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Originally posted by Joey Canoli
I'll even agree with you here and agree that 7's collapse "looks" like a CD. However, it doesn't "sound" like a CD. So I'm unsure of what to think.
Originally posted by pteridine
reply to post by JacKatMtn
Given the damage to the building and its unusual design [how did NYC ever approve the construction of such a cobbled together monstrosity?] Silverstein likely felt that it would be easier [and more profitable] to start over than to try to repair a severely damaged building. Aside from the insurance payout, which we all know was a consideration, stabilization of buildings on the verge of collapse would have slowed everything down; clean-up, recovery, rebuilding, etc. My bet is that had #7 not collapsed, it would have to have been brought down.
If the towers had not collapsed, how would they have been repaired? Who would work on them? How long would it take to repair them? How would materials be moved to the damage? As I have stated before, leaving them standing would have provided far more problems than having them collapse.
Originally posted by Joey Canoli
You argue that IF a single column is compromised, it shouldn't matter since the other 47 stories were intact. There's a couple of serious and fatal flaws there:
1- it is a misrepresentation of what is in the NIST report to state that there is a single column failing. It states that they believe that a floor beam failed,which then fell onto the floor below, which caused it to fail. The floor collapse progressed both vertically and horizontally, until several columns were unrestrained. Then col 79 buckled, followed by others close by, as evidenced by the east penthouse collapsing into the building. Then the interior collapse progress of the columns occured, as evidenced by the horizontal progression of penthouse collapses. This continued until a sufficent number of int columns were buckled that left the now ALSO unrestrained ext columns unable to carry the load of the remaining shell. That's when the global collapse occurs.
Why not collapse when we were unrestrained for 5 stories or 6 stories?
Because a column or group of columns that is unrestrained for 4-6 stories will have more load capacity than ones that are unrestrained for 8 stories. This is simple structural mechanics, and one that you should know.
You seem to agree with the part of the Bazant paper where it says that a 1% resistance from plastic hinges is indeed good engineering science. So what kind of acceleration factor does engineering tell you that will be achieved with that amount of resistance?
Originally posted by Joey Canoli
You ARE aware that the collapse slowed again after the "freefall" period, right?
I think you're confusing yourself here.
IF.... ~8 stories worth of the 47 story building had columns that were poorly restrained, and IF one accepts the engineering fact that a column failing plastically will give only about 1% resistance to the falling mass, then it follows that IF there is a "freefall" period, then the "freefall" distance should be roughly equal to that 8 story distance. And, that is exactly what's seen.
Then, as you point out correctly, when the remaining undamaged structure impacts, the fall will slow to less than "freefall". This is also what is seen.
So what's the beef?
2- you argue that 47 stories of columns should be able to prevent the collapse initiation, yet agree that in the towers, also agree that the collapse initiation at the plane impact point to be plausible. These 2 statements are at odds. With the towers, you realize that an initiation point doesn't rely on what happens over the height of the building, but depends on what's happening on a localized horizontal level. And yet with 7, you argue that what matters is what matters is the state of the entire 47 stories, rather than remaining consistent with the engineering principle of collapse initiation being dependent on the conditions on a localized horizontal level. Your statements about the state of the entire 47 stories will only have an effect on the speed of the collapse while it's collapsing, not whether or not it can innitiate or not.
Originally posted by Orion7911
and don't twist the issue by arguing semantics how these witnesses' testimony were not talking about explosions related to CD.
Originally posted by Joey Canoli
True. But if there is a horizontal internal collapse, as evidenced by the penthouses again, there will be fewer columns to provide load carrying capacity.
Originally posted by Azp420
I also said that whether or not a single failing column provides any resistance to free fall, the other 47 stories worth of mostly undamaged structure would have most definitely given a significant amount of resistance to free fall. Another way of putting it is that 47 stories of structure would have taken a massive amount of energy to rip apart. Energy that (officially) comes from the mass of the falling building's kinetic energy. If kinetic energy is being used up the falling mass is either decelerating, keeping a constant velocity or accelerating at a slower acceleration than it other wise would be, i.e. accelerating at the slower rate than acceleration due to gravity, g~9.81m/s/s or whatever units you guys use. For the acceleration of the WTC7 to maintain g, it means none of its kinetic energy which it converted from gravitational potential energy has been used to turn 47 stories of structural steel and concrete into rubble. That energy came from a different source. There is evidence to suggest thermite or nano-thermite etc.
Originally posted by pteridine
Originally posted by Azp420
Lol no. In terms of structural collapses they don't get more symmetrical than that. What should have happened when the top section of the tower leaned over as you stated, is that it continued on that trajectory, taking the path of least resistance to the ground, which is not changing course and plowing straight through the rest of the structure. The falling top section that started falling to the side was magically pulled in by some forces that the OS doesn't mention so we should all just forget about them. To paraphrase Bill Hicks, go back to sleep America, your government is in control.
I am amused by the "path of least resistance" arguments that many repeat without question. The top of the tower tipped at the hinge point and struck the lower part of the building. Why do you think it changed course? It appears that gravity pulled it straight onto the lower part of the building. For it to magically leap into space would have required large amounts of energy that weren't there, so for this case the "path of least resistance" is onto the lower part of the building.
If you were to describe your version of what the collapse should have looked like, how would it differ from what happened and why?
Why do you think it changed course?
It appears that gravity pulled it straight onto the lower part of the building.
If you were to describe your version of what the collapse should have looked like, how would it differ from what happened and why?
Originally posted by Azp420
I think it is obvious to the audience that you have entirely missed the point of my posts or you are only able to provide arguments against trivial points and semantics.
You are yet to tell me what is wrong with my conservation of energy statements which have been the meat of my posts.
I apologize if NIST are officially saying several unrestrained columns initiated the collapse, I recently read an official NIST document which stated it was only a single column.
They change their story so frequently I don't have the time to keep up to date with the latest version.
For all I care, those columns could have ceased to exist and it wouldn't have any implications on my conservation of energy statements.
Yes, this is the exact point I was trying to make, well done. These are fire proofed steel columns which have ONLY JUST exceeded their load carrying capacity. That doesn't mean they suddenly have turned to wet noodles.
I assume you are unaware that steel actually gets stiffer and stronger while it is yielding.
I have not seen any testing or calculations to show these columns or a similar test specimen would provide about 1% resistance to free fall.
Wind resistance can provide more than 1% resistance to free fall at these velocities
Saying a series of these columns unrestrained for ~8 stories would provide about 1% resistance to free fall is laughable.
I could be wrong, and the columns actually provided about 1% resistance but it doesn't change my point.
Originally posted by Azp420
Sure maybe several columns failed first or something but essentially the rest of them have simultaneously turned into wet noodles.
Again putting words in my mouth so that you have something other than the meat of my posts to debate.
Originally posted by Azp420
The penthouses are on the roof. Please elaborate on how this translates to a horizontal collapse low down in the building.
Where is the problem you have with my conservation of energy claims?
Where do you suggest the extra energy came from to completely dismantle the 47 stories of mainly undamaged structure?
it is ludicrous to claim that somehow several unrestrained for ~8 stories columns have managed to cause every other column (there is a huge amount of columns) around the same floor level to also become unrestrained. During this time they have waited for all the columns to be ready and held off from vertical failure of the structure. Then when all the columns are ready to go (all have now become unrestrained for 8 stories) they simultaneously collapsed in a spectacular free fall fashion, due to there being 8 floors worth of literally no structure! You will bring up some sort of trivial problem with my description but you are essentially saying that somehow for a vertical length of 8 stories every single column at a certain level in the building managed to simultaneously or almost simultaneously go from being perfectly capable from supporting the above mass of the building to being completely unable to support that mass and only providing about 1% resistance to free fall. I'm sure you don't want to look like a fool so how would you describe it? Sure maybe several columns failed first or something but essentially the rest of them have simultaneously turned into wet noodles.
Originally posted by Azp420
You challenged my post and have failed to prove my statements about conservation of energy wrong,
Originally posted by Joey Canoli
I've given you the mere outline of what a supposed education should be giving you.
1- exterior collapse initiation happens after the horizintal interior collapse initiation begins, and the load capacity of some of the remaining columns has only just been exceeded.
3- the ext enters "freefall", with the distance/time being dictated by the unsupported lengths of ext columns.
4- once this length is "used up", and the undamaged parts of the structure need to be broken up, the fall slows down
All your questions have been answered logically and with evidence.
You have unsupported claims.
You're right about one thing though. Readers can clearly see who won the debate, and it ain't you.
Huh? I gavr you the link to Bazant's paper. In it, he describes, and gives the calculations for, determining how at initiation, there's about 12% resistance given by buckling columns in the plastic phase. And how as the collapse progresses, as more plastic hinges form, it drops to 1%.
Guess you missed that?
Originally posted by Joey Canoli
Originally posted by Azp420
I could be wrong, and the columns actually provided about 1% resistance but it doesn't change my point.
It should. If there's only 1% resistance being given, what would the difference in acceleration be?
Originally posted by Azp420
When the top section of the tower (this happened significantly on one of the towers, I forget which one and don't have time to check) started leaning over just after collapse initiated it was moving in a trajectory which was NOT perpendicular to the ground but at a downwards and sideways angle. For this downwards and sideways momentum to be corrected, a force must act on the sideways component in the opposite direction. I would expect to see the falling top section either arrested when it reaches undamaged structure or it to continue on its original trajectory and topple off the side of the structure (its center of gravity was well to one side).
Originally posted by Azp420
You claim that you believe the NIST version of events so please provide a link as to where NIST states that every single interior and exterior column simultaneously becomes unrestrained for ~8 stories, then somehow simultaneously yield, then somehow simultaneously form a plastic hinge along their section. Oh what's that? You can't? This is essentially what you are claiming, yes?
LOL except the fall didn't slow down.
The structure continued to accelerate through itself (at a rate not far from free fall).
When you watch a video of collapse, you don't see the structure drop for ~8 stories then noticeably slow as the rest of the undamaged structure impacts with itself, slowly destroying itself floor by floor until the roof line reaches the ground as you claim is the case
It is one smooth drop of the entire structure, it smoothly builds up to free fall and smoothly comes back down from free fall.
Do I need to post a link to a high school physics book to prove to you that the law of conservation of energy is scientifically accepted or so that you know how to apply it?
Not at all. I know you are a huge fanboy of Bazant but I was under the impression the paper he wrote was dealing with the twin towers.
In the twin towers the fire proofing was supposedly blown off the columns
and much hotter jet fuel fires supposedly burned.
If you want to then apply his findings to WTC7 where the majority of the structure was undamaged then that's your call but I'll stick with what I have learned in my degree.
Originally posted by Azp420
Almost zero. The rest of the undamaged columns would pick up the stack.
No where does even NIST claim that all columns around the perimeter and all interior columns simultaneously form plastic hinges at the moment of collapse initiation.
Originally posted by Joey Canoli
At significantly less than g acceleration, correct?