Just a quick collapse question

[MG1962]

The NIST report mentions that no pancaking happened.

Now just so I have this clear in my mind. They are talking about events up to the point of failure....Not the actual collapse itself. IE the fire weaken floors failed together, then the upper sections of the buildings just began falling

Am I reading that right?

[R.Mackey]

Correct. NIST does not describe what happens after the collapse initiation. What they say didn't happen is not "pancaking," but instead the "pancake hypothesis," i.e. the idea that the floors failed first, and the initial column buckling occurred only after loss of the floors and the lateral support they provided. NIST's hypothesis suggests -- indeed, requires -- the floors to be mostly intact until after the initial buckling occurs.

There is evidence in NIST, however, that supports buckling after collapse initiation. Read the description of recovered truss seats in NCSTAR1-3, their failure modes, and think about what this means for the floor connections.

[Algebra34]

The NIST report mentions that no pancaking happened.

Now just so I have this clear in my mind. They are talking about events up to the point of failure....Not the actual collapse itself. IE the fire weaken floors failed together, then the upper sections of the buildings just began falling

Am I reading that right?

I believe that they meant the initiation wasn't a pancake.

[MG1962]

Thanks guys, I'm a bit rusty at this debunking stuff. Have not done any since before Gravy retired. have found this forum... I swear it feel like 2006 all over again lol

[BasqueArch]

The NIST report mentions that no pancaking happened. Now just so I have this clear in my mind. They are talking about events up to the point of failure....Not the actual collapse itself. IE the fire weaken floors failed together, then the upper sections of the buildings just began falling.
Am I reading that right?

In sequence:

1) The heat-weakened concrete-topped floor trusses sagged.

2) They pulled in the heat weakened perimeter columns in some walls,3 to 4 feet.

3) The weakest wall perimeter columns buckled first (east wall of Tower 2, south wall of Tower 1).

4) The top block tilted toward the failed wall.

5) Due to the pivoting top block the remainder of the columns in that floor sheared (horizontal forces) or buckled (vertical forces) beginning at a tilt of 2.8 degrees from vertical. (Bazant)

6) Because of the pulled in perimeter columns and top block tilt, the fractured upper columns were offset at initial failure from the columns below.

7) Because of this offset, the columns above did not hit the columns below, they instead crushed the thin slabs below. Therefore "No Jolt" at impact. (The weight of all the floors above concentrated only on each column's footprint in one case was about 200,000 lbs static load, landing on a 14x14" floor footprint that could only support about 150 lbs static load)

8) The floor slabs then pancaked yes pancaked at the rate of 8-14 floors per second past the uncrushed perimeter and core columns.

9) The perimeter and core tall unsupported, non-crushed columns thereafter toppled to the ground.

10) The collapse of the upper part of Tower1 was 12.82 s. or 65.5% slower than freefall (7.74 s.). The collapse of the upper part of Tower2 was 10.49 s. or 47.3% slower than freefall (7.71 s.) according to the Lamond-Doherty seismic records. -Bazant.
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You can't reason someone out of something they weren't reasoned into. -Swift

[leftysergeant]

People shrieking about the absence of a stack of pancakes do not realise that the floors more resmembled waffles falling on a stack of randomly-selected desk chairs and other obsacles.

[dropzone]

I now want waffles, rather than an explaintion that the first floor, struck in quick succession by the floors above it, settled into a proper pancake of the floors below. I'm passing the bill to you, Lefty.

[Newtons Bit]

From the NIST FAQ:

NIST’s findings do not support the “pancake theory” of collapse, which is premised on a progressive failure of the floor systems in the WTC towers (the composite floor system—that connected the core columns and the perimeter columns—consisted of a grid of steel “trusses” integrated with a concrete slab; see diagram below). Instead, the NIST investigation showed conclusively that the failure of the inwardly bowed perimeter columns initiated collapse and that the occurrence of this inward bowing required the sagging floors to remain connected to the columns and pull the columns inwards. Thus, the floors did not fail progressively to cause a pancaking phenomenon.

There's a difference between the "pancake collapse" as illustration by FEMA and just general progressive collapse (commonly referred to as "pancaking").

[TruthersLie]

People shrieking about the absence of a stack of pancakes do not realise that the floors more resmembled waffles falling on a stack of randomly-selected desk chairs and other obsacles.

Hey lefty...

what they also miss is that there is evidence of pancaked floors..
we have interviews with iron workers at ground zero talking about 14 floors pancaked one on top of each other in an 8 foot section.

And that isn't counting the 4floors in the "meteorites."

Or the easily found images of pancaked floors at ground zero
http://www.stevespak.com/fires/manhattan/void.jpg

http://www.stevespak.com/fires/manhattan/wtc6.html
The best one is the one above the one I posted here. It shows multiple levels pancaked together.

[leftysergeant]

Judging from the apparent thickness of the slabs in the meteorite and the location of those you showed above, I would think that the majority of the pancakes formed at the lower levels after there was so much debris in all directions that the only way the floors could fall was straight down.

At higher levels, where the debris was less compacted, there would have been a more chaotic twisting and turning and a lot of stuff escaping over the side.

Simple fact of it is that when you drop one concrete slab on top of another, both tend to shatter to some degree. Thus, the broken floors would tend not to pile up in an orderly fashion. (I am assuming that the floors, like the columns, would have been increasingly light on the ascending floors, and that the trusses would thus comprise a greater portion of their bulk, and that they would, thus, be more easily twisted into non-stacking forms.0

[leftysergeant]

http://www.stevespak.com/fires/manhattan/void.jpg

http://www.stevespak.com/fires/manhattan/wtc6.html


Oh, yeah, about the concrete being all "pulverized"....

[Sam.I.Am]

I am assuming that the floors, like the columns, would have been increasingly light on the ascending floors, and that the trusses would thus comprise a greater portion of their bulk, and that they would, thus, be more easily twisted into non-stacking forms.

Why would you assume that? The columns were carrying 110 floors and columns at the lobby level and 1 floor at the 110th floor. Each office floor was carrying roughly the same load no matter where it was located in the building.