An email from a Conspiracy theorist, and I have no idea how

[Gravy]

Heiwa, you shouldn't need to be told this, but explosives leave distinctive blast patterns, fragmentation or cut patterns, residue, remains of initating devices, and sonic and seismic signatures, absolutely none of which were detected anywhere, at any attack scene, on 9/11.

Your entire argument is one from ignorance. You refuse to even read the NIST report (Um, hello? The planes didn't enter the towers llke a knife through butter and did not leave cookie-cutter holes. I suggest you look into the outboard wing and vertical stabilizer impacts. NIST covers all this in great detail.

Stop arguing from ignorance. Get informed. You are making an absolute fool of yourself.

NIST NCSTAR 1: Federal Building and Fire Safety Investigation of the World Trade Center Disaster: Final Report of the National Construction Safety Team on the Collapses of the World Trade Center Towers

[FONT=arial,sans-serif] NIST NCSTAR 1-1 [/FONT]Design, Construction, and Maintenance of Structural and Life Safety Systems

[FONT=arial,sans-serif] NIST NCSTAR 1-2 [/FONT]Baseline Structural Performance and Aircraft Impact Damage Analysis of the WTC Towers

[FONT=arial,sans-serif]NIST NCSTAR 1-3 [/FONT]Mechanical and Metallurgical Analysis of Structural Steel

[FONT=arial,sans-serif]NIST NCSTAR 1-4 [/FONT]Active Fire Protection Systems

[FONT=arial,sans-serif] NIST NCSTAR 1-5 [/FONT]Reconstruction of the Fires in the World Trade Center Towers

[FONT=arial,sans-serif]NIST NCSTAR 1-6 [/FONT]Structural Fire Response and Probable Collapse Sequence of the World Trade Center Towers

[FONT=arial,sans-serif]NIST NCSTAR 1-7 [/FONT]Occupant Behavior, Egress, and Emergency Communication

[FONT=arial,sans-serif]NIST NCSTAR 1-8 [/FONT][FONT=arial,sans-serif]The Emergency Response Operations[/FONT]

NIST WTC 7 Interim Report (2004) – Go

The FEMA World Trade Center Building Performance Assessments – Go

The ASCE Pentagon Building Performance Report – Go

 

[T.A.M.]

There is ample and highly compelling evidence that the floors not only failed to support the columns sideways, but that they actually exerted a lateral force on the columns. Look for some photos of the inward bowing of the exterior columns, then tell me that those columns are adequately laterally supported.

Dave

Thank you for explaining, in part, what I was trying to convey. My point was that there had to been any number of forces acting on the columns just prior to and during collapse. TO assume that the only significant force acting on the columns during this time was vertical is incorrect. As a result, unless you know all the forces acting on the steel during collapse, and can differentiate them from a piece of steel that only had impact damage, no collapse damage, then it would be useless to try and seperate the columns into those damaged "only by impact" and those "only by collapse".

TAM

 

[Belz...]

I thought that was clear from previous observations? At impact sideways the perimeter steel column is allegedly cut or sheared off laterally in two locations by aluminium structure with the steel bit in between being removed inward. The steel column was not cut in one location only with the two ends being bent inward. The surfaces of the cut areas will provide more info how it took place, e.g. if it was a plane or whatever.

When the column collapses due to gravity the excess forces are in the longitudinal direction and the ruptured surfaces will appear completely different.

That is why forensic examination of the core columns was also very important. Did they break due to gravity axial collapse or were they cut off laterally by explosive devices of CD? The ruptured surfaces would clearly indicate which. There are some photos of ruptured core columns where the ruptured surfaces seem to have been subject to heat/cutting = CD.

Yeah, yeah.

You know what makes MY blood boil ? The theory of gravity.

Why ? If there was a CONSTANT acceleration of 9.8 m/s² at the surface of the Earth, you'd be SQUASHED into pulp by this force. Think about it. Nonsense.

 

[Dave Rogers]

Maybe I'm missing something here, but when the floor trusses begin sagging, doesn't the sag itself make the straight-line distance between the end points of the truss shorter because of the curve of the sag since the length of the truss does not change? This would create a non-axial load on the columns, right?

Which, of course, would result in the inward bowing of the perimeter columns that was actually observed just prior to the collapse.

I think Heiwa is assuming that there were only vertical forces present, in which case I can imagine that the collapse would be difficult to explain. However, the real world is rather more three-dimensional than that.

Dave

ETA: I think TAM just raised the same point. Heiwa, do you realise that there were forces involved that were not vertical, and that these alone may have been capable of causing collapse?

 

[Gravy]

You have not read message #288? Anyway - the floor truss could only transmit the small weight on and of the truss itself to the columns. No substantial gravity load in a perimeter column can be transmitted through the truss to the core column as shear. The truss connections to the column are too weak and the truss itself lacks capability to transfer big shear loads.

Had you read the NIST report, you would know that this work was done via the hat truss.

Why are you wasting everyone's time with your completely uninformed opinions?

The NIST report is full of guess work and unproven estimates of various parameters, e.g. exaggerated temperatures 30-40 minutes after first impact, and thus very unreliable.

And we should take your word for this? Show us.

Stupid suggestions that the steel would melt are encouraged, etc.

9/11 deniers are the ONLY ONES making those assumptions. Clear enough?

The fire was only due to furniture, office equipment and decorations burning.

Of course, Heiwa. An office fire can't buckle large insulated columns.

You really know your stuff.

The jet fuel burnt at once in the fire ball or poured down to the street. So no high temperatures could ensue. And no global collapse could ensue.

Plan on getting anything right today? Plan on reading the documents you pretend to critique? Plan on supporting your claims...ever?

 

[Belz...]

You have not read message #288?

Yeah. I don't see any formal proof.

Anyway - the floor truss could only transmit the small weight on and of the truss itself to the columns. No substantial gravity load in a perimeter column can be transmitted through the truss to the core column as shear.

So your contention is that the floors had no structural component whatsoever ???

 

[Gravy]

Which, of course, would result in the inward bowing of the perimeter columns that was actually observed just prior to the collapse.

Actually, inward bowing of the south tower's east face was observed within 18 minutes of flight 175's impact.

More reports of bowing, "glowing red," and fears of imminent collapse:[FONT=arial,sans-serif][/FONT]

[FONT=arial,sans-serif]Firefighter Brendan Lowrey: "We started walking south to the command center when a Police Officer stopped us and said, "hold up, guys. I have helicopters --" he was on the cell phone "--on the cell phone here." And he says, "when this one comes down, it's coming right for us." Meaning coming up West Street.

​

NYPD Aviation Units: Minutes after the south tower collapsed at the World Trade Center, police helicopters hovered near the remaining tower to check its condition. "About 15 floors down from the top, it looks like it's glowing red," the pilot of one helicopter, Aviation 14, radioed at 10:07 a.m. "It's inevitable."

Seconds later, another pilot reported: "I don't think this has too much longer to go. I would evacuate all people within the area of that second building." Source
[/FONT]

[FONT=arial,sans-serif]10:20 NYPD – Aviation 14 states the WTC 1 is leaning. (NYPD, McKinsey & Company) NIST NCSTAR 1-8, p. 227

Federal engineering investigators studying the destruction of the World Trade Center's twin towers on Sept. 11 said New York Police Department aviation units reported an inward bowing of the buildings' columns in the minutes before they collapsed, a signal they were about to fall.

"The NYPD aviation unit reported critical information about the pending collapse of the building,'' said Sivaraj Shyam- Sunder, who heads the institute, at a press briefing in New York. "Any time that information could have been communicated faster to the emergency responders in the buildings, it would have helped save lives."

According to Shyam-Sunder, the concave bowing of the steel was seen on the sides of the towers opposite where the planes hit them. At 10:06 a.m. that morning, an officer in a police helicopter reported that ``it's not going to take long before the north tower comes down.'' This was 20 minutes before it collapsed. In another radio transmission at 10:21 a.m., the officer said he saw buckling in the north tower's southern face, Shyam-Sunder said. Source[/FONT]​

 

[AZCat]

Which, of course, would result in the inward bowing of the perimeter columns that was actually observed just prior to the collapse.

I think Heiwa is assuming that there were only vertical forces present, in which case I can imagine that the collapse would be difficult to explain. However, the real world is rather more three-dimensional than that.

Dave

ETA: I think TAM just raised the same point. Heiwa, do you realise that there were forces involved that were not vertical, and that these alone may have been capable of causing collapse?

That's what I thought. Thanks for confirming.

 

[Heiwa]

Plan on getting anything right today? Plan on reading the documents you pretend to critique? Plan on supporting your claims...ever?

The NIST reports are full of nonsense. Thanks for the examples. So 30 tons of jetfuel arrives at abt 500 mph and slices through the WTC2 south wall during 0.2 seconds - nothing happens ... and then the jetfuel stops inside the tower!! Magic! Paranormal. Some scrap continues forward ... but the jetfuel stops. And then there is this magic, paranormal ball of fire.

As you gentlefolk attending JREF forum already should be aware of, I do not believe the 0.2 second video show of the plane slicing through the south wall of WTC2 is real. It is amateur Photo-shop animation (+ 10 seconds of something approaching the south wall prior that).

What does it mean?

A. That no 30 tons of jetfuel arrived/sliced through the south wall of WTC2 at 500 mph!

B. That the fire ball we see on the videos of WTC2 is not caused by subject jetfuel!!

I have to admit that I got quite depressed and unhappy when concluding B. It would have been easier to accept the magic, paranormal show and forget about it. It seems many NIST 'experts' do the same in various ways.

Any comments? But please, no insults, etc. I am quite a nice and extremely happy guy.

 

[Heiwa]

Maybe I'm missing something here, but when the floor trusses begin sagging, doesn't the sag itself make the straight-line distance between the end points of the truss shorter because of the curve of the sag since the length of the truss does not change? This would create a non-axial load on the columns, right?

The structural functions of the floors are described in my message #263. Apart from that the floor provided a horizontal fire division between the floors. The weight on/of that floor is small. When/if it sags due to heat it will produce a small axial force on the columns as the connection floor/columns is intact. But not enough to pull the perimeter columns inward. The latter are much stronger than that carrying the whole load of the section above. They are also interconnected by the spandrels. And they are not heated up to any extent.

 

[Belz...]

The NIST reports are full of nonsense.

Like what ?

What are your qualifications that allow you to dismiss the work of so many knowledgeable people ?

So 30 tons of jetfuel arrives at abt 500 mph and slices through the WTC2 south wall during 0.2 seconds - nothing happens ... and then the jetfuel stops inside the tower!! Magic!

Not magic...



Just burning straw.

Paranormal. Some scrap continues forward ... but the jetfuel stops.

Who said it stopped ? Didn't you see the giant fireball ?

As you gentlefolk attending JREF forum already should be aware of, I do not believe the 0.2 second video show of the plane slicing through the south wall of WTC2 is real.

Of course you don't. If you did, it would demolish your theories.

Of course, that's just you ignoring the THOUSANDS of people who saw that impact.

It is amateur Photo-shop animation

You couldn't even begin to tell me how someone could photoshop something like this LIVE.

B. That the fire ball we see on the videos of WTC2 is not caused by subject jetfuel!!

False dichotomy. Your lack of imagination has no effect on reality.

I have to admit that I got quite depressed and unhappy when concluding B. It would have been easier to accept the magic, paranormal show and forget about it.

I don't believe in magic. I believe that jet fuel burns explosively. Otherwise they wouldn't use it as jet fuel.

 

[Trifikas]

Out of my own curiousity, when the Floor truss sags (and I'm probably going to botch the wording of this), Since it's mass is centered away from the columns, does it have the mechanical advantage of acting like a lever, with the fulcrum and resistance at the column and it's own mass being the effort? Or is it a moot point, since the sagging truss is still connected at both sides, the forces balance out?

If it has a mechanical advantage, Does it become greater or lesser as it sags more and more?

 

[Heiwa]

Out of my own curiousity, when the Floor truss sags (and I'm probably going to botch the wording of this), Since it's mass is centered away from the columns, does it have the mechanical advantage of acting like a lever, with the fulcrum and resistance at the column and it's own mass being the effort? Or is it a moot point, since the sagging truss is still connected at both sides, the forces balance out?

If it has a mechanical advantage, Does it become greater or lesser as it sags more and more?

It becomes less! The weight on top of the floor (the furniture & Co) sagging it is burning and goes up in smoke and out of the windows. And the floor is more like a net ... just hanging on the columns. That's why it is sagging.

 

[Heiwa]

I don't believe in magic. I believe that jet fuel burns explosively. Otherwise they wouldn't use it as jet fuel.

OK - you order 30 tons jetfuel to heat your house and you intend to fill it in the tank in your garage.

The jetfuel arrives at 500 mph through your garage door within 0.2 seconds. Please advise how you intend to fill your tank in that time.

 

[Trifikas]

It becomes less! The weight on top of the floor (the furniture & Co) sagging it is burning and goes up in smoke and out of the windows. And the floor is more like a net ... just hanging on the columns. That's why it is sagging.

Well, the mass becomes less as it burns away, but I was really wondering if the mechanical advantage (if there is one) would increase or decrease. Even a net, if you strung it up between two poles, if you pushed on it would pull the poles inward. The higher up on the poles the net is attached, the easier it is to bend the poles by pushing the net. So there has to be some kind of mechanical advantage somewhere in the example, and by extention somewhere in the towers.

Meh, like I said, just curious.

 

[AZCat]

The structural functions of the floors are described in my message #263. Apart from that the floor provided a horizontal fire division between the floors. The weight on/of that floor is small. When/if it sags due to heat it will produce a small axial force on the columns as the connection floor/columns is intact. But not enough to pull the perimeter columns inward. The latter are much stronger than that carrying the whole load of the section above. They are also interconnected by the spandrels. And they are not heated up to any extent.

No you misunderstand. The sagging floors produce a transverse load on the columns because of the sagging, along with the axial load from the weight.

 

[JimBenArm]

Wouldn't the weight of, say, a big honkin' airplane sitting on top of the floor also contribute a bit to the sagging and pulling of the columns? Maybe?

 

[AZCat]

Wouldn't the weight of, say, a big honkin' airplane sitting on top of the floor also contribute a bit to the sagging and pulling of the columns? Maybe?

A couple of people looked at that in another thread (I think it was this one but I'm not sure) and IIRC the result was ~25 lbs/sqft max extra weight.

 

[The Almond]

Well, the mass becomes less as it burns away, but I was really wondering if the mechanical advantage (if there is one) would increase or decrease. Even a net, if you strung it up between two poles, if you pushed on it would pull the poles inward. The higher up on the poles the net is attached, the easier it is to bend the poles by pushing the net. So there has to be some kind of mechanical advantage somewhere in the example, and by extention somewhere in the towers.

Meh, like I said, just curious.

To answer your question, mechanical advantage (in the engineering sense) usually refers to moving parts. Structural engineers don't usually discuss things in terms of mechanical advantage.

The word you're looking for is torque, and yes, your string between two poles does exert a torque on the pole's connection to the ground.

Let's imagine a string tied to a rock that's suspended between two poles. Said rock causes the poles to make a 30 degree positive angle with the horizontal (assuming that counterclockwise is positive). Because the system is not moving, we know that the sum of forces in the Y direction is zero by Newton's first law. Thus we know that:

The weight of the rock = Y component of the force in the first string + Y component of the force in the second string.

The y component of the force in the string is the tension of the string times the Sine of the horizontal angle. Thus the equation becomes

W = T*Sin(30) + T*Sin(30)

Ok, next step is to follow the string to its connection with the pole, and follow the pole into the ground. I'm going to assume that the pole sticks into the ground like a nail sticks into wood. That means that any force transferred to the pole will be carried into the ground.

The string is pulling on the pole in two ways. The X component creates a moment couple with the ground as well as an X reaction with the ground that is equal and opposite to the string X force (Newton's 3rd law). The Y component increases the total gravity load on the pole.

The torque created by the string and the ground can be described in this way:
Torque = [X component of the string] * [Distance between the string and the ground]

Since we know the string makes a 30 degree angle with the horizontal, we know the X component of the string is T*cos(30). Thus, the equation becomes:
Torque = T*cos(30)*Distance from ground

So, to answer your question, I would suggest a spreadsheet with columns labeled as such:
Weight of Stone Angle with Horizontal Distance from Ground Tension in String X Component Torque

You can choose any values you want for weight of the stone, angle with the horizontal and distance from ground. The other three values will calculate based on those dependent variables.

What you will see is that as your angle decreases your torque will increase. That means that for extremely small angles, the torque is very high.

To relate this to the twin towers, the moment exerted on the poles is greatest when the floors sag at low angles. This is coupled with the out of plane loading exerted by the Y component force. When the columns bend, the gravity component no longer exists in the same plane as the column, creating further moments.

I would like to dedicate this lengthy response to my statics teacher Dr. E. Harry Law. Without his social life destroying marathon homework sets, this answer would not have been possible.

 

[Corsair 115]

As you gentlefolk attending JREF forum already should be aware of, I do not believe the 0.2 second video show of the plane slicing through the south wall of WTC2 is real. It is amateur Photo-shop animation (+ 10 seconds of something approaching the south wall prior that).

Ah, excellent, another person forwarding the "the videos are fake, special effects shots!" line of thinking.

Let me break out my handy checklist of special effects related questions to see if you actually have any understanding of the history and techniques involved in special effects and if you have any eye for detecting them.

To determine your knowledge of effects techniques and history:

What's stop-motion animation? What's front screen projection? What's rear screen projection? What's an optical printer? How does the use of an optical printer compare to how today's effects are done? How does the foreground miniature effect work? What's a matte painting? What's a travelling matte? What did the development of the motion-controlled camera mean to special effects work?

To determine your eye for detecting a special effects shot:

In the movie Aliens, there's a scene in which the character of Ripley demonstrates her proficiency in using the powerloader. The vehicle is a full-size, on-set effect. Watch how it moves; do you notice anything odd about the way it moves, and if so, what? There's also a shot with another powerloader in the background; can you describe what kind of effect was used to create it? If you have a good eye for spotting special effects, answering the foregoing questions should be fairly easy.