[W:57: 1585]Evidence that 9/11 was an inside job.

[gerrycan]

Oh boy...

Below is my quote where I asked you if the main double trusses in the red circles have also been referred to as "tranverse trusses" because of the "perspective view". To which you replied "Yeah." in the following quote. I put the "Yeah." in nice, big, red letters so you couldn't miss it.

"Trusses that get called transverse because they are running at 90 degrees to the perspective of the panel they are on, or 90 degrees from the perspective being discussed."

I even said it right there in the bit you quoted. :lamo

 

[SanderO]

I can't tell where Gerry is going with his detailed analysis. The building movements are all the result of elements: slabs, trusses, columns, braces, connections and either failing or seeing loads exceeding their capacity. When buildings burn structural elements fail, collapse and push or pull remaining parts of the structure when they do.

It may be possible to model the sequence of failures beginning with the damage from the plane strike. Or maybe it's a waste of time.

NIST dropped the ball when global collapse occurred and that was some they could have and should have explained. Others went on to do that and identified it as runaway open office structure destruction - ROOSD. There was a paper predicting this in multi story column free long span floor systems... hull and core.

NIST however modeled an initiation driven by sagging floor trusses which they claimed pulled the facade in, causing it to misalign and buckle.

However the initiation may have been driven by failures inside the core, causing warping / distortion/ misalignment and buckling. As the core supported both the antenna and the interior side of the OOS floor slabs... the core failure more than likely explain the collapse of the antenna and the pulling, pushing and misalignment of the facade panels.

However we can only model and speculate on the PROGRESSION which led to the top dropping and ROOSD beginning which led to the total collapse.

I suppose devices could produce the same failures that heat did. Why hasn't anyone shown how and where these device were? How this was engineered? Why the two towers collapse initiations were different? How were these devices placed? And what were they?

 

[mike2810]

I can't tell where Gerry is going with his detailed analysis. The building movements are all the result of elements: slabs, trusses, columns, braces, connections and either failing or seeing loads exceeding their capacity. When buildings burn structural elements fail, collapse and push or pull remaining parts of the structure when they do.

It may be possible to model the sequence of failures beginning with the damage from the plane strike. Or maybe it's a waste of time.

NIST dropped the ball when global collapse occurred and that was some they could have and should have explained. Others went on to do that and identified it as runaway open office structure destruction - ROOSD. There was a paper predicting this in multi story column free long span floor systems... hull and core.

NIST however modeled an initiation driven by sagging floor trusses which they claimed pulled the facade in, causing it to misalign and buckle.

However the initiation may have been driven by failures inside the core, causing warping / distortion/ misalignment and buckling. As the core supported both the antenna and the interior side of the OOS floor slabs... the core failure more than likely explain the collapse of the antenna and the pulling, pushing and misalignment of the facade panels.

However we can only model and speculate on the PROGRESSION which led to the top dropping and ROOSD beginning which led to the total collapse.

I suppose devices could produce the same failures that heat did. Why hasn't anyone shown how and where these device were? How this was engineered? Why the two towers collapse initiations were different? How were these devices placed? And what were they?

I don't know either where gerrycan is going with his posts. The problem I see is no one knows for sure what the exact damage was done by the aircraft impact and resulting fires. We know where the aircraft hit the building. Simulations can estimate what happened. The simulation is not 100% correct. Much like fire simulations. Based on known factors the models simulate the building fire. It is still an estimate.

AE911T may some day come up with a CD simulation that represents the collapse as close to what really happened. So what? We know CD can take a building down. They would have to show evidence of explosives, prep work, explain how the CD was not disturbed by the crash and fires, etc.

 

[gerrycan]

I suppose devices could produce the same failures that heat did. Why hasn't anyone shown how and where these device were? How this was engineered? Why the two towers collapse initiations were different? How were these devices placed? And what were they?

So you think the long span floor beams in the 2 way SW corner sagged and pulled perimeters in up to C357 ?

Personally, considering that the SW corner is the same panel layout as the NE corner we just looked at in great detail, I would have to say that the transfer truss is less stiff than the perimeters and would surely fail way before any perimeters got pulled in.

Still, it's undeniable that they did pull in somehow. Wasn't sagging floor trusses though. They can't do it.

 

[SanderO]

So you think the long span floor beams in the 2 way SW corner sagged and pulled perimeters in up to C357 ?

Personally, considering that the SW corner is the same panel layout as the NE corner we just looked at in great detail, I would have to say that the transfer truss is less stiff than the perimeters and would surely fail way before any perimeters got pulled in.

Still, it's undeniable that they did pull in somehow. Wasn't sagging floor trusses though. They can't do it.

I am not an engineer. But it seems to me that sagging is not the cause the the movement of the facade... in or out. More likely it seems to be would be the slab... acting like a stiff plate pushed or pulled the facade (and could be either at different levels). These plates would move depending on what the core side was "doing".

NIST seems to look to the fires outside the core as drivers... I would suggest it was fire largely inside the core which drove the movements

 

[gerrycan]

I am not an engineer. But it seems to me that sagging is not the cause the the movement of the facade... in or out. More likely it seems to be would be the slab... acting like a stiff plate pushed or pulled the facade (and could be either at different levels). These plates would move depending on what the core side was "doing".

NIST seems to look to the fires outside the core as drivers... I would suggest it was fire largely inside the core which drove the movements

Agreed. There's no way those trusses could possibly pull in the perimeter columns at the SW corner of the building, opposite to the impact face. They would simply push off the transfer truss and that area is less stiff as we learned from the NE corner. I cannot see how these get pulled in without the core corner failing.

Given that this happens a good few minutes before the collapse, it could be that the corner around the core 1001 dropping was what pulled them in.

 

[gerrycan]

I can't tell where Gerry is going with his detailed analysis.

We've defined the elements and layout at the NE corner of the N face and established that the long span trusses and bridging area is more stiff than the short span one way zone it frames into.

The initial movement in the building was at the diagonally opposite corner at the SW a good few minutes before the building failed, when the perimeter columns were pulled in about to column 357 near the SW corner.

The perimeter columns opposite the transfer truss at the SW 2 way corner are stiffer than the transfer truss that supports the long span trusses at the core end and the trusses are transverse in that area. The long spans don't have enough purchase on the perimeters to pull them in by way of sagging, and would fail the transfer truss way before they pulled on the perimeter anyhow.

 

[mike2810]

The problem with gerrycan's analysis is looking at small section at a time and not accounting for the other forces in the building that were at play.

 

[gerrycan]

The problem with gerrycan's analysis is looking at small section at a time and not accounting for the other forces in the building that were at play.

The section I am talking about is identical to the area we looked at already and covers around 11 floors. The difference in stiffness is consistent in the building from floor 9 to 107 with the exception of the MER levels.

 

[SanderO]

something was going on at the SE corner area... I forgot but was it large fires?

Look at this site for a good database of visuals

World Trade Center Evidence-Based Research

 

[gerrycan]

something was going on at the SE corner area... I forgot but was it large fires?

Look at this site for a good database of visuals

World Trade Center Evidence-Based Research

The pulled in perimeters area at the South face are circled in blue.


The question remains, what pulled them in. I say most probably core failure around the 1001 corner somewhere. The trusses simply can't do it and I cannot think of another scenario that would result in what was observed.

 

[mike2810]

something was going on at the SE corner area... I forgot but was it large fires?

Look at this site for a good database of visuals

World Trade Center Evidence-Based Research

This site has been brought to gerrycan attention in other threads. Seems the site present a good analysis of building movement.

It is my opinion we will never be able to figure out what joint, bolt, weld , etc failed first. Nor will we be able to tell 100% what happened next.
There are way to many variables in play.

 

[ozeco41]

...It is my opinion we will never be able to figure out what joint, bolt, weld , etc failed first. Nor will we be able to tell 100% what happened next.
There are way to many variables in play.

That is spot on target and reveals one of the most serious barriers to reasoned debate of the complexities of Twin Towers collapse initiation. (And alternatively it is a most fruitful area for debating trickery sending discussion round in circles to be sure it goes nowhere. I doubt that most truthers who employ it OR those debunkers who fall for the trap even realise what the process problem is. and that is self fulfilling prophescy because most of them are "left brainers" )

The issue is a failure of discussion process because most technical debaters are "details focussed" - a "left brained" focus if I borrow a metaphor. It is an endemic risk with engineers. They NEED all the details and their thinking halts or locks up when details are not and cannot ever be known.

Examples if anyone wants them but I'll just leave the issue on the table supporting your comment Mike2810.

 

[gerrycan]

That is spot on target and reveals one of the most serious barriers to reasoned debate of the complexities of Twin Towers collapse initiation. (And alternatively it is a most fruitful area for debating trickery sending discussion round in circles to be sure it goes nowhere. I doubt that most truthers who employ it OR those debunkers who fall for the trap even realise what the process problem is. and that is self fulfilling prophescy because most of them are "left brainers" )

The issue is a failure of discussion process because most technical debaters are "details focussed" - a "left brained" focus if I borrow a metaphor. It is an endemic risk with engineers. They NEED all the details and their thinking halts or locks up when details are not and cannot ever be known.

Examples if anyone wants them but I'll just leave the issue on the table supporting your comment Mike2810.

No. The issue right now is that the trusses at the SW corner don't have enough purchase on the perimeter columns to pull them in because the transfer truss they frame into is less stiff.

Sure, we could now find every element, nut, bolt and connection but nobody is suggesting that level of detail at the minute. The areas of the building concerned are being discussed in broad terms and the question of the bowing perimeters has been asked with the general detail of the elements provided.

 

[ozeco41]

The question remains, what pulled them in.

Well it is a question. I'm not sure it "remains" since explanations have been available for years.

The trusses simply can't do it and I cannot think of another scenario that would result in what was observed.

The trusses can't do WHAT? All they needed to do was initiate inward bowing until until the critical p-delta point is passed and the column continues to buckle under the existing applied "axial" load. The commonest error in past years was to check the available distance of centenary sag to see if the floor joist could pull the perimeter in by the full amount of observed buck. It probably wasn't enough length but the starting assumption was wrong. Then the separate question about "were the joists and their attachments to the perimeter strong enough to pull the perimeter into the inwards bowing?" But that point is moot given that your suggested mechanism relies on being strong enough:

I say most probably core failure around the 1001 corner somewhere.

...which would rely on the joists imposing the pull n force on the perimeter. And subject to the same "two stage" issue of initial pull in THEN self buckling under the applied vertical load.

 

[gerrycan]

The trusses can't do WHAT? All they needed to do was initiate inward bowing until until the critical p-delta point is passed and the column continues to buckle under the existing applied "axial" load.

And all I have to do is run at 100mph to get to work in 5 minutes. Doesn't mean I can do it.
The tell with my running would be my inability to demonstrate that I had that ability, but then again, I'm not claiming I can do something that I can't.

Show. Don't tell.

 

[ozeco41]

No. The issue right now is that the trusses at the SW corner don't have enough purchase on the perimeter columns to pull them in because the transfer truss they frame into is less stiff.

Sure, we could now find every element, nut, bolt and connection but nobody is suggesting that level of detail at the minute. The areas of the building concerned are being discussed in broad terms and the question of the bowing perimeters has been asked with the general detail of the elements provided.

Which doesn't address the point Mike2810 made nor my comment in support of him. In fact it confirms what I actually said.

 

[ozeco41]

And all I have to do is run at 100mph to get to work in 5 minutes. Doesn't mean I can do it.
The tell with my running would be my inability to demonstrate that I had that ability, but then again, I'm not claiming I can do something that I can't.

Show. Don't tell.

Evasion noted.

 

[gerrycan]

Which doesn't address the point Mike2810 made not my comment in support of him. In fact it confirms what I actually said.

The issue is detail surely. The level of detail Mike's on about hasn't been discussed. Isn't being discussed. And probably wouldn't be discussed here anyhow.

 

[gerrycan]

Evasion noted.

I am asking you to demonstrate to me how the perimeters could be pulled in by the sagging trusses as you and NIST claim. You said it had been demonstrated many times. Point me to it. Somewhere with the numbers preferably.

ADD no NIST please. I'm sure we both realise that they added a 5kip force to the perimeter to get it to sag.

 

[SanderO]

A few points. Please read some of the non technical discussions and musings on the World Trade Center Evidence-Based Research

especially these On the Limits of Science and Technology where the entire problem of nailing the exact details of the events is revealed.

Gerry is making assumptions about a corner moving in... and this in itself means the slab pulls in both axes. Sounds to me more like the entire corner slab may be translating being well anchored to the core side. Maybe. Truss failure I believe has been "ruled out".

++++

The system is very complex, damaged severely by the plane hitting the tower... and the elements and forces are simply impossible to resolve to the detail level. It's a fool's errand. What seems to make more sense to to define gross processes which are observable... such as ROOSD or the Euler buckling of the "spire" and remaining core columns... or the antenna drop.... the tile of the top of tower 2 and so on.

The collapse occurred because axial load paths failed... the floor slabs collapsed (ROOSD) because they saw capacity exceeding their design parameters... and this was a runaway process where failing debris and or failed connections to columns enabled massive areas of floor slabs and contents to collapse. The top of the towers contained very large superimposed dead loads and fires broke out and there were explosions immediately after the plane hit. Collapse of parts of the top mech floors could have been another factor.

We witnessed two identical designs (except for the mech floor 7 and the antenna) collapse in a similar manner. The difference in form seems to be attributable to the difference in where the planes struct the towers. This in itself strongly suggests that the plane strikes were the start... and that fires were the undoing. The structural design OOS led to ROOSD.

++++

Unless and until a comprehensive CD scenario is set forth which produces the visuals we observed... the collapses were a complex set of failures from mechanical damage plane and fire caused.... and the EXACT sequence with details remains unimportant... and even unattainable.

I found the ROOSD explanation more than sufficient to explain the collapse part below the plane strike zones... and Euler buckling to explain the demise of the columns which survived ROOSD. NIST was silent on this I believe and simply called it global collapse. A true cop out and a PR error.

 

[SanderO]

Gerry... why don't you suggest all the possible mechanisms which could explain movements of the facade?

If the inward bowing (or outward) observed is local... does this suggest buckling? If buckling why? Newly acquired redistributed loads? heat weakened columns? Lost of lateral bracing? All of the above? How did the loads get to those columns?

Were the columns of the 2 way area as strong as those of the one way areas? (I don't know)... were the face columns on the short span side weaker than those on the long span side? Were the columns bearing the transfer trusses stronger than others? Were all facade panels of equal axial capacity? What were the axial loads on the corner panels compared to the adjacent panels?

 

[gerrycan]

NIST was silent on this I believe and simply called it global collapse. A true cop out and a PR error.

Just on this point for now. It wasn't a PR error. It was, and still is a chance to improve the safety of tall buildings and enhance public safety. NIST abandoned their charter by walking away from their incomplete report having done nothing more than hand waved through a few code amendments.

"global collapse ensued" just doesn't cut it. We agree on that 100%.

 

[gerrycan]

Gerry... why don't you suggest all the possible mechanisms which could explain movements of the facade?

If the inward bowing (or outward) observed is local... does this suggest buckling? If buckling why? Newly acquired redistributed loads? heat weakened columns? Lost of lateral bracing? All of the above? How did the loads get to those columns?

Were the columns of the 2 way area as strong as those of the one way areas? (I don't know)... were the face columns on the short span side weaker than those on the long span side? Were the columns bearing the transfer trusses stronger than others? Were all facade panels of equal axial capacity? What were the axial loads on the corner panels compared to the adjacent panels?

That's a lot of questions Sander. Without scrolling back, you typed something the other day about the slab moving and I meant to remind you that there were construction joints in the floor. Always in the one way zone to minimise shear.

While I still don't see how fire could accomplish this building failure, there is potential for the joints in the floor system to be subjected to excessive shear should the building start to move in and around the core. I don't see an alternative yet to the SW corner core dropping and pulling on the perimeter that way. Now that is the kind of failure that could potentially overstress the floor joints on many levels.

I know they were along the centrelines on the 107th storey, but I haven't checked for their presence/location elsewhere yet, but I imagine there will be at least 2 in each slab. I can't recall anyone ever accounting for these in any analysis. Have you ?

 

[SanderO]

That's a lot of questions Sander. Without scrolling back, you typed something the other day about the slab moving and I meant to remind you that there were construction joints in the floor. Always in the one way zone to minimise shear.

While I still don't see how fire could accomplish this building failure, there is potential for the joints in the floor system to be subjected to excessive shear should the building start to move in and around the core. I don't see an alternative yet to the SW corner core dropping and pulling on the perimeter that way. Now that is the kind of failure that could potentially overstress the floor joints on many levels.

I know they were along the centrelines on the 107th storey, but I haven't checked for their presence/location elsewhere yet, but I imagine there will be at least 2 in each slab. I can't recall anyone ever accounting for these in any analysis. Have you ?

No...

I think the facade movements were buckling related... caused from loss of bracing and load redistribution. I doubt the slabs pulled... but if they did anything it would be a local push.. possibly driven by core column displacement or buckling.

I believe the slabs role in the collapse was almost exclusively in the ROOSD phase.

++++

If central core columns became non performing... whatever loads they were conveying down to the foundation had to be taken by other columns... The columns above the failed ones would obviously be hanging from the hat truss. And it may have be the path to redistribute loads to the perimeter core columns... leading to these columns being over loaded and buckling.

Loads have to go somewhere when axial load paths are interrupted or destroyed. We know... can see multiple facade and core columns were severed. It's not as if those columns were unneeded. And the FOS may simply not have been adequate in ALL cases to maintain stability.

Columns and axial load paths destroyed means whatever FOS was there before... was knocked down.