Merged New video! Architects and Engineers - Solving the Mystery of Building 7

[tfk]

Are the two instances of slightly more than 1G acceleration of the collapse likely instances when a) the structural resistance was at a minimum plus b) the internal core column(s) that had already failed actually provided a very slight downwards force by pushing down on horizontal supports?

Exactly.

There are actually several possible explanations for the "over G" periods. You've identified one.

Here's the heart of the matter. There is nothing in Newton's laws that prohibits an object from falling faster than G.

Truthers assert that, for a falling object:

a_max = g.

What Newton's law really says is the following:

a_cg = F_total/mass

Where
a_cg = acceleration of body's center of gravity
F_total = total forces acting on body.
mass is obvious.


The maximum value of a_cg is equal to g ONLY when the force of gravity is the one and only force acting on the body.

This is referred to as an "isolated body in free fall". In other words, nothing else exerting a force on the body. In other words, nothing else touching the body.

Unfortunately for the truther argument, the facade walls of WTC7 are as far from "isolated bodies" as one can get. They were firmly attached to the rest of the support structure of the building.

That internal support structure started falling earlier than the facade walls. They got a head start on the facade, and at hundreds of places, they were still attached to the external wall.

If I were to tie your ankle to a rope attached to a heavy weight, and push the heavy weight off of a tall building, and someone were only watching your acceleration, then it would appear to be >G when the rope went taut.

The fact that truthers cannot see the building behind the external wall does not mean that the laws of physics were violated. Any more than someone not being able to see the weight at the end of the rope tied to your ankle means that your fall violated the laws of physics.

tom

 

[cjnewson88]

Windsor Building, fire fought, building totaled. One Meridian Plaza, fire fought, building gone. Even fires fought do not mean buildings survive.

Beachnut you need to get your facts in order or truthers will tear you apart. Neither the Windsor building or One Meridian Plaza collapsed.

The top floors (minus the concrete inner core) of the Windsor building which were steel framed collapsed from fire, the inner core and remainder of the building stood (which makes perfect sense, they were made of concrete, not steel).

One Meridian Plaza didn't fail at all, the fires were stopped by sprinkler systems on one of the upper floors. In saying that, the steel floor beams and girders within were severely damaged (buckled) from the fires, however the builders were not of similar design to WTC buildings, and hence did not fail.

 

[Edx]

Beachnut you need to get your facts in order or truthers will tear you apart. Neither the Windsor building or One Meridian Plaza collapsed.

he isnt saying they collapsed, he is saying they were destroyed and had to be demolished

 

[Zeuzzz]

The way he worded it was misleading then, as I got the same meaning from the words 'totaled' and 'building gone' as above.

 

[Dave Rogers]

Yawn.

I never said the force of gravity stopped acting on the ball, or WTC7 for that matter.

What makes no sense in your argument is the statement; "While the ball is in motion, neglecting air resistance, this is the only force acting on it."

Clearly, the ball is moving upward because of an initial force F1.

Your argument only addresses the gravitational attracting force G, gravity. You do not address the force opposing gravity. The upward force F1, which made the ball oppose gravity in the first place.

So at the point where the ball stops, we have the canceling sum of the two forces (F1, upward, and G, downward, gravitational), I'll use illustrative numbers here, (+1) + (-1) = zero.

So based on Newton's second law, this sum of the two forces, zero equals the mass M times its acceleration a. We know the mass M is a real value greater than zero, so. if 0=M x a, then a must also equal zero.

So, as I previously stated, an object that is not moving, "has no velocity or acceleration."

That condition is met when the upward force, F1, equals the gravitational force, T=zero for my purposes.

velocity = the speed of something in a given direction.

acceleration = the increase in the rate of speed of something.

So, for a time of zero duration, and a velocity of zero, there is zero increase in the rate of speed.

Thus acceleration is also zero.

Back to you sylvan8798

MM

This is without a doubt the most thorough demonstration I have seen for some time of a total failure to grasp simple Newtonian mechanics. I'd try to explain what's wrong with it, but it's difficult to know where to start, because the depth of misunderstanding and wilful ignorance it displays is so profound. In the example I gave, at no point in the time interval described by the graph is there any force but gravity acting on the ball; MM's upward force F1 simply does not exist. He's saying that, if he throws a ball in the air, an upward force acts on it until it reaches the top of its trajectory; I wonder where he imagines that force comes from.

Dave

 

[Dave Rogers]

Hang on, is there a point to all this mechanics?

I've totally forgotten or original point made.

The point is that Miragememories doesn't understand anything about Newtonian mechanics whatsoever; in particular, he doesn't even understand what a force is, or what acceleration is. Any statements he makes about the acceleration of WTC7, what forces may be the causes of that acceleration, and what forces cannot be the causes of that acceleration, should be interpreted with that in mind. In particular, if those statements disagree with those made by people who do understand what acceleration and force are, it should be useful in assigning relative weight to the two opinions.

Dave

 

[tsig]

First order of business, fire-induced collapses are never an expectation for modern concrete and steel office towers and to date there is nothing but theory to support a belief that such a thing is possible.

The collapse of WTC7 from fire has never been proven beyond theory.

Of course if a person, like yourself David, wants to believe such a collapse (WTC7) is fire induced, than that is your prerogative. But it doesn't make it anymore credible.

You keep waving your pretty little curve around like it is all the NIST required to make their case.

Charts, graphs, computer simulations etc. are all examples of analysis tools that are only as good as the data that fuels them, and in the case of models, the validity of the data and the quality of the algorithms.

At any rate David, why do you keep hand waving about what you feel is my interpretation of the NIST's Stage 1?

It is Stage 2 that holds my primary interest.

Of course you don't want to discuss Stage 2 because the NIST admitted that it was a freefall stage.

A total, high speed collapse, including seconds of freefall, is a highly unrealistic expectation in a building fire, and the NIST spent 7 years wringing their hands, desperately trying to formulate a theory.

They obviously did not think a fire-unduced collapse was a realistic expectation.

A controlled demolition does explain it. Unfortunately, as we all know, the NIST wanted to avoid that scenario like the plague. They confined their investigation into controlled demolition to just the use of RDX applied to Column 79.

If they hadn't dismissed and/or ignored the eyewitness testimony about explosives, and had they looked for nanothermite residue, and proven its non-existence, the whole controversy about WTC7 would likely never have gained so much momentum.

But just like you David, the NIST did not want to find out that not all the terrorists were in the planes on 9/11.

MM

That's why they don't use fire proofing insulation on the steel...oh wait.

 

[sylvan8798]

One Meridian Plaza didn't fail at all, the fires were stopped by sprinkler systems on one of the upper floors. In saying that, the steel floor beams and girders within were severely damaged (buckled) from the fires, however the builders were not of similar design to WTC buildings, and hence did not fail.

I know you are trying to say they didn't out and out collapse, but you should know that structural engineers use the word "failure" in a much less restrictive sense. If a structure doesn't perform as intended then that is a "failure". One Meridian Plaza most certainly "failed" in any sense of the term with which engineers would use it. Just FYI.

 

[sylvan8798]

The maximum value of a_cg is equal to g ONLY when the force of gravity is the one and only force acting on the body.

This is referred to as an "isolated body in free fall". In other words, nothing else exerting a force on the body. In other words, nothing else touching the body.

Unfortunately for the truther argument, the facade walls of WTC7 are as far from "isolated bodies" as one can get. They were firmly attached to the rest of the support structure of the building.

That internal support structure started falling earlier than the facade walls. They got a head start on the facade, and at hundreds of places, they were still attached to the external wall.

tom

Reading this makes me wonder - was the building ever really in a state we would consider "free fall" (as in only gravity acting on it), or was it just yanked down by the interior in such a manner that at some points in time the acceleration actually matched that of free fall?

 

[Oystein]

Reading this makes me wonder - was the building ever really in a state we would consider "free fall" (as in only gravity acting on it), or was it just yanked down by the interior in such a manner that at some points in time the acceleration actually matched that of free fall?

It is most obvious that a major portion of a building, such as the entire upper half of the the north wall, cannot ever be in pure freefall, devoid of any other forces acting upon it. This would require that not only all columns from the east to west corner be severed, but also all floor-to-wall connections, again from east to west and from the 47th down to the column buckle level (8th floor maybe), be severed almost simultaneously. This cannot be done with CD and go unnoticed, and it also cannot happen in a natural collapse progression. Very obviously we are observing a net acceleration resulting from severak forces acting in several directions. Dominated by gravity for sure, but there's always also yanking down and structural resistance up. And lateral forces pulling in or pushing out or yanking sideways.

 

[Dave Rogers]

Reading this makes me wonder - was the building ever really in a state we would consider "free fall" (as in only gravity acting on it), or was it just yanked down by the interior in such a manner that at some points in time the acceleration actually matched that of free fall?

That's a good point. Since there don't appear to be any regions of the acceleration curve that reasonably approximate to a horizontal line, it seems much more like the latter. And that's an important, if subtle, point. The appearance of the acceleration curve suggests that numerous forces were acting on the facade, and that over an arbitrarily chosen period of time those forces could be time-averaged to a sum not significantly different to mG. While that can be described quantitatively as near freefall, it certainly can't be described qualitatively as near freefall.

But what that exposes is a very subtle fallacy of equivocation perpetrated by truthers. By saying that the acceleration was quantitively close to 1G, nothing is implies about additional forces except that, on average, their vector sum is close to zero. By then equivocating this to mean near freefall, truthers add the implication that all additional forces are individually and separately close to zero, and that therefore anything capable of exerting forces must have been absent. But this is unproven, and can't be proven; the information necessary to investigate the separate magnitude of the parts is absent from the sum.

So, yes, to some extent the term "near freefall" is a red herring; it assumes a conclusion not proven by the data available.

Dave

 

[Cl1mh4224rd]

Sorry I feel nub for asking, but can someone explain to me why, in two places, does the green line move above 0 acceleration? Did WTC7 begin to fall upwards at some stage? or is this just representing the building is resisting G for these brief moments?

[qimg]http://www.internationalskeptics.com/forums/picture.php?albumid=553&pictureid=3555[/qimg]

I would assume it's because their measurement were based on the video that was shot that day, which probably weren't the highest of quality. A bit of a margin of error...

I'll take that as a concession.

I wouldn't. He's clearly attempting to abandon the very simple case for the more complex case so that he can hide his ignorance behind the complexity of WTC7's collapse.

 

[Grizzly Bear]

That's why they don't use fire proofing insulation on the steel...oh wait.

Well, we design buildings to not collapse as much as possible, in other words prevent it before it has the chance to start. MM simply misses the point that it's possible for the design parameters to be exceeded either by an engineering mistake or say, an event that pushes the design beyond the expectations of designers. He's only seen demolitions on TV, so he/she thinks those are the only ways ever for buildings to collapse. There's no such thing as analytical thinking there.

 

[Miragememories]

"Reading this makes me wonder - was the building ever really in a state we would consider "free fall" (as in only gravity acting on it), or was it just yanked down by the interior in such a manner that at some points in time the acceleration actually matched that of free fall?"

"It is most obvious that a major portion of a building, such as the entire upper half of the the north wall, cannot ever be in pure freefall, devoid of any other forces acting upon it. This would require that not only all columns from the east to west corner be severed, but also all floor-to-wall connections, again from east to west and from the 47th down to the column buckle level (8th floor maybe), be severed almost simultaneously. This cannot be done with CD and go unnoticed, and it also cannot happen in a natural collapse progression. Very obviously we are observing a net acceleration resulting from severak forces acting in several directions. Dominated by gravity for sure, but there's always also yanking down and structural resistance up. And lateral forces pulling in or pushing out or yanking sideways."

Cannot be in "pure freefall" as compared to some other form of freefall?

So it is back to the; "the collapse looks just like a controlled demolition but since we won't accept any proof that it was", it can't be, argument.

CD clearly explains the observed freefall collapse.

The NIST calculation of Stage 2 freefall was based on the observation of "the entire upper half of the the north wall" doing what you now claim was not pure freefall.

"Very obviously we are observing a net acceleration resulting from severak forces acting in several directions. Dominated by gravity for sure, but there's always also yanking down and structural resistance up. And lateral forces pulling in or pushing out or yanking sideways."

That is so absurd, it makes it obvious why you guys would rather keep the discussion centered around a dropping ball.

MM

 

[LSSBB]

So it is back to the; "the collapse looks just like a controlled demolition but since we won't accept any proof that it was", it can't be, argument.

It doesn't look like a Controlled Demolition. The inside falls, then a little later the outside falls. No explosions, no squibs, no Wile E. Coyote with a detonator, nothing of the sort.

 

[NoahFence]

So it is back to the; "the collapse looks just like a controlled demolition but since we won't accept any proof that it was", it can't be, argument.

No. YOU'RE back there. No sane, rational or intelligent person looks at a controlled demolition, then at WTC 7 and says they look alike. And if you're on the ground in front of it when it happens, or after during cleanup?

Night and day. Black and white. Completely different.

 

[NoahFence]

That is so absurd, it makes it obvious why you guys would rather keep the discussion centered around a dropping ball.

Why do you people insist on keeping the discussion centered around WTC 7?

Is it because you know damn well that if you try to tie everything together controlled demo looks pretty stupid?

Don't answer that (not that you will...)

we already know the answer.

 

[tfk]

Noah,

Wait just a minute, here...

No. YOU'RE back there. No sane, rational or intelligent person looks at a controlled demolition, then at WTC 7 and says they look alike. And if you're on the ground in front of it when it happens, or after during cleanup?

Night and day. Black and white. Completely different.

I must disagree.

You just have to "adjust" your data acquisition parameters a tad.

If you:

1. eliminate your hearing
2. unplug any pesky seismometers
3. close your eye or turn away from any annoying flashes
4. refuse to allow experts to examine the debris pile for any evidence of det cord, explosives residue, etc.
5. keep all the explosive-sniffing rescue dogs far away
6. make sure that there are no demolitions experts nearby at the critical moment
7. don't examine any of the nearby buildings for the evidence of explosive shockwaves (broken glass on the back side of the buildings, for example)

... and probably about 5 other conditions that I can't think of at the moment ...

... why, THEN, it looks just like a controlled demolition.

Which means, in truther-speak, "it fell straight down. Kinda fast. As one giant unit."

But, wait a minute.

"Straight down" is the ONLY way that a latticework building like wtc7 (or a thin walled tall structure like its external shell) can possibly fall. (Recall the "tipping criteria" that neither the towers nor the wtc7 external shell could possibly meet.)

"Really quick" is the only way that a massive, tall structure can fall, if the failure mode is a very low energy consuming mechanism like "buckling".

As for "as one giant unit", well, here we run into a problem. It didn't. It's provable, it's demonstrable that the building did not collapse as a unit, but that the internal elements failed first. And what the truthers interpret as "the building" is merely the eternal shell.

Gee, imagine the coincidence.

The only two features that this collapse has in common with controlled demolitions happen to overlap pretty much any collapse that structure could have suffered.

And the third criteria is simply false.

Who'd a thunk it...?!


tom

 

[DGM]

.
3. close your eye or turn away from any annoying flashes

tom

Tom:

I've been to (4 now) demolitions and the flashes are usually not visible. The charges are wrapped to avoid flying debris.

Naturally the "kick in the chest" from the shock-wave will be a dead give-away that explosives were used. That's why my deaf friend loves going to these, she can "hear" the charges going off (The smile on her face is why I like going with her).

 

[funk de fino]

Cannot be in "pure freefall" as compared to some other form of freefall?

So it is back to the; "the collapse looks just like a controlled demolition but since we won't accept any proof that it was", it can't be, argument.

CD clearly explains the observed freefall collapse.

[qimg]http://img263.imageshack.us/img263/9872/set3sccompositeua1.png[/qimg]

The NIST calculation of Stage 2 freefall was based on the observation of "the entire upper half of the the north wall" doing what you now claim was not pure freefall.

"Very obviously we are observing a net acceleration resulting from severak forces acting in several directions. Dominated by gravity for sure, but there's always also yanking down and structural resistance up. And lateral forces pulling in or pushing out or yanking sideways."

That is so absurd, it makes it obvious why you guys would rather keep the discussion centered around a dropping ball.

MM

Step away from your keyboard and count to zero.