9/11 Question ('Squibs'?)

[☭proletarian☭]

Did the 9/11 Commission or anybody else ever explain what these apparent 'explosions' are below the main collapse?

I don't recall any explanation of this phenomenon ever being offered.

 

[Trojan]

air pressure, as the building collapsed, air was forced down and out

 

[☭proletarian☭]

air pressure, as the building collapsed, air was forced down and out

Could you source that, please?

 

[eots]

air pressure, as the building collapsed, air was forced down and out

the pressure from a cloud of pulverized concrete..???

 

[Big Black Dog]

I am not an engineer and don't have a clue but I would strongly suggest that flying an airplane into the building didn't help it any. I believe that the fires that resulted from the plane crashing into the buildings did indeed weaken the structure and cause it to collapse as they say it did. I think any other explanation is just a fishing trip for some wild different conclusion. To believe the "government" or any other group other than the terrorists is responsible for the collapse of the WTC is foolish in my humble opinion. I think the reason for the collapse should be taken on face value and everybody should move on to something constructive.

 

[Midnight Marauder]

Did the 9/11 Commission or anybody else ever explain what these apparent 'explosions' are below the main collapse?

I don't recall any explanation of this phenomenon ever being offered.

Photoshop.

 

[☭proletarian☭]

Did the 9/11 Commission or anybody else ever explain what these apparent 'explosions' are below the main collapse?

I don't recall any explanation of this phenomenon ever being offered.

Photoshop.

frame-by-frame in video aired on Fox News, MSNBC, and every other major news outlet within hours of the event?

Get serious or get out of the thread.

 

[☭proletarian☭]

I am not an engineer and don't have a clue

Enough said. The rest of your post was irrelevant.

 

[Midnight Marauder]

Did the 9/11 Commission or anybody else ever explain what these apparent 'explosions' are below the main collapse?

I don't recall any explanation of this phenomenon ever being offered.

Photoshop.

frame-by-frame in video aired on Fox News, MSNBC, and every other major news outlet within hours of the event?

You're sure that's the source? You hotlinked these from "reopen911" website.

Get serious or get out of the thread.

You run the joint now? How about you just PUT me out of this thread?

 

[Fizz]

air pressure, as the building collapsed, air was forced down and out

Could you source that, please?

http://www.civil.northwestern.edu/p...TC Collapse - What Did & Did Not Cause It.pdf

 

[Fizz]

air pressure, as the building collapsed, air was forced down and out

the pressure from a cloud of pulverized concrete..???

do you have any common sense hidden anywhere? if so, pull it out for a second.

 

[☭proletarian☭]

air pressure, as the building collapsed, air was forced down and out

Could you source that, please?

http://www.civil.northwestern.edu/people/bazant/PDFs/Papers/00%20WTC%20Collapse%20-%20What%20Did%20&%20Did%20Not%20Cause%20It.pdf

It's not showing :/

Can someone let me know whether it's just my machine?

 

[☭proletarian☭]

I can't tell for certain in the videos, are those windows or parts of the wall blowing out.

 

[eots]

air pressure, as the building collapsed, air was forced down and out

Could you source that, please?

http://www.civil.northwestern.edu/p...TC Collapse - What Did & Did Not Cause It.pdf

I believe he was looking for an official explanation not one of your pdf files that go nowhere

 

[Midnight Marauder]

Could you source that, please?

Index of /people/bazant/PDFs/Papers

It's not showing :/

Can someone let me know whether it's just my machine?

It's actual science and mathematics. It's anathema to both you and your machine.

It loaded just fine over here.

 

[Big Black Dog]

I am not an engineer and don't have a clue

Enough said. The rest of your post was irrelevant.

OK, genius. What the fuck is it then? You don't seem to be open to common sense. It's real easy to know when you haven't taken your medications.

 

[Baruch Menachem]

From the link:

Abstract: Previous analysis of progressive collapse showed that gravity alone suffices to explain
the overall collapse of the World Trade Center (WTC) towers. However, it remains to be checked
whether the recent allegations of controlled demolition have any scientific merit. The present analysis
proves that they do not. The video record available for the first few seconds of collapse is shown to
agree with the motion history calculated from the differential equation of progressive collapse but,
despite uncertain values of some parameters, it is totally out of range of the free fall hypothesis, on
which these allegations rest. It is shown that the observed size range (0.01 mm—0.1 mm) of the
dust particles of pulverized concrete is consistent with the theory of comminution caused by impact,
and that less than 10% of the total gravitational energy, converted to kinetic energy, sufficed to
produce this dust (whereas more than 150 tons of TNT per tower would have to be installed, into
many small holes drilled into concrete, to produce the same pulverization). The air ejected from the
building by gravitational collapse must have attained, near the ground, the speed of almost 500 mph
(or 223 m/s, or 803 km/h) on the average, and fluctuations must have reached the speed of sound.
This explains the loud booms and wide spreading of pulverized concrete and other fragments, and
shows that the lower margin of the dust cloud could not have coincided with the crushing front. The
resisting upward forces due to pulverization and to ejection of air, dust and solid fragments, neglected
in previous studies, are found to be indeed negligible during the first few seconds of collapse but not
insignificant near the end of crush-down. The calculated crush-down duration is found to match a
logical interpretation of seismic record, while the free fall duration grossly disagrees with this record.

I have to admit to a non engineer much of this sounds Chinese, but if you concentrate on what they are saying, it is perfectly consistent.

The link works. try again, read it carefully. It is worth the effort

 

[eots]

if it is pulverized how does it have the mass to crush the floor beneath why ? does the collapse never slow significantly ?

 

[Baruch Menachem]

The direct answer the to the OP question

Velocity of Air Ejected from the Tower
An upper bound on area through which the air initially contained within every story gets
expelled (Fig. 3a) is Aw = 4ψahc , where 4ahc = area of one perimeter wall, a = 64 m = width
of the side of square cross section of tower, hc = 3.69 m = clear height of one story = distance
from the bottom of a story slab to the top of the underlying slab, and ψ = vent ratio = ratio
of unobstructed (open) area of the perimeter walls to their total area (ψ
≤ 1). The initial
mass of air within one story is ma = ρa a2 hc , where ρa = 1.225 kg/m3 = mass density of air at
atmospheric pressure and room temperature. Just outside the tower perimeter, the air jetting
out (Fig. 3a) must regain the atmospheric pressure as soon as it exits (White 1999, p.149), and
its temperature must be roughly equal to the initial temperature (this is a well-known general
feature of exhausts, e.g., from jet engines (White 1999, p.149) or pipes (Munson et al. 2006)).
So, the mass density of exiting air ρ
≈ ρa .
The time during which the top slab collapses onto the lower slab
≈ ∆t = hc / ̇z = time
during which the air is expelled out (which is only about 0.07 s for stories near the ground).
Conservation of the mass of air during the collapse of one story requires that ρAw (va ∆t) = ρVa .
Solving this equation gives the average velocity of escaping air just outside the tower perimeter:
va = Va
ψAw ∆t =
a ̇z
4ψhc (7)
Since the velocity of the crushing front near the end of North Tower crush-down is, according
to the solution of Eq. (2), ̇z = 47.34 m/s (106 mph), the velocity of escaping air near the end
of crush-down is
va = 64m × 47.34m/s
4ψ
× 3.69m
=

 

[Baruch Menachem]

if it is pulverized how does it have the mass to crush the floor beneath why ? does the collapse never slow significantly ?

Answer here:

Inabsorbable Kinetic Energy
First, let us review the basic argument (Baˇzant 2001; Baˇzant and Zhou 2002). After a drop
through at least the height h of one story heated by fire (stage 3 in Fig. 2 top), the mass of the
upper part of each tower has lost enormous gravitational energy, equal to m0 gh. Because the
energy dissipation by buckling of the hot columns must have been negligible by comparison,
most of this energy must have been converted into kinetic energy
K = m0 v
2
/2 of the upper
part of tower, moving at velocity v. Calculation of energy Wc dissipated by the crushing of
all columns of the underlying (cold and intact) story showed that, approximately, the kinetic
energy of impact
K > 8.4 Wc (Eq. 3 of Baˇzant and Zhou 2002).
It is well known that, in inelastic buckling, the deformation must localize into inelastic hinges
(Baˇzant and Cedolin 2003, sec. 7.10). To obtain an upper bound on Wc , the local buckling
of flanges and webs, as well as possible steel fracture, was neglected (which means that the
ratio
K/Wc was at least 8.4). When the subsequent stories are getting crushed, the loss m0 gh
of gravitational energy per story exceeds Wc exceeds 8.4 by an ever increasing margin, and so
the velocity v of the upper part must increase from one story to the next. This is the basic
characteristic of progressive collapse, well known from many previous disasters with causes
other than fire (internal or external explosions, earthquake, lapses in quality control; see, e.g.,
Levy and Salvadori 1992; Baˇzant and Verdure 2007).

I have to admit reading some of this makes my head hurt. I am not an engineer, nor do I play one on TV.

The whole thing works according to Newton. The collapse moves at a logarithmic rate from floor to floor. it is not increasing at one second per second, but it is coming close. The mass driving downward pushes harder on each additional story.