kid meatball
Critical Thinker
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I would agree to the addition of the highlighted portion. Given that that is clearly not at all what happened in the case of 7, CD is a non starter.
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I would agree to the addition of the highlighted portion. Given that that is clearly not at all what happened in the case of 7, CD is a non starter.
JayUtah
Penultimate Amazing
True, the pattern of demolition is carefully tailored to the nature of the building and the constraints of the environment. They are not necessarily one way or the other. But that's the point -- MM's premise is that symmetry is a hallmark of controlled demolition and asymmetry is somehow a hallmark of natural collapse. There's no theoretical or empirical basis for either statement.
They don't see them as weaknesses, and they know full well their believers won't either. When you beg the question, rely upon lay supposition, and aim your claims only at laymen, you'll get a predictably strong response from laymen. It takes skill and knowledge to know how things really work, and we harp on such things as "symmetrical = controlled demolition" because it has to be said somewhere that this isn't how the world works, and to remind people that this, among other things, they can verify for themselves once they are motivated to look.
Weasel words aside, have no noticed that no one on planet Earth cares what you have a problem with?
The Salomon Brothers Building.
LSSBB
Devilish Dictionarian
Exactly.
jaydeehess
Penultimate Amazing
Delft University architecture building.
Small fire, a coffee machine suffered an electrical malfunction. Fire engulfed a large portion of the structure then, quite suddenly a third of the entire building collapsed.
The AE911T analysis would require that this large section of the building must have had explosive removal of all support of that portion of the structure.
However, we know that's not true.
Therefore the premise is not supported.
For about the gazillionth time;
Some initiating event caused the failure of column 79. The result saw the in falling of the east mechanical penthouse(EPH). The debris fall likely destroyed the eastern portion of the core system, very probably including TT1. The core relied on the heavy lateral bracing at its eastern extremity. The compromising of that lateral bracing and the continuing debris fall led to an east to west progression of failure in the core.
As the core begins failing the vertical kink appears on the north facade from lowest visible floor to the rooftop. The existence of this kink indicates that perimeter columns proximater to the kink had failed very low on the structure.
Loss of core means the upper 40 storey structure would lean to the south. That 40 storey structure rested upon a foundation built eight storeys up, above the preexisting Con-Ed substation. The tilt and loss of core columns would cause the cantilever trusses at the eight floor to shift north.
All of the above would cause the transfer of loads to remaining perimeter columns. Tilted, or buckled columns offer NO vertical support and the transfer of basically all loads to first the entire perimeter, then the northern tilt of most of the north face perimeter below eighth floor would result in complete and rapid overload of perimeter frame.
In addition, the south perimeter had already suffered major structural damage including loss of NW corner, and the kink in the north facade indicates that just prior to global collapse phase, a few perimeter columns there had already failed.
Small fire, a coffee machine suffered an electrical malfunction. Fire engulfed a large portion of the structure then, quite suddenly a third of the entire building collapsed.
The AE911T analysis would require that this large section of the building must have had explosive removal of all support of that portion of the structure.
However, we know that's not true.
Therefore the premise is not supported.
For about the gazillionth time;
Some initiating event caused the failure of column 79. The result saw the in falling of the east mechanical penthouse(EPH). The debris fall likely destroyed the eastern portion of the core system, very probably including TT1. The core relied on the heavy lateral bracing at its eastern extremity. The compromising of that lateral bracing and the continuing debris fall led to an east to west progression of failure in the core.
As the core begins failing the vertical kink appears on the north facade from lowest visible floor to the rooftop. The existence of this kink indicates that perimeter columns proximater to the kink had failed very low on the structure.
Loss of core means the upper 40 storey structure would lean to the south. That 40 storey structure rested upon a foundation built eight storeys up, above the preexisting Con-Ed substation. The tilt and loss of core columns would cause the cantilever trusses at the eight floor to shift north.
All of the above would cause the transfer of loads to remaining perimeter columns. Tilted, or buckled columns offer NO vertical support and the transfer of basically all loads to first the entire perimeter, then the northern tilt of most of the north face perimeter below eighth floor would result in complete and rapid overload of perimeter frame.
In addition, the south perimeter had already suffered major structural damage including loss of NW corner, and the kink in the north facade indicates that just prior to global collapse phase, a few perimeter columns there had already failed.
jaydeehess
Penultimate Amazing
Yes. In addition to the sequence of collapse that MM, and every truther I have had the pleasure of observing, wishes to completely ignore, a building is simply not a Newtonian "particle".
It is a connected system_ of subsystems, of individual structural members.
We know that it is quite possible to build a connected system of parts that, when allowed to drop, can have some parts exceed gravitational acceleration. That is because the falling system is not a simple Newtonian particle.
One example
Here, compression in one part of the system results in tension in another.
There is also rotational effects in which if one were to measure the travel of a point on an object it would give over-g results even though the object as a whole does not exceed 'g'.
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You didn't even mention that the columns at the north face were supported on the ends of cantilevers at floor 8... no axial coupling to the foundations for at least 75% of the north face. When the structure at the south end of the cantilevers collapsed or was translated a significant distance... the cantilevers ceased to function and the perimeter columns on their north ends had no support... and the curtain wall was connected to the columns and spandrels.
The east and west perimeter from ground up to floor 8 was a braced frame with diagonal members and only 3 columns axially connected to the foundations... Braced frame probably folded like a plate inward...
And finally the south perimeter had a 5 story tall lobby and the perimeter columns there were unbraced for those 5 floors.
So the entire 40 stories of the tower above floor 7 was *built in the air* with a rube goldberg but very robust structure to carry it.... load transfer systems all laterally interconnected... and a disaster waiting to happen if part of that load transfer system failed....
It did.
The east and west perimeter from ground up to floor 8 was a braced frame with diagonal members and only 3 columns axially connected to the foundations... Braced frame probably folded like a plate inward...
And finally the south perimeter had a 5 story tall lobby and the perimeter columns there were unbraced for those 5 floors.
So the entire 40 stories of the tower above floor 7 was *built in the air* with a rube goldberg but very robust structure to carry it.... load transfer systems all laterally interconnected... and a disaster waiting to happen if part of that load transfer system failed....
It did.
jaydeehess
Penultimate Amazing
You are correct , I did not mention those other significant details. Though I have in the past described in my own words, what your first paragraph explains.
I have also referred to the upper 40 storeys as having been built upon an eight storey elevated foundation. That is, isn't it, the whole reason for the core's heavy east-west bracing?
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I don't know if the core has especially robust bracing in the E-W direction. There was a main beam which was at the south end of the 8 MG17 cantilevers and it connected/braced the columns 64, 67, 70 and 73... Both TT1 and TT3 were framed into this E-W beam.
The transfer structures essentially supported column lines which could not be brought axially down to the foundation... So they were not lateral braces as much as sort of bridges carrying column line *mid* span.
The transfer structures essentially supported column lines which could not be brought axially down to the foundation... So they were not lateral braces as much as sort of bridges carrying column line *mid* span.
Attachments
Animal
Master Poster
From my understanding of my structural engineer from a (low) high rise project I did that had lots of transfer beams........because they are rigid....they concentrate loads.....so once things started to fail it fails bad.
JayUtah
Penultimate Amazing
In a sense, yes. A transfer beam (simplistically considered) is supported at its two ends by robust piers. On top of the transfer beam you place other columns. These support structure upward, but the load doesn't transfer axially (i.e., in a straight vertical line) to the ground. It transfers to the beam, which transfer the load laterally to the piers at either end. If these piers or the beam itself fails, all the structure that depends on the transfer beam suddenly has zero support.
Or.... a transfer beam is like a bridge... and the span supports the columns... ergo the *building* above. The spans in this case were *over* Con Ed transformers.
My question for years has been... why didn't they build 7wtc on the vacant lot across West Street... and instead use the *air rights* to the Con Ed property? That.... to me seems insane.
My question for years has been... why didn't they build 7wtc on the vacant lot across West Street... and instead use the *air rights* to the Con Ed property? That.... to me seems insane.
Animal
Master Poster
It was a more involved discussion than that
I probably simplified it a bit too much. It involved discussion of failure (this was post 9/11) and dispersal / concentration of loads (though this was a post tension concrete structure, so that may make some difference) I do not pretend to be and expert at structural design even though technically I can do it......(it is far cheaper and quicker to hire an expert)jaydeehess
Penultimate Amazing
I stand corrected, thanks.
Animal
Master Poster
The air rights were probably cheaper than the vacant property. There could have been a host of other reasons......setback requirements (daylight rules) existing utilities etc etc that may have made it a better deal to build where they did.
Maybe... but I doubt it... non of your reasons make sense and of course the site was built on later.
Based on whose assessment?
And other factors.
Deliberately trying to sound smart by using ten-cent words.
Subjective term with no technical or industry definition.
Misuse of term to sound more impressive.
1. Again, by whose criteria?
2. Yes, if you ignore all the other buildings it hit.
3. And the fact that the penthouse collapsed asymmetrically.
Complete lack of examples any other CDs exhibiting such properties, despite multiple requests. Asserting belief as indisputable fact. Use of the term "realistic" despite the fact that the vast majority of relevant professionals do not endorse the CD theory. Denial of the ways in which the collapse did not resemble a CD, such as the lack of structural pre-weakening, and barotrauma, and big, conspicuous charges planted on the walls, and explosions consistent with explosives, especially in light of your assertions that it didn't resemble a conventional CD in other aspects.
So much wrong in one sentence.
I've been trying to make the "Schrodinger's Competence" happen for years now, but it doesn't seem to be working.
I wouldn't use the term "'boogers".
JayUtah
Penultimate Amazing
Be that as it may, a building was built on the Con Ed site and it did have the structural attributes now under consideration. Those attributes include transfer beams and trusses and other load transfer techniques that affected the qualitative and quantitative structural redundancy in the building. These specifically address the notion that large visible portions of the building depended in some cases on relatively isolated structural elements and that when those elements were compromised, it affected a disproportionately greater fraction of the structure.
DGM
Skeptic not Atheist
The fact of the matter is. There has not been any evidence found that suggests the transfer system had any impact in the collapse initiation. I know you think different but the bottom line is, there was no evidence of fires or conditions that would cause collapse in their area.
Also. the reason for this design had to do with the fact the ConEd foundation was designed for a smaller building. It was always meant to be built on top of. WTC 7 used a combination of existing and new caissons to carry the load. It's inaccurate to say it was a poor choice simply because you suspect the transfer system was a poor design.
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jaydeehess
Penultimate Amazing
I think it is quite probable that TT1 was compromised to uselessness as part of the same debris fall that led to progression of core failure. As JSO points out, it consisted of several bolted members and if any of them were broken by debris fall it would not be far from failing the whole TT1 truss system.
I don't think it probable that initial failure was TT1 though. Not enough evidence for that imvho.
I don't think it probable that initial failure was TT1 though. Not enough evidence for that imvho.
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