Merged David Chandler (ae911) sez "WTC7 was in free fall part of the time"

Hi!

I recently come across some youtube videos posted by "David Chandler". In it he uses footage of WTC7 and a software called "Physics Toolkit" to make the point that during a short intervall of the collapse, WTC7 was in fact in free fall, that NIST ignored this and that it is a sign of CD.

David Chandler said:

Contrary to the August 2008 NIST report on WTC7, the acceleration of Building 7 has been measured and is found to be indistinguishable from the acceleration of gravity over a period of about 2.5 seconds during the fall. Freefall indicates zero resistance. It also indicates that the energy of the falling mass is not available to do work on the lower structure (i.e. such things as breaking, bending, crushing, etc.) A video detailing the measurement process and commenting on the results is posted on the AE911Truth YouTube channel, accessible through http://www.ae911truth.org/freefall. The video responds to the recently released NIST WTC7 document.

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http://www.911blogger.com/node/17685


First video from may this year:



Second one from september:



I'm not experienced enough in the art of collapsing buildings or usage of Physics Toolkit, but could someone help me out here? What does he mean, and what merits does his argument have, if any?

I responded to this in the other thread, so I'll just repeat my post here.

Chandler actually proves to my satisfaction that for about 2.5 seconds, the top northwest corner accelerated at the same rate as gravity would accelerate it.

The problem is how Chandler then interprets this. He believes this can only be due to controlled demolition. He thinks that NIST covered up this period of freefall with deceptive language.

Nothing of the sort. NIST measured from the very beginning of the descent of the top northwest corner to where they both stop, at the height of the 29th floor. The time it took the building to fall is 40% slower than it would be if the building had accelerated at the rate of gravity for the entire time. There's no deception here. Math is math.

The building encountered significant resistance during this time, so much so that it could offset a period of 2.5 seconds where the corner was essentially in freefall.

And NIST's explanation does allow for this period of freefall. The western core (remaining after the eastern interior has collapsed) is yanking the perimeter down behind it, and since it begins to pull apart at the seventh floor, the core has to fall about that far before it encounters significant resistance from below. As soon as it does, the building slows again and begins to crush up.

At least, that's how this layman understands it.

boloboffin said:

The building encountered significant resistance during this time, so much so that it could offset a period of 2.5 seconds where the corner was essentially in freefall.

At least, that's how this layman understands it.

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The analysis covers 5 seconds:

The first second the acceleration of the top is small = plenty of resistance/support by the structure below (and above) the 29th floor.

The following 2.5 seconds the acceleration is 9.81 m/s² = no resistance at all by the structure below the 29th floor - the whole top part above floor 29 is in the air!! Only gravity (g = 9.81 m/s²) acts on it.

The last 1.5 seconds the acceleration ot the top is again small = plenty of resistance again by the structure below the 29th floor (or what remains of it).

The average acceleration during the 5 seconds is about 0.5 g, but that does not mean anything.

So the question is what happens below floor 29 during those 2.5 seconds when the top part was accelerating at g = 9.81 m/s²? Why doesn't the crumbling structure below floor 29 provide any resistance to the top part as it does before and after those 2.5 seconds?

The columns between ground and floor 29 are supposed to crumble due to the weight/load of the structure above floor 29 applied to them in combination with local failures caused by thermal expansion of supporting members of these columns.

But during 2.5 seconds the 49 columns below floor 29 do not offer any resistance at all. They are not there! Blown away?

Heiwa said:

The analysis covers 5 seconds:

The first second the acceleration of the top is small = plenty of resistance/support by the structure below (and above) the 29th floor.

The following 2.5 seconds the acceleration is 9.81 m/s² = no resistance at all by the structure below the 29th floor - the whole top part above floor 29 is in the air!! Only gravity (g = 9.81 m/s²) acts on it.

The last 1.5 seconds the acceleration ot the top is again small = plenty of resistance again by the structure below the 29th floor (or what remains of it).

The average acceleration during the 5 seconds is about 0.5 g, but that does not mean anything.

So the question is what happens below floor 29 during those 2.5 seconds when the top part was accelerating at g = 9.81 m/s²? Why doesn't the crumbling structure below floor 29 provide any resistance to the top part as it does before and after those 2.5 seconds?

The columns between ground and floor 29 are supposed to crumble due to the weight/load of the structure above floor 29 applied to them in combination with local failures caused by thermal expansion of supporting members of these columns.

But during 2.5 seconds the 49 columns below floor 29 do not offer any resistance at all. They are not there! Blown away?

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Are you saying that the support was blown up 1 second after it had already failed? Boy, I hope this conspiracy is fully revealed someday, just so I can see how friggin awesome and complex it really was.

Heiwa said:

The average acceleration during the 5 seconds is about 0.5 g, but that does not mean anything.

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Pay no attention to that average acceleration behind that curtain.

So the question is what happens below floor 29 during those 2.5 seconds when the top part was accelerating at g = 9.81 m/s²? Why doesn't the crumbling structure below floor 29 provide any resistance to the top part as it does before and after those 2.5 seconds?

The columns between ground and floor 29 are supposed to crumble due to the weight/load of the structure above floor 29 applied to them in combination with local failures caused by thermal expansion of supporting members of these columns.

But during 2.5 seconds the 49 columns below floor 29 do not offer any resistance at all. They are not there! Blown away?

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When you quoted my post, you deceptively snipped away the part where I explained this. Here it is again, bolded for your edification:

boloboffin said:

...The building encountered significant resistance during this time, so much so that it could offset a period of 2.5 seconds where the corner was essentially in freefall.

And NIST's explanation does allow for this period of freefall. The western core (remaining after the eastern interior has collapsed) is yanking the perimeter down behind it, and since it begins to pull apart at the seventh floor, the core has to fall about that far before it encounters significant resistance from below. As soon as it does, the building slows again and begins to crush up.

At least, that's how this layman understands it.

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Now feel free to knock holes in that. I am a layman in this and welcome actual criticism from anyone. But don't play sophistic fallacy games and expect to get away with it here, Heiwa.

I did some math. According to the measurements by Chandler, the building is moving about 1.5 m/s when it begins freefall, and then hits 26.5 m/s 2.5 seconds later.

Using this site:

http://www.ajdesigner.com/constantacceleration/cadisplacement.php

I first calculated the average velocity (14 m/s), and then the actual distance traveled during this 2.5 seconds. It's 35 meters.

Now according to the figures provided by Chandler from NIST, the elevation of the top of Floor 29's windows was 683' 6" and the elevation of the top of the parapet wall was 925' 4". The difference is 241.83 feet for the 18 floors, an average height of 13.4 feet, or 4 m.

So, since the building falls 35 m in 2.5 seconds, it falls about 9 floors distance in that time.

The buckling of the building model (Figure 3-14 in NCSTAR_1A (page 38, pdf 76)) is between floors 7 and 14, 7 floors distance (or 28 m). The entire building would have been in virtual freefall during this time. If during the buckling, two more floors were destroyed (one on top and one on bottom), then the distance the top of the roof drops in freefall is fully explained.

Again, I'm a layman. Any structural engineers that want to jump in and correct me, please do so.

Heiwa said:

The average acceleration during the 5 seconds is about 0.5 g, but that does not mean anything.

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But a free fall would require a 1g average acceleration.

Is that mean that after seven years of screaming "free fall speed" a truther actually took the time to measure WTC7 collapse time and found out that it wasn't free fall. Can we consider the the "WTC7 free fall" claim debunked now?

Panoply_Prefect said:

Hi!

I recently come across some youtube videos posted by "David Chandler". In it he uses footage of WTC7 and a software called "Physics Toolkit" to make the point that during a short intervall of the collapse, WTC7 was in fact in free fall, that NIST ignored this and that it is a sign of CD.



http://www.911blogger.com/node/17685


First video from may this year:



Second one from september:



I'm not experienced enough in the art of collapsing buildings or usage of Physics Toolkit, but could someone help me out here? What does he mean, and what merits does his argument have, if any?

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I can help you. The free fall proves that WTC 7 was a controlled demolition. Science has proved that.

What science can't prove is who set the explosives. Some believe that Osama bin Laden set them. Others believe Saddam Hussein set them. And some think Dick Cheney or Larry Silverstein did it.

I can help you. The free fall proves that WTC 7 was a controlled demolition. Science has proved that.

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Galileo said:

I can help you. The free fall proves that WTC 7 was a controlled demolition. Science has proved that.

What science can't prove is who set the explosives. Some believe that Osama bin Laden set them. Others believe Saddam Hussein set them. And some think Dick Cheney or Larry Silverstein did it.

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That is a dumb statement. Good job offering no proof. BTW, the WTC7 fell slower than free fall. You failed to do your own work.

boloboffin said:

Chandler actually proves to my satisfaction that for about 2.5 seconds, the top northwest corner accelerated at the same rate as gravity would accelerate it.

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In order to do the type of analysis that he is talking about we first have to know where he got the video and the camera. The weird thing is that they could be doing analysis on video that is missing information. You have optical distortions that you need to correct for which you can't do with that software package (Technically, don't need the camera).
EDIT:
After re-watching five seconds of the movie he validated my opinion. He's a )*(Y&(*&ing moron that isn't an engineer because an engineer wouldn't be caught dead doing the moronic, half brained, idiotic things he is trying. YOU DON'T CALIBRATE THE FREAKING IMAGE USING LINES DRAWN ACROSS IT. IT'S A BLOODY DAM COMPLICATED PROCESS. WARNING. WARNING. DO NOT FALL FOR STUPIDITY. THEIR ANALYSIS IS STILLBORN.
EDIT EDIT:
I was right. He's a mathematician/physicist. You would think the electrical (Yes this is electrical engineering's domain.) engineers would help out.

I still don't fully understand the fault... Does anyone know the software he uses (Linked above)? Does it in fact do what he claim it does? What is it typically used for?

Physics ToolKit, previously named World-in-Motion, is a useful educational tool for lecture, lab, and student assignments.

Click to expand...

Video analysis software with videos covering common topics in mechanics, sound and electromagnetic fields and waves.

Click to expand...

What error margin does it have? (eg, he claims it shows freefall, in the first video he calibrates on different markers and still get values close to what he claims shows free fall). Eg how exact must the measurement be to draw the certain conclusion that it is indeed "freefall" and not just due to pixelerrors or speed of the shutter of the camera or what have you (just making examples here). How exact a measurement do you get by doing what Chandler does with this particular toolkit?

Galileo said:

I can help you. The free fall proves that WTC 7 was a controlled demolition. Science has proved that.

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Well if that is true, Im equally interested in learning that. Im just trying to understand what Chandler actually does. Feel free to help out explaining this.

Panoply_Prefect said:

I still don't fully understand the fault... Does anyone know the software he uses (Linked above)? Does it in fact do what he claim it does? What is it typically used for?

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Judging from the website high school physics labs. True video analysis software would be Matlab, or even OpenCV.

boloboffin said:

Again, I'm a layman. Any structural engineers that want to jump in and correct me, please do so.

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Any structural engineers inhouse that can help me understand Chandlers little demo? Technoextreme says that optical distortions could umm... distort the results, however Chandler does two or three different measures which all, so he claims, shows freefall. This would indicate that there would have to be helluva distortion to make his claim invalid. Is he correct in this assertion?

Apparently his claim made it into the San Luis Obispo County Tribune in a piece written by "Mark Phillips a retired mechanical engineer" (and yes, it contains a lot of standard trutherism, including Jowenko):

http://www.sanluisobispo.com/182/v-print/story/466920.html

Because the collapse of WTC 7 is not obscured by smoke or debris it is possible to measure its rate of descent with considerable accuracy.
David Chandler, who believes it was an inside job, has done a very precise measurement (see “WTC7 in Freefall” on YouTube) and found that for approximately 2.5 seconds, WTC 7 fell at a rate that is indistinguishable from freefall. This means that for those 2.5 seconds, thousands of tons of structural steel and concrete offered essentially zero resistance. This is impossible given the official theory but is consistent with a controlled demolition.
NIST avoids this problem by using a longer time span and calculating an average acceleration. In this way it hides the evidence that disproves its theory.

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Panoply_Prefect said:

Any structural engineers inhouse that can help me understand Chandlers little demo? Technoextreme says that optical distortions could umm... distort the results, however Chandler does two or three different measures which all, so he claims, shows freefall. This would indicate that there would have to be helluva distortion to make his claim invalid. Is he correct in this assertion?

Apparently his claim made it into the San Luis Obispo County Tribune in a piece written by "Mark Phillips a retired mechanical engineer" (and yes, it contains a lot of standard trutherism, including Jowenko):

http://www.sanluisobispo.com/182/v-print/story/466920.html

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I like the way both you and Heiwa have made SURE to quote my admission of being a layman.

Tell you what. If you have problems understanding Chandler's presentation, that's not the fault of any structural engineer here. Take it up with Chandler.

I'm quite sure, also, that one or two of the structural engineers we have inhouse have been able to look at this thread. If they didn't see anything wrong with my answer, I would say the ball is in your court to find something wrong with it yourself.

So get cracking.

Panoply_Prefect said:

Any structural engineers inhouse that can help me understand Chandlers little demo? Technoextreme says that optical distortions could umm... distort the results, however Chandler does two or three different measures which all, so he claims, shows freefall. This would indicate that there would have to be helluva distortion to make his claim invalid. Is he correct in this assertion?

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Why are you asking the wrong type of engineer? It's the equivalent of asking an electrical engineer why the mechanism involved in the collapse of the World Trade Center. The reason why I can't give you a straight answer is because of the complexity involved. You have the distortions caused by the camera which would make lining up any of the straight lines close to impossible because a straight line would not be straight even though you knew the line was straight to start with. You may or may not have lost informattion from the compression method.

boloboffin said:

I like the way both you and Heiwa have made SURE to quote my admission of being a layman.

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Actually there was no malicious intent in doing so, I just quoted a smaller part of your post to hook onto your call for structural engineers to join in. I don't see Heiwas posts as he is on my ignore list.

boloboffin said:

Tell you what. If you have problems understanding Chandler's presentation, that's not the fault of any structural engineer here. Take it up with Chandler.

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I've contemplated that, but I'm not sure if that would do any good - after all he has already presented his case (but if he reads this thread, feel free to join in). Instead I've written the makers of the Physics Toolkit to see what they have to say about Chandlers "experiment"

boloboffin said:

I'm quite sure, also, that one or two of the structural engineers we have inhouse have been able to look at this thread. If they didn't see anything wrong with my answer, I would say the ball is in your court to find something wrong with it yourself.

So get cracking.

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I'm still not sure I understand it, thats why Im asking for more input, its not a criticism of your argument.

/PP

technoextreme said:

The reason why I can't give you a straight answer is because of the complexity involved. You have the distortions caused by the camera which would make lining up any of the straight lines close to impossible because a straight line would not be straight even though you knew the line was straight to start with. You may or may not have lost informattion from the compression method.

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I think I get it: Chandler uses the known width of the building (at least in the may-video), to calibrate the software. The software uses a straight red line, which Chandler gives the value of the known width. However if the building is angled even the smallest, the calibration will be off. The more the angle, the longer/shorter the red line, the more error.

Is this correct or is it more to it?

Panoply_Prefect said:

I think I get it: Chandler uses the known width of the building (at least in the may-video), to calibrate the software. The software uses a straight red line, which Chandler gives the value of the known width. However if the building is angled even the smallest, the calibration will be off. The more the angle, the longer/shorter the red line, the more error.

Is this correct or is it more to it?

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Yes. In most optical systems straight lines in a picture become curved. The pictures on wikipedia show the distortion but the effects are exaggerated for clarification purposes. http://en.wikipedia.org/wiki/Distortion_(optics)

technoextreme said:

Yes. In most optical systems straight lines in a picture become curved. The pictures on wikipedia show the distortion but the effects are exaggerated for clarification purposes. http://en.wikipedia.org/wiki/Distortion_(optics)

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I also noted that on his homepage he has noted that is may-version recieved critisism:

David Chandler said:

The previous analysis of the freefall acceleration was criticized (legitimately) for using a horizontal calibration measurement for analyzing purely vertical motion. Any distortion or stretching of the video could throw off the measurement. In this new video, the calibration utilizes NIST's data for the heights of the roofline and the 29th floor to do a vertical calibration. The result is a measurement even closer to idealized freefall: 9.88 m/s^2.

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He has also removed a video with the following explanation:

David Chandler said:

I removed this video because when I did additional runs at different resolutions, I always got extreme accelerations, but not the same amounts in the same places. This made me skeptical of the procedure. Finding accelerations from position data involves double numerical differentiation, a process that can amplify "noise" in the data. The raw data in this analysis is the inherently noisy positional measurement
of cloudy material, and the conclusions were based on the short term variations in the acceleration. This raises the likelihood that the extreme accelerations are artifacts. The WTC7 measurements (above) do not suffer the same defect because (1) they are measuring the motion of a more definite point of solid material, and (2) the conclusions are based on long term average acceleration.

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I recieved a reply from the maker of Physics Toolkit yesterday - I'm at work now so I dont have the mail in front of me, but apparently the software is limited to using a fixed resolution of the video, I think it was 480x320 pixels. As I understand it this means that no matter what resolution of video you input, the software will always only use 480x320. I imagine this would limit the exactness also?

Panoply_Prefect said:

I recieved a reply from the maker of Physics Toolkit yesterday - I'm at work now so I dont have the mail in front of me, but apparently the software is limited to using a fixed resolution of the video, I think it was 480x320 pixels. As I understand it this means that no matter what resolution of video you input, the software will always only use 480x320. I imagine this would limit the exactness also?

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Hmm.Then I would wage it is nearly useless at least in this case,since error might be quite large,which would explain why it arrived at freefall.

But it is bit nonsensical limitation...

Just my 2 lurk-cents.

Klimax said:

Hmm.Then I would wage it is nearly useless at least in this case,since error might be quite large,which would explain why it arrived at freefall.

But it is bit nonsensical limitation...

Just my 2 lurk-cents.

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Here is the full reply:

The tool uses a 480 by 360 pixel image, so this limits
length measurement in the video. Then, one must know
some distance in the video and the frame rate of the
video. So, image quality and knowing length and time
are important. These, along with marking the video,
will be sources of error.

Click to expand...

Panoply_Prefect said:

Klimax said:

Hmm.Then I would wage it is nearly useless at least in this case,since error might be quite large,which would explain why it arrived at freefall.

But it is bit nonsensical limitation...

Just my 2 lurk-cents.

Click to expand...

Here is the full reply:

The tool uses a 480 by 360 pixel image, so this limits
length measurement in the video. Then, one must know
some distance in the video and the frame rate of the
video. So, image quality and knowing length and time
are important. These, along with marking the video,
will be sources of error.

Click to expand...

Click to expand...

I think (no time for calculation) that from certain distance (in dozens,at best hundreds meters) one pixel will cover quite a big area rendering caluclation nearly useless - too big error.Even best quality will not offset resolution.

Sorry for similarity in my posts,but your memory proved to be good source.(Since I took into account video quality,distance and such...)

I just realized, NIST actually mentions the freefall Chandler is talking about, explicitly:

NIST said:

In Stage 2, the north face descended at gravitational acceleration, as the buckled columns provided negligible support to the upper portion of the north face. This free fall drop continued for approximately 8 stories or 32.0 m (105 ft), the distance traveled between times t = 1.75 s and t = 4.0 s.

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This means that Chandler has the freefall at 2,5 seconds, NIST at 2,25. Chandlers timeframe allows for a 9 (or 8,75) story drop, NIST 8 stories.

AFAIK that is.

That section you quoted was not in the draft report, Panoply. They went back, evidently in response to the Chandler/AE911Truth video, and did the closer analysis. Good on them.

And good on you for making sure this point was explained clearly.

As far as I understand you can even see the tilt in this video:

http://www.dailynewscaster.com/2008...e-of-building-seven-and-north-tower-collapse/

My analysis vindicated by NIST

The final NIST report on WTC7 concedes freefall (acceleration at 9.81 m/s^2) for ~2.25 seconds. They re-did the analysis and tracked a point midway along the roofline of the building. My analysis followed the NW corner of the building. The fact that two points so widely spaced underwent simultaneous freefall with instantaneous onset indicates that support was knocked out across a major portion, if not all, of the building for at least 8 stories. There are another 8 stories, by the way, where resistance was minimal. The velocity didn't stabilize until it was descending at ~30 m/s. NIST was forced to revisit the issue because their own analysis (two data points to find an average acceleration over an interval in which there was not constant acceleration) was so transparently fraudulent. No competent physicist or engineer could endorse such a procedure, and the professionals at NIST apparently agree with me. There are plenty of competent people at NIST and they seem to have triumphed over the political hacks that are running the NIST investigation (i.e. the NIST coverup).

Apparently I can't leave links when I'm new to the forum, and I don't plan to hang around this forum after this post, but I just wanted to point out to you guys that your argument is now not with me but with NIST.

The coverup continues and we have more to uncover. Stay tuned for more neat physics demos.

--David Chandler

davidschandler48 said:

The final NIST report on WTC7 concedes freefall (acceleration at 9.81 m/s^2) for ~2.25 seconds. They re-did the analysis and tracked a point midway along the roofline of the building. My analysis followed the NW corner of the building. The fact that two points so widely spaced underwent simultaneous freefall with instantaneous onset indicates that support was knocked out across a major portion, if not all, of the building for at least 8 stories. There are another 8 stories, by the way, where resistance was minimal. The velocity didn't stabilize until it was descending at ~30 m/s.

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Welcome to the Forum.

I feel compelled to point out that, in NIST's actual collapse hypothesis, the support (the core) in fact was knocked out for over ten stories in the region you claim, and there was no remaining support from below at the perimeter. NIST did not require any explosives for this condition to arise.

davidschandler48 said:

NIST was forced to revisit the issue because their own analysis (two data points to find an average acceleration over an interval in which there was not constant acceleration) was so transparently fraudulent. No competent physicist or engineer could endorse such a procedure, and the professionals at NIST apparently agree with me. There are plenty of competent people at NIST and they seem to have triumphed over the political hacks that are running the NIST investigation (i.e. the NIST coverup).

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I don't believe this is true. NIST acknowledged your observation, but that is because it appears to be correct, within the limits of experimental error. What is at issue is the interpretation of that observation. NIST certainly does not agree with you that explosives are the only thing that could cause it, and neither do I.

davidschandler48 said:

Apparently I can't leave links when I'm new to the forum, and I don't plan to hang around this forum after this post, but I just wanted to point out to you guys that your argument is now not with me but with NIST.

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You are required to have 15 posts before including links, however an abbreviated link is welcome in the meantime.

In any case, I disagree. What you have found is an effect. NIST agrees with that effect. What you are now claiming instead is a cause, but you have not demonstrated that your cause is the one and only explanation. Until you do so, our argument remains with you.

To stimulate further discussion, may I also point out that we have accepted the possibility of very high accelerations, approaching 1 g, all along. See this thread for an example of such a discussion, concluding that the actual descent rate could indeed wind up within the margin of error of "free fall," yet have nothing whatsoever to do with explosives. I remind readers that the thread starter is under no circumstances a "government stooge" or what have you, but instead approached the problem from the opposite initial viewpoint.

Furthermore, supposing there were explosives used, one expects their placement would result in a very similar core damage sequence to the one that NIST found likely as a result of fire. This suggests that NIST and a typical CD hypothesis would be indistinguishable on the basis of a roofline velocity test. Instead we look to other tests, such as the sound and blast effect on windows, and these rule conclusively against explosives.

Feel free to propose your own hypothesis if you think you have a better one. I have yet to hear one that is even vaguely plausible.

I'd like to point out that the draft report is where I found the information about floors 7-14 buckling. You are claiming deception based on one small section of the report, without considering everything that NIST said.

I've added a section to my AE911Wiki about all of this. You can read it here, if you like. Nothing new that isn't here, though.

And yes, now that the elections are well and truly over, I'm going to be updating the site again.

I still don't fully understand the fault... Does anyone know the software he uses (Linked above)? Does it in fact do what he claim it does? What is it typically used for?

Quote:
Physics ToolKit, previously named World-in-Motion, is a useful educational tool for lecture, lab, and student assignments.
Quote:
Video analysis software with videos covering common topics in mechanics, sound and electromagnetic fields and waves.
What error margin does it have? (eg, he claims it shows freefall, in the first video he calibrates on different markers and still get values close to what he claims shows free fall). Eg how exact must the measurement be to draw the certain conclusion that it is indeed "freefall" and not just due to pixelerrors or speed of the shutter of the camera or what have you (just making examples here). How exact a measurement do you get by doing what Chandler does with this particular toolkit?

Howdy Panoply,

Nice to meet cha. I ought to be able to help you out with this. I'm an experienced mechanical engineer, so this stuff is straight forward.

A couple of quick comments:

Physics ToolKit is intended is for exactly this sort of analysis. And it can do a superb job. As long as you know the fine details of how to implement it. If you know about & pay attention to all these details, you can get spectacular results. Ignore the wrong one and it's GIGO, as they say.

The math & physics of the idealized problem are trivial. The details of what are going on mechanically are not. The real world problem is engineering, not physics. In other words, messy with complications.

In Chandler's case, he did everything right in his calculations. Then he blew ONE thing - he did not try to QUANTIFY the forces resisting the collapse. He stayed all "touchy-feely" and assumed that they would be large enough to be seen in the deceleration of the outer wall. He assumed wrong.

And THEN... demonstrating a classic case of "a little bit of knowledge can get you into a lot of trouble", he began drawing conclusions about things that he does NOT know about: 1. structures, 2. NIST's motives, 3. NIST's competence & 4. NIST's collective nefariousness.

He is absolutely correct in his fundamental objection about the NIST results. That is, that publishing a gross average acceleration instead of a more detailed acceleration "smears out" some of the details about what is going on. NIST's "40% decrease compared to free fall" is misleading, and highly dependent upon the arbitrarily selected interval over which they take their average. One point to Chandler.

However, the crucial point here is that Chandler's results agree EXACTLY with NIST's. Chandler didn't have to do this work at all. He replicates EXACTLY NIST's graph shown in Fig 12-77 on page 603 of NCSTAR 1-9 (Vol 2). This is page 265 of the downloadable pdf file. The slope of the best fit linear curve is "32.196". (Keeerist, don't they teach kids about "significant digits" any more??!!! It should be 32.2, probably ±0.5 or so.) A glaring omission in both papers is an error analysis - a CRITICAL component of any competent engineering paper.

But BOTH Chandler & NIST's results show that the wall IS essentially "in free fall" during this interval.

Chandler's somewhat snarky comments (mis)interpreting WHY they did so are both annoying and off-base. I've written reports exactly like this. I've had managers & lawyers & CEOs beating on me about phraseology. If the phrasing "significantly" changed the interpretation of my work, I've always refused to budge. If it was soft & subjective, I'd find some compromise that got the accurate message across, but did not hand a bludgeon to a perverse, adversary who might NOT be interested in "playing fair".

The fact is that the level of detail that one puts into engineering report that is intended for public consumption is an ART, not science. It's a judgment call, and NIST decided to paint the woodwork with a 4" wide brush, and Chandler wants to use a 1" wide one.

The main difference is that Chandler discusses this segment of the curve in detail. And some pencil-neck manager at NIST clearly decided that "NOBODY says 'free fall'. We'll be fighting these bozos for years."

And his ultimate conclusion ("In short, the evidence is clear. We are witnessing not the collapse of a building, but its demolition") is utter nonsense.

The correct conclusion is "The outer wall DID fall at approximately free fall acceleration for this period of time. And what this means is that the resisting forces were insignificant COMPARED TO the weight of the walls".

Putting this into work & energy terms, his results show that the work done in destroying the REMAINING structure that supported the walls (not the WHOLE building structure) was insignificant COMPARED TO the kinetic energy available to do that work.

The forces are not zero. They are simply too small to be resolved within this data. They are masked by forces that are orders of magnitude greater. The same applies to the work to demolish the REMAINING wall supports.

A couple of things to remember:

The internal structure of WTC7 had already been destroyed BEFORE the walls begin to fall. Therefore, the work required to destroy those elements will NOT show up by decreasing the downward acceleration of the walls. [This is in direct contrast to the Towers, where the work to destroy each floor DID slow down the descent of the upper block significantly.]

Once any component has detached itself from the walls (or the upper block, in the case of the towers), its destruction or pulverization will NOT show up in a decreased acceleration of the walls (or upper block) sImply because the forces exerted on the component in its destruction are not transmitted back to the upper block.

Note that, before 0.8 seconds (Chandler data), there are clearly internal structures still supporting the wall. They are in the process of failing. At 0.8 seconds, some critical component near the bottom of the structure fails, and complete collapse begins. This type of failure (resisting ... resisting ... resisting ... complete failure!) is absolutely typical of large structures. The same thing happened in the towers.

After 3.2 seconds (Chandler data), the downward acceleration of the wall decreases for the following reason.

In the velocity vs. time graph, acceleration appears as the slope of the graph. One can INFER the forces if one knows the mass of the object being acted upon - in this case, the wall of the building, by the old "F = m A" equation. Note that, for a given force, smaller masses mean greater accelerations.

The upward force transmitted to the wall by the destruction of the lowest floor is APPROXIMATELY constant. It is actually a series of short-duration impulses of approximately constant magnitude. It is the force required to snap the bolts & welds holding each column to the one below it. However the mass of the wall is constantly decreasing because it is being chopped off at the bottom. Therefore a constant upward force will produce a continuously increasing effect (the effect being a reduction in the downward acceleration) of the wall.

I hope this helps.

There are a bunch of additional interesting things that appear in this data, but I figured that was enough to digest in a first serving...

tomk

925 feet sure seems high for a 47-story building, doesn't it?

jhunter1163 said:

925 feet sure seems high for a 47-story building, doesn't it?

Click to expand...

I've noticed this, too. WTC 7 was not 925 feet tall. However, the NIST report says that figure is "elevation," so I'm thinking that this is sea level, somehow, even though it would surprise me to think of 7 being that high off sea level on the end of Manhattan Island. Isn't most of that southern part reclaimed land?

Since this figure and the other used (the elevation of the 23rd) floor are off by the same amount, the end result of calculations are the same. But that 925 figure startled me as well.

Yep, it's high. It should be about 12.3 feet per story. Unless they had majorly modified structures. Such as the 2nd story was above the Con Ed power station...


tk

One of the very cool things that this whole exercise proves is that "you can't screw with real data". The data is the data. And those who believe that NIST (or anyone else) can just make up data are deluded.

And it shows that the correct response to "bad analysis" is "good analysis". NOT "all analysis is untrustworthy."

Unfortunately, for all of us, our lack of knowledge about fields outside of our own experience require that we possess a well-tuned epistemology. That requires that we develop the skills to distinguish real experts from both fake ones & "less than maximally competent" ones.

A healthy BS-o-meter always helps, of course.

PP., BTW, I sent Mr. Phillips an email & invited him to join in the discussion.

tk

I find it "interesting", one might say "lacking in confidence" that the ability to add comments to either of Mr. Chandler's videos has been disabled.

www(dot)youtube(dot)com(slash)watch?v=gC44L0-2zL8&watch_response
And
www(dot)youtube(dot)com(slash)watch?v=atSd7mxgsGY

Mr. Chandler, if you come back, would you care to explain why this is?

tk

Oops.

The height of the building is not due to the substation. Bad to guess like that. I know better.

Here are disagreeing details on the height of WTC7.

This resource puts the roofline at 571'. AND at 525' ("... the building's floor space and height of 160 m were ..."). Go figure...? www(dot)emporis(dot)com/en/wm/bu/?id=114932

NIST says:
"WTC 7 was an irregular trapezoid, approximately 100 m (329 ft) long on the north face and 75 m (247 ft) long on the south face, 44 m (144 ft) wide, and 186 m (610 ft) tall.

Structurally, WTC 7 consisted of four "tiers."

• The lowest four floors housed two two-story lobbies, one each on the center of the south side of the 1st and 3rd floors. The north side of the 1st and 2nd stories was the Con Edison substation. The remainder of the north, east, and west sides of these four stories was conference space, offices, a cafeteria, etc.

• Floors 5 and 6 were mechanical spaces. Within the volume bounded by the 5th floor slab and the 7th floor slab were three transfer trusses and a series of eight cantilever transfer girders. As their names indicate, these steel assemblies distributed the load of the upper floors of WTC 7 onto the structural frame of the Con Edison substation and the structure of the lowest four floors of WTC 7.

• Floors 7 through 45 were tenant floors, all structurally similar to each other. The exception was a reinforcing belt truss around Floors 22 and 23.

• The 46th and 47th floors, while mainly tenant floors, were structurally reinforced to support special loads, such as the cooling towers and the water tanks for fire suppression."
___

47 stories, 610' tall, average height 13'/story. I don't know if this includes the penthouses.

From photos, I'd estimate the penthouses as approximately 2 stories tall.

I'd use the roofline of 571'. And I'd recommend Mr. Chandler (or anyone else looking to perform this analysis) get their hands on some blueprints.

tk

Last comment of the height of the towers.

Looking around, it appears that the blueprints have been hard to come by. The CTers keep claiming that they've been "suppressed" by NIST.

But one could EASILY recreate the height from the FEA images provided in the WTC7 report. These models are constructed using accurate dimensional data, and the print out will also be precisely accurate to the best of NIST's information, of course.

The WTC7 final Final report suggests that the whole structure collapsed when column 79 between floors 11 and 13 failed.

Falling debris inside did not contribute!

So the whole building relied on only one component - column 79 between floors 11 and 13!!

I made a FEM/beam model of a tower 100 x 50 x 144 metres with 50 columns of which 24 are inside the structure (all 5 meters apart) and 40 floors (89 beams connecting the columns at every floor) and loaded it so that the maximum combined stresses in all components were 0.3 x yield (columns getting stronger at the bottom). And then I removed one internal column between floors 11 and 13 (the top part of the column was thus not connected to ground any more but hanging in the air). No collapse occurred! Just load distribution to adjacent internal columns and slightly higher stresses there.

It seems that my structure has more redundancy than WTC7.

Actually, I have never read such an awful report as the NIST WTC7 report. Pure propaganda! The structural analysis after initial failure is simply not correct.