World trade centre collapse, 9/11 conspiracy

[billvon]

I have noticed that no one has provided a link where "scientists" and "engineers" have discussed the Center of Gravity of 27 stories of building 900 feet above the ground tilted at about 22 degrees. Yeah right, I'm nutty and this site is scientific.

From JOM (The Member Journal of the Mineral, Metals and Materials Society) issue 53, page 8-11.

"As the joists on one or two of the most heavily burned floors gave way and the outer box columns began to bow outward, the floors above them also fell. The floor below (with its 1,300 t design capacity) could not support the roughly 45,000 t of ten floors (or more) above crashing down on these angle clips. This started the domino effect that caused the buildings to collapse within ten seconds, hitting bottom with an estimated speed of 200 km per hour. If it had been free fall, with no restraint, the collapse would have only taken eight seconds and would have impacted at 300 km/h.1 It has been suggested that it was fortunate that the WTC did not tip over onto other buildings surrounding the area. There are several points that should be made. First, the building is not solid; it is 95 percent air and, hence, can implode onto itself. Second, there is no lateral load, even the impact of a speeding aircraft, which is sufficient to move the center of gravity one hundred feet to the side such that it is not within the base footprint of the structure. Third, given the near free-fall collapse, there was insufficient time for portions to attain significant lateral velocity. To summarize all of these points, a 500,000 t structure has too much inertia to fall in any direction other than nearly straight down."

 

[billvon]

This is one of the reasons for ROFLMAO

Like I said, keep rolling around on the floor rather than learning any physics. Much easier that way.

Fourth: If the south tower deflected on impact then the north tower had to also. The Purdue simulation does not move. Since energy had to be lost deflecting the building the damage calculation of the Purdue simulation had to be WRONG!

EVERY simulation makes assumptions. NO simulation is 100% accurate, nor can it be.

No wonder you are always rolling on the floor; you don't understand even the most basic aspects of simulation.

 

[Kittamaru]

No wonder you are always rolling on the floor; you don't understand even the most basic aspects of simulation.

More importantly, it appears he doesn't understand the basics of physics, such as inertia...

 

[psikeyhackr]

More importantly, it appears he doesn't understand the basics of physics, such as inertia...

Oh sure, inertia only applies to moving masses not stationary ones. The stationary mass does not slow down the moving mass on impact in your cartoon physics.

Basic physics. The centre of gravity doesn't fall outside of the base support. It needs to be around 45 degrees before that occurs. Also, the building section tilted is still connected to the non tilted part so even less of the 22 degree spill will be in effect.

So how did you pick 45 degrees? Half of a right angle? BRILLIANT! How much the center of gravity deviates from its normal position will be proportional to the sine of the angle:

the sine of 45 is 0.707
the sine of 30 is 0.5
the sine of 22 is 0.374

So that leaves the question of how far the center of gravity is up the tilted mass from the pivot point. We are talking about the top 27 stories of a 110 story skyscraper with mostly 12 foot stories. 324 feet. Actually the mechanical floors werE taller but let's ignore that.

324 * 0.374 = 121 feet

So the top of a structure 200 feet wide could deviate 121 feet from its design position.

But there is something peculiar about the mechanical floors and where the aircraft hit the south tower.

NIST_NCSTAR1-2A.PDF
41, 42, 43, 75, 76, 77 (mechanical levels); 107, 108, 109, 110, and roof (hat truss region) of both towers.

NIST_NCSTAR1-2A.PDF
For floor 109 (mechanical floor), sheet BC1-3 indicates LL = 150 psf. However, for consistency with the design criteria for other mechanical floors, this live load was applied in two parts, as LL = 75 psf and additional SDL = 75 psf.

According to the NIST floor 77 and 109 were mechanical floors. The aircraft impacted the south tower at the 81st floor. So the break in the building was just above one of the sections of mechanical floors.

But what was different about mechanical floors?

NIST_NCSTAR1-2A.PDF
The area outside the core was framed either in trusses (typical on tenant floors) or in rolled structural steel shapes (typical on mechanical floors). Truss-Framed Floors––The majority of the floors of the WTC towers were tenant floors where the areas outside of the core were constructed of steel trusses acting in a composite fashion with concrete slabs cast over metal deck.

NIST_NCSTAR1-2A.PDF
The mechanical floors were 5 ¾ in. concrete slabs on 1 ½ in. metal deck outside the core. The deck spanned in the direction of the primary beams and was supported typically at 6 ft 8 in. intervals by a 4C5.4 deck support channel. A 2 in. concrete topping slab was placed on top of the structural slab. The core area was framed similarly to the core of the truss-framed floors, but the steel beams were typically larger, and the concrete slab was 6 in. deep. The beam-framed floors above the mechanical mezzanine had a 7 3/4 in. normal weight concrete slab on 1 1/2 in. metal deck, while the core slab was 8 in. normal weight concrete.

NIST_NCSTAR1-2B_Chaps1-8.PDF
The exterior wall in the WTC 2 impact zone included a mixture of 100, 200, 300, and 400 series panels due to the proximity of the mechanical floors.

Mechanical levels were 14 feet tall instead of 12 and constructed more heavily to support greater loads. The towers were 1362 and 1368 feet tall. If all of the levels were 12 feet that would be 110 * 12, 1320 feet. Where were those extra 40+ feet? Where were the motors that ran the elevators? Where was the air conditioning and heating equipment to maintain the environment in a building which did not have windows that could open? Not the "mechanical floors" by any chance? So did the heavier weight of the construction and all of the weight of that equipment do anything to the center of gravity of the tilted section?

Then there is the matter of the core of the tower. The core was 135 feet by 85 feet. The NIST report says the core supported 53% of the buildings weight. That means ones side of the perimeter only supported 12% of the weight. Depending on which way the top tilted the center of gravity only had to move from 43 to 8 feet to be beyond the outher edge of the core and put most of the weight on one side of the perimeter.

the sine of 22 is 0.374
324 * 0.374 = 121 feet

By the way, the top of the building also had the hat truss to shift the center of gravity toward the top.

So why shouldn't we have detailed data on the distributions of steel and concrete in the building to analyze this SCIENTIFICALLY?

You guys do not look at what data is available to get a scientific idea of what could happen, but then want to dish out psychological BS to imply other people are stupid!

Of course sine calculations and quotes from the NIST must be indications of intellectual dishonesty from my deranged mind since you brilliantly scientific individuals cannot possibly be wrong.

Funny how no "scientists" or "engineers" from our legitimate institutions have said anything about the center of gravity of the tilted top of the south tower in SEVENTEEN YEARS (minus 3 months).

I downloaded the NIST report and burned it to DVD years ago so the searches were not too much of a problem. Long ago I searched for "center of gravity" and "center of mass" also. The NIST uses both terms maybe a couple of dozen times. Whenever they use "center of mass" they are talking about the aircraft. Whenever they use "center of gravity" they are talking about the a structural component simulated in the SAP 2000 program. Neither is ever used in relation to the top of the south tower.

 

[psikeyhackr]

The searchibility of the Internet is just so cool!

http://www.internationalskeptics.com/forums/showthread.php?t=238384

They never say anything about the mechanical floors regarding their effect on the center of mass.

 

[Kittamaru]

Oh sure, inertia only applies to moving masses not stationary ones. The stationary mass does not slow down the moving mass on impact in your cartoon physics.

Uh... why would it?

Example - you have a series of 10 platforms built around a central pole. Each platform weighs 10 tons. The support struts holding up the platforms can hold a maximum load of 15 tons. Due to structural damage, the top three platform gives way, landing on the one underneath them - a combined mass of 30 tons (minimum) landing on the 4th platform.

Exactly how much resistance do you think those supports will give, considering they are being subjected to a weight twice their maximum load landing on top of them while moving, increasing the force being put upon them significantly... so, in essence, you are asking it to hold 10 tons of stationary platform and 30 tons of falling platform.

I'll give you a hint - the reduction in the rate of collapse would be nearly imperceptible to the human eye.

 

[David C]

So how did you pick 45 degrees? Half of a right angle? BRILLIANT!

No. I thought you meant the North Tower, which is essentially a cube. The centre of mass is centre to this, needing the base to tip 45 degrees before the COG falls outside of it. For rectangular structures it is obviously less of an angle.

How much the center of gravity deviates from its normal position will be proportional to the sine of the angle:

Where are you getting this from?

So that leaves the question of how far the center of gravity is up the tilted mass from the pivot point. We are talking about the top 27 stories of a 110 story skyscraper with mostly 12 foot stories. 324 feet. Actually the mechanical floors werE taller but let's ignore that.

324 * 0.374 = 121 feet

So the top of a structure 200 feet wide could deviate 121 feet from its design position.

That is not correct. I don't know what maths you are using for this. Here is a graphical illustration of the 27 floors(324 pixels) and the base(200 pixels). The COG is in the centre of the shape. It has been tilted 22 degrees and shows the COG still falls within the base. What is obvious is that the COG line to ground is not 121 pixels along the base line, it is 164. If you dispute this please show why.

 

[psikeyhackr]

No. I thought you meant the North Tower, which is essentially a cube. The centre of mass is centre to this, needing the base to tip 45 degrees before the COG falls outside of it. For rectangular structures it is obviously less of an angle.



Where are you getting this from?



That is not correct. I don't know what maths you are using for this. Here is a graphical illustration of the 27 floors(324 pixels) and the base(200 pixels). The COG is in the centre of the shape. It has been tilted 22 degrees and shows the COG still falls within the base. What is obvious is that the COG line to ground is not 121 pixels along the base line, it is 164. If you dispute this please show why.

Since when was the tilt of the north tower 20 to 25 degrees?

The 324 is the total height of the block. The 121 would be how much the top moved horizontally. I said the movement was PROPORTIONAL to the sine.

Your drawing the CoG as being at the geometric center of the block is an ASSUMPTION. I am assuming no such thing. That is why I provided information about the Hat Truss and the Mechanical Floors. We do not have the data to know how far up the structure the CoG was.

Is your concept of science based on ASSUMPTIONS or collecting Relevant Data?

And you ignore the width of the core also. Great Science! Beat on me for not knowing physics!

ROFL

 

[psikeyhackr]

Uh... why would it?

Example - you have a series of 10 platforms built around a central pole. Each platform weighs 10 tons. The support struts holding up the platforms can hold a maximum load of 15 tons. Due to structural damage, the top three platform gives way, landing on the one underneath them - a combined mass of 30 tons (minimum) landing on the 4th platform.

Exactly how much resistance do you think those supports will give, considering they are being subjected to a weight twice their maximum load landing on top of them while moving, increasing the force being put upon them significantly... so, in essence, you are asking it to hold 10 tons of stationary platform and 30 tons of falling platform.

I'll give you a hint - the reduction in the rate of collapse would be nearly imperceptible to the human eye.

Oh really!!!

You are saying the Conservation of Momentum disappeared?

Example:

3 equal masses moving 30 ft per second. Momentum is mass times velocity therefore 90 units

Conservation of momentum:

m1*v1 + m2*v2 = (m1+m2)*v3

(90 + 0)/4 = 22.5 = v3

That deceleration does not even take into account the energy that must be used up breaking supports that had to be strong enough to hold 10 tons against gravity. That conservation of momentum equation applies to any masses but the strength of supports would change.

So you are saying that observers would not notice a change from 30 ft per second to 22.5 ft per second? Even if videos were made and could be watched repeatedly? That is the issue with 9/11. How much would people notice in the shock of the moment?

 

[David C]

Since when was the tilt of the north tower 20 to 25 degrees?

Not relevant to the 45 degree statement I made is it? I misread your post. I don't claim to be a 911 fact collector, thank you for the correction. I find the whole thing a bit bizarre, people thinking the collapse was a demolition when the towers clearly gave way where the planes hit. I have no idea how anyone can think explosive charges could stay safely in place after a plane hits them. I am not suggesting you think this btw, but if you do - you have my sympathy.

The 324 is the total height of the block.

As drawn.

The 121 would be how much the top moved horizontally. I said the movement was PROPORTIONAL to the sine.

Then proceeded to do a direct multiplication that is clearly wrong. I asked you where you got this from. Not saying it's wrong, but your figure of 121 most certainly is.

If as an example, you had a bottom heavy object with COG at almost ground level, your sine angle is total nonsense.

Your drawing the CoG as being at the geometric center of the block is an ASSUMPTION.

And an extremely reasonable one. Each floor is identical in construct.

I am assuming no such thing.

Well what the hell ARE you saying?

That is why I provided information about the Hat Truss and the Mechanical Floors. We do not have the data to know how far up the structure the CoG was.

We've got more than enough to make a reasoned guess at dead centre.

Is your concept of science based on ASSUMPTIONS or collecting Relevant Data?

Both when needed. The centre of a uniform structure is a fair assumption.

And you ignore the width of the core also.

No. I simply took what you claimed and put it in visual format.

Great Science!

The central core goes back to my original statement about how the lean is offset by the building still being attached to the tilted section. I ignored nothing.

Beat on me for not knowing physics!

ROFL

Where did I?

 

[psikeyhackr]

And an extremely reasonable one. Each floor is identical in construct.

I provided quotes from the NCSTAR1 report and specified which of the 50some reports they were in, describing the construction of the mechanical floors and which floors they were. I also mentioned the Hat Truss that was at the top of the building.

I do not know where the center of gravity was and have said many times that was need to know the tons of steel and tons of concrete on every level.

 

[Kittamaru]

Oh really!!!

You are saying the Conservation of Momentum disappeared?

Example:

3 equal masses moving 30 ft per second. Momentum is mass times velocity therefore 90 units

Conservation of momentum:

m1*v1 + m2*v2 = (m1+m2)*v3

(90 + 0)/4 = 22.5 = v3

That deceleration does not even take into account the energy that must be used up breaking supports that had to be strong enough to hold 10 tons against gravity. That conservation of momentum equation applies to any masses but the strength of supports would change.

So you are saying that observers would not notice a change from 30 ft per second to 22.5 ft per second? Even if videos were made and could be watched repeatedly? That is the issue with 9/11. How much would people notice in the shock of the moment?

In all honesty, no, they probably would not - especially not when obscured by dust, debris, etc (plus, of course, the fact that they are watching how many hundreds of people die... tends to shake people up a bit).

However, you forgot to account for something in your equation - gravity. There is a constant acceleration being applied to the falling mass - the supports are taking up not just the weight of the mass being added and the kinetic energy it already contains, but also the force of gravity attempting to continue accelerating the falling debris.

In my example, that force would probably be minimal. In the WTC collapse, though... lets take the south tower - 110 stories tall. Impact was between 77th and 85th floors. So, if we presume the initial point of failure was around floor 85, that puts 25 stories + all the stuff on the roof bearing down. That mass, once in motion and given the acceleration of gravity, is tremendous.

 

[David C]

I provided quotes from the NCSTAR1 report and specified which of the 50some reports they were in, describing the construction of the mechanical floors and which floors they were. I also mentioned the Hat Truss that was at the top of the building.

I do not know where the center of gravity was and have said many times that was need to know the tons of steel and tons of concrete on every level.

You don't know. No problem. Now kindly answer the rest of my post.

This:-

I asked you where you got this from. Not saying it's wrong, but your figure of 121 most certainly is. If as an example, you had a bottom heavy object with COG at almost ground level, your sine angle is total nonsense.

This:-

Well what the hell ARE you saying? Are you claiming the tower was demolished? How did the charges survive an aircraft impact?

And this:-
The COG was within the base support, what more is there to argue? Are you suggesting that the perpetrators managed to manipulate gravity and make the "obviously out of balance tower" fall incorrectly? We see clearly this vast, immense, chunk of building fall straight through the lower portion.

I ask again, what exactly could possibly be wrong that you think they did?

 

[gamelord]

If the towers naturally fell on their own, that does not preclude the possibility it was an inside job.

The terrorists could, still, have been following the orders of the Bush administration.

Uh no. The conspiracy takes the form of a majority who marginalizes and oppresses a minority. The conspiracy theorist thus is part of this minority that is demonized and persecuted. It happened with Jews. It happened with blacks. It happened with gays. And it happens with women in Muslim countries. The conspiracy is always the ones in power. The conspiracy theorists are the warriors against this oppressive power. They're the ones who change the system. They're the ones the mainstream paints as lunatics, as paranoid, as "conspiracy theorists" with 30 psychological traits so you can quickly point them out in public and shame them.

That is the inherent mathematics of conspiracy.

Has nothing to do with race.

For instance in town of salem, there are 3 mafia and 10 townies.

The nature of conspiracy is implied a small group of people, is plotting against the majority.
If they were majority then they would have transparency. So conspiracies will always be about a small group of people plotting something.
The smaller the group, the more believable it is.
If it was the majority, then it would not be a conspiracy, but something else.

 

[billvon]

If the towers naturally fell on their own, that does not preclude the possibility it was an inside job.
The terrorists could, still, have been following the orders of the Bush administration.

It is hard to keep track of all the conspiracy theories out there.

So we have "the airplanes were missiles." Then when pictures and videos were shown, it became "missiles with hologram generators to make them look like airplanes." Then it was airplanes, but the hijackers were US agents and the air force was "ordered to stand down." Then the planes were accepted as real, but terrorists used "nanothermite" to blow up the building. Then it was "superthermite." Then there was a story how the Air Force shot down Flight 93 so the deception wouldn't be discovered. Then Israeli agents did it.

I actually hadn't heard the "the towers fell on their own but the terrorists were acting on presidential orders" before. I will add that one to the list.

 

[gamelord]

I am curious to see an actual simulation have the plane hit into the building. I think I saw on youtube before but I wasn't confident of the physics. I think if someone used the rigs and rods sim for Beam.ng but they would have to use a supercomputer.

 

[James R]

Interesting to see a thread on the psychology of conspiracy theorists (here) degenerate into an off-topic debate about a particular conspiracy theory.

Most of the features I pointed to in the opening post of the original thread can be seen right here, as a living, breathing, example.

Thank you for the practical demonstration, conspiracy theorists!

I have split off the 9/11 "inside-job" conspiracy nonsense to its own thread, and you're welcome to continue the "debate" here.

 

[James R]

psikeyhackr:

To which part of the collapse do you think conservation of momentum is relevant, exactly?

Clearly, conservation of momentum does not apply overall. For starters, gravity is an external force that acted the whole time on the building during the collapse, and any system subject to a net external force does not conserve momentum.

I assume the point you're trying to make is more subtle than the plainly-wrong claim that the momentum of each of the falling floors must have been conserved at all times, for some unknown reason.

Could you please expand on whatever point it is that you're trying to make?

 

[David C]

psikeyhackr - has he gone? I've got some unanswered stuff, surely he can help me out

 

[iceaura]

They never say anything about the mechanical floors regarding their effect on the center of mass.

They would make it harder to move sideways.
Point to consider: in order to knock a floor sideways as a unit - tip the tower - the center of mass from that floor on up has to be lifted a bit (over the vertical supports involved, which if they do not collapse act as radii of the circle of tip so to speak, and if they do collapse do so down the inside of the building).

I actually hadn't heard the "the towers fell on their own but the terrorists were acting on presidential orders" before. I will add that one to the list.

The one that has the terrorists acting on their own but abetted by the US government, which was only surprised by the scale of the attack they had carefully failed to interrupt, belongs in that subcategory as well.
It's the one I've found hardest to dispute - incompetence of that degree is difficult to distinguish from complicity, and the alacrity with which the Federal responses were launched, wish lists ready to hand, contrasts sharply with that administration's low level of readiness and capability in all other matters of governance.