How the WTC Core Supports Weakened.

SBrown

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The WTC towers had 47 cores that ran vertical the length of the building. How did these vertical supports fail all along the length of the building? I could see failure if they were horizontal, but vertical columns would hold under any plausible crushing scenario. I do not see a pancake or falling weight snapping all these core columns over and over again on the way down. This just does not make sense.
 
SBrown said:
The WTC towers had 47 cores that ran vertical the length of the building. How did these vertical supports fail all along the length of the building? I could see failure if they were horizontal, but vertical columns would hold under any plausible crushing scenario. I do not see a pancake or falling weight snapping all these core columns over and over again on the way down. This just does not make sense.
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Why does that not make sense? Are you thinking that only vertical forces were acting on the columns?
 
Buckling:

"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." Eagar paper in JOM

We've been over this.

Also, as anybody who's ever studied statics or structural mechanics knows, if you load a column too much it will bow, and create opposing lateral forces inside the column. QED.
 
R.Mackey said:
Buckling:

"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." Eagar paper in JOM

We've been over this.

Also, as anybody who's ever studied statics or structural mechanics knows, if you load a column too much it will bow, and create opposing lateral forces inside the column. QED.
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Do you just ignore the existance of core columns or are you just not educated on this subject?
 
Funny, I was thinking of asking you the same thing, but decided not be so rude.

The outer box columns bowing outward means the load sags, and pushes outward on the box columns. If there is no collapse, e.g. static analysis holds, Newton's 3rd law applies -- this outward push is balanced by an inward push on the interior columns.

Even without the buckling, a gross overload will cause vertical columns to enter a bending mode and probably snap in the middle.

I would hazard a guess that I am far more educated on the subject than you are, but I am perfectly willing to explain. Are you willing to learn?
 
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R.Mackey said:
Funny, I was thinking of asking you the same thing, but decided not be so rude.

The outer box columns bowing outward means the load sags, and pushes outward on the box columns. Newton's 2nd law applies -- this outward push is balanced by an inward push on the interior columns.

Even without the buckling, a gross overload will cause vertical columns to enter a bending mode and probably snap in the middle.

I would hazard a guess that I am far more educated on the subject than you are, but I am perfectly willing to explain. Are you willing to learn?
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So this "bowing" and pushing, pulling and "probably" snapping happened all at once or a few floors at a time?

WTC_Core_03.jpg
 
I don't understand your question. Clearly the collapse was sequential in nature, although if you put that much runaway force into a structure, the load will become critical very, very quickly. Once we can no longer treat the problem statically, it becomes difficult to say whether the failure is one floor at a time (in rapid, uninterrupted succession) or whether it spans a larger area.

The question is also academic at that point.
 
SBrown said:
The WTC towers had 47 cores that ran vertical the length of the building. How did these vertical supports fail all along the length of the building? I could see failure if they were horizontal, but vertical columns would hold under any plausible crushing scenario. I do not see a pancake or falling weight snapping all these core columns over and over again on the way down. This just does not make sense.
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No, what doesn't make sense is Chewbacca living on the planet Endor with the Ewoks. That does not make sense. I mean, he's a 7-foot tall Wookie living with 3-foot tall Ewoks. Ladies and gentlemen of this supposed jury, THAT DOES NOT MAKE SENSE!

J. Cochran
 
SBrown, it's great to come here with legitimate questions and issues that you would like to discuss. But that's not what you do. Every time you've started a thread, you've done so with a huge chip on your shoulder. You back your statements with opinions, and when those are countered with facts, you become snippy and insulting.

Why are you doing this?
 
Gravy said:
SBrown, it's great to come here with legitimate questions and issues that you would like to discuss. But that's not what you do. Every time you've started a thread, you've done so with a huge chip on your shoulder. You back your statements with opinions, and when those are countered with facts, you become snippy and insulting.

Why are you doing this?
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Are you talking to coalesce or me?:confused:
 
coalesce said:
No, what doesn't make sense is Chewbacca living on the planet Endor with the Ewoks. That does not make sense. I mean, he's a 7-foot tall Wookie living with 3-foot tall Ewoks. Ladies and gentlemen of this supposed jury, THAT DOES NOT MAKE SENSE!

J. Cochran
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So you are a Star Wars fan....super, you are also a idiot...super.
 
SBrown said:
Are you talking to coalesce or me?:confused:
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As my reply was addressed to you, and as you did what I'm talking about juat a few posts ago, yes, SBrown, I was talking to you. I've asked you to do this before, but you don't seem to get it: please re-read your posts and try to imagine how they sound to others.
 
Gravy said:
As my reply was addressed to you, and as you did what I'm talking about juat a few posts ago, yes, SBrown, I was talking to you. I've asked you to do this before, but you don't seem to get it: please re-read your posts and try to imagine how they sound to others.
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My question to you still stands and is the only reply that was not to a snide remark from addon.
 
SBrown, take it to PM. I'm leaving this discussion as your conduct leaves much to be desired.

The reason the collapse doesn't make sense to you, as you indicated in your first post, is because you are inexperienced in the subject. http://en.wikipedia.org/wiki/Solid_mechanics has a reasonable reference listing at the bottom -- this will give you sufficient grounding in the underlying physics, if you are willing to learn. If possible, I would also reccommend you ask an educator in your area, as the fundamentals can be explained by any engineering teacher at any level. I would, however, advise you to seek consultation with an open mind.

Arrogance cannot teach.
 
SBrown said:
I am thinking you have decided to not understand.
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No, I don't understand because your writing is unclear. I've also asked this before of you: do you have anything positive to add here? If so, proceed.
 
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