

[catnhatnh]

This is my first thread to 9/11.I am neither an engineer nor any kind of expert.But in several threads I have seen the 1987 Bridgeport Connecticut collapse of the L'ambiance plaza cited to support the "pancaking" building theory-I was there and it does not.
L'ambiance was an eight to ten story "twin tower" residential unit undergoing construction when the collapse occurred in March of '87.28 or 29 workers were instantly killed when the project did in fact "Pancake".Now as they say, the rest of the story...At the time of the collapse L'ambiance was perhaps 40 percent complete-I don't know what degree of completion experts would award it-all main vertical components were in place.The project was utilizing a "lift slab" technique wherein floor members are assembled at ground level around the vertical members and slabs are poured into this framework and the jacked up the vertical columns to their proper heights and welded into place.this process was near completion on the second tower.Throughout the project teams of construction worker were already advancing the next stage of the project...if I remember a large number of those killed were electricians and core borers (concrete drillers) on lower floors running conduits for the main electrical trunks. While jacking one of the last (top) floors into place, a main jack kicked out leading to a sequential failure of both towers.
Why does this not support the "pancake theory"? Well as I have stated this was an ongoing project and most floors had at least partial connection to the vertical columns, the collapsing floor had NO connection,other floors had not been vertically shored internally and no perimeter walls were even started....I cannot speak to what additional bracing at the vertical columns remained to be completed but I can say in no way did a BUILDING collapse....Rather a set of partially constructed frames did....
In the aftermath of the osha investigation,new regulations were placed on the "lift slab" method-most obviously that unnecessary workers (those not directly related to lifting and securing operations) were banned from the site during lifting operations and connecting operations...All in all "too little AND too late..."
So if they bring up L'ambiance, tell em it ain't so-I was there and I say so....

[pauldp]

1. Got any pics? n/t

[catnhatnh]

2. Sorry....

...no pictures.After the collapse a sealed perimeter was established around the site complete with plywood paneling to prevent certain explotative photography (such as the removal of the remains,this took more than a week) and I worked inside the perimeter for only 12 hours on the second day.I was way too busy to have time for snap shots....news agencies released many photos of the scene at the time.They may be found elsewhere on the net....About the only remarkable item (in comparison to 9/11 events) were that verticals, though bent and twisted remained in long pieces- in some posts others mentioned this was not the case in 9/11 and if this were true I would be suspicious.Many vertical bolt flange joints did not fail and left the workers with tons of long twisted sections to be cut before they could be hoisted clear....

[pauldp]

3. Interesting. Yep at the WTC the steel was made into mincemeat. n/t

[catnhatnh]

4. YES...

that is important....but I've heard that and seen no proof...I'm saying that at the collapse I worked, the verticals had to be cut and cleared....if that was the case at WTC why did those split to bite sized??? Show me photos of vertical flange failures or why there are none....that's really important...If no long verticals why not....plenty where I was...

spelling as always....

[LARED]

5. The columns were constructed in relatively small sections

and bolted together at the box flange. See images of perimeter columns

[pox americana]

6. Note the massiveness of the structural core (shown in the first photo)

and the size of the columns (protruding from slab) in the second photo.

This says:

1) The idea of failing floor trusses producing a collapse of the central cores, which were 100 feet wide, filled with massive steel columns, and extensively crossed braced, is ridiculous.

2) There were 287 such columns, which look to be about four feet wide, in each tower. They all would have had to fail SIMULTANEOUSLY to produce the symmetrical collapses that occurred on 9/11. What kind of "fire" is going to do that?

p.s. all highrise columns are constructed in sections.

[pox americana]

8. One more thing:

There's a floor truss shown in this photo (in red, on the right). Note the relation of the truss to the central core:




a) The truss is relatively short (maybe 50 feet), leaving 100 feet for the structural core (the towers were 200 feet square).

b) The core is obviously holding up the truss, NOT THE OTHER WAY AROUND.

[LARED]

12. Columns will buckle

1) The idea of failing floor trusses producing a collapse of the central cores, which were 100 feet wide, filled with massive steel columns, and extensively crossed braced, is ridiculous.


regardless of how massive they are if the slenderness ratio and unsupported (ie no cross bracing) length falls outside of acceptable ranges

http://www.du.edu/~jcalvert/tech/machines/buckling.htm

http://physics.uwstout.edu/statstr/Strength/Columns/cols71.htm#Example%208.1a

When the cross bracing failed from the floors pancaking, the columns will only stand unsupported for so long.


2) There were 287 such columns, which look to be about four feet wide, in each tower. They all would have had to fail SIMULTANEOUSLY to produce the symmetrical collapses that occurred on 9/11. What kind of "fire" is going to do that?


There were not 287 columns, there were 47 core columns that started out as quite massive at the lower elevations, but got progressively smaller as the towers height increased.

[pox americana]

13. Show me any evidence of buckling

and we'll talk.

[LARED]

14. look here

http://thewebfairy.com/nerdcities/WTC/WTC_apndxD.htm

[pox americana]

15. No buckled columns there

that I could find. No mention of buckling, buckled, buckle, or buckl* either.

Maybe I missed something?

[LARED]

16. Do you know what a buckled column looks like? (n/t)

[pox americana]

17. Show me. (n/t)

[MrSammo1]

114. Never ask a

Truth Minister for proof!

[vincent_vega_lives]

120. Buckled

[pox americana]

122. You're getting a little warmer

but no cigar. That's a built-up core column that was blown apart -- there was a plate on the front that must have been completely blown off. What happened to the remaining elements after that is irrelevant, as its engineered strength would have been lost.

And note the exterior box columns behind it, showing signs of high-temperature oxidation but no signs of buckling.

[philb]

86. Does anyone have similar steel beams from a demolition and has

anyone tried to compare what the beams at WTC looked like to those of a building brought down by controlled demolition?

[petgoat]

18. 47 core columns

"47 core columns that started out as quite massive at the lower
elevations, but got progressively smaller as the towers height
increased."

My understanding is that they were 36 inches by 14 inches throughout,
but at the towers' bases they were built of 4 inch plate and at the top
they were built of lighter plate.

[LARED]

19. As I understand it the core columns were

fabricated out of W14 X 730 wide flange steel shapes. These are 14" by 22". The shape was built-up in the lower areas of the towers by adding plate to the four sides making it a box shape and stronger by increasing it cross sectional area. I would guess at the lowest level they easily may have been 36" wide.

At some level moving up the shapes of the column was changed from a box to the basic W shape at 14" by 22".

[pox americana]

20. 2x110x287 = 63,140 buckled columns

that would have been produced by "progressive collapse," minus the number damaged by the initial collisions, and assuming that it works in both directions (heh, something did).

So where are they?

[LARED]

21. I'm sure what you're posting means something to you

Care to explain it?

[pox americana]

22. It means that there was no "progressive collapse,"

and there was no "pancaking," and gravity did not bring down the building, and the NIST is lying, because there is no evidence of buckling.

Clear enough?

[LARED]

23. You are proposing an interesting scenario

In real controlled demolitions steel buckles in order for the structure to collapse.

So it seems you are proposing that the WTC'ers was not the victim of controlled demolition.

Tell me more.

[pox americana]

24. If there are no buckled columns

there was no progressive collapse. It's that simple.

But you can keep spinning all day.

[LARED]

25. No buckled columns, no controlled demolition either

Listen, this is your logic, you can't have one without the other.

So if there's no buckled columns what do you think made the towers collapse

[pox americana]

26. Not so.

Those were 110-story supertalls, not 12-story housing blocks. There was too much structure for conventional demolition (like WT7), so as far as I can tell, they just blew them completely apart. They only used gravity to get the debris out of the air, not to collapse the structures.

[LARED]

27. So all 63,140 columns had explosives attached to them? (n/t)

[pox americana]

28. Only in the foundations and structural cores is my guess.

Easy to get to, lots of space, inconspicuous, and evidently very effective.

[MercutioATC]

29. Then why wouldn't the OTHER columns be buckled?

Either ALL of the columns had explosives attached or they didn't. If they didn't, the columns without explosives would have buckled (if your assertion bears any merit).

See why this doesn't seem to make a lot of sense?

[pox americana]

30. Nope. The exterior columns just blew off.

Don't you remember seeing them?

[MercutioATC]

31. So the exterior columns weren't wired with explosives?

You're contending that they were blown off by the force of the explosives attached to the interior columns?

[pox americana]

34. That's my guess, yes.

And that's how it looks in the photos.

[MercutioATC]

35. For that to be plausible, ALL of the interior columns would have had to be

rigged with esplosives (otherwise, they'd buckle). In addition, those explosions would have to occur on EVERY floor simultaneously (otherwise some interior columns would buckle and the outer columns woundn't be "blown off" of the building.

...either that, or your premise is flawed.

[pox americana]

36. The outer columns weren't holding up the building.

They were only holding up themselves and part of the floors, so they didn't need to be wired, because it really didn't matter if they were blown off or not, and some of them on the bottom weren't.

But they sure as heck didn't buckle, either.



As for timing all I can say is that yes, it was a very carefully controlled sequence.

[janedoe]

51. This is an excellent illustration!

So, why are the floors no longer attached to these walls?
Why are portions of these beams missing?
I can't help but notice how straight all of these members are. So, why didn't the horizontal beams or vertical beams plastically deform any of these members, when they were ripped from it?

[LARED]

32. Just blew off

like magically? No explosives were used on them?

You can have it both ways. If the core and foundation were rigged with explosives for a controlled demolition, then the perimeter columns had to have buckled. And you state the building was a controlled demolition. The column can't just blow off the building with no explosives

[pox americana]

33. Look at your own pictures

and you'll see exterior columns flying around (in those 2 x 3 H sections, or pieces of them) just outside the debris cloud.

[LARED]

37. So you maintain the perimeter columns were blown off by the explosives

located on the core structure.

If that's true then you are stating the explosives had enough force to cut the core steel and blow out the perimeter columns located something like 50 feet away.

Do they make explosives like that?

[janedoe]

41. Reading material for LARED

"Do they make explosives like that? "

If you need to ask that question, you may want to catch up on your physics background. Here's where you can get started.

http://www.csi.ad.jp/ABOMB/index.html

[LARED]

44. This is a great opportunity for you to teach me something

How do they make explosives that cut large steel columns and blow out columns 50 feet away.

[petgoat]

45. Controlled Demolition Expert Van Romero Said

it looked just like a controlled demolition. He said the job could have
been done with "a relatively small amount of explosives placed in
strategic points."

Ten days later he retracted his opinion that the collapse was "too
methodical" to have resulted from the fires. He said he believed the
fire brought the towers down. But he didn't retract his statement that
it looked like a controlled demolition to him, or his statement that
small amounts of explosives would have been sufficient.

[janedoe]

46. You asked, "Do they make explosives like that? "

You seemed unaware of these new 20th century explosives. Did that site answer your question?

[LARED]

48. Nope no answers

I guess I'll have to depend on you teaching me something about how the inner columns were cut and the outer columns were blown away.


After all you are a structural engineer and materials expert. It should be s simple task

[pox americana]

49. Maybe it was fertilizer.

Does it matter? It obviously worked whatever it was.

[LARED]

64. Of course it matters

You are attempting to make a case that is not possible.

That the inner 47 columns were rigged with explosives that had the capability of blowing all the outer column out on every floor because as you claim there were zero columns that failed from buckling.

[pox americana]

67. No, and no.

No, it doesn't matter what they used, because such explosives obviously exist. Remember Hiroshima?

And no, the outer columns didn't need to be blown out (although some may have been, simply to chop them up) because they weren't structural and couldn't have stood more than the few stories they did without the core.

As I already explained and illustrated above. :)

[LARED]

68. Remember Hiroshima?

Now I've heard everthing. :rofl::rofl::rofl::rofl::rofl:

So if the outer column did not get blown out I take it you now agree columns buckled?

[pox americana]

71. I think if you understood what buckling is,

what causes it, and what it looks like, we could save a lot of repetition.

But to answer your question, I don't understand what you're asking.

[LARED]

72. LOL, OkeeDokee. (n/t)

[pox americana]

80. To answer your question, no, they wouldn't have buckled,

they would have bent or sheared.

At least I think that was your question.

[LARED]

84. Buckled column can be bent

In fact most buckling failures of columns are from bending. It is far more unlikely that a column failed axially.

On another point, how would columns fail by shearing?

Please explain.


Here's a hint; Goggle "Euler failure" if you really are interested in learning about column failure. Or start here.

http://www.mech.uwa.edu.au/DANotes/buckling/intro/intro.html

[pox americana]

85. Now look up bending. It doesn't mean what you think it means.

It's a distinct form of failure.

Okay here we go: the exterior columns didn't "fail" by shearing; the floor connections were sheared by the force of the explosions. "Bending" is what broke them apart. Note that in all those pictures of flying columns, most if not all are still straight. They're not "bent" in the common sense, but structural "bending" is what broke them apart.


edit: I imagine there was also shearing at the column connections.

[vincent_vega_lives]

121. "new 20th century explosives"

Are you trying to say RDX?

Aint no shaped explosive charge going to cut a steel column AND blow out the perimeter walls 50' away. Shaped charges are focused for a reason and are poor when it comes to area effects.

Conventional charge large enough to both cut the core columns and blast out the perimeter columns ON EVERY FLOOR would need to be very large and would have done so much wide spread damage that would have made sequential blasting impossible.

[janedoe]

42. You're an engineer, right?

So, with you impressive knowledge, you must know exactly where they needed to place explosives, and exactly what magnitudes of explosives were required.

Please enlighten us. What magnitude of explosives would be required and exactly where would each of them need to be placed in order to bring the building down?

[LARED]

43. They didn't need to place explosives

I know little of explosives. Only what I learned as a kid lighting M-80 and stuff I leaned when I put on my Google cowboy hat. (quite a bit actually, but still a layman at best)

Now on the other hand you are a structural engineer and materials expert while I am a mechanical engineer. Meaning you have near perfect credentials to tell this forum why explosives were required to collapse the towers and how it was done. How much was used, where, and the proper timing to get the job done.

Please don't simplify your response. I am quite familiar with technical reports and most non-technical members seem to be able to grasp the concepts.

I humbly await your response.

[janedoe]

47. You say that they didn't need to place explosives.

How do you know? How could the building collapse in 10 seconds* without explosives?

*10 seconds is the value given in the 9-11 commission report.

[vincent_vega_lives]

123. How could it not fall in the time it did?

What would have prevented it from doing so? How long do you think it would have taken once initiated without explosives?

Because the explosive arguement must be that explosives were placed at the point of impact and initiated, allowing gravity to do the rest, OR explosives were placed on EVERY floor, which is what you seem to be arguing. Are you claiming that it would have been IMPOSIBLE for the buildings to collapse as they did without explosives planted on EVERY floor, because that scenario is FAR more complicated, risky, manhour intensive and likley to fail in at least one of the instances.

[janedoe]

38. I agree.

It was essentially blowing them to pieces, but with a plan.
The two towers seemed to have had a different sequence for the top part, but the same for the bottom part. I assume this was because of the different height of that top chunk.

Top WTC2: The charges progressed up from the damaged zone while at the same time progressing downward from the damaged zone. That top chunk was getting out of control and they did a super job of correcting for it. There's no way ahead of time they would know the exact location of that damaged zone, which is why I believe they had to have feedback sensores to adjust the timing. I also suspect that the job of that helicopter was to assess which program to run and on which floors to initiate it.

Top WTC1: The charges got the top part under control, first, then did the rest. It began by knocking out the center columns just before the outer charges went. This started the building to fold into itself, locally, as if that part were a short building. That seemed to control the chunk above the damaged region quite nicely.

Bottoms: It seems that they had every XX number of floors wired to take out every single column around the perimeter of a floor -- to make this look like a progressive collapse. But, one of them (I don't remember which) was below the plane hole and the other was above, as though that just happened to be the closest.
I believe the rest of it was made to look like a progressive collapse, but it also controlled how the stuff fell. The charges progressed down, being set off faster than the speed of gravity, which was similar in both. This "second stage" of the even was as pox described... just blowing it to bits. But the sequencing downward made a good cover story.

[pox americana]

39. Yep that tipping top is the giveaway.

I'd really like to know how they screwed it back on.

[janedoe]

40. Calling all gremlins....

Don't worry, they'll be here soon and explain it to us. :-)

[Name removed]

50. Deleted message

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

[janedoe]

52. He seems to avoid those questions.

http://www.democraticunderground.com/discuss/duboard.php?az=show_mesg&forum=125&topic_id=49321&mesg_id=49787

I wonder if anyone else knows this answer.

[LARED]

54. The irony is well worth the price of admission

Based on your claim of being a structural engineer and materials expert, I have asked you to provide some technical expertize regarding a number of issues. None have been addressed, yet you accuse me of avoiding questions.

Are you really a structural engineer and materials expert?

[Make7]

57. Neither tower collapsed in ten seconds.

The 911 commission report is incorrect.

http://www.911review.com/errors/wtc/times.html

-Make7

[LARED]

53. Thanks for reminding me

This is a very crude energy balance. Not meant to be rigorous in any way shape or form; only meant to get a feel for the forces at work.


PE = KE (kinetic energy) of the towers moving down + W (work energy) of the towers breaking up.

If 1/3 of the PE energy is converted to work the equation now looks like this;

1/3 PE = W

Substituting;

PE = KE (falling) + 1/3 PE( breaking up)

So ; PE = 3/2 KE

Doing the math again

mgh = 3/2 * 1/2 m v^2

solving for v

v = (4/3 gh)^0.5

V= 73.2 m/sec

Solving for t

t = 2 * H / v (for free fall)

t = 11.2 sec

So if 1/3 of the potential energy went into destroyng the building, the building falls in 11 + sec's, still well within the observed fall time.

[janedoe]

55. Why did you choose 1/3 PE to break up the building?

Also, what height did you use? The whole height of the building?

[Make7]

56. Reply to "what height did you use?"

LARED wrote:
V= 73.2 m/sec

Solving for t

t = 2 * H / v (for free fall)

t = 11.2 sec

Did you become an engineer without passing any algebra courses? Can't you figure out the height used in his calculation with the information given? Not very impressive.

-Make7

[janedoe]

58. Impulse?

Thanks for your answer.
I didn't know if his equation applied to the whole thing, or if it was per floor, or iteratively, or what.

According to your take on it, the height produced by that equation is the height of the building. So, did the motion start instantly? Where did the impulse come from? How did the first floor get up to speed, instantaneously?

LARED stated (and shall I assume you validated it with your algebra?) that the total time for collapse was 11.2 seconds.

Now, you've said that is wrong, and cited 14 to 16 seconds. Does that mean that LARED's fudge factor "W" needs to be fudged a little more to produce this answer?

[Make7]

59. 1/3 PE

The motion of what? The whole building? No, I don't think it started instantly. Some parts of the structure failed before others - when there was no longer enough intact structure to support the mass of the building, gravity caused it to accelerate towards the ground.

His calculation was meant to demonstrate that if 1/3 of the potential energy was converted to work for breaking up the building, the collapse time would be 11.2 seconds. He did not state that he believed that was the actual collapse time. (see his post 10 seconds is far too short)

Yes, for his calculations the amount of PE he used for breaking up the building would need to be increased for a longer collapse time. Probably around 3/5 PE for a 15 second collapse.

-Make7

[janedoe]

60. Hard Science vs. fudge factors

Thank you for validating my point, that LARED would need to increase his fudge factor in order to produce the answer in the back of the book.

What I find so interesting is that LARED assumes it will take LESS energy to pulverize a floor than the PE of the floor it's supporting. Golly, how did the building even support its own weight all these years?

I find it interesting that you say the speed was not constant (your post #59), that the building accelerated downward, yet you tried to insult me for not assuming it was constant (your post#56).

I never said that my illustrations were intended as exact models of the events. However, I have said that these were meant to demonstrate various concepts. I did this honestly and openly, as approximations for various conditions. We do not know how much of the kinetic energy is consumed by pulverizing the material. Also, with the horizontal distribution of material shot from the building, it is clear that not all of the potential energy was spent in the vertical direction.

I provided several different approximations to account for the kinetic energy spent in pulverizing the building material. I did this to demonstrate the expected range of collapse times, which were based on hard science, not secret fudge factors. I did not pick the answer I thought it should be, then back calculate the fudgefactor needed to arrive at that selected answer.)

So, where is your own model?
What is the EXACT amount of energy required to pulverize the building? In the spirit of your post on the other discussion thread, your model would prove ABSOLUTELY NOTHING unless these values were EXACTLY CORRECT. This exact information will never be known. So, doesn't that mean it's impossible for you to ever come up with anything useful for anyone? What kind of thinking is that?

It's not about the EXACT number!
I've put a lot of time into preparing and posting this information, and it's time I really don't have to spend. But, I felt it was important to have information available for those who really wanted to have an understanding of what folks were talking about. Telling someone that the "answer" is some specific value does little to help their understanding. It's not about the exact number; it's about the range of realistic values, and what variables influence them. It's about giving folks the tools that will allow them to form their own conclusion.

If you don't like the conclusion you come up with because it's painful, I understand. I don't like it, either. But, shooting the messenger won't change the facts. Understanding the facts can only help. It'll at least get you off the koolaid, allowing you to plan the solution.


For those interested, here are links to my posts of these example cases.
http://www.democraticunderground.com/discuss/duboard.php?az=show_mesg&forum=125&topic_id=48327&mesg_id=48389
http://www.democraticunderground.com/discuss/duboard.php?az=show_mesg&forum=125&topic_id=48327&mesg_id=49900
_________________________________________________________________________

Here is a link to a video, showing the detonation wave moving ahead of the free-fall of debris.
http://www.911research.com/wtc/evidence/videos/docs/wtc2_demolition_waves.mpg
The following picture shows the detonations ahead of free-fall speed of the particles. If the building is collapsing downward, what are those well-defined narrow clouds moving upward and outward in what appears to be a radial direction?

[Make7]

61. shooting the message

Perhaps you skimmed over the beginning of LARED's Post #53.

LARED wrote:
This is a very crude energy balance. Not meant to be rigorous in any way shape or form; only meant to get a feel for the forces at work.

I guess you can say his calculations aren't exact, but he said so himself before even presenting his example.

janedoe wrote:
I find it interesting that you say the speed was not constant (your post #59), that the building accelerated downward, yet you tried to insult me for not assuming it was constant (your post#56).

I never said anything about the speed being constant or accelerating in that reply (Post #56). LARED showed you exactly how he arrived at his answer. Solving for the actual height that he used is a simple algebra problem. Being an engineer I thought you should be able to handle that. Apparently I was right, you did solve for the height and arrived at the correct answer. However, I do find it interesting that you seem to be intentionally misrepresenting what I have written.

janedoe wrote:
So, where is your own model?
What is the EXACT amount of energy required to pulverize the building? In the spirit of your post on the other discussion thread, your model would prove ABSOLUTELY NOTHING unless these values were EXACTLY CORRECT. This exact information will never be known. So, doesn't that mean it's impossible for you to ever come up with anything useful for anyone? What kind of thinking is that?

It's not about the EXACT number!
I've put a lot of time into preparing and posting this information, and it's time I really don't have to spend. But, I felt it was important to have information available for those who really wanted to have an understanding of what folks were talking about. Telling someone that the "answer" is some specific value does little to help their understanding. It's not about the exact number; it's about the range of realistic values, and what variables influence them. It's about giving folks the tools that will allow them to form their own conclusion.

Where is my model? I didn't know I was required to come up with one.

You posted various scenarios that you believe illustrate concepts that prove what is or is not possible. I replied because I don't feel that they take into account enough of the factors involved to be realistic enough to be predictive of the behavior of the collapse of the Twin Towers. I don't think they prove anything.

Exact numbers are not required for modeling. Models are useful for calculating the ranges that certain parameters will realistically fall within, but you can't model a situation and leave major factors out (i.e. momentum transfer) and say that your results are truly modeling the event in question.

In Post #8 of the thread where you introduced your models, you said at one point that "...if some part must stop and then restart its decent every 10 floors, the total collapse time must be more than 10 seconds. Also, consider the energy required to pulverize the 10 floors between each 'pancake.'" Okay, the time must be more than 10 seconds. I agree, it was more than ten seconds. Now we are supposed to consider the energy used for pulverization. Alright - how many seconds do you think that will add to the collapse time?

That post starts with the heading: "The Case for Controlled Demolition." You proceed to prove that the building could not have fallen without explosives by misrepresenting the dynamics of a progressive collapse. If that qualifies as giving people information to reach their own conclusions, then I have - my conclusion is that your modeling does not prove the case for controlled demolition.

janedoe wrote:
If you don't like the conclusion you come up with because it's painful, I understand. I don't like it, either. But, shooting the messenger won't change the facts. Understanding the facts can only help. It'll at least get you off the koolaid, allowing you to plan the solution.

You don't know me. Why would you think any conclusion I might make would be painful for me?

I thought my replies were illustrating that I disagree with the conclusion you draw with the modeling you have done. I thought that was shooting the message, not the messenger. (Although I admit I was making fun of you for asking what height LARED used when you could have easily calculated that yourself.)

Presented with the same set of facts, people often reach different conclusions. That doesn't necessarily mean they don't understand them, they may just have a different interpretation of what the facts mean.

-Make7

[pox americana]

77. There has been no evidence of compression failure

of the structural elements brought forward, and there is plenty of evidence of columns which did not experience compression failure but would have had to in order for the NIST "message" to be accurate, so there's no point dreaming up fudge factors to fit a theory which is obviously wrong.

[Make7]

78. Are you talking to me? ( n/t )

[pox americana]

79. Only if you'd like to answer.

But please don't feel any pressure. :)

[janedoe]

87. Pox, you are right!

After LARED posted his "engineering analysis," I immediately replied (post#55), asking,

Why did you choose 1/3 PE to break up the building?

Also, what height did you use? The whole height of the building?

Curiously, LARED never responded to that message. I wonder why? 
But later, Make7 did, as if he understood the analysis and was ready to defend it.


In post #56, Make7 presented LARED's following equations and implied that it is an "algebra" problem (note, not calculus).

(Make7, stated this, again, in his post#61.)

V= 73.2 m/sec
Solving for t
t = 2 * H / v (for free fall)
t = 11.2 sec

If this is a simple algebra problem, and he provided the constant, V, am I to assume V = v?
If so, then he is saying that V is the constant of proportionality, showing t is directly proportional to H.   If v is constant, maybe H is not constant? 


In any case, it appears that LARED's fancy math simply decreases gravity by the value of his "fudge factor." In other words,
if W= k x PE, where W is the work of crushing the building, 
k is his fudge factor,
PE is the potential energy of the entire building's mass, if all of it is placed at the very top of the building, then
g* = g x (1 - k), where g is normal gravity, and 
g* is the reduced value of gravity.

Referring to LARED's "analysis," (with which Make7 seems satisfied).
LARED stated (post#53), that his analysis was "meant to get a feel for the forces at work." Ummm... for the forces needed to do what, crush the building in a giant trash compactor? So, what are those forces? I fail to see how LARED's analysis could model a progressive collapse, where one floor collapses onto the next, and the next, and the next,... all the way down to the ground. Perhaps LARED is simply saying that he didn't believe it was a progressive collapse. (Now, that would make sense.)

Also, I question the applicability of LARED's analysis, which places a constant weight on the very top of the building and then calculates the free-fall time of that weight, using an arbitrarily reduced value for gravity. (Note, by doing this, he is also assuming that every floor has the same resistance, and that the entire building's weight stays on the top floor throughout.) It's as though he's used another building (of equal weight) to crush this one.



If the time of collapse is between 14 and 16 seconds, as Make7 claims it is, why not reduce gravity by 60%? Then, you'd get "the right answer" ...well, if Make7 has "the right answer." ( Let's play "dial an answer.") Hmm... the 911-commission report said it fell in 10 seconds; Make7 has the value of 14-16 seconds. Hey, let's just split the difference to be safe. 

As an engineering professor, I am all too familiar with students who, as a last resort, apply some miraculous "fudge factor," in order to produce the answer in the back of the book. Most popular? 1/2 or 1/3, or the inverses of those values. You'd have been better off with the most popular pick of 1/2. 

So, what was the scientific justification for k = 1/3?

Make7 has not been arguing with LARED's analysis, only my examples. Perhaps he understands where my numbers come from? If so, I take that as a complement. My objective was to present concepts (free of mystery fudge factors) in a way folks could understand them. If he does not understand where my numbers come from, why is he so upset? Lastly, does he understand where LARED's numbers come from? 

Perhaps choosing the right fudge factor to get the answer... is like "fixing the facts around the policy?"

So, what proof do we have of the actual collapse time, not the time it took the dust to settle, but the duration of changing forces banging on the ground? Knowing this answer will make it a lot easier for us to calculate it. ;-)
Perhaps the following evidence will help:

The red graph at the bottom, for the collapse of WTC#1, has the start of collapse marked at 16.42 seconds. Within 10 seconds, the signal settles out. Compare this to the top graph, showing what happened when the plane hit WTC1. It appears to take longer for the signal to settle out. Why do you think that tells us about the collapse?

[LARED]

88. Wow, I'm impressed, not only are you a structural engineer

and materials expert, you have become a engineering professor. If you don't mind me asking where do you teach?

A few quick comments. I don't have the time to address your confusion regarding my simple energy model, but rest assured I will get back to you in a reasonable amount of time. One thing to think about is the thing is based on energy transformations.

and

You should do a little research on seismic graphs. The the graph you think gives you a collapse time is a combination of a number of waveforms superimposed on each other. S and P waves plus some others. To make it more complicated these waves generated by a seismic event arrive at different speeds, hence different times, and different magnitudes. So the bottom line is unless you are a structural engineer, materials expert, engineering professor, and seismologist you can't determine fall time from the graphs.

[janedoe]

90. Were you impressed enough to do your homework?

By the way, I am an engineering professor, not "a engineering professor," as you posted it. (I'll assume this was a typo.)

My profession is known by others on this site. You must have missed their references to it. Regardless of my profession, your "analysis" does not support progressive collapse -- or even anything relevant to explaining a "collapse" of the WTC.


In your post (post#88), you wrote:

...I don't have the time to address your confusion regarding my simple energy model, but rest assured I will get back to you in a reasonable amount of time.

Who said I was confused? ;-)

In your post (post#88), you wrote:

So the bottom line is unless you are a structural engineer, materials expert, engineering professor, and seismologist you can't determine fall time from the graphs.

If that is true, how were you able to determine this? By reviewing your trash-compactor analysis, it's fairly easy to conclude that you are not an expert.


Let's see... I identified your fudge factor in how much time? I suspect it will take you much longer to come up with a new one.

Here's a hint to help you get started: use "k" in place of your "1/3" value and keep all variables as variables. Now, simplify your equations down to your "free-fall" equation. It simplifies down to the free-fall of a body, using the reduced value of gravity, g* (g* = g x (1 - k), where g is normal gravity).

But, to arrive at this, your energy equation (containing the fudge factor) used the entire mass of the building, calculating the potential energy it would have, if all of its mass were located on the roof. This is why I felt it was appropriate to ask about the height in my reply (post#55), as well as your fudge-factor choice of 1/3:

Why did you choose 1/3 PE to break up the building?

Also, what height did you use? The whole height of the building?

Curiously, you chose not to answer these questions. I assume that was because you realized your mistakes and was too embarrassed. But, by your recent comments (post#88), I see that is not the case.

In conclusion, there was something useful your trash-compactor analysis demonstrated. With the entire mass of the building used as the force of a giant trash compactor (which we know cannot be the case), you showed about the same time as the 911-commission report said it would take for a progressive collapse. So, it doesn't seem possible that the building would collapse in that amount of time, floor-by-floor, if the weight of one floor at a time was all that was pushing on the building.

In closing, I would like to complement you for posting something, even if it was not correct. That took guts.

[AZCat]

93. So now we're nitpicking...

spelling, grammar and punctuation?

Oh goody - more childish distractions.

[janedoe]

94. I feel sad

for you, if this is the only thing you were able to understand in my post. I am sorry that it was too complex for you.

[LARED]

95. Regarding your confusion;

your "analysis" does not support progressive collapse -- or even anything relevant to explaining a "collapse" of the WTC.

Well for starters it was not supposed to explain anything relevant to a collapse. What is shows is a simple energy model of how work energy impacts the fall time. It clearly support a progressive collapse. As a progressive collapse by definition requires that PE be converted into work energy. BTW, since we are now nitpicking grammar, putting quotes around the word collapse is sort of silly as even if the WTC was the victim of CD it still collapsed.

Who said I was confused? ;-)

Ahhh, that would have been me.

If that is true, how were you able to determine this? By reviewing your trash-compactor analysis, it's fairly easy to conclude that you are not an expert.

If I was an expert in reading seismic graphs I would have given you an answer. I was merely pointing out your interpretation of the graph you posted was incorrect. Incorrect because unless you are a seismologist that can understand and extract the superimposed data you cannot determine fall time by looking at the graph. You do understand what superimposed data is, yes?

Now to address your confusion.

The model simply states the reality of the collapse from an energy perspective. (greatly simplified) The potential energy (PE) is all of the available energy. The kinetic energy (KE) is the energy used as the mass converts from potential energy to velocity as it fall under the influence of gravity. The work energy is the energy used in destroying the building as it fell. The net effect of the work is that it slows the fall of the tower. While you characterize this as a fudge factor to get the right answer, it is really derives a constant to change the influence of gravity that is related to how much potential energy is transformed to work.

To put it more simply the model characterizes how the work energy slows the time from a free fall condition.

To recap

mgh = 3/2 * 1/2 m v^2 or PE = correction constant of gravity * KE.

It is important to notice the mass cancels. You are incorrect in stating the model has the entire mass sitting on top. The model simply predict how long it would take an entity sitting on the top floor to reach the ground if some of its energy was converted to work rather than all of it energy being convert to KE.

solving for v

v = (4/3 gh)^0.5 This is solving final velocity under it new conditions

V= 73.2 m/sec

Solving for t

t = 2 * H / v (for free fall) Once you know it's final velocity you can quite easily find it's fall time.

t = 11.2 sec

The intent of this model is only to point out that a huge amount of energy can go into destroying the tower having only a small impact on the fall time. This is in contrast to your model that completely ignores work energy and has each floor coming to a complete stop at the same instant the floor below it starts to move under the influence of gravity, and gravity alone. The graphs are pretty and I'm sure convincing to some, but they in no way shape or form describe what happened during the collapse.

On a final note, just looking at your chart showing a fall time of 99 seconds (or what ever it was) gives me pause regarding your stated credentials. It is hard to fathom a structural engineer, materials expert and professor would buy into and advocate such an obvious piece of sophistry. I find it rather incredulous to believe you are an engineering professor.

[janedoe]

91. Perhaps you need some help?

Let me help you.
I will lay it out so that anyone should be able to understand.

Refer to your post#53:

PE = KE (kinetic energy) of the towers moving down + W (work energy) of the towers breaking up.
If 1/3 of the PE energy is converted to work the equation now looks like this;
1/3 PE = W
Substituting;
PE = KE (falling) + 1/3 PE( breaking up)
So ; PE = 3/2 KE
Doing the math again
mgh = 3/2 * 1/2 m v^2
solving for v
v = (4/3 gh)^0.5
V= 73.2 m/sec
Solving for t
t = 2 * H / v (for free fall)
t = 11.2 sec
So if 1/3 of the potential energy went into destroyng the building, the building falls in 11 + sec's, still well within the observed fall time.

From your equation, 1/3 PE = W
I will use k as the variable for your fudge factor, instead of using your arbitrarily chosen value of 1/3. This way, we can see where it ends up. That's the beauty of staying with variables.

So, your equation
PE = KE (falling) + 1/3 PE( breaking up), becomes
PE = KE + k PE, or
PE(1-k)=KE ..........,........(1)
__________________________________________
you show:

PE = mgh .............,........(2)
KE = 1/2 m v^2 ........,....(3)
__________________________________________
substitute equations (2) and (3) into equation (1), resulting with

mgh (1-k)=1/2 m v^2 ..,..(4)
Your results show that you assumed both masses were the same, so they cancel, resulting with

2gh (1-k)= v^2 ..........,..(5)

where g is normal gravity, k is the fudge factor, and v is the velocity developed by dropping the mass from height h.
__________________________________________
__________________________________________
Now, you use the following equation,
t = 2 * H / v (for free fall)

Where did that come from?
Let's see... "Free-fall" implies constant acceleration, where the object is initially at rest.

Let a = constant acceleration.

v = at .................,........(6)
h = 1/2 a(t^2) ......,.......(7)


(Integrate a over time = 0 to t, to get the equation for v, and
integrate v over time = to t, to get the equation for h, the distance the object has dropped at time t.)
v = at, where v is the velocity at time t, the time the object has been falling, and h is the distance traveled at time t.

rewrite equations (algebra)
a=v/t ..........................(6a)
a=2h/(t^2) ..................(7a)

set (6a) = (7a), resulting with
v=2h/t .........................(8)

Note, this is the equation you presented for free fall, at constant acceleration.
__________________________________________
__________________________________________
Now, for equation (5), we need v*v, so, to simplify, let's multiply the v's from equation (6) and (8), producing,

v*v = v^2 = 2ha ...........(9)

Now, substitute equation (9) into (5), producing

2gh (1-k)= v^2 = 2ha ...(10)

simplifying this (2h cancels), you have

g(1-k) = a ...................(10)

So, your fudge factor of "k" is merely decreasing the magnitude of gravity by some arbitrary factor. In my earlier post, I referred to this value, a, as g*.

__________________________________________

Better yet, substitute equation (7) into equation (10), producing,

k= 1 - 2h/(gt^2) .............(11)

This way, you'll be sure to pick the right fudge factor for the "correct" collapse time, once it's been decided.
You may want to keep this equation handy. ;-)

[spooked911]

92. This may be a dumb question, but if we plug the known time in your

equation, k= 1 - 2h/(gt^2), can we learn what K is? And can that help us in other calculations/analyses?

[Name removed]

102. Deleted message

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

[LARED]

96. Thanks for the offer

But, I'll pass.

I not real impressed when the best a structural engineer, material expert, and engineering professor, (and possible seismologist) can do is rearrange equations algebraically. While missing the entire purpose of the relationship defined by PE = KE (kinetic energy) of the towers moving down + W (work energy) of the towers breaking up.

Since you are a structural engineer, material expert, and engineering professor, (and possible seismologist), can't you provide something of substance. Not too complicated, perhaps apply some energy methods to keep the math simple. After all this type of analysis is something you have trained for six or seven years (at a minimum) to do.

Come'on don't be bashful show us your stuff.

[spooked911]

97. I'm not claiming to be any of those things-- that would be

janedoe who is the expert and that is who I was responding to.

[LARED]

98. I did respond to janedoe not you.

At least the "response to" link says so.

[spooked911]

99. sorry, when the posts get all lined up like that it is hard to tell

your post was right below mine. In my web browser anyway.

[janedoe]

103. Glad I could help!

I notice that your post was more than 7 hours after mine.
I'm glad you found my post helpful. Thanks.

But, you neglected to show how your calculations demonstrate anything relevant to the collapse of the WTC. The WTC didn't drop from 1350 feet onto the pavement below (or even from 1368 feet). Your "analysis" simply shows the time it would take to drop the WTC from that height, with an arbitrary value of reduced gravity.

Please review my post *91, equation (4).

mgh (1-k)=1/2 m v^2 ......(4)

And I commented after that equation, "Your results show that you assumed both masses were the same, so they cancel,.."

This means that you are saying the entire mass of the building falls from height h, and stays intact. And, after the entire mass of the building falls distance h, that entire mass will be traveling at speed v when it hits the ground.

This is why I suggested it needs to be a calculus problem. The potential energy you showed, was for the entire building to be located at 1350 feet above the ground.

It only seems logical that the top of the 109th floor has only the mass of one floor pushing on it. And, floor 108 has the mass of only two floors pushing on it... etc.

The entire building is not falling; it is collapsing.
Your model was of a falling building, not a collapsing building, and definitely not a progressively-collapsing building.

[LARED]

107. It's hard to believe you have missed the point so entirely

First of all, the absolute value PE for the building is found by using the centroid of the building. Not the top. As you have pointed out correctly the model defines a factor for gravity to express how much it's influence is reduced due to work being done. That influence is assumed to be uniform over the entire structure simply because it is a very simple model. Finding fall time from the top of the building using this gravity factor is perfectly useful and instructive. Is it exact? Of course not but it does tell us that huge amounts of work enegy can be done by the structure without extending the fall time to 99 sec as you have indicated.

The model simply compares the transformation of energy from potential to kinetic and work energy. And yes, of course developing a continuous function describing this relationship would be quite useful. You claim to be the structural engineer, materials expert, and engineering professor, so why not give it a try and tell me how you made out. I'd be more than happy to review it for you. You really are best tasked for this job as I've been and engineer of twenty years and am a bit rusty at deriving mathematical models.

[janedoe]

108. Thank you, Thank you, Thank you,

for letting me know that all of my efforts weren't wasted. That was kind of you! And thanks for acknowledging your error.

Perhaps you can make an errata post and correct your numbers. I'm sure it's too late to edit your posts. Now that you will be using 1/2 of the potential energy that you originally used, do you think it will take a little longer than 11.2 seconds? Maybe close to 16 seconds? (If you use a building height of 1368 feet, t = 16.0 seconds instead of 11.2 seconds.)

I know you can make these calculations, now that you have finally seen your error. But, I thought I'd help you get off to a good start.

[Make7]

117. Let me ask you this:

If the PE is calculated using the center of the mass, shouldn't you also use the center of the mass for the velocity in KE?

If so, why are you not using that height to calculate the time?

If not, please explain.

Thanks,
Make7

[Make7]

118. Maybe you need some help?

One of your objections to LARED's "model" is that he didn't use the center of the mass for potential energy. Which is a somewhat valid point, but you failed to use the center of the mass for kinetic energy in your "correction." Let's do some calculations using the center of the mass for both with LARED's equations:

   PE = KE + 1/3 PE
   PE = 3/2 KE
   mg(h/2) = 3/2 (1/2 mv²)
   v = (2/3 gh)^0.5

   v = 171 ft/sec

But here you used the full height for the rest of the calculation:

   t = 2 h / v
   t = 2 * 1368 / 171

   t = 16.0 seconds

(Please correct me if you arrived at your answer of 16 seconds differently.)

But here is what you should have done:

   t = 2 (h/2) / v
   t = 2 * (1368 / 2) / 171

   t = 8.0 seconds

So now we know how long the lower half of the building takes to collapse. (If 1/3 of the PE is used to overcome resistance.)

But who cares? That's not really very useful at all. Let's see if we can rectify that. (Isn't math fun!)

We know the time and distance for the first half of the collapse so we can easily calculate the rate of acceleration:

   a = 2 h / t²

Ohhhh...I almost forgot...it should be the height for the center of the mass:

   a = 2 (h/2) / t²

   a = 21.375 ft/sec²

Now I am just going to assume the rate of acceleration remains constant for the rest of the collapse. (After all, as LARED said, this is just a "very crude energy balance.")

Alrighty then - we know the velocity at the 8 second mark and we also know how much height is left of the collapsing building (not surprisingly it is h/2), let's find the final velocity:

   v_final = (v_initial² + 2 (h/2) a)^0.5

   v_final = 242 ft/sec

And now we can calculate the time it takes for the top half to fall to the ground:

   t = 2 (h/2) / (v_initial + v_final)

   t = 3.31 seconds

Here comes the interesting part - when I add the time for the bottom half and the top half together, I get 11.31 seconds. But the really interesting part is that I got 11.30 seconds with LARED's original equation when I used 1368 ft for the height and 32.16ft/s² for gravity. I must be doing something wrong.

Adding to the coincidences, that also matches the results I get with my simple spreadsheet comparing the rates of acceleration for different collapse times to gravity. Go figure. Please.

:) Make7

[Make7]

100. Now that LARED has had a chance to respond...

...I'd like to say that, in my opinion, you waiting only 4 1/2 hours before posting this was not really allowing LARED a reasonable amount of time to respond.

I realize you were probably excited to finally figure it out and post it, but he did say he would get back to you in a reasonable amount of time and you were not even gracious enough to give him that.
____________________

janedoe wrote (addressing LARED):
Now, you use the following equation,
t = 2 * H / v (for free fall)

Where did that come from?
blah, blah, blah...

Try this:

displacement = velocity * time
average velocity = (v_i + v_f) / 2

replacing velocity with average velocity:

displacement = (v_i + v_f) * time / 2

since we know initial velocity is zero:

displacement = v_f * time / 2

or

h = v * t / 2

t = 2 * h / v

janedoe wrote (addressing LARED):
...Make7 presented LARED's following equations and implied that it is an "algebra" problem (note, not calculus).

I believe that is algebra, or maybe you can show me the calculus I inadvertently used. Thanks for your assistance.

-Make7

P.S. I think it takes a lot a guts to post the things you do.

[Name removed]

101. Deleted message

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

[janedoe]

104. Thank you for validating my point.

Thank you for validating my point. Yes, it had to be controlled demolition!

[Make7]

106. Don't thank me yet.

So, I take it you agree with the following:

1. I said it was an algebra problem because it was an algebra problem.
   
2. I understand how you arrived at your theoretical collapse times in your "models".
   
3. I understand the calculations LARED used in his example.
   
4. Seismic data is not an accurate way to measure collapse times. (You have previously stated that WTC7 collapsed in 6.5 seconds, but the seismic data says 18 seconds. Which one do you think is the actual time?)
   

Actually, I was hoping for a more detailed explanation of how it was possible for WTC1 to collapse in 8 seconds. Oh, well.

-Make7

[janedoe]

109. I don't think you really want me to answer those questions.

It will embarrass you and you will be unhappy.
I fail to see any other purpose for your post.

[Make7]

110. Well maybe you could answer just this one,...

...since your overwhelming concern for my welfare seems to motivate you not to answer.

Do you think the seismic data is correct for the collapse time of WTC7? (I assure you that any answer that you may give to this question will not embarrass me or make me unhappy.)

-Make7

[janedoe]

111. I do not see what you question has to do with

your welfare. Perhaps you meant warfare?

[Make7]

112. No, I did not mean warfare.

Do you think using the seismic data for the collapse time of WTC7 gives an accurate time? YES or NO.

[Make7]

113. If I didn't know any better, I would think you were trying to avoid...

answering my questions. But since you have pointed out that you will not provide answers to save me embarrassment and also to not cause me unhappiness, I can just assume that you have my best interests at heart and are not actually avoiding the issues.

-Make7

[Make7]

105. Undeleted message: Algebra vs. Calculus

janedoe wrote:
...Curiously, LARED never responded to that message. I wonder why?
But later, Make7 did, as if he understood the analysis and was ready to defend it.

In post #56, Make7 presented LARED's following equations and implied that it is an "algebra" problem (note, not calculus).

(Make7, stated this, again, in his post#61.)

V= 73.2 m/sec
Solving for t
t = 2 * H / v (for free fall)
t = 11.2 sec

Please show me how calculus is required to solve for height in the example above.

janedoe wrote:
If the time of collapse is between 14 and 16 seconds, as Make7 claims it is, why not reduce gravity by 60%? Then, you'd get "the right answer" ...well, if Make7 has "the right answer." ( Let's play "dial an answer.") Hmm... the 911-commission report said it fell in 10 seconds; Make7 has the value of 14-16 seconds. Hey, let's just split the difference to be safe.

How did you come up with that 60% figure?

If we are just going to split the difference, I'd like to change my answer to 20 seconds. :)

janedoe wrote:
Make7 has not been arguing with LARED's analysis, only my examples. Perhaps he understands where my numbers come from? If so, I take that as a complement. My objective was to present concepts (free of mystery fudge factors) in a way folks could understand them. If he does not understand where my numbers come from, why is he so upset? Lastly, does he understand where LARED's numbers come from?

I've already shown how I believed you arrived at your numbers. (remember?) Since you did not point out the error of my ways, I assumed that I was correct in my calculations. Perhaps you can explain in more detail.

Yes, I do understand where LARED's numbers come from, and I understand the point he was trying to make. I don't disagree with his example, in fact I did something similar and came up with pretty much the same results he did, but I used a simple spreadsheet to calculate different rates of acceleration. (chart) LOL! Check out the thread title. :)

janedoe wrote:
?pic

The red graph at the bottom, for the collapse of WTC#1, has the start of collapse marked at 16.42 seconds. Within 10 seconds, the signal settles out. Compare this to the top graph, showing what happened when the plane hit WTC1. It appears to take longer for the signal to settle out. Why do you think that tells us about the collapse?

Is it really your contention that the seismic data is an accurate measure for the collapse times?

Here's what they reported from the Lamont-Doherty Earth Observatory:

Summary of seismic observations of the two impacts and the three collapses:

 Date         Origin Time    Magnitude      Time       Dominant   Signal
                (UTC)      (Richter Scale)  (EDT)      Period     Duration      Remark
---------------------------------------------------------------------------------------------------
09/11/2001    12:46:26±1        0.9        08:46:26    0.8 sec    12 seconds    first impact
09/11/2001    13:02:54±2        0.7        09:02:54    0.6 sec     6 seconds    second impact
09/11/2001    13:59:04±1        2.1        09:59:04    0.8 sec    10 seconds    first collapse
09/11/2001    14:28:31±1        2.3        10:28:31    0.9 sec     8 seconds    second collapse
09/11/2001    21:20:33±2        0.6        17:20:33    0.7 sec    18 seconds    Building 7 collapse

http://www.ldeo.columbia.edu/LCSN/Eq/20010911_wtc.html

So the second collapse only took 8 seconds? I'd love to hear an explaination of how a 1368 ft. tall building totally collapses in 8 seconds. Care to give it a try?

I'm sure many in the 9/11 truth community will be disappointed to find out that it took 18 seconds for WTC7 to collapse, that puts a big hole in their near free-fall speed "proof". I'll let you explain to them how this data is accurate and irrefutable. Good luck.

Of course the video footage seems to contradict those times, but I guess it's possible that the videos have been doctored in some way. From every angle. Even the live broadcasts.

-Make7

[vincent_vega_lives]

119. Yes and the massive concrete core bunker is clearly visible

:eyes:

[pox americana]

124. Call it whatever you want.

No points off for creative writing. What it shows is that the core was structurally independent of the floor diaphragms, so no "progressive collapse" could have been produced by failing floor trusses.

[vincent_vega_lives]

126. I was refering to Christophera's "proof" of demolition theory.

Progressive collapse could have been produced by a structural failure at multiple points, the trusses only being a peice of it. Once trusses began to fail, the structure was compromised, unless you think the floors could have pancaked between the inner core and outer walls all the way down to the ground?

[pox americana]

127. "Progressive collapse" could only have been produced two ways:

1. Failure of every column-floor connection, which would have produced rotation (tipping or twisting, like a collapsing box or card table), which didn't happen, or

2. Compression failure of every column, which would have produced 63,140 buckled columns, which didn't happen either.

And if there had actually been any "pancaking," the floor diapghrams would have been left hanging from the core, like awnings, or else just fallen off. The core would have been left standing.

[seatnineb]

125. You are correct in observing that there is no concrete .........

.....that has been applied to the core structure at this juncture.


You will also notice that the concrete has yet to be applied to the floors.

The corrugated steel that would later be embedded between the concrete (applied to the floor) and the trusses ,is very much in evidence in this photograph.

[vincent_vega_lives]

128. So was this concrete core

poured or prefab slabs?

[catnhatnh]

7. OK....

...You and I are WAY opposed on this.I put this up merely to say that L'ambiance in NO way supports the "pancake" theory I've seen elsewhere.As I stated, this does NOT support a "pancake" theory as it was nowhere near a completed "building"...that's a fact, Jack...
So whether or not you like it, either vertical member flanges fail, or they do not...where I was they did not....Where in the WTC steel were intact vertical columns running to 4-6-8 floors at a time???They sat there in Bridgeport....Many twisted as you would expect in your way-hot theories of steel bending...But no steel needed heat here....what happened was a building with 85% of it's weight with very little cross bracing was caused to fail...the only pertinent question I bring from the rubble is this:how did yours break at vertical flanges????If hot they could have bent...ours did,cold and unsupported....if yours were hot from fires they should have both bent easier and left longer verticals,but they didn't right?In short L'ambiance doesn't compare,but it most definitely can point....

[pox americana]

9. You are so right.

L'Ambiance was a construction accident, and 9/11 was a demolition. No relation whatsoever.

Here's a link I found to some information the L'Ambiance collapse:



http://www.eng.uab.edu/cee/reu_nsf99/ambiance.htm#ruins

[catnhatnh]

10. It doesn't look familiar, but could be so....

...it looks much "cleaner" than I recall....remember there were no perimeter walls....those brought out the second day were horrendous...But the important part to me is to look at what vertical steel did in the absence of any heat during a full collapse...draw your own conclusions....

[catnhatnh]

11. Just for fun....

....that was my point....in it's own way horrendous...but when cited here-at best a diversion..

[pox americana]

62. The pancaking at L'Ambiance was NOT a result of column failure.

The temporary floor connections failed.

In fact, I'd be surprised if there's ever been a pancaking failure of the kind described in the NIST report of ANY steel-frame highrise, for ANY reason, including earthquakes. Concrete columns, yes. Steel columns, no.

They'd have to be ridiculously underdesigned.

[LARED]

63. Maybe I missed it , but no one is making the case

that the L'ambiance collapse was a result of column failure.

So why are you telling us this?

[pox americana]

66. The NIST is making the case that pancaking brought down WTC 1 and 2.

And I'm saying that that kind of column failure is unprecedented and (in my very strong opinion) impossible.

[LARED]

69. The difference is the NIST is backing up their findings

with scientific analysis. Your opinion (no matter how strong it might be) is only backed up by your experience.

[pox americana]

70. No, they are backing up unsubstantiated claims

which are apparently unprovable with speculation and incomplete "modeling" of events which appear to have been physically impossible.

That's not science, it's science fiction.

[LARED]

73. Sorry that not what's happening

The NIST is performing a science based inquiry utilizing models, empirically found data, and direct evidence to discover what happened.

Is it perfect?

No.

But it is vastly superior to the method of repeating your opinion endlessly as if the number of times you say it makes it more accurate or believable.

[pox americana]

74. I have seen no evidence of column buckling in the collapse of either tower

and the NIST theory falls apart without it. There IS plenty of evidence of columns which did not buckle (every photograph I've seen).

That's an empirical fact. The NIST theory is unprecedented and implausible and until they provide some "empirical evidence" to support it there is every scientific reason to reject it.

[LARED]

75. How ironic

I just got do explaining why the NIST method is far superior to your method

But it is vastly superior to the method of repeating your opinion endlessly as if the number of times you say it makes it more accurate or believable.

And you continue to repeat your opinion.

Do understand the difference? The NITS is using well established scientific methods based on known information. Your method is simply an opinion from someone without any known or displayed knowledge that give your opinion credibility.

[pox americana]

76. When they find some evidence to support their claims, let us know. (n/t)

[Ice4Clark]

65. I just ran across a site that showed some unusual images and

a video.

The page is titled Strange Collapse of the Spire.

Could you all pop over and have a look and see what you think?

It shows "An odd remnant of the core of the north tower remained standing for about 15 seconds after the main collapse, then seemed to abruptly disintegrate into a narrow column of dust where huge steel box columns had been."


Here's a clip.

and a couple stills.






His conclusion:

Something inescapably strange is going on in these pictures, something no official explanation of the collapses has come close to accounting for. Beyond this I make no claims, and have no insider knowledge. Based on the photographic evidence there can be no question that explosives, and possibly other weapons systems based on "black technologies" were used in the WTC demolitions. Otherwise one can only suppose that the laws of physics underwent a profound but temporary change on September 11, 2001, as indeed the political and moral climate of our country underwent a dark and fateful change. And it is precisely this change that was clearly the intent behind the vast high-tech magic show that was 9/11. In politics as in physics, things do not happen for no reason.

[pox americana]

82. He's right.

The structural evidence does not support any collapse theory other than explosive demolition.

[spooked911]

83. Yes, I've seen this-- it is amazing and very very weird.

What would make steel shatter into dust like that?

Theory: probably the same thing they used to bring down the towers-- just that the charges were delayed here for some reason.

[LARED]

89. What would make steel shatter into dust like that?

With the amount of mass involved nothing does, that why it did not shatter or vaporize. It simply is an image of the spire falling, leaving a dust trial in it's path.

[pox americana]

81. One more glaring problem with the NIST gravity theory:

If the columns didn't buckle (and the evidence says they didn't), then the connections would have had to fail.

But if the connections had failed, there would have been rotation (like a folding card table collapsing).

But the only rotation I saw was the tipping top, and it somehow stopped rotating. And then the buildings just went down. No rotation.

No rotation, no connection failure.

And since we've already ruled out compression failure, that leaves...

????

[philb]

115. Could pancake collapse throw a 30 ton steel beam 390 feet?

in horizontal direction? what kind of huge horizontal force would a collapse exert?
How could that be possible?
http://www.gallerize.com/150%20WINDY%20TOWERS%20OF%209-11%20One.htm

[pox americana]

116. Not unless they used mortar instead of nuts, bolts, rivets, welds

and concrete to hold the building together.

The problem with all those flying beams and columns is that gravity could have deformed them, but it couldn't have produced the lateral force required to shear their connections.