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Failure mode in WTC towers

beachnut said:
Gregory is an expert fence sitter who is listed under the Patriots Question for 9/11 truth. He signed a petition blaming US officials for the murders and of course he is a full blown truther with Scholars for 9/11 Truth & Justice a bunch of fence sitters who have nut case ideas on 9/11 and publish false information to blame others for 9/11. This alone is reason to know his word is independent and not biased on these issues. If you use judgment and knowledge you can use what Gregory says with a grain of salt.
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In the past week Gregory has pretty much gotten off the fence on the Twoofer side.
Other then that you are spot on.
 
Myriad said:
NIST:

With continuously increased bowing, as more columns buckled, the entire width of the south wall buckled inward. Instability started at the center of the south wall and rapidly progressed horizontally toward the sides. As a result of the buckling of the south wall, the south wall significantly unloaded (Fig 5-3), redistributing its load to the softened core through the hat truss and to the south side of the east and west walls through the spandrels. ... The section of the building above the impact zone tilted to the south (observed at about 8°, Table 5-2) as column instability progressed rapidly from the south wall to the adjacent east and west walls (see Fig. 5-8), resulting in increased gravity load on the core columns.
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Great, this is what I was asking for. Thank you.
 
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bofors said:
Great, this is what I was asking for. Thank you.
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No problem. Note that there's a separate chapter for collapse initiation of the South Tower, following the page I cited.

For what it's worth, I reasoned that the vertical progressive collapse had to be preceded by a horizontally progressive failure, before I read NIST's conclusions. (Though I was glad to have my conjecture confirmed by experts, NIST isn't my basis for arguing that point. That's also why I'm pretty sure that the upcoming report on WTC7 will also describe a horizontally progressing failure, a few seconds after the initiating events, within less than a second before the global collapse began. In that case, though, it seems there was a pause for dramatic effect, and I'm eager to hear NIST's theory or theories as to why.)

Also, I think NCSTAR could have done better at clarifying the important distinction between the two different kinds of "progressive" events. They were writing for a critical audience, but not a hostile one.

Respectfully,
Myriad
 
K A Seffen suggests a variation of Bazant that during gravity driven collapse the tower of height L and uniform density po consists of four parts:

A rigid upper block lambda L that is intact all the time during collapse.

An intermediate block beta L between the upper block and a 'crush front' that apparently consist of semi-broken parts (completely unclear to me).

A part that has disappeared with assumed height alfa L

A lower, intact part (1 - lambda - beta - alfa) L below the 'crush front'.

Lambda is apparently constant during the collapse.

What beta is, is completely incomprehensible to me but should be 0 just before impact at t = 0 and then be variable until the collapse is completed at t = t(end), thus beta is a function of time t.

Alfa is also a function of time t.

How the density po behaves between t = 0 and t = t(end) is also a mystery. It is evidently constant in the upper and lower parts, but what about density of the beta L part? If the density there is increased, it can explain what alfa is. (The disappeared part alfa is in fact compressed into part beta).

Thus the density increases in the beta L part according Seffen during collapse - a new phenomenon!

Photos of the WTC collapses show that material, dust and smoke are pushed outwards at high speed, which is not explained by Seffen.

Thus - during collapse according Seffen a rigid part lambda L floats on a mysterious part beta L (of broken, compressed material?) that in turn floats on the intact structure below a strange crush-front. It is quite magic actually and could only have been invented by a blind scientist in an ivory tower.
 
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Heiwa said:
K A Seffen suggests a variation of Bazant that during gravity driven collapse the tower of height L and uniform density po consists of four parts:

A rigid upper block lambda L that is intact all the time during collapse.

An intermediate block beta L between the upper block and a 'crush front' that apparently consist of semi-broken parts (completely unclear to me).

A part that has disappeared with assumed height alfa L

A lower, intact part (1 - lambda - beta - alfa) L below the 'crush front'.

Lambda is apparently constant during the collapse.

What beta is, is completely incomprehensible to me but should be 0 just before impact at t = 0 and then be variable until the collapse is completed at t = t(end), thus beta is a function of time t.

Alfa is also a function of time t.

How the density po behaves between t = 0 and t = t(end) is also a mystery. It is evidently constant in the upper and lower parts, but what about density of the beta L part? If the density there is increased, it can explain what alfa is. (The disappeared part alfa is in fact compressed into part beta).

Thus the density increases in the beta L part according Seffen during collapse - a new phenomenon!

Photos of the WTC collapses show that material, dust and smoke are pushed outwards at high speed, which is not explained by Seffen.

Thus - during collapse according Seffen a rigid part lambda L floats on a mysterious part beta L (of broken, compressed material?) that in turn floats on the intact structure below a strange crush-front. It is quite magic actually and could only have been invented by a blind scientist in an ivory tower.
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I'm not a fan of this per se, but it looks like another attempt at accounting for more variables in the collapse progression. Blind is really a bad term, lazy may be more accurate while retaining the same level of offensiveness you desire.

Mass shedding is complex to model. The actual mass falling outside the footprint is hard to determine. For the most part dust obscurs any photos that would help. Is it a constant? Is it a function of time? Is it a function of height or some combination therein? I've argued, unsuccessfully mind you, that the entire exterior did not contribute to the progression. Lateral forces appear to have ejected much of the exterior outside of the footprint in all directions. Good luck finding consensus on this in any camp, and that's the easy part.
 
Heiwa said:
K A Seffen suggests a variation of Bazant that during gravity driven collapse the tower of height L and uniform density po consists of four parts:
...
An intermediate block beta L between the upper block and a 'crush front' that apparently consist of semi-broken parts (completely unclear to me).
...
What beta is, is completely incomprehensible to me but should be 0 just before impact at t = 0 and then be variable until the collapse is completed at t = t(end), thus beta is a function of time t.
...
Thus the density increases in the beta L part according Seffen during collapse - a new phenomenon!
...
Thus - during collapse according Seffen a rigid part lambda L floats on a mysterious part beta L (of broken, compressed material?) that in turn floats on the intact structure below a strange crush-front. It is quite magic actually and could only have been invented by a blind scientist in an ivory tower.
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Yes, who would imagine that tens of thousands of tons of broken compressed material might still retain its mass, inertia, kinetic energy, and ability to exert destructive force on the structure below? We all know that broken concrete and steel and filing cabinets turn into fluffy weightless stuffed kitties that fly away over the rainbow to Neverland.

Just like we know that storm waves can't ever damage offshore platforms because no matter how big the waves are, they're nothing but soft cuddly water molecules that aren't even rigidly attached together and they just pass harmlessly around metal structures.

Respectfully,
Myriad
 
Myriad said:
Yes, who would imagine that tens of thousands of tons of broken compressed material might still retain its mass, inertia, kinetic energy, and ability to exert destructive force on the structure below? We all know that broken concrete and steel and filing cabinets turn into fluffy weightless stuffed kitties that fly away over the rainbow to Neverland.

Just like we know that storm waves can't ever damage offshore platforms because no matter how big the waves are, they're nothing but soft cuddly water molecules that aren't even rigidly attached together and they just pass harmlessly around metal structures.

Respectfully,
Myriad
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Water has density 1 ton/m3 and, according Arkimedes, my old teacher, the uniform density of the volume of a ship hull below waterline is also 1 ton/m3 = ship floats. But Arkimedes never used terms like uniform density that Seffen introduces. The ship hull below waterline is mostly air with very low density. Ships also float in liquid mercury, etc. It has nothing to do with uniform density.
Seffen uses uniform density to cover up the fact that the upper block of WTC1 is mostly air! Seffen uses uniform density to make the impression that the upper block is solid and rigid and can then impinge or impact on something that is not solid and rigid below that becomes a strange beta L part that nobody knows what it is. Thousands of broken pieces of steel/concrete? Except that the upper block lambda L floats like a a ballon on it! Arkimedes would laugh in his bath tub! Eureka!

The impetuous Seffen tries to impress the impious Nist scientists with his imponderable ideas comparing WTC with a party ballon. Simply bad science. Like the essential conclusions of the Nist report.
 
Heiwa:

Why are you so obsessed with DENSITY?

The laws governing the collapse of WTC 1 & 2 all involve MASS:

F = Ma; KE = 1/2 Mv^2; PE = Mgh.

Now you can substitute (density x volume) for M in these equations if you want, but then you need to consider the volume as well.....

So tell me Heiwa, which weighs more: a kilogram of feathers or a kilogram of lead?
 
Apollo20 said:
So tell me Heiwa, which weighs more: a kilogram of feathers or a kilogram of lead?
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It depends on which definition of "kilogram" Heiwa uses - his or the world's - and if he uses the same definition for each case.

Honest.
 
Apollo20 said:
Heiwa:

Why are you so obsessed with DENSITY?

So tell me Heiwa, which weighs more: a kilogram of feathers or a kilogram of lead?
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You mean Seffen, so better ask him? I only work with force N, distance (meter = m) and energy Nm (or Joule, same thing, clever guy). Easy to handle. Sometimes with pressure Pa (N/m²).

I was amazed when Seffen of Cambridge university (it is in England) suggested that the upper block lambda L, very solid and rigid but with little density, was floating on another block beta L with bigger density during the collapse. BBC (English TV station) apparently announced it like some new Newtonian principle that would explain the WTC1 collapse. And now Seffen has got the same nonsense published in some American journal (JoEM 2/08 pp 127-132). It proves to me that US scientists and engineers are pretty useless. Or probabaly harrassed by security thugs outside their offices that now have taken over over there? It also explains the low level of discussion at the JREF. Too many thugs there too!
 
Not only the mass distribution is important but also the strength, the strength will, like the mass, in general increase when you go to the bottom.
 
Major_Tom said:
According to NB and Norseman, the very front of the collapse wave is caused by the perimeter columns of the upper block falling within the perimeter of the lower block, thereby severing the collections between the flooring and the perimeter.
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I want to get back to this proposed mode of failure, where debris from the upper block somehow funnels into the bottom block to creates some kind of progressive collapse.

What is the general model of floor failure for this mode?

Does an entire floor fail all at once or in pieces?
 
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They say that the whole top section funneled, try to imagine it, if you can't I don't blame you.

v3nkpi.gif
 
Hi Einsteen,

The green ones go in the triangular holes, the blue ones go in the square holes, and the red ones go in the round holes.

Or, you can lift the yellow plate with the holes out of the way, and put the green, red, and blue blocks directly into the box.

Did you have any other questions you need help with?

Respectfully,
Myriad
 
Myriad said:
Hi Einsteen,

The green ones go in the triangular holes, the blue ones go in the square holes, and the red ones go in the round holes.

Or, you can lift the yellow plate with the holes out of the way, and put the green, red, and blue blocks directly into the box.

Did you have any other questions you need help with?

Respectfully,
Myriad
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Meh, you are thinking inside the box.
 
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