Speed of progression of column failure may not be relevant to a strict definition of a progressive collapse, but it's very relevant to an analysis of the WTC collapses. If the perimeter of the roof falls as one, all the perimeter columns must have failed together. We've seen videos of progressive collapses and videos of controlled demolitions, and only the controlled demolitions show the roof edge drop without completely breaking apart. In fact, even standard controlled demolitions seem to cause more initial destruction to the roof line than we see in the videos of the WTC7 collapse.
First of all, you need to establish that the speed of WTC 7's collapse indicates intentional demolitions, and not a single one of you fantasy spinners to date has been able to do that. Hell, you don't even do it here, and that's after you explicitly mention it. If you understood that the core descending pulling the floors along caused the perimeter columns to buckle, then you'd understand why the collapse looked the way it did. It looked that way because the roof and upper floors were intact above the area of column buckling. And it started to come apart as it fell; watch videos of the "kink" that develops in the roofline.
You don't need demolitions to explain what you see; what you need is to understand the sequence of events occurring within the tower.
Are we talking about the same core, or even the same building?
You tell me which of the buildings you're referring to. This is what you said:
When the amorphous rubble falls onto the top floors of the lower section, you want the connections between the floor trusses and the perimeter columns to shear, hurling columns for hundreds of feet, while the connections between the same floor trusses and the core beams hold firmly enough to bring down the strongest columns of the core.
Normally, when people are discussing floor truss seats on perimeter columns shearing, they're discussing the main towers, which is why I posted what I did. Added to that is your mention of columns being hurled "for hundreds of feet", which didn't happen in
any case; being lever armed from an upper floor of a 110 story tower to land in around the 20th floor of a building across the street is not the same thing as being "hurled" by explosives. However, it
is something that you conspiracy peddlers tend to only bring up in conjunction with the main towers, not WTC 7.
But if you're discussing 7 World Trade's failure modes, then, you need to state it, and not confuse matters by citing events associated with the main towers. Truss 2 in 7 World Trade did indeed fail at their column-truss connections, but if I recall correctly, it was a
core column connection, not a perimeter one. Most of the column failure modes noted to have been significant in 7 World Trade's collapse were buckling.
In sum,
you tell
me which building you're referring to. Regardless, if you're talking about the main towers, the act of the floor trusses being forcibly sheared from their seats could on it's own be enough to at least buckle columns, if not shear them from each other. Being hit eccentrically by falling debris is something else that can cause them to come apart at their connection points. But even if somehow the seats failed and the trusses sheared away without pulling the columns off axis (an impossible situation, as far as I can tell), and no debris impacted the columns off axis (a ridiculous proposition), the columns could indeed not stand on their own, not for any reasonable vertical height at least. The few columns standing at the end of the collapse proves this; you see most of them slowly collapse while the dust is settling, and only a very small number remained upright. And they weren't all that tall, not relative to the height of the building.
Note, too, in the image you linked that the vertical box column is indeed laying nearly on it's side, which validates my argument that the columns could not stand on their own.
Even if the beams could be smashed away from the columns, the columns might topple over eventually, but I've yet to see a plausible reason for them to completely fall apart as the collapse is progressing.
You have no basis for this belief. The whole design of the towers is a testament to the fact that the columns could not stand on their own. Once again, they provided vertical support
only; it took the entire structure, core and perimeter columns laterally supported by the floors, to stand. Leave out the lateral supports, they can not stand. How are they supposed to? Compare how slender they are relative to the building's height. That by itself, without all the other information available, should tell you why they couldn't.
One thing we all have in common here is we know the buildings were demolished. Some of us want to expose it, others want to cover it up.
Assertions are not proof. The evidence that exists rules out intentional demolitions.
Working out the energy totals in the whole system is an excellent way to avoid doing a meaningful analysis. Without a plausible mechanism to transfer the energy of the falling rubble onto the load-bearing structure below, there's no global collapse.
Without a plausible mechanism to transfer the energy of the falling rubble onto the load bearing structure below? One exists. It's called "impact". Duh. Rubble impacts floors; trusses shear off from seats, collapse continues. Perimeter and core columns are no longer tied to each other, floors are falling. What keeps the columns standing at that point? Especially in the light of the forces severing the floors
and the debris hitting the columns off their vertical axis?
Each lower core beam had to be hit by something from above to shear at least one of its connections with the columns. If the upper floor beams lifted off the seats easily, they could only hit the beams below with their own energy, not the combined energy of the whole upper block.
What in God's name are you referring to here? If you're talking the Main Towers, the beams
were the columns. All the vertical elements were columns; all the horizontal elements were floor trusses and assemblies. And rubble
did impact those floors and severed them from the columns, the force of which could have easily caused the vertical columns to separate from each other at their connection points. Furthermore, you're serving word salad again: Most of the energy was spent against the floor truss to column connections; you don't need to defeat the strength of the columns to cause the main towers to collapse; all you need to do is slam out the elements tying the core and perimeter columns together. There was more than enough mass to do that had it landed on the floors gently, let alone at the accelerating rate it was falling at.
If you're talking about tower 7, you're miles away from the collapse progression in your description. The loss of column 79 set into action a series of floor failures which removed lateral support for interior columns, which then buckled and caused exterior columns to fail. Debris impacting was only part of the story, and only in the case of trusses 1 and 2 were significant in causing truss-column connection failure. So once again: You tell me which building you're referring to. Your generic, superficial description suggests the main towers, but you're the one being neither specific nor clear.
And: The "upper beams" lifted off their seats easily? That describes
none of the collapses. In the main towers, the trusses were torn from their column seatings, which is expected when such an overload occurs; they're not expected to handle 10+ stories of weight, that wasn't the column-to-truss seat's job, that was the duty of the columns themselves. If you're talking WTC 7... well, for the umpteenth, your description does not apply to it. The initial failure there was a column failure causing sympathetic floor failures (they descended) causing column buckling.
Imagine WTC7 was brought down by a two-stage controlled demolition where one column is taken out first, then 7 seconds later, the remaining 80 columns are removed. The interior columns are removed slightly before the perimeter ones, so that the sides will fold inward to minimize damage to neighbouring buildings. In what way would the collapse mechanism of such a controlled demolition be visibly different from what we see in the videos from 9/11. I'm talking about the sequence and rate of column failures, not periphery characteristics, such as flashes and expulsions.
In that imaginary scenario, I imaging that it would indeed "look" somewhat similar. So what? What's that supposed to prove? Superficial similarities in appearance do not narrow down the possibilities to explosives only, and on top of that, such a scenario would certainly not
sound similar. Furthermore, in the case of explosives demolitions, you wouldn't be lacking characteristic blast effects on neighboring buildings, nor barotraumatic effects on rescuers and victims nearby.
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Look, you need to step back and actually study the collapses. Ignoring your need to inject explosives into the discussion, you are most definitely not discussing the failure modes that occurred in any of the collapses. You do not properly describe the structural elements of either the main towers or WTC 7, nor do you properly recite the series of failures that occurred in either case. You do not even have the level of knowledge regarding the collapses that RedIbis or Christophera had, and your arguments suffer because of it.
Study what happened. Study the failure modes. You're way behind in your level of knowledge, and your continued desire to insist on explosives use does not rescue your argument, not when you don't even describe non-controversial aspects of the collapse properly. Study first,
then come back here and make your arguments.
