First Point of Substantive Discussion.
5 and 6 "Would the Same apply if collapse started at floors 106-108"
So, your answer is yes... no matter where collapse initiated that it would progress through.
Whilst for WTC1 with ~10 less floors above the cascade failure level - far less tilt - far less weight.
Yes, because the collapse started more central in the building, which raises a problem. The segment that breaks off from the structure is no longer acting to "pull" in the rest of the structure. In other words, the load on the outer walls had less load on them at that point and so this requires an explanation. (You see the columns cut more clearly from other angles, allowing the top block to fall as it did)
Second Point of Substantive Discussion.
7 "columns from the ground to act as a spear"
Well spotted. That aspect - broadened slightly - is the key to understanding how the "initiation" became "progression". And it is a central aspect of the next set of points you raise.
Recall that I have adversely commented on the lack of understanding of cascade failure - put bluntly it is an area that debunkers routinely get wrong. Mainly because they rely on simplified one-dimensional modelling which came from a paper by Bazant and Zhou two days after the event. I wont complicate the discussion at this point.
You literally answered this like a politician. .. a lot of words and no substance.
So, the columns that are untouched act like Spears punching through the floors, losing some height perhaps as the 30 or 40 floors drops around them.
So, if we say that each spear broke through 1 floor at the cost of 1 floor of its length, that leaves the core columns standing 40-50 floors.
The two starting premise issues we need to discuss are:
a) "Tilt v Topple" where the issue is not one of pedantry; AND
b) The related issue of why "Tilt" stopped and "Fall" won the race against "Topple" and "Tilt".
(Recall my disclaimer about "outline" explanations. The following is an outline - details later if needed.)
(p) "Tilt" occurred in both towers because more columns failed on one side - less failed on the other side. The side where more columns failed earlier dropped causing the observed tilt.
(q) If that tilting had continued it could have resulted in "topple' i.e. the top block falling over the side and falling outside the footprint of the lower tower.
(r) It did not lead to topple. The Top Block did not fall outside the lower tower perimeter. Portion did. Most did not. And that aspect will be the second part of this three parts(??) of explanation.
(s) BECAUSE the impact and fire damaged zone was undergoing a cascade failure in which more and more columns failed UNTIL there were too few left to hold up the Top Block
(t) At the point in time when the Top Block started to fall it immediately failed any remaining columns which were "trying valiantly" to hold up the top.
Pause there to consider that the tilting<>toppling needed some columns holding up the top block and acting as a pivot for the tilt/topple. No holding up pivot - no tilt/topple. So:
At the time that the point of maximum tilt which was more for WTC2 than for WTC1 (22[SUP]o[/SUP] for WTC2 IIRC) all support was removed AND - no more tilt - no possibility of topple.
That's because with the wtc1 especially, the damage was a lot more central. So, the collapse would tend towards the missing "cone" of damage.
Also, look closely at the movement of that top block as it tilts. It tilts and a section does topple, you said 20%. Let's go with that. The face that toppled enters the could as 1 piece, and exits the cloud as demolished pieces.
It's falling as 1 piece, then comes out of the dust a 1-3 seconds later as completely broken apart
There may have been a little bit of horizontal or rotational velocity - very small.
Right, and with the mass the size of the top block does not require much velocity to gain a lot of momentum, you know that when you add a downward speed vector to a horizontal vector. That horizontal element of speed does not vanish.
That said,
BUT rapid downwards falling resulted.
And - my estimated 80% falling inside the lower perimeter. 20% falling outside.
Let's accept that as true, at the 80% point, I could see how you could argue that the outside wall cut the groove through which they would separate. (Even if I lack the words to describe the effect in a technical manner).
That explains that damage, now that face and the 20 % of the structure that toppled outward, how do you explain the damage after that? There is allegedly no further forces acting on it aside from gravity.
And - this is where your point about "spear(s) comes into play. Because the portion of the Top Block which was overhanging the lower tower perimeter would fall onto the "spears" of the lower tower. I prefer to refer to it as "knife edge" rather than "spears" or "spear" as you did but leave it there for now.
We can go further into those aspects later - I've already outlined the explanation of what actually happened on another thread.
I see you agree with me here... Although that leaves 20% on the other side that only gets hit with very little... That means a stronger collision on each floor and increasing with each floor, yet the floors dropped at a consistent rate.
