Self-correcting tilt explained?

[leftysergeant]

In watching some of the videos of the collapse of the south tower over the last few days, it seems to me that, at the moment of collapse, the north face of the top part seems to move slightly to the north.

This has led me to speculate that, when the core columns failed they did so in a way that led the top columns to slip off the core to the north. This would, of course, cause the upper part to lean to the south. The remaining columns below the collapse would then serve as a stop to keep it from toppling off to the side. I am visualizing the north side to have more floors in tact at the instant of failure to maintain a center of gravity somewhat to the north, at least at the point where upper and lower parts are inter-acting.

Not being an engineer, I have a little trouble modelling this, but thought that some of the engineers here might understand what I am trying to relate.

It could be that I am just seeing some confusing visual effect from the camera angle or the puffs of smoke that squeezed out of the north face at the time of initiation. I have to admit that my eyes are not as sharp as they were forty years ago.

Am I on a track that I should explore a little further here?

 

[rcronk]

100% pulverized dust can't have a "tilt" to it. Just kidding.

I had heard that the vertical resistance of the outer wall (rather than, or in addition to, the core) would keep debris within the outer walls, but I'm not a structural engineer, etc. so that's really just hearsay since I heard it and didn't link to it.

Are there any current (non-truther) theories about this tilt correction? If so, what are they. If not, why not? Is it relevant to any theory? How?

 

[Architect]

Sounds like one for Newton's Bit, to be honest. And RMcK.

 

[jaydeehess]

Does anyone have a link to the video that leftysargeant is watching or to another of the south tower that shows the tilt to correct itself?

I understood that the tilt stops. However does the upper section actually then straighten up?

The tilt never had the upper section moving the center of mass of that section past the perimeter of the lower section. Thus when the 'hinge' on the far side gives way the upper section falls and when it does the angular momentum now would be causing it to rotate about that center of mass and NOT as it was, at the hinge. The movement of the upper section would have the center of mass moving straight down while rotating slowly about the center of mass. At least if that was all there was to it. In reality of course the upper section was impacting the lower section accross the entire lower section. IF the center of mass had moved far enough AND the impact was hard enough then the upper section could have broken at about the place where it extended past the perimeter. In fact a large block can be seen in some videos falling ahead of the dust. This could be part of the upper block of floors that sheared away from the rest shortly after it sank into the dust cloud of the collapsing building.

LS, you are saying that when the 'hinge' failed that the upper block's core columns slid down the north side of the lower block's core columns and brought the upper block core more in line with, but slightly to the north of, the lower block. That could be possible and would result in tearing the south side trusses away from the core while allowing the north side trusses to stay connected until their associated floor pans hit lower floors.

Like you I am not an engineer. I can envision what may have occured but cannot describe it well.

 

[leftysergeant]

I must learn how to do a screen capture on videos. The clearest image of what I am picking up here is to be found in Gravy's video debunking CD.

At about 33:40, I paused the video to examione the collapse of the south tower just after initiation. Running a straight edge along the corners of the standing and moving portions on both sides, I find that the corner of the toppling portion on the right of the screen seems to somewhat over-lap the lower margin of the collapse zone to the outside. The left side shows that the corner of the top part is settling into the interior of the building. This suggests to me that the core columns from the top, when they separated from the lower columns, slid off to the right, so that the standing core became a fulcrum on which it righted itself, and kept the center of gravity from shifting any more to the left.

Again, I am not sure how to model this in an engineer's terms, or whether, ul;timately, it is of great use or significance in explaining why the whole affair did not just fall into the street, sparing the rest of the building, as the twoofers seem to think it should have.

Or maybe someone has done this to death already and it just went over my head, if I read it at all.