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

[mrppy@fix.net]

tomk states:

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

hi tomk,



your critique that the conclusion mr. chandler derives from the now established fact that wtc fell at free fall for (2.5 or 2.25) seconds was not supported by any calculations is correct.

but neither is your conclusion.

i'm sure you will agree that a quantitative analysis of what the resistive forces are and how much they would slow the descent of the building (or just the exterior if you believe nist) is a complicated affair. i will readily acknowledge that it is beyond my ability to do so. but i can point out the following.

1) any work done by gravity on the structure during the descent will result in slowing the descent below that of free fall.

2) some of the work done on the structure during the descent includes the bending and/or breaking of structural steel as it is disappearing from view as the building falls.

3) just prior to the collapse of wtc 7 the north side (as shown in the video) shows little evidence of significant fires. thus, the vast majority of the structural steel that holds up the north wall is not significantly affected by heat and was therefore at its full strength during the collapse.

4) in answering a question posed by mr. chandler dr. shyam sunder, lead investigator for wtc 7, stated during a technical briefing that accompanied the release of the wtc 7 draft report that,

"...a free fall time would be an object that has no…uh… structural components below it."

since we all agree that the exterior wall of wtc 7 DID have structural components below it, and we all now agree that there was a period of time in which (at least the exterior of) wtc DID fall at (essentially) free fall, it would appear to me that his statement is incompatible with nist's own conclusions.

dr. sunder appears to get quite confused when he claims the video evidence of the collapse of 17 floors is 3.9 seconds but the time for the structural MODEL [emphasis in original] is 5.4 seconds, "... because there WAS [emphasis in original] structural resistance that was provided in this particular case. And you had…you had a sequence of structural failures that had to take place and everything was not instantaneous.”

so if we are to take dr. sunder at his word, nist's model correctly acknowledges the structural elements that would slow the descent but the video evidence does not (!) however the report itself does not suffer from this logical inconsistency, stating that the video evidence and the model both reflect the slower descent time.

i find the entire response by dr. sunder rather enlightening. he seems to have a considerable degree of difficulty answering mr. chandler's question, starting and stopping with an unusual amount of "ums" and "uhs". he even feels compelled to explain (to a technical audience) that,

"...gravity is the loading function that applies to the structure…um…at…um…applies….to every body…every…uh…on…all bodies on…ah…on…um… this particular…on this planet not just…um…uh…in ground zero…um…the…uh…"

while i am no psychologist, it appears to this layman that dr. sunder is lying and (to his credit) is quite conflicted about it.

i was so taken by this exchange that i listened to dr. sunder's response a dozen or more times so i could accurately transcribe it. after reading mr. chandler's question regarding the rate of descent, dr. sunder replied:

“Well…um…the…first of all gravity…um…gravity is the loading function that applies to the structure…um…at…um…applies….to every body…every…uh…on…all bodies on…ah…on…um… this particular…on this planet not just…um…uh…in ground zero…um…the…uh…the analysis shows a difference in time between a free fall time, a free fall time would be an object that has no…uh… structural components below it. And if you look at the analysis of the video it shows that the time it takes for the…17…uh…for the roof line of the video to collapse down the 17 floors that you can actually see in the video below which you can’t see anything in the video is about…uh… 3.9 seconds. What the analysis shows…and…uh…the structural analysis shows, the collapse analysis shows that same time that it took for the structural model [emphasis in original] to come down from the roof line all the way for those 17 floors to disappear is…um… 5.4 seconds. It’s…uh…, about one point…uh…five seconds or roughly 40% more time for that free fall to happen. And that is not at all unusual because there was [emphasis in original] structural resistance that was provided in this particular case. And you had…you had a sequence of structural failures that had to take place and everything was not instantaneous.”

so along with dr. sunder and nist, i have no problem assuming that the descent of wtc 7 would be slowed enough by the structural elements below it to show up in a measurement of the type conducted by mr. chandler if the official conspiracy theory is correct. certainly if the building WAS brought down by controlled demolition, this is what one would expect and what one DOES observe in other examples of buildings that are incontrovertibly brought down by controlled demolition.

but i will acknowledge that this conclusion is perhaps tainted by the additional evidence that building 7 was brought down by controlled demolition which includes:

1) eyewitness reports of explosions

2) expert opinions that the building was demolished (see jowenko at youtube)

3) much evidence of molten steel. there are eyewitness accounts of molten steel in the rubble of all 3 buildings weeks after 9/11 including this one from leslie robertson, structural design engineer of the twin towers and supporter of the official conspiracy theory:

“As of 21 days after the attack, the fires were still burning and molten steel was still running.”

even more compelling, there are 3 independent metallurgical studies (including one from the usgs) that all found evidence of molten steel using scanning electron microscopy. the one by steven jones (which references the other 2) can be viewed online at the journal of 9/11 studies. it is titled "extremely high temperatures during world trade center destruction"

but as even nist acknowledges:

"In no instance did NIST report that steel in the WTC towers melted due to the fires. The melting point of steel is about 1,500 degrees Celsius [2,800 degrees Fahrenheit]. Normal building fires and hydrocarbon (e.g., jet fuel) fires generate temperatures up to about 1,100 degrees Celsius [2,000 degrees Fahrenheit]. NIST reported maximum upper layer air temperatures of about 1,000 degrees Celsius [1,800 degrees Fahrenheit] in the WTC towers (for example, see NCSTAR 1, Figure 6-36)."

so this is a real problem for supporters of the official conspiracy theory. i have yet to see even an attempt to explain this data and have little regard for defenders of the official conspiracy theory who ignore this fact.

4) photographic evidence of wtc 7 just prior to collapse shows the north side with only few and very small fires. nist claims that the other side, obscured from view by smoke and debris, was more fully engaged. this asymmetrical fire loading would lead me to conclude that the building, if was going to fall at all, would topple towards its weak side. i would also not expect asymmetric fires to result in a symmetric collapse due to entropy and the 2nd law of thermodynamics. finally, since steel weakened by heat will get stronger as it yields (work hardening), i would expect to see the building sag and twist slowly, perhaps haltingly. it would be great if we could compare the 9/11 collapses with other steel high rise collapses due to fire, but i am not aware of a single example. defenders of the official conspiracy theory should compare the fires on 9/11 with a really intense fire like that at the windsor tower in madrid, spain. though clearly engulfed much more completely by fires that are far hotter and burned far longer, the building was still standing the next day.

there is, of course, much more but i think this will suffice for now. if this results in an intelligent and respectful reply then i'll be encouraged to continue this dialog. i have also put out a challenge to supporters of the official conspiracy theory that i am willing to discuss this topic in public (san luis obispo, ca. area) with anyone who is reasonably competent to defend the official version of events. so far, no one has taken me up on this offer.


cheers,


mark philliips
atascadero, ca.

 

[PhantomWolf]

defenders of the official conspiracy theory should compare the fires on 9/11 with a really intense fire like that at the windsor tower in madrid, spain. though clearly engulfed much more completely by fires that are far hotter and burned far longer, the building was still standing the next day.

I noted this as I skimmed through. Ummmm.... The Winsor Tower had a concrete core. Only the concrete part remained standing, the Steel parts all collapsed progressively until they hit a strengthened concrete and steel beam floor. Also the fires in WTC 1, 2 & 7 were bigger and hotter then the Winsor's fires.

 

[mrppy@fix.net]

I noted this as I skimmed through. Ummmm.... The Winsor Tower had a concrete core. Only the concrete part remained standing, the Steel parts all collapsed progressively until they hit a strengthened concrete and steel beam floor. Also the fires in WTC 1, 2 & 7 were bigger and hotter then the Winsor's fires.

after reading this i looked into the widsor tower fire and now agree with some of the above. it was a concrete reinforced structure and some of the building did collapse. the construction was different enough for this to be a bad comparison. i don't, however, agree that the fires in WTC 1,2 and 7 were either bigger (as a % of building size) or hotter than they were in the windsor tower, but i'm not sure it matters much due to the differences in construction.

thanks for the heads up, i'm always glad to learn more.

cheers,

mark

 

[tfk]

hi tomk,

your critique that the conclusion mr. chandler derives from the now established fact that wtc fell at free fall for (2.5 or 2.25) seconds was not supported by any calculations is correct.

Howdy Mark,

Some part of my meaning has gotten crossed here, Mark. I stated that "Mr Chandler (& NIST) both show from analysis of the video evidence that the exterior wall DOES fall at near free fall acceleration during this interval." It wasn't a calculation, except for calculating that the slope of the v vs. t curve is approximately 32.2 ft/sec^2.

but neither is your conclusion.

i'm sure you will agree that a quantitative analysis of what the resistive forces are and how much they would slow the descent of the building (or just the exterior if you believe nist) is a complicated affair. i will readily acknowledge that it is beyond my ability to do so. but i can point out the following.

1) any work done by gravity on the structure during the descent will result in slowing the descent below that of free fall.

Mark, this sentence is squirrelly. The "work done by gravity" (well, actually the force of gravity) is what is causing it to fall. Did you mean to say that "any work done to demolish the structure during the descent will result in slowing the descent below that of free fall."??

2) some of the work done on the structure during the descent includes the bending and/or breaking of structural steel as it is disappearing from view as the building falls.

Some. But very little. As evidenced by a very small percentage of the beams in the rubble pile having been torqued to failure. The vast majority are straight and broken into segments that snapped at the connections to adjacent structures (the beams above & below, and the cross truss bracing). This immediately shows that the failure mode was NOT beams bending & failing, but bolts & welds snapping.

Please don't bother pulling up a few photos of bent beams. I've seen them. I am talking percentages here. I invite you to examine these photos in detail & estimate what percent of the columns are torqued TO FAILURE & what percent are still straight.

http://911research.wtc7.net/wtc/evidence/photos/docs/ground_zero_arial2_ort.jpg
http://911research.wtc7.net/wtc/evidence/photos/docs/us/us_wtc35.jpg
http://911research.wtc7.net/wtc/evidence/photos/docs/us/us_wtc36.jpg

3) just prior to the collapse of wtc 7 the north side (as shown in the video) shows little evidence of significant fires. thus, the vast majority of the structural steel that holds up the north wall is not significantly affected by heat and was therefore at its full strength during the collapse.

Close. If you had said "not significantly weakened by heat", you would have been right. Unlike the towers, the steel was NOT weakened by extremely elevated temps (600 to 900°C). This is exactly what NIST says.

Unfortunately, "not significantly affected by heat" is wrong. In that the "significant effect" was simply thermal expansion at beam temps around 300°C, which snapped joints. Structural members losing their connections to other structural members DOES qualify as a "significant effect".

4) dr. shyam sunder... stated ...
"...a free fall time would be an object that has no…uh… structural components below it."

since we all agree that the exterior wall of wtc 7 DID have structural components below it, and we all now agree that there was a period of time in which (at least the exterior of) wtc DID fall at (essentially) free fall, it would appear to me that his statement is incompatible with nist's own conclusions.

First, please stop with the "we all agree..." nonsense until AFTER we have agreed to something. It is unseemly for an ENGINEER to be appealing to popular consensus. Most of us are FAR too individualistic and just plain ornery to play that card.

C'mon, Mark. You're an ME. This ain't hard.

How about "... has no substantial structural component below it"? And what does substantial mean in this context? It means "large compared to the loads placed upon it".

Do the sides of an aluminum Coke can constitute a "substantial structural component"? You bet, if there happens to be an ashtray sitting on top of the can.

Are they substantial if you drop a 50 pound block of concrete from 30' above it? Heck no. So what constitutes "substantial" is inextricably tied to the load that the structure is being asked to support.

Now, will the coke can "slow down" the acceleration of the 50 pound block? You bet. Will you be able to measure that decrease in acceleration with a video camera & this software? No way.

And THIS is the core of my (& NIST's) argument, that there was very little of the structural support of the external walls still intact when their collapse began.

The fact that the vast majority of the internal structure of the building had long since (~ 10 seconds) failed is indisputable from the collapse of the penthouses. Sequencing video evidence of reporters on the street hearing the collapse begin with lateral motions of the roofline of the building, you can reliably push the start of the collapse of the internal structure back 18 seconds before the external walls began to fall.

dr. sunder appears to get quite confused ...

"...gravity is the loading function that applies to the structure…um…at…um…applies…."

while i am no psychologist, it appears to this layman that dr. sunder is lying and (to his credit) is quite conflicted about it.

I am not particularly interested in Dr. Sunder's comments. Lets talk engineering, shall we.

ALL of us have realized the PERFECT response in numerous situations - about an hour AFTER the conversation.

I find it facile and somewhat distasteful that you would conclude that Dr. Sunder (and necessarily a couple hundred other engineers working on the project) are all lying, because Sunder did not answer an extemporaneous question with sufficient aplomb.

Let's stick with OUR field, engineering, and leave the psychology to others.

... but i will acknowledge that this conclusion is perhaps tainted by the additional evidence that building 7 was brought down by controlled demolition which includes:

1) eyewitness reports of explosions

The 500 or so rapid-fire, sequenced 140 db explosions that NOBODY reported? That everyone hears at real CDs. Those explosions?

And the 500 or so rapid-fire, sequenced, 140 db explosions that somehow managed to elude the microphones of every video camera? Those explosions?

2) expert opinions that the building was demolished (see jowenko at youtube)

3) much evidence of molten steel...

4) photographic evidence of wtc 7 just prior to collapse shows the north side with only few and very small fires...

cheers,

mark philliips
atascadero, ca.

There is nothing in the topics that you brought up that has not been competently debunked. But let's leave these other issues for another time. The topic here was Chandler's analysis. Focus is necessary in these discussions. We can get to those later if you wish.

cheers,

tk

 

[tfk]

Mark,

Science & engineering is all about learning principles, not incidents. The fact that most of the Windsor Towers were still standing after the fire is an incident. Buried inside the complex results are principles.

The lessons (i.e., principles) of the Windsor Towers fire are clear.

ALL of the structural steel that was insulated (by concrete or "fire protection") survived.
ALL of the structural steel that was uninsulated failed.

Here is an excellent summary: http://www.mace.manchester.ac.uk/pr...Study/HistoricFires/BuildingFires/default.htm

Be sure to read the Analysis section at the bottom.

regards,

tom

 

[peteweaver]

Mark,

Science & engineering is all about learning principles, not incidents. The fact that most of the Windsor Towers were still standing after the fire is an incident. Buried inside the complex results are principles.

The lessons (i.e., principles) of the Windsor Towers fire are clear.

ALL of the structural steel that was insulated (by concrete or "fire protection") survived.
ALL of the structural steel that was uninsulated failed.

Here is an excellent summary: http://www.mace.manchester.ac.uk/pr...Study/HistoricFires/BuildingFires/default.htm

Be sure to read the Analysis section at the bottom.

regards,

tom

Tom I'm guessing you've not read much of Manchester university's structural fire engineering website.

Or you'd have noticed this:

Sprays are normally applied in situ as profile protection and can be easily applied to complex structural steel detail. The cement or gypsum based materials may contain mineral fibre, expanded vermiculite, expanded perlite, other lightweight aggregates or fillers. The coatings are often susceptible to mechanical damage.

And this:
http://www.mace.manchester.ac.uk/pr...s/strucfire/Quick Solutions/steel/default.htm
Which says it is unsafe for steel columns to reach temperatures above 550 degrees C.

In cases where fire protection has been physically damaged by a plane, or another building hitting the structure, fire resistance drops considerably.

And perhaps you'd notice that the steel in fire forum (which Professor Colin Bailey is a member of) is of the opinion that structural damage and fire brought down the wtc's.

 

[tfk]

Pete,

LOOK AT YOUR JERSEY! LOOK AT MY JERSEY! HIT THE GUYS THAT HAVE A DIFFERENT COLOR JERSEY!!
Sorry, old football axiom...

Tom I'm guessing you've not read much of Manchester university's structural fire engineering website.

Or you'd have noticed this:

And this:
http://www.mace.manchester.ac.uk/pr...s/strucfire/Quick Solutions/steel/default.htm
Which says it is unsafe for steel columns to reach temperatures above 550 degrees C.

In cases where fire protection has been physically damaged by a plane, or another building hitting the structure, fire resistance drops considerably.

And perhaps you'd notice that the steel in fire forum (which Professor Colin Bailey is a member of) is of the opinion that structural damage and fire brought down the wtc's.

I'm not sure what I said that got you buzzing, but I do believe that we're on the same side.

Be that as it may, did you disagree with any statement that I made about the Windsor Towers fire? Because I agree 100% with the MACE analysis.

It is clear that the damage, the fires and the compromised insulation brought down the towers.

In this thread, we are talking about WTC7 tho. And that building did not have removed insulation. And the structural damage, while significant, did not play a role in the initiation of its collapse.

In WTC7, the failure happened at beam temps below 300°C, and were the result of design quirks & thermal expansion of the beams. Not of weakening of the beams.

BTW, there is no step function to the "safe vs. unsafe" temps (e.g., 550°C) for steel or any other metal. 550°C is simply a rounded off version of 1000°F (actually 540°C), a temp at which the tensile strength has dropped to about 50% of room temp value. The strength continues to drop to 15% @ 800°C and 10% @ 900°C.

If you check the NIST's NCSTAR1-3 Fig 7-9, page 112, you'll see a typical Tensile strength vs temp curve.

Prof Bailey is, of course, right in the case of the towers. But we're talking about WTC7 here, not the towers.

BTW, it will be instructive for you to go find the curve of the tensile (or flex) modulus of structural steel vs. temp.

A pop quiz for you: Which played a more important role in the collapse of the towers? The degradation of the strength or the degradation of the modulus?

tk

 

[PhantomWolf]

after reading this i looked into the widsor tower fire and now agree with some of the above. it was a concrete reinforced structure and some of the building did collapse. the construction was different enough for this to be a bad comparison. i don't, however, agree that the fires in WTC 1,2 and 7 were either bigger (as a % of building size) or hotter than they were in the windsor tower, but i'm not sure it matters much due to the differences in construction.

thanks for the heads up, i'm always glad to learn more.

cheers,

mark

As a percentage of the building they weren't this is ture, but in sheer size they were, the Winsor tower was quite a small building. The fires were around the same temperature in all four fires, it's just that in the WTC case the fires were inside an acre of floor whereas the Winsor it was closer to the windows and more obvious. Also there are lots of photos of the Winsor Tower taken at night so it appears brighter and bigger.

 

[jhunter1163]

What did you make your structure out of, Heiwa?

 

[Panoply_Prefect]

I note that Chandler has changed the text on his homepage:

http://www.911speakout.org/#WTC7Freefall

Now the wording is a bit more extatic:

Breakthrough!! [FONT=Arial, Helvetica, sans-serif]The analysis presented in the WTC7 Freefall video (below) was submitted as an official "comment" on the preliminary WTC7 report and appears to have played a significant role in forcing them to do a new analysis.[/FONT]
(...)
The fraudulent analysis that had been carried out by NIST was so blatant that they were forced to do a new analysis.

However I fail to see how the added text best can be described as "a new analysis"? The draft included a description that actually describes, albeit in cruder detail, how the building fell, with the collapse of floor 7-14 and the building above falling as a single body (NIST " the entire building above the buckled-column region moved downward as a single unit, resulting in the global collapse of WTC 7").

It was already in the report.

 

[boloboffin]

Exactly. In fact, they kept the original analysis in the report. It's not like they retracted or anything.

If Chandler wasn't using this as P.R. to hype idiotic notions, he could be proud that he helped flesh out the knowledge about this event in a notable way. However, the myopia caused by 9/11 CT has distracted him from reality: his comments have helped confirm NIST's analysis. So I've added this incident to the Top 10 Boneheaded Mistakes of the group. Trying to expose the government but only helping to prove the government's theory? Priceless.

 

[tfk]

Another egregious error a second of Mr. Chandler's analyses.

In this analysis:
http://www.youtube.com/watch?v=Ah2hTMOlD5s

Mr. Chandler is implying that the maximum horizontal speed attainable by any object thrown from the tower is equal to the downward velocity of the upper block. He doesn't say as much verbatim in this video. In one of his other analyses, he does. Here, he has backtacked to "it is significant to notice".

His comment would be correct if we were colliding billiard balls. Fortunately for Conservation of Energy laws, we are not.

There are two sources of energy that can be tapped to give these huge girders a significant horizontal velocity.

One of them is the stored energy within the beam itself. These beams are loaded. They have a spring constant to them, although they are very stiff springs. Ergo, they are storing a significant amount of energy. They are compressed springs. If loaded in pure compression, the amount of energy is equal to E = 0.5 * P * d (where P = load & d = deflection from zero load state).

This is not likely to give a huge amount of "bounce" if suddenly the constraints are removed. And the bounce would be in line with axis of the column.

However, if the column is bowed by the collapse, as they are certain to be, there can be an enormous amount of energy stored in the flexed column. As soon as the constraints on a bowed column are released, it is not surprising in the slightest that one would get enormous horizontal velocities.

This effect can be easily replicated with a credit card and ones thumb & first finger. Hold the credit card with the thumb & first finger along the short sides. Place the edges of the card near the outside edges of your fingers. Slowly bring your thumb & finger together, bending the card. Suddenly, the card will spring free of your thumb & finger, traveling MUCH faster than your fingers were moving.

The energy was stored in the bending of the card and released when the card's constraints (i.e, connections to your fingers) failed.

There is no mystery or violation of conservation of energy principles in these video images. The material ejected horizontally at high speed doesn't need the help of explosives any more than the credit card did.

tk

 

[technoextreme]

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.

Unless you know what quantization error is then you have no qualifications as to whether or not the software can do what you claim it does.

 

[mrppy@fix.net]

tjk,

Some part of my meaning has gotten crossed here, Mark. I stated that "Mr Chandler (& NIST) both show from analysis of the video evidence that the exterior wall DOES fall at near free fall acceleration during this interval." It wasn't a calculation, except for calculating that the slope of the v vs. t curve is approximately 32.2 ft/sec^2.
Your criticism of chandler was NOT with the result of his video analysis or his claim that wtc 7 fell at free fall for 2.5 seconds. Your criticism was that his conclusion BASED on that data was not supported by calculation. His conclusion was that free fall was evidence of controlled demolition.

I agreed that he did not do any calculations to prove that conclusion, but neither did you when you stated that the structural resistance that remained in the building was so small that it could not be detected within the margin of error of the descent measurement.


Mark, this sentence is squirrelly. The "work done by gravity" (well, actually the force of gravity) is what is causing it to fall. Did you mean to say that "any work done to demolish the structure during the descent will result in slowing the descent below that of free fall."?
Ok, “work done by gravity” was a bit of a shortcut but I would have thought it was pretty clear. The individual steps are:

While standing the building has potential energy equal to each bit of mass times the gravitational constant of 32.2 feet per second squared times it’s height above some reference (in this case the street). If the building falls with no resistance. It will fall at free fall until it hits the ground. At that point, the gravitational potential energy will have been converted into kinetic energy (mass times velocity squared). Since energy is conserved, if there is any work done during the collapse (such as bending or breaking of steel), then the kinetic energy at the end cannot be the same as the case where no work is done during the collapse. This will show up as a speed slower than would be the case with free fall and that would be the result of a descent with an acceleration less than 32.2 feet per second squared. (jeez!!)

So YES, i do mean that any work done to demolish the structure during the descent will result in slowing the descent below that of free fall.

Some. But very little. As evidenced by a very small percentage of the beams in the rubble pile having been torqued to failure. The vast majority are straight and broken into segments that snapped at the connections to adjacent structures (the beams above & below, and the cross truss bracing). This immediately shows that the failure mode was NOT beams bending & failing, but bolts & welds snapping.

And here we go again. Your assertion, based on the pictures of the pile of rubble, that the resistance would have been small and thus not noticed during the descent. I certainly don’t agree with your assertion that these photos show “…immediately…” that the failure mode was not beams bending and failing, but bolts and welds snapping. In fact, when I look at those photos I see evidence of a lot of work required to create the zillion little pieces we see.

Originally Posted by mrppy@fix.net 3) just prior to the collapse of wtc 7 the north side (as shown in the video) shows little evidence of significant fires. thus, the vast majority of the structural steel that holds up the north wall is not significantly affected by heat and was therefore at its full strength during the collapse. Close. If you had said "not significantly weakened by heat", you would have been right. Unlike the towers, the steel was NOT weakened by extremely elevated temps (600 to 900°C). This is exactly what NIST says. Unfortunately, "not significantly affected by heat" is wrong. In that the "significant effect" was simply thermal expansion at beam temps around 300°C, which snapped joints. Structural members losing their connections to other structural members DOES qualify as a "significant effect".
No, I meant exactly what I said. Most of the steel was not near any significant fire, being many floors away. While conduction would have allowed some of the distant steel far from the fires to be warmed somewhat, I think it is safe to say that most of the steel was not significantly affected by heat. Not enough to weaken the steel nor enough to expand it significantly. NIST does claim that the failure mode was expansion but this was steel in the vicinity of the fires. This says nothing about the steel far away from the fires.


Originally Posted by mrppy@fix.net 4) dr. shyam sunder... stated ... "...a free fall time would be an object that has no…uh… structural components below it." since we all agree that the exterior wall of wtc 7 DID have structural components below it, and we all now agree that there was a period of time in which (at least the exterior of) wtc DID fall at (essentially) free fall, it would appear to me that his statement is incompatible with nist's own conclusions. First, please stop with the "we all agree..." nonsense until AFTER we have agreed to something. It is unseemly for an ENGINEER to be appealing to popular consensus. Most of us are FAR too individualistic and just plain ornery to play that card. C'mon, Mark. You're an ME. This ain't hard.
I did not think I was going out on a limb saying that we all agree that the exterior wall of wtc 7, which looked perfectly normal just prior to the collapse, still had structural components in it. If I’m talking to someone who would take issue with THAT, then clearly I’m in the wrong place.

I am not particularly interested in Dr. Sunder's comments. Lets talk engineering, shall we.
Mr. sunder was the lead investigator of the WTC collapse and he was the one making the technical presentation of nist’s findings so I think his comments are quite relevant. but given what he said, I can well understand why you would not want to talk about it.


1) eyewitness reports of explosions The 500 or so rapid-fire, sequenced 140 db explosions that NOBODY reported? That everyone hears at real CDs. Those explosions? And the 500 or so rapid-fire, sequenced, 140 db explosions that somehow managed to elude the microphones of every video camera? Those explosions?
There were over a hundred accounts of first responders (fdny and emt personnel) that mentioned explosions of some sort. Many were of the rapid “boom, boom, boom” sort you mention.

Your comments are based on the assumption, not justified in my opinion, that if wtc 7 was brought down by controlled demolition it would have been done in the same manner as more public CDs. but alternative means of cutting the steel may have been used that might have reduced the level of explosions required precisely to help conceal it. This is precisely the sort of thing we might discover if we had a new, independent and thorough investigation. As nist acknowledges, they didn’t consider controlled demolition and you can’t find what you don’t look for.

Originally Posted by mrppy@fix.net 2) expert opinions that the building was demolished (see jowenko at youtube) 3) much evidence of molten steel... 4) photographic evidence of wtc 7 just prior to collapse shows the north side with only few and very small fires... cheers, mark philliips atascadero, ca. There is nothing in the topics that you brought up that has not been competently debunked. But let's leave these other issues for another time. The topic here was Chandler's analysis. Focus is necessary in these discussions. We can get to those later if you wish.
While you get bent out of shape when I assume that we agree there were structural elements in the exterior wall of wtc 7, you expect me to swallow your statement that the other items I mention have all, “…been completely debunked.”

Mentioning the other paths of investigation that lead to the same conclusion is how the scientific method works.

I’m particularly interested in any intelligent explanations for the presence of the molten steel. So if you don’t want to discuss it here, perhaps you could point me to where this has been, “…completely debunked.”

i'm afraid i don't have the patience for this sort of discussion. i've had to spend far too long explaining the very simple or justifying the very obvious while you ignore what you find inconvenient. it appears that your purpose is to wear down your opponent rather than have an intelligent conversation.

i'm not interested in that game.

so congratulations!! you win.


Cheers,


mark

 

[R.Mackey]

While standing the building has potential energy equal to each bit of mass times the gravitational constant of 32.2 feet per second squared times it’s height above some reference (in this case the street). If the building falls with no resistance. It will fall at free fall until it hits the ground. At that point, the gravitational potential energy will have been converted into kinetic energy (mass times velocity squared). Since energy is conserved, if there is any work done during the collapse (such as bending or breaking of steel), then the kinetic energy at the end cannot be the same as the case where no work is done during the collapse. This will show up as a speed slower than would be the case with free fall and that would be the result of a descent with an acceleration less than 32.2 feet per second squared. (jeez!!)

So YES, i do mean that any work done to demolish the structure during the descent will result in slowing the descent below that of free fall.

Welcome to the Forum.

We all acknowledge the above. However, it is very clumsy to estimate the energy consumed during collapse from the collapse time, since the collapse time scales with the square root of energy consumption. Put another way, the difference in energy between a delay of zero (compared to true free fall) and a mere 0.5 seconds is huge. There are no measurements accurate enough to estimate the overall collapse time to better than +/- 1 second or more, since the base is obscured in every single video, therefore there will always be large uncertainties. See this thread.

The amount of energy absorption is also sure to be lower than you suppose. Energy = force times distance, and the distance required to buckle any given steel element is not very far -- only a few percent of its original length. We expect WTC 7, therefore, to lose only 5 to 15% of its gravitational energy as it falls, less if the collapse happens inside out and we cannot see what happens in the interior. This is not enough to reliably detect on video. The situation in WTC 7 is very unlike WTC 1 and 2, where in addition to buckling, there was also momentum transfer as the descending mass kept inelastically hitting the lower structue. This momentum transfer dominates the delay, and it did not occur in WTC 7 due to the collapse geometry.

Furthermore, you are arguing about "free fall" over a small portion of the collapse, not the whole thing. For a small portion, the perimeter basically was in "free fall." We agree with this. During this isolated instant of time, there was little resistance felt. That's because its supports, both within and below, had already failed. NIST treats this, and did so before Mr. Chandler ever burst on the scene.

We are arguing, again, not with the result, but with the cause. An "ordinary" collapse is a possible cause. You and Mr. Chandler claim it is not, but you fail to articulate why this must be so. To the rest of us, why WTC 7 fell as quickly as it did, and the potential for periods of near free-fall, are no mystery whatsoever. You are therefore arguing from ignorance.

I’m particularly interested in any intelligent explanations for the presence of the molten steel. So if you don’t want to discuss it here, perhaps you could point me to where this has been, “…completely debunked.”

Threads on this topic are legion. In brief:

• There is no evidence of molten steel
• There is considerable evidence against molten steel
• Molten steel is not found in any controlled demolition
• There is considerable evidence against any thermite-like device
• No one has yet advanced a coherent theory of collapse that includes molten steel

That's about as thorough as debunking gets.

 

[tfk]

HI Mark,

Your concluding paragraph showed a bit of impatience. I'm going to pare back the issues, and address only about half of your response. Otherwise it gets too long. We can cover the rest later, of course. I've eliminated some trivia.

I agreed that he did not do any calculations to prove that conclusion, but neither did you when you stated that the structural resistance that remained in the building was so small that it could not be detected within the margin of error of the descent measurement.

Correct. I did not do this calculation. Of course, it is an enormously complex calc, one that is appropriately done with FEA, as NIST did. And I don't have the resources, or inclination, to duplicate the analysis that NIST has already performed.

And I'll argue here that that analysis is not necessary. That the conclusion is self evident from the data.

Ok, “work done by gravity” was a bit of a shortcut but I would have thought it was pretty clear. The individual steps are:

While standing ... 32.2 feet per second squared. (jeez!!)

Heck, Mark. You could have just said "yes, as you phrased it".

I certainly don’t agree with your assertion that these photos show “…immediately…” that the failure mode was not beams bending and failing, but bolts and welds snapping.

This is precisely what I hope to change your mind about, Mark.

By the time that ANY structural beam has "buckled", it has already gone thru enormous amounts of plastic strain. You can not get around this with A36 & huge welded box columns. Any columns that has buckled must have a large residual deflections in it. It will NOT be lying on the ground anything close to straight.

Here is a great catalog of pictures from Ground Zero.
http://911research.wtc7.net/wtc/evidence/photos/groundzero.html

Tell me the percent of columns that are still virtually straight. My guess: 98% or so.

Ergo, the vast majority of columns did NOT buckle.

My guess is that zero of them buckled as a failure mode. That, in every case, the fasteners & welds gave way long before the beam itself buckled.

Your assertion, based on the pictures of the pile of rubble, that the resistance would have been small and thus not noticed during the descent.

My only conclusion, from looking at the rubble pile, is that "beam buckling" was not the predominant failure mode.

My as-yet-unproven assumption is that, without beam buckling, the snapping of relatively small bolts and shearing of small welds becomes the most likely failure mode. If you have an alternative to this, I'm all ears.

My judgment is that snapping these constraints is going to take a tiny amount of force (and energy) compared to what it would take to cause the beams to buckle.

And this leads to my overall conclusion: that any energy balance analysis that is based on beam buckling as the predominant failure mode will WAY overestimate the amount of kinetic energy that is "lost" to building disassembly during the collapse.

In fact, when I look at those photos I see evidence of a lot of work required to create the zillion little pieces we see.

And I see a small amount compared to the amount of work it would have taken to buckle all of those beams.

One obvious points that I'd like to make: Any destruction of any component that happens after that component has detached from the upper block (in the case of the towers), from the exterior wall (for WTC7) or after any component has hit the ground will not slow that block or wall's rate of descent at all.

... I think it is safe to say that most of the steel was not significantly affected by heat.

My point (reflecting NIST's findings) is that NONE of the steel, in or out of the fires, was weakened by the fires, since none of it got above about 300°C.

The collapse initiation was due to thermal expansion resulting in snapped connectors, but the failure propagation was purely mechanical. One component failing, dragging down the next, dragging down the next. And that the failure propagated horizontally from column 79 outward towards the external walls of the building.

I did not think I was going out on a limb saying that we all agree that the exterior wall of wtc 7, which looked perfectly normal just prior to the collapse, still had structural components in it. If I’m talking to someone who would take issue with THAT...

I am afraid, Mark, that I AM going to take issue with that statement. Sorry.

A 47 story wall has, within it, practically zero structural strength. A wisp of a breeze will knock it down. In order for it to be stable, it must be connected to a second wall (or some vertical structure) that is horizontally displaced some distance from it. The amount of horizontal displacement needed for stability is directly related to the height of the wall. Two wall, thus separated & connected, will mutually support each other.

In the case of the towers, the supports for each wall extended thru the structures to the opposite side of the building. Once the building started collapsing, that "displaced" supports started disappearing fast. Not only that, but those collapsing structures also became an asymmetric load dragging down the external wall. Remove those horizontally displaced supports and the exterior wall, while it has lots of structural components, doesn't have the structural integrity to hold itself up.

Mentioning the other paths of investigation that lead to the same conclusion is how the scientific method works.

Again, let's finish one before moving on to the next. I'll happily talk about any of them. I don't expect you to take my word for anything.

I’m particularly interested in any intelligent explanations for the presence of the molten steel. So if you don’t want to discuss it here, perhaps you could point me to where this has been, “…completely debunked.”

I'd be happy to talk about this one with you.

i'm afraid i don't have the patience for this sort of discussion. i've had to spend far too long explaining the very simple or justifying the very obvious while you ignore what you find inconvenient. it appears that your purpose is to wear down your opponent rather than have an intelligent conversation.

While I appreciate them, your explanations have not been necessary. I have 38 years' worth of the theory & practice.

I don't ask you to ignore anything. Simply to stay on topic, which is, at the moment, Chandler's analysis.

There will be less "wearing down" if we stay confined to fewer issues. So I'll stop here.

Regards,

Tom.

 

[tfk]

According to an e-mail that I received from Mr. Phillips, it appears that he has decided to not debate in this forum or in personal emails.

This is a phenomenon that mystifies me. I suggested to a person that I was debating on another forum that he fetch a mechanical or structural engineer from AE911 to come over & debate. A couple of their engineers sent over some cryptic questions about format for the debate. I suggested "conversation". And then they declined.

It is astonishing that, on a subject that they seem so convinced, and one that is so crucially important to our country (should their theories be true, I'd be first in line with a pitchfork & torch), they appear to be singularly uninterested or lazy in applying themselves to any real analysis.

 

[Mr.Herbert]

The truthers seem to all be doing the Snoopy Happy dance in regards to the findings of Mr. Chandler.

In laymen terms, can anyone please explain to me what he found that NIST didn't?

I understand he calculated that part of the collapse was in free fall for a brief time. I also understand that NIST made this apparent in their original document, yet updated their final draft with what Mr. Chandler reported.

 

[R.Mackey]

In laymen terms, can anyone please explain to me what he found that NIST didn't?

Sure.

Nothing, that's what.

The Truth Movement is doing the "happy dance" because either (a) they think any period of near-freefall implies explosives, which it does not; or (b) they think NIST acknowledging them at all justifies their existence, if not their beliefs.

Talk about a non-issue...

 

[Sizzler]

WTC7 in freefall for 2.25 seconds:Chandler vs. NIST

http://911blogger.com/node/18771#comment

A few months back I posted a video by David Schandler where he claims to have demonstrated for 2.5 seconds WTC7 fell at rate indistinguishable from free-fall.

Schandler now claims that in NISTs final report, it is admitted that WTC7 fell at a rate indistinguishable from free-fall for 2.25 seconds.

So assuming he isn't lying about the NIST report (don't have time to check it myself at the moment), what are the ramifications of this, if any? Is free-fall for 2.25 seconds plausible? And does that even match NIST's models?

ETA: REPEATED THREAD. SORRY!!!

ETA2: Actually this is a new video, I guess this isn't the same topic at the other thread. Maybe they should be merged? Anyway, any thoughts on the new video?