The 9/11 Forum

I recommend estimating the errors in the data extracted from the video. From this, one can determine error bars for the speed and acceleration. I opine these are larger than you might currently suppose.

As it is, I fear I have no confidence in there being any statistical significance in changes of acceleration.

David B. Benson wrote:I recommend estimating the errors in the data extracted from the video. From this, one can determine error bars for the speed and acceleration. I opine these are larger than you might currently suppose.

As it is, I fear I have no confidence in there being any statistical significance in changes of acceleration.

It sounds like you don't believe there was a jolt. Is that what you are implying?

T_Szamboti --- It is not a matter of belief. It is a matter of proper scientific, in this case, statistical, practice. Define two hypotheses:

H0: Only slow changes in acceleration;

H1: A jolt.

Apply statistics to determine if H0 can be rejected in favor of H1 with any reasonable degree of confidence, even 80% although 90% is commonly the minimum allowed (one chance in ten you are wrong). I have my doubts that this is possible with just the one video analyzed so far.

David B. Benson wrote:T_Szamboti --- It is not a matter of belief. It is a matter of proper scientific, in this case, statistical, practice. Define two hypotheses:

H0: Only slow changes in acceleration;

H1: A jolt.

Apply statistics to determine if H0 can be rejected in favor of H1 with any reasonable degree of confidence, even 80% although 90% is commonly the minimum allowed (one chance in ten you are wrong). I have my doubts that this is possible with just the one video analyzed so far.

First, there is a basis in scientific logic for the jolt (and it isn't a slow change in acceleration, it is a deceleration which is observed) as it is the only mechanism which would provide for the load amplification of the statically insufficient load above to cause destruction of the building below and itself.

With that in mind the fact that it is observed in a situation, which obviously needed it, is not the unsupported stretch you are making it out to be here.

Your doubt and call for more study seems to be what is somewhat unfounded here.

T_Szamboti wrote:First, there is a basis in scientific logic for the jolt as it is the only mechanism which would provide for the load amplification of the statically insufficient load above to cause destruction of the building below and itself.

False, in general. You are making assumptions about the behavior of the structure, a structure about which you know very little.

With that in mind the fact that it is observed in a situation, ...

My scientific skepticism is merely asking you to perform a standard hypothesis comparison. As is normal in science. Especially as I don't see it in the graphs presented nor in the smearogram.

Your disbelief seems to be what is somewhat unfounded here.

I neither "believe" nor "disbelieve".

But let me suggest a simplier, preliminary comparison between two models:

H0: After the first fraction of a second, constant speed. This model requires but two parameters for the best line fit to the drop data via linear regression.

H1: After the first fraction of a second, constant acceleration up to time t1. At and after t1, constant speed. This model requires four parameters. Determine the best fitting four parameters, that is those five which minimzee the sum of the squares of the residuals.

Use the corrected Akaike Information Criterion (AICc), see

http://en.wikipedia.org/wiki/Akaike_information_criterion

to correctly treat the paucity of the data. Here are suggested break points in the differences of the two AICcs (not original with me):

AIC diff support for equivalency of models

0-2 substantial

4-7 weak

> 10 none

So if the difference in the AICs is small, there is no way to say that one model is better than the other.

I have now done 3 more or less equivalent drop and velocity vs. time plots for the ABC, WTC 1 and WTC 7 building failures.

The ABC Building "verinage" demolition shows a clear jolt 5 - 6 meters or 1.2 seconds into the collapse corresponding to the two floor-height collapse initiation mechanism seen in the Mort d'un Batiment video. Subsequent jolts at 8 meters, (1.6 seconds) and 11 meters, (2 seconds) are seen in the velocity vs. time plots due to the failures of the next two floors.

The NIST Camera 3 video of the collapse of WTC 7 shows some interesting, (and DBB, very reproducible), "jolts" at 2.4, 3.4 and 4.1 seconds,..... for Building 7, it's hardly a "jolt-free" collapse!

The Sauret video of the demise of WTC 1 is actually very noisy, making detection of a jolt difficult, but a little data smoothing shows a monotonic, jolt-free, roofline descent. (The Sauret video noise is probably caused by camera shake + atmospheric refraction effects due to the very long range (5 km?) involved in shooting the video.)

Nevertheless, I believe the absence of a jolt in the collapse of WTC 1 proves very little about what actually happened to WTC 1 on 9/11 and it certainly does not rule out a natural collapse.

I think the very massive hat truss sitting atop WTC 1 is the key .......

Dr. G wrote:I have now done 3 more or less equivalent drop and velocity vs. time plots for the ABC, WTC 1 and WTC 7 building failures.

The ABC Building "verinage" demolition shows a clear jolt 5 - 6 meters or 1.2 seconds into the collapse corresponding to the two floor-height collapse initiation mechanism seen in the Mort d'un Batiment video. Subsequent jolts at 8 meters, (1.6 seconds) and 11 meters, (2 seconds) are seen in the velocity vs. time plots due to the failures of the next two floors.

The NIST Camera 3 video of the collapse of WTC 7 shows some interesting, (and DBB, very reproducible), "jolts" at 2.4, 3.4 and 4.1 seconds,..... for Building 7, it's hardly a "jolt-free" collapse!

The Sauret video of the demise of WTC 1 is actually very noisy, making detection of a jolt difficult, but a little data smoothing shows a monotonic, jolt-free, roofline descent. (The Sauret video noise is probably caused by camera shake + atmospheric refraction effects due to the very long range (5 km?) involved in shooting the video.)

Nevertheless, I believe the absence of a jolt in the collapse of WTC 1 proves very little about what actually happened to WTC 1 on 9/11 and it certainly does not rule out a natural collapse.

I think the very massive hat truss sitting atop WTC 1 is the key .......

Dr. G, I am glad to see you were honest enough to admit to the evidence of jolts in the abc tower and WTC 7.

The abc tower was a publicly announced controlled demolition and two stories were removed to allow the upper block to fall at near freefall speed onto the lower block. WTC 7 had a freefall for 2.25 seconds or six stories and then there where jolts. The likelihood of that freefall occurring without columns being removed is extremely remote and so the reality that WTC 7 was a controlled demolition is highly probable.

However, full freefall isn't necessary to have a complete natural collapse, or where gravity is being used to collapse the building after removing a number of floors in a controlled demolition, but a jolt is necessary for the load amplification needed to overcome the factor of safety of the columns below, due to the statically insufficient load above. You don't have that in WTC 1 and the possibility of a smooth natural collapse without load amplification is so remote as to be silly.

Without evidence for a jolt it appears that at least key columns of WTC 1 were simply being removed for the nine stories we have been able to measure the fall of it's upper block. It is most likely that outer core columns were removed since it explains the inward bowing of the perimeter columns and would be enough to cause collapse while some resistance remained, although insufficient to prevent the collapse, and keep the fall at a level less than gravity.

The hat truss weight in the Twin Towers is insignificant to any collapse scenario as it was considered in the column sizing. The load above the columns was far less than their capacity and they simply aren't collapsing without load amplification or being removed in some way. Additionally, the hat truss could not have transferred enough vertical load to cause overload of the core columns. They were intended to transfer lateral loads and their perimeter column connections would not withstand the level of vertical loading required to overload the core columns and cause them to buckle.

The NIST Camera 3 video of the collapse of WTC 7 shows some interesting, (and DBB, very reproducible), "jolts" at 2.4, 3.4 and 4.1 seconds,..... for Building 7, it's hardly a "jolt-free" collapse!

Can we see the plots for WTC7?

It would be nice to see these jolts and how they relate to the period of effective freefall to campare it to ABC.

WTC 7 had a freefall for 2.25 seconds or six stories and then there where jolts.

Tony, where can we see this in the form of a graph and data?


Dr G says:

Nevertheless, I believe the absence of a jolt in the collapse of WTC 1 proves very little about what actually happened to WTC 1 on 9/11 and it certainly does not rule out a natural collapse.

This is a complex question.

I think if we first compare ABC with WTC7 and ask ourselves why are seeing jolts and relative freefall where we do, and then try to apply what we learn to the case of an upper block which is originally "tipping", the answer may become apparent.

Major_Tom wrote:

The NIST Camera 3 video of the collapse of WTC 7 shows some interesting, (and DBB, very reproducible), "jolts" at 2.4, 3.4 and 4.1 seconds,..... for Building 7, it's hardly a "jolt-free" collapse!

Can we see the plots for WTC7?

It would be nice to see these jolts and how they relate to the period of effective freefall to campare it to ABC.

WTC 7 had a freefall for 2.25 seconds or six stories and then there where jolts.

Tony, where can we see this in the form of a graph and data?

Tom, David Chandler's three part video about the fall of WTC 7, available on the left side of

http://www.AE911truth.org

showed the graph data for the WTC 7 fall and the final NIST WTC 7 report released in Nov. 2008 was revised to show the freefall in graphic form, after acknowledging that Chandler was right. The NIST graphic is here on page 46.
http://wtc.nist.gov/NCSTAR1/PDF/NCSTAR%201A.pdf

Tom, David Chandler's three part video about the fall of WTC 7, available on the left side of

http://www.AE911truth.org

showed the graph data for the WTC 7 fall and the final NIST WTC 7 report released in Nov. 2008 was revised to show the freefall in graphic form, after acknowledging that Chandler was right.

But are jolts included? We have some very good stuff on this forum. We don't have a problem with the freefall claim. But it would be nice to show jolts and freefall in the same graphs.

Maybe quite interesting.

Major_Tom wrote:

Tom, David Chandler's three part video about the fall of WTC 7, available on the left side of

http://www.AE911truth.org

showed the graph data for the WTC 7 fall and the final NIST WTC 7 report released in Nov. 2008 was revised to show the freefall in graphic form, after acknowledging that Chandler was right.

But are jolts included? We have some very good stuff on this forum. We don't have a problem with the freefall claim. But it would be nice to show jolts and freefall in the same graphs.

Maybe quite interesting.

Chandler's graph shows the velocity of the roof completely levels off in WTC 7 with no additional acceleration for a measureable period after the 2.25 second freefall. This is probably a jolt and then there is another level off/probable jolt a short time later. While these level offs do not show actual deceleration at the roof 33 stories above, this would be due to the local failures I spoke of yesterday. With the abc tower we got an actual deceleration of the roof and not just level off, since the upper block was only six stories high and the velocity not nearly as high as that of the 80 to 100 foot freefall of WTC 7's 33 story upper block.

I believe structural and inertial calculations could be performed to show that the actual decelerations at the impacts had to be very high to stop the acceleration of the roof of WTC 7 33 stories above.

T_Szamboti wrote:Additionally, the hat truss could not have transferred enough vertical load to cause overload of the core columns.

False. On another thread I explained where you could find the data contradicting your claim.

David B. Benson wrote:

T_Szamboti wrote:Additionally, the hat truss could not have transferred enough vertical load to cause overload of the core columns.

False. On another thread I explained where you could find the data contradicting your claim.

Nonsense. You have not shown that the perimeter column connections of the hat truss could support a vertical load great enough to overload the core columns.

I looked at the NIST references you gave and they only discuss the hat truss transferring loads that are orders of magnitude lower than what would be required to do what you claim, and I told you that.

T_Szamboti wrote:I looked at the NIST references you gave ...

Then you didn't look very carefully. Try again.

David B. Benson wrote:

T_Szamboti wrote:I looked at the NIST references you gave ...

Then you didn't look very carefully. Try again.

Oh, I looked carefully enough.

You need to stop playing around with answers like this and references that don't match what you claim. In your defense, I am not sure if you fully appreciate what you are claiming though.

I'll tell you what, you get the sizes of the beams that formed the hat truss outriggers and I will show you that they could not take the shear and bending stresses of the vertical loads necessary to do what you claim. The connections could not be stronger than the beams themselves.