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How WTC 7 was pulled down

Off-topic derail split to Abandon All Hope. Please stick to the topic.
Replying to this modbox in thread will be off topic  Posted By: LashL
 
Grizzly Bear said:
Can somebody remind me again how fast a building should come down? Is there a standard that's ever been established? :rolleyes
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I think ae911truth have proved that is impossible for tall buildings to fall down. I am sure that engineers will take a lot of heart from this news, since it makes their lives so much easier.
 
triforcharity said:
Wow, that is almost a ******* stundie!

LATERAL support does NOTHING when it comes to VERTICAL loads.

But hey, that is cool.
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I suspect you misunderstand, although not as much as MM fails to follow basic structures.

He's trying to argue, I think, that even rotated or buckling columns would have had some support from the bracing. This completely overlooks the limited support that such bracing would, in fact, provide outside of its original load paths and likewise the fact that the floors in the areas of the fires/impacts appeared to collapse.

But it's still an own-goal for MM, I have to stress.
 
Telltale Tom said:
I think ae911truth have proved that is impossible for tall buildings to fall down. I am sure that engineers will take a lot of heart from this news, since it makes their lives so much easier.
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Prior to 9/11 the industry slogan was "Steel: because it never fell down before"
 
Telltale Tom said:
I think ae911truth have proved that is impossible for tall buildings to fall down. I am sure that engineers will take a lot of heart from this news, since it makes their lives so much easier.
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I must admit, it was certainly an earth shattering revelation for the guys at my architecture school! ;)
 
Telltale Tom said:
I think ae911truth have proved that is impossible for tall buildings to fall down. I am sure that engineers will take a lot of heart from this news, since it makes their lives so much easier.
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Around 1990, when mobile phones were young, bulky and expensive, there was a well known TV ad for pagers to aid the elderly making emergency calls. The clip featured an old lady, on the floor, who called into her pager:

Help me! I have fallen down, and I can't get up!​

When in 1991 the Soviet Union dissolved, it was unclear for a few months who got to be in charge of the space program, with the result that an unfortunate cosmonaut, already orbiting earth for a few months, was forced to establish a new world record for longest trip in space. Some comedy show then aired a spoof of the above ad. The words of the Russian cosmonaut could now apply to tall buildings:

Help me! I have gotten up, and I can't fall down!​

:D
 
alienentity said:
That's false. There is plenty of experimental confirmation. Please get knowledge. This has already been covered many times, you can read all about the fire science, the models etc...
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What exactly are you calling experimental confirmation here? NIST hasn't shown their model come down, and neither has anyone else produced a model to serve as experimental confirmation that impact damage and fires could bring a building down anywhere near as quickly and completely as WTC 7 came down.
 
kylebisme said:
What exactly are you calling experimental confirmation here? NIST hasn't shown their model come down, and neither has anyone else produced a model to serve as experimental confirmation that impact damage and fires could bring a building down anywhere near as quickly and completely as WTC 7 came down.
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Why should I, a layman, be concerned that YOU have a problem with how the WTC7 fell?
 
Newtons Bit said:
Lateral support is everything when it comes to compression loads.
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I will stand corrected.

Now, just for clarification.

I have a column that is supported by lateral beams.

The column has buckled due to increased load.

Will the column still buckle if the lateral bracing is there?

Maybe I misunderstood what MM said.

In that case, I will apologize.
 
triforcharity said:
I will stand corrected.

Now, just for clarification.

I have a column that is supported by lateral beams.

The column has buckled due to increased load.

Will the column still buckle if the lateral bracing is there?

Maybe I misunderstood what MM said.

In that case, I will apologize.
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Yes. One thing to point out: the spacing of the bracing will dictate whether or not the compression element buckles elastically or inelastically. Compression elements that buckle inelastically will develop plastic hinges. These hinges will absorb a large amount of energy as the buckle continues. In other words, something that buckles inelastically won't fall at roughly g until the hinges rupture.
 
Newtons Bit said:
Yes. One thing to point out: the spacing of the bracing will dictate whether or not the compression element buckles elastically or inelastically. Compression elements that buckle inelastically will develop plastic hinges. These hinges will absorb a large amount of energy as the buckle continues. In other words, something that buckles inelastically won't fall at roughly g until the hinges rupture.
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Thank you for the engineering lesson. I certainly appreciate it.

(Going to library at school tomorrow to look up Elastically, inelastical Buckling)

I stand corrected.



MM,

See how that works? Someone pointed out that I was wrong, and I LEARNED where I went wrong, decided to research it, and concluded that Newtons was correct.

It's really not that bad.
 
Telltale Tom said:
I think ae911truth have proved that is impossible for tall buildings to fall down. I am sure that engineers will take a lot of heart from this news, since it makes their lives so much easier.
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The taller you make them the less likely they will fall because they will have more building below them.
 
kylebisme said:
What exactly are you calling experimental confirmation here? NIST hasn't shown their model come down, and neither has anyone else produced a model to serve as experimental confirmation that impact damage and fires could bring a building down anywhere near as quickly and completely as WTC 7 came down.
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No one has produced a model to serve as experimental confirmation that CD could bring a building down anywhere near as quickly and completely as WTC 7 came down.
 
triforcharity said:
Thank you for the engineering lesson. I certainly appreciate it.

(Going to library at school tomorrow to look up Elastically, inelastical Buckling)

I stand corrected.



MM,

See how that works? Someone pointed out that I was wrong, and I LEARNED where I went wrong, decided to research it, and concluded that Newtons was correct.

It's really not that bad.
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You gave in, you are weak. I will club your woman and drag her home to my cave thereby orphaning your children. Your capacity to hunt will be severly affected and your status among the tribe diminished. You will be reduced to "gatherer" and forced to work amongst the females plucking fruit from the taller trees. Your dog, no longer fattened by the discarded animal protein from your table will wander and you will collect stray felines in its absence.

Meh, it's not even a guy thing is it? Truthers just don't want to learn.
 
Newtons Bit said:
Where's the change in potential energy in your equations? Hmm?
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You raise a good point because, in general, unless we take into account the PE, we cannot judge the cause of collapse solely by looking at the output response. This was not previously explained.

The energy and entropy regimes are different approaches to the same problem. The condition for which a system is unstable in the entropy regime (ΔS > 0), will occur at the same point in the potential energy regime (det Πij = 0 ). So for purposes of determining stability, the two approaches are equivalent.

However, the entropy approach was taken so that we wouldn’t have to solve the entire Π for WTC7. The reason we are able to simplify the problem into directly comparing the output to input energy is because of the fortuitous, straight down, free-fall phase. This allows us to relate the symmetry to stability. In all bifurcation processes (such as buckling) breakdown of symmetry in the response leads to instability. Symmetry-breaking is a general principle throughout nature (for example, it’s the operating principle in failed controlled demolitions). WTC7’s lack of loss of symmetry at collapse implies that it suffered no change of state (e.g. stability to instability), but that it was stable (strict minimum) throughout. For this reason we can treat it isentropically, and directly compare the input energy to the output energy. This is analogous to the original example of dropping a brick.
 
Dave Rogers said:
Given that your first post on this subject claimed outright that the collapse of WTC7 violated the Second Law, and that you've now retreated to the position that it is in principle calculable whether the collapse of WTC7 violated the Second Law but this has not been done, are you therefore admitting that your initial claim was unsupported by the evidence, and hence a serious error on your part?

Dave
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I never meant to imply that I have actually reached a conclusion or that one is possible by such a simple approach. I was meant more to challenge others to think about the points raised in the original post.

I find it an interesting idea to explore; perhaps others will as well.
 
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