How the WTC Core Supports Weakened.

So I am not following the proper protocols here?

My second post on this thread was a question to you Gravy.

Why do I need to take this to pm?
 
SBrown said:
So they snapped then?

What about every 10-15 feet?
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In the Ground Zero Museum, there will be beams and columns exhibited, recovered from the site. Currently, they are being stored. Here you can listen to an NPR story on it. Note that they speak of 30 to 50 foot segments. These will eventually be on display for you to visit if you like; I doubt very much that they are lying here.

The link also shows "the compression"; a chunk of material that was originally 4 stories of the building, compressed into about 4 feet. Just to give you some idea of the sheer amount of force available to bend the colums and beams.
 
SBrown said:
So you are a Star Wars fan....super, you are also a idiot...super.
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Actually, I was aiming for "dumbass," but "idiot" will do.

You will forgive me, however, if I choose not to engage in name-calling.

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

Nearly every large building has a redundant design that allows for loss of one primary structural member, such as a column. However, when multiple members fail, the shifting loads eventually overstress the adjacent members and the collapse occurs like a row of dominoes falling down.

The perimeter tube design of the WTC was highly redundant. It survived the loss of several exterior columns due to aircraft impact, but the ensuing fire led to other steel failures. Many structural engineers believe that the weak points—the limiting factors on design allowables—were the angle clips that held the floor joists between the columns on the perimeter wall and the core structure (see Figure 5). With a 700 Pa floor design allowable, each floor should have been able to support approximately 1,300 t beyond its own weight. The total weight of each tower was about 500,000 t.

As the joists on one or two of the most heavily burned floors gave way and the outer box columns began to bow outward, the floors above them also fell. The floor below (with its 1,300 t design capacity) could not support the roughly 45,000 t of ten floors (or more) above crashing down on these angle clips. This started the domino effect that caused the buildings to collapse within ten seconds, hitting bottom with an estimated speed of 200 km per hour. If it had been free fall, with no restraint, the collapse would have only taken eight seconds and would have impacted at 300 km/h.1 It has been suggested that it was fortunate that the WTC did not tip over onto other buildings surrounding the area. There are several points that should be made. First, the building is not solid; it is 95 percent air and, hence, can implode onto itself. Second, there is no lateral load, even the impact of a speeding aircraft, which is sufficient to move the center of gravity one hundred feet to the side such that it is not within the base footprint of the structure. Third, given the near free-fall collapse, there was insufficient time for portions to attain significant lateral velocity. To summarize all of these points, a 500,000 t structure has too much inertia to fall in any direction other than nearly straight down.
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Article is a bit old--I think the "angle clips" hypothesis has been revised since this one was published.

It's difficult enough to keep structural steel aligned during construction, let alone after a huge portion of the finished building collapses. They don't just bold and weld girders together and have it all work. There is a lot of effort involved in keeping the structure from warping because of temperature changes, wind, etc. during construction. Once the collapse started the tremendous forces just ripped everything apart--as one might expect.
 
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SBrown said:
So I am not following the proper protocols here?

My second post on this thread was a question to you Gravy.

Why do I need to take this to pm?
Click to expand...
And others answered your question before I got to it. That happens a lot on forums. If I disagreed with their answers, I would say so.

I didn't say you need to take this to PM. I asked you to re-read your posts and try to imagine how they sound to others.
 
SBrown said:
So you are a Star Wars fan....super, you are also a idiot...super.
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No, they're a South Park fan. If you can't get your pop culture right, how can we trust your conclusions about the WTC?
 
SBrown said:
So people here are expected here to know every detail of a cartoon called South Park? I have never seen it.
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I have, and it is funny and has nothing to do with buckling and columns..
SBrown, if you are seriously asking, I propose an experiment for you.
Go get a length of spaghetti--uncooked, please. you will notice that it is very strong if you try to push both ends lengthwise--in compression. IF you hold it in the middle, with one end on the table, uou can put something very heavy on the other end, and it will not break. Now, remove your grip from the middle, and watch it break into a large number of pieces.
How much weight a column will support is a function of its slenderness ratio, that is, its total length compared to its cross-sectional geometric moment-of-inertia and area.
So, with 6 pieces of 2inch length spaghetti set verticaly, you could support say, the first 2 volumes on the Encyclopedia Britannica. Make those lengths 4 inches, and things get wobbly. 6 inches, and you have little bitty pieces of spaghetti again.
That is exactly what happened when several floors got taken out--the 2" chunks are now suddenly 6 inches long-the hand was removed.
The floors, you see, made the columns keep their relationship to each other. They were the hand in the middle of the stick. When that went away. they snapped-broke, bent and everything in between.
That help?
 
Hi SBrown. With all due respect, I don't really see what you're hoping to accomplish by posting here. Your threads seem to follow the same general pattern: (1) Ask a question that has been thoroughly discussed and answered in other threads, (2) Become snippy and rude when someone tries to provide an answer you don't like, and finally (3) Spend the rest of the thread complaining how everyone here treats you badly.

Take this very thread for example. Your OP question has been discussed and answered so many times already in this forum, it seems almost inconceivable that you missed it. You certainly couldn't have searched the forum first before posting it. Then, when R.Mackey posts a perfectly civil and reasonable answer (post #5), you reply with a post (#7) that can only be described as snotty and insulting. Why did you do that? What possible reason can you have for being so rude, if you were truly interested in seeking an answer to your question? (And if you weren't seeking an answer, then by definition you're trolling.) Finally, you derail your own thread by asking about irrelevancies (e.g. South Park).

So in all seriousness, I'd really like to know: Why do you do this?
 
twinstead said:
I suspect it's some sort of time passing technique while waiting for real evidence and objective investigation.

Just a thought...
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Absolutely 100% correct! Allow me to explain....

For the past few months, this board has been bombarded with people from the Loose Change camp who wholeheartedly believe that the WTC was a set-up by the government. All manner of theories were presented as to how the gub'mint planted explosives in the steel columns during construction, how to towers couldn't POSSIBLY pancake the way they did and that it HAD TO BE A PLOT. Well, as someone who had to evacuate my office in the Empire State Building that morning and then watch the towers collapse before my eyes, I take conspiracy theories like this a little more personally that others. If you search this board, you will find more than enough links that rationally show that what we saw is exactly what happened. No evil neo-cons, no shoddy construction, just plain ol' physics.

The tone of your opening post, SBrown, suggested to me that you were convinced that it had to be more than just weakened steel, brought about by unimaginable temperatures and blunt-force trauma, collapsing upon itself. If I misinterpreted your opening post as an intent to expose an evil one-world gub'mint plot, but instead as an open-minded inquiry, then I apologize for jumping to a hasty and incorrect conclusion. If, however, you feel that it was a plot, then I must invoke the Chewbacca defense because that is all the seriousness that the plot, and all those who believe in it, deserve.

Michael
 
rwguinn said:
I have, and it is funny and has nothing to do with buckling and columns..
SBrown, if you are seriously asking, I propose an experiment for you.
Go get a length of spaghetti--uncooked, please. you will notice that it is very strong if you try to push both ends lengthwise--in compression. IF you hold it in the middle, with one end on the table, uou can put something very heavy on the other end, and it will not break. Now, remove your grip from the middle, and watch it break into a large number of pieces.
How much weight a column will support is a function of its slenderness ratio, that is, its total length compared to its cross-sectional geometric moment-of-inertia and area.
So, with 6 pieces of 2inch length spaghetti set verticaly, you could support say, the first 2 volumes on the Encyclopedia Britannica. Make those lengths 4 inches, and things get wobbly. 6 inches, and you have little bitty pieces of spaghetti again.
That is exactly what happened when several floors got taken out--the 2" chunks are now suddenly 6 inches long-the hand was removed.
The floors, you see, made the columns keep their relationship to each other. They were the hand in the middle of the stick. When that went away. they snapped-broke, bent and everything in between.
That help?
Click to expand...


No because pasta is not 4foot thick steel.
 
SBrown said:
No because pasta is not 4foot thick steel.
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It's also not holding up tons of building. What was used was what we call an 'example'. In this case, the example was an experiment regarding how stress can buckle vertical support, but on a smaller scale. In what way does this 'example' not enhance your understanding? Are you being intentionally dense or do you need further explanation of how the example was similar to the actual collapse of columns being described?
 
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