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WTC 2 Progressive Tilt

femr2

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Apr 21, 2009
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Simple request...

Does anyone have any visual evidence of progressive tilt of the upper block of WTC 2 during the 20 minutes prior to initiation ?

I've looked in detail at countless photographs, and have not been able to detect progressive tilt at all.

Ideally I'd like to be able to locate two images from a very similar viewpoint which show an increase in tilt angle.

Very small angular changes can be detected if the images are analysed correctly, but of course the higher the resolution of the images, the better.

I'm not asking for opinion at all, but simply photographic resources which confirm such a behaviour.
 
femr2 said:
Simple request...

Does anyone have any visual evidence of progressive tilt of the upper block of WTC 2 during the 20 minutes prior to initiation ?

I've looked in detail at countless photographs, and have not been able to detect progressive tilt at all.

Ideally I'd like to be able to locate two images from a very similar viewpoint which show an increase in tilt angle.

Very small angular changes can be detected if the images are analysed correctly, but of course the higher the resolution of the images, the better.

I'm not asking for opinion at all, but simply photographic resources which confirm such a behaviour.
Click to expand...

How do you know such "tilt" occurred (source), and how much tilt is there supposed to be? So we know what to look for...

(I am offering an opinion though you didn't ask for one: I don't think any tilt could have been visible without collapse immediately commencing)
 
Oystein said:
How do you know such "tilt" occurred (source), and how much tilt is there supposed to be? So we know what to look for...

(I am offering an opinion though you didn't ask for one: I don't think any tilt could have been visible without collapse immediately commencing)
Click to expand...

I confess, I don't remember what the timeline was for individual events in the collapse progression itself. I, too, recalled the tilt being an artifact of the initiating failure. But I may not be recalling that accurately; I'll have to defer to those folks here better versed in that info than I am.

NCSTAR 1-6 made mention of the tilt. I'll go through it again when I get the time, but now's not a good time for me to do that.
 
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Oystein said:
How do you know such "tilt" occurred (source), and how much tilt is there supposed to be? So we know what to look for...

(I am offering an opinion though you didn't ask for one: I don't think any tilt could have been visible without collapse immediately commencing)
Click to expand...

Progressive tilt is one of the factors suggested to confirm CC creep, so I'm trying to find it.

The scale of tilt will be slight, as if present a tilt of around 2 degrees would result in CC failure, and collapse would then ensue.

The higher the image resolution, the smaller any detectable angular change can be.
 
femr2 said:
Progressive tilt is one of the factors suggested to confirm CC creep, so I'm trying to find it.

The scale of tilt will be slight, as if present a tilt of around 2 degrees would result in CC failure, and collapse would then ensue.

The higher the image resolution, the smaller any detectable angular change can be.
Click to expand...

Suggested by whom? Where?
What is CC?
 
ElMondoHummus said:
I confess, I don't remember what the timeline was for individual events in the collapse progression itself. I, too, recalled the tilt being an artifact of the initiating failure.
Click to expand...
Thanks. Progressive tilt was loosely associated with inward bowing, which puts the timescale roughly during the 20 minutes prior to initiation.

Even some high resolution photographs which can be confirmed as being within the right period of time would be useful, if they are from the right *side* of the tower, as I can then do the extra leg-work myself.

I've found nowt in any of the image sets I've looked at so far.
 
femr2 said:
Thanks. Progressive tilt was loosely associated with inward bowing, which puts the timescale roughly during the 20 minutes prior to initiation.

Even some high resolution photographs which can be confirmed as being within the right period of time would be useful, if they are from the right *side* of the tower, as I can then do the extra leg-work myself.

I've found nowt in any of the image sets I've looked at so far.
Click to expand...

How do you know the search is worth the effort?
How did this idea get into your head?
 
Iirc there is something written about the leaning of WT2 in "102 minutes", but I'm at work right now, so can't look it up. If still relevant by then, I'll look it up tonight.
 
femr2 said:
The scale of tilt will be slight, as if present a tilt of around 2 degrees would result in CC failure, and collapse would then ensue.
Click to expand...

As much as 2 degrees? That's more than a two metre drop of one side relative to the other; I'd have thought perimeter column failure would occur well before that. Are you sure you've got your orders of magnitude right?

Dave

ETA: Missed your last post re definition of CC, but still I don't see how the structure could deform this much without severing half the perimeter which would most likely initiate collapse on its own.
 
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Dave Rogers said:
As much as 2 degrees? That's more than a two metre drop of one side relative to the other; I'd have thought perimeter column failure would occur well before that. Are you sure you've got your orders of magnitude right?

Dave

ETA: Missed your last post re definition of CC, but still I don't see how the structure could deform this much without severing half the perimeter which would most likely initiate collapse on its own.
Click to expand...

2 degrees is a max I think. Would need to dig out the sources, but pretty sure it was based on the transition point for a buckle to occur.

I accept that it could be less.

May well be that the scale is undetectable in all available imagery, but if I can find it, I will. If photos are good enough, very small angular changes can be detected (even sub-pixel) which could well be down to 10ths of degrees.

If I can find it in visual form, then it does strengthen the case for creep significantly.
 
Based on the perimeter column bowing that I've seen pictures of, I wouldn't think that that side of the building would have dropped more than three or four inches - a column would have to bow a lot to drop the height more than that. And two or three inches would just be about 0.07 degrees of tilt.
 
CurtC said:
Based on the perimeter column bowing that I've seen pictures of, I wouldn't think that that side of the building would have dropped more than three or four inches - a column would have to bow a lot to drop the height more than that. And two or three inches would just be about 0.07 degrees of tilt.
Click to expand...

NIST suggested ~12inches.
3% of a 36ft column is ~13inches.

What level of bow in a CC would you suggest with that level of drop ?
 
Alferd_Packer said:
aren't there some indications of tilt from just after the aircraft impact?
Click to expand...

I think you are referring to the building swaying heavily due to the impact. I think Frank Di Martini mentioned 20 feet regarding WTC1.
 
Measurement of progressive tilt prior to initiation is theoretical. NIST's models predict up to about ten inches of creep in the support columns before initiation of collapse. This translates into a fairly small angle.

There were spoken reports that the top appeared to be leaning well before collapse, just as there were for WTC 1, but I am not aware of any photography of high enough resolution to capture this clearly. Shortly before the collapse, of course, the tilt was so large that it was unmistakable.

Have to be careful here what we mean by "initiation."
 
R.Mackey said:
Measurement of progressive tilt prior to initiation is theoretical. NIST's models predict up to about ten inches of creep in the support columns before initiation of collapse. This translates into a fairly small angle.

There were spoken reports that the top appeared to be leaning well before collapse, just as there were for WTC 1, but I am not aware of any photography of high enough resolution to capture this clearly. Shortly before the collapse, of course, the tilt was so large that it was unmistakable.

Have to be careful here what we mean by "initiation."
Click to expand...

The best quality imagery you are aware of would be very handy. I doubt many/anyone has attempted to look at very small angular deformations. With decent imagery I'm confident in identifying 10th of a degree angles.

I suggest initiation in this context ranges from, what, 30s prior to the rapid tilt beginning ? It's clear from WTC 1 tracing that some tilt/movement preceeded estimated t0 initiation by a few seconds.

I'm looking really at the preceeding 20 minutes, during the period indicated for IB development.
 
R.Mackey said:
Have to be careful here what we mean by "initiation."
Click to expand...

Have to be careful, also, to define what we're measuring relative to what. Tilt doesn't measure absolute creep, it measures differential creep between the two sides of a structure. If the core experienced similar levels of creep across its entire structure, there wouldn't necessarily be a tilt at all. So, although the presence of tilt would be strong evidence for creep, its absence wouldn't be strong evidence against it.

Dave
 
Dave Rogers said:
Have to be careful, also, to define what we're measuring relative to what. Tilt doesn't measure absolute creep, it measures differential creep between the two sides of a structure. If the core experienced similar levels of creep across its entire structure, there wouldn't necessarily be a tilt at all. So, although the presence of tilt would be strong evidence for creep, its absence wouldn't be strong evidence against it.

Dave
Click to expand...

Sure, though the NIST model predicts uneven creep...
292834536.jpg


Best quality photographs available would be well handy so I can actually try and find it.

ETA: As far as I can tell, NIST used a 56 minute timing from impact to collapse. Might estimate the expected values closer to the 56 minute mark by using the earlier NIST model values and extrapolating. Image is at 43 minutes.
 
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