More accurate fall times for the towers

[Debunking911]

This is a more accurate fall time graphic for the towers than have been posted on conspiracy theory sites. It takes the transfer of energy on impact into account.

[sabbat hunter]

1. excellent post

great graph, dispels myth of free fall.

*applause*

[Debunking911]

2. Thanks

911myths has a problem with the link but here it is saved on google.

http://72.14.203.104/search?q=cache:nC1U0dNyD8gJ:www.911myths.com/WTCREPORT.pdf+WTCREPORT.pdf+&hl=en&gl=us&ct=clnk&cd=1

I believe it took even longer because every video I've seen from ground level shows ten seconds just for the perimeter columns outside the building falling at free fall to hit the ground. I believe the actual figure is around 13-14 seconds. But it's impossible to know due to the debris cloud. Anyone who says they know for sure is lying. Even the NIST. All we can due is estimate.

[libertypirate]

42. It's still 80 undamaged floors collapsing without resisting the load

they had resisted for years... They just instantly fell apart by their own load..

BTW, Some jacks graphic is about as conclusive my opinion, it's a graphic; I don't shovel opinions because people deserve better.

If anyone wants accurate fall times just look up the seismographs which show the order and magnitude of energy being released by said falling buildings.

Anyway the only funny thing about the pattern in the seismographs is they match an explosion coupled to the ground, closest match to them I could find is a nuke test in india. Just an FYI the 1992, bombing of the WTC didn't show up on a seismograph... It wasn't coupled to the foundation.

[KJF]

3. More accurate in what way?

NIST says the towers "came down essentially in free fall".
NISTNCSTAR1-6, p. 320/402

The 9/11 Commission says "the South Tower collapsed in 10 seconds".
Main Report, p. 305

911 Research says it took 15-16 seconds.
http://911research.wtc7.net/wtc/analysis/collapses/freefall.html

Who's more accurate and deserving of our trust?

[Debunking911]

5. As I said...

It doesn't matter what the NIST said about "essentially" in free fall. The fact is it wasn't and I don't think the NIST implied it was. "Essentially" could means close to but not free fall. The difference between 9 second free fall and 13-14 or even 16 seconds is all "Essentially" free fall when one considers 60 second minutes and 60 minute hours. But for videos like Loose Change to give the impression it fell at free fall is misleading because there argument rests on "NO RESISTANCE". That doesn't take into account the resistance the building put up. It's impossible for the NIST, FEMA, the commission report or anyone to know for sure but anyone can view the videos taken from ground level looking up and know the collapse took longer than 10 seconds. That includes the fact that the first debris to hit the floor was NOT from the top of the towers but from the impact levels. Some of the top of one tower could be seen at around the 60th floor judging by the surrounding buildings.

The commission report is not a technical paper so proving it's wrong means nothing. A straw man.

Each WTC building collapse occurred at virtually free-fall speed (approximately 10 seconds or less).

http://www.physics911.net/reynolds.htm

Not every web site has the same information.

It's a logical fallacy to think that just because one report is wrong that they all are or that bombs must be inserted to explain the collapse. Just as it would be a logical fallacy for me to point to physics911.net and say "Who's more accurate and deserving of our trust?"

The other fact that must be stressed is that the buildings put up even more resistance than Greening calculated. Had Greening calculated 18 seconds and it fell in 16 it might be a cause for pause but as it stands greenings paper seems to be in line with other structural engineers.

The point is there was enough energy to drop the massive building in 13 seconds WITHOUT bombs. That it took longer only helps the collapse due to fire argument and not hurt it.

[KJF]

7. Well, I don't like Loose Change either

And there are a number of points you raise that could be profitably discussed, but I think I'll just focus on one and leave out the rhetoric:

"The point is there was enough energy to drop the massive building in 13 seconds WITHOUT bombs."
What, specifically, do you mean by that?

[Debunking911]

24. I don't see

how I can be more clear. Physics by structural engineering professors prove the building can fall at the speed it did without explosives. Some of the conspiracy theorist say the speed is proof the building was blown up. That's not proof of anything. In fact it only proves how deceptive some conspiracy theorist are. I have seen a graph by someone who drops ten floors at a time as if every ten floors the floors stopped then started falling again. They say the floors should have fallen in 30 seconds. You don't have to be a physics major to know what transfer of momentum is. Anyone who ever played pool knows. That explains the fall times without explosives involved.

[KJF]

37. You appear not to have answered my question

"The point is there was enough energy to drop the massive building in 13 seconds WITHOUT bombs."
If you believe there was enough energy to drop the massive building, then you must think you have figures for:
(1) The amount of energy in the buildings;
(2) The amount of energy needed to drop the buildings.

What are they?

[FourScore]

4. how quickly do demolished buildings fall?

Do they fall at free-fall or is their s slight delay? Anything between 9-15 seconds is pretty darn fast for those buildings to fall IMHO.

[Debunking911]

6. We have never seen other buildings this size collapse..

because there have never been buildings built like this hit by airliners at 500 miles an hour before. Published papers by structural engineers say the time was enough without bombs. Here is yet another one...

http://www.public-action.com/911/jmcm/sciam/

[dailykoff]

8. A panel discussion is not a "published paper"

and a reporter for Scientific American is not a structural engineer. In any case he says in a pull-out quote:



In case you can't read it: "Computer simulations indicate the building material fell almost unrestricted at nearly the speed of free-falling objects."

He also goes on about "a rapid-sequence 'pancaking' phenomena in which floor after floor was instantly crushed and then sent into near free fall to the ground below" so it's a load of b.s. anyway.

[Debunking911]

9. How do you know more than a structural engineer?

Are you one?

You are also asking me if I can't read when you obviously missed this...

The difference between 9 second free fall and 13-14 or even 16 seconds is all "Essentially" free fall when one considers 60 second minutes and 60 minute hours. But for videos like Loose Change to give the impression it fell at free fall is misleading because there argument rests on "NO RESISTANCE"."

So if he says "Computer simulations indicate the building material fell almost unrestricted at nearly the speed of free-falling objects." it doesn't mean it fell at the speed of a free falling object. It only says "Computer simulations" say it's well within the fall time witnessed without factoring in explosives in the simulation. But to suggest it didn't have resistance goes against physics. The physics are all there in the articles.

Jones is not published in a scientific journal yet he says hes "Published" What I showed you is published in Scientific American but it discusses the MIT papers below.

http://www.sciam.com/article.cfm?articleID=000B7FEB-A88C-1C75-9B81809EC588EF21

http://web.mit.edu/civenv/wtc/

Then there are these. All which may have differnet hypothesis for collapse but are PEER REVIEWED published papers. Not ONE published paper exist saying the towers could not have collapsed by fire. NOT ONE.

Eagar, T.W., & Musso, C.
"Why Did the World Trade Center Collapse? Science, Engineering, and Speculation"
JOM v. 53, no. 12, (2001): 8-12.

Newland, D.E., & Cebon, D.
"Could the World Trade Center Have Been Modified to Prevent Its Collapse?"
Journal of Engineering Mechanics v. 128, no. 7, (2002):795-800.

Bazant, Z.P., & Zhou, Y.
"Addendum to 'Why Did the World Trade Center Collapse? - Simple Analysis" (pdf)
Journal of Engineering Mechanics v. 128, no. 3, (2002): 369-370.

The fact is the floors pancaked after the perimeter columns were pulled in. The proof is the core which could be seen standing seconds after the collapse. Where did the floors go if they did not go straight down around the core? Assuming they didn't just fly away they fell striaght down. "Pancake". NIST never said "Pancaking" caused the collapse but it was an end result.

[dailykoff]

12. You forgot the kitchen sink

but it wouldn't help, because none of this made-for-TV propaganda holds any water.

[Debunking911]

20. As opposed to the Made-for-Internet propaganda?

Propaganda which is making a few people rich on DVD and donation sales.

I prefer not playing this game but I can.

[dailykoff]

21. You mean those crappy websites people keep plugging on DU?

Yeah it's a scandal. :eyes:

[Debunking911]

32. Insults are three legged stools for social midgits.

Please don't attack me for giving another POV. One which I have been researching for months on my own now. Because I feel those controlled demolition conspiracy theory sites are just as crappy as you think mine is. The difference is I just give everyone else the information I dug up on my own and let others deside for themselves which is crappy.

[dailykoff]

34. Remember garbage in garbage out?

If you make a lovely website and fill it with "research" from FoxNews.com it's still garbage.

[FourScore]

13. No one has answered my question.

It's pretty straight-forward. How quickly do demolished buildings fall? Do they fall at free-fall or is there a slight delay?

Let's say, for example, that a 30-story demolished building has an extra 1.2 seconds delay added to the fall time--rather than falling at free-fall. Then it wouldn't surprise me if a 106 story building has 3.6 seconds added to it's fall if it were professionally demolished.

It's quite simple really...There must be data on this even prior to 911.

[mirandapriestly]

14. Someone put a video of a controlled demolition on here

a few weeks ago. I just tried to find it , but couldn't. It was not free fall, in fact it took longer for that building to come down in a controlled demolition than it did for the towers and it was maybe a third of the height. I don't know why people quibble over it being exactly free fall. If a 110 story building "pancaked", it would take one second per floor , which is 110 seconds , so even with the few added seconds of the "more accurate" time, it still totally disproves a "pancake collapse" I don't understand what the significance of proving EXACT free fall. I mean , of course there is going to be something of an obstacle to the building falling evening if all constraints were removed.

[Debunking911]

17. No it wouldn't take one second per floor.

You are misinformed. If the building pancaked it would speed up because it not only transfered momentum to the next floor but added the weight of the next floor when it crashed down on the one below the next. One floor turns to two, two floors collect the third, the three floors collect another... now you have four floors hitting one and this only continues to grow. After a few floors collect the hundreds of bolts and connections holding a floor up became easy to cut.

[mirandapriestly]

25. I can see what you mean but

you can't put a time frame on it (iow exactly how much time is subtracted because of the momentum) and there is no reason why it would take a shorter amount of time then the controlled demolition I linked below. Do you think more floors would take LESS? If you are quoting from Scientific American then YOU are misinformed, btw.

[FourScore]

18. .

[mirandapriestly]

23. Here is a controlled demolition

(no I'm not linking to the wtc, lol, that's all that comes up under controlled demolition on yahoo)

They have a clock running at the bottom, but it starts a little before the detonation, it looks like it is about a minute and I think the building is 30 stories? in any case there are a lot fewer floors than wtc and it takes longer, you get the picture;)...

[FourScore]

27. link?

[mirandapriestly]

36. Here it is, sorry

I went to all that trouble to dig it up, then I forgot to post it.

http://www.dfw.com/multimedia/dfw/news/archive/0318implosion1/index.html

[FourScore]

22. Exactly.

BTW mirandapriestly, I always seem to agree with your posts. Your insight is pretty valuable. THanks for responding.:)

[dailykoff]

19. Around 30 seconds for a 30-story highrise

demolished in Texas on March 18, 2006:

"(CBS 11 News) It took less than 30 seconds for the Landmark Tower, once Fort Worth's tallest building, to be reduced to rubble during a scheduled implosion. CBS 11 News had crews scattered throughout downtown Fort Worth to document the implosion of the 30-story Landmark Tower."

http://cbs11tv.com/seenon/local_story_077141215.html

[FourScore]

26. Actually the fall talkes about 6 seconds

If you start the clock at the moment you see the buildings begin to fall (not at the moment of seeing explosions) then it takes about 6 seconds. The dust cloud sure looks familiar. Still the question remains: Surely some demoition expert has figured out how long a demolition fall takes compared to free fall. Perhaps there are varying factors such as the type of demolition materials used. But still...there must be data on this somewhere. Thanks for this link. It is helpful.

[Debunking911]

33. I saw an article which said 13 1/2

News orgs take creative license with things like that. 13 seconds may seem like 30 when someone is back in the office writing an article after the fact. Others my roll a tape and double check before writing.

[Jazz2006]

52. Here's a good view of the Landmark Tower implosion, btw.

http://video.google.com/videoplay?docid=6979955002470780153&pl=true

[Debunking911]

30. You're missing the point.

The conspiracy sites were saying the building fell at free fall and that proves CD. They say it didn't put up resistance because the columns were taken out before the building collapsed, hence the speed. I never said CD's are shorter, some conspiracy sites say that.

The landmark is a perfect example. It's not a tube in a tube design like the towers. It had a web of steel I-beams spread out evenly. It didn't have small 5/8's bolts holding trusses in place. Each floor had large steel I-beams underneath holding them up. This 1950 construction would have been overkill in 1975. In fact many say structural engineers 9/11 proves we should go back to that more expensive yet safer design. We shouldn't be relying on fire proofing after the building is built as with the towers. We should be building the fire proofing into the design as we did in the past.

[Jazz2006]

35. None of them fell at free fall rates, that's true.

The collapses were all caught on video. The times cited by various and sundry conspiracy sites are often driven by their agendas. Nobody - not even non-conspiracy sites - can be sure of the timing because of the debris and massive dustclouds obliterating the site. But taking into account all of the video and audio and live evidence, there is no way that the towers collapsed at free fall speed.

The repeated but unsubstantiated assertions to the contrary are just that - repeated and unsubstantiated.

[Old and In the Way]

38. I think it would be a function of timing and location of charges.

Let's say you have two 100 story buildings, side by side. If you wired one building such that every floor's vertical members were detonated at once and the other was wired to knock out only the 90th floor, I have to think that the former would be close to freefall while the later would be somewhat slower. The resistance of the 10 stories would be greatest at the 89th floor and progressively less as each lower floor has more mass impacting on it until it is ully collapsed. I guess I don't know how much "hold" time we could expect the 89th floor to withstand the 10 story mass that impacts it. If we knew that, I'd think you could calculate an expected time for the entire building to collapse.

I would think that a model could be constructed to test the later scenario...it would be quite interesting to see what a model would predict for total collapse time as compared to the actual events. If the theoretical model would predict, say, 25 seconds, then I'd have to wonder if there was charges placed to help the collapse along. If it would predict 15 seconds, then the events would have fallen as expected.

[Old and In the Way]

10. So the collapse events pretty muched matched the freefall

over the 1st 3 seconds, then decelerated? I would have thought that it would encounter the most resistance at the beginning of the event and then accelerated as more mass overcame the initial resistance of each floor. On the tapes I've scene, it looks pretty constant from beginning to end.

[Debunking911]

15. It's a second

to hit one floor. Obviously the first floor free fell to the one below without resistance. (NO floor slowing it down) It wasn't untill the floors hit the one below it that it would slow down. In some videos you can even hear it speed up as the explosive sound of an acre of concrete crashes down on the one below.

[petgoat]

11. More accurate than the 9/11 Commission? Impossible!

They said 10 seconds, and 10 seconds it is. They had access to the greatest
minds in the nation.

[Debunking911]

16. Commission report is not the NIST report.

The NIST is the one who had the greatest minds in the nation working on this. The NIST report final only came out toward the middle of last year so how could the commission know what was in the report?

[eomer]

28. Bending/fracturing of the steel supports delays the descent 0.3 seconds

for WTC2 and 0.5 seconds for WTC1:

Table 1 shows that the bending/fracturing of the steel supports delays the descent of
WTC 1 by only 15.3 milliseconds for the first impact and by a steadily decreasing
time interval thereafter. The full calculation for the total collapse of the Twin Towers
shows that inclusion of the delay from the bending/fracturing of the steel supports
adds only about 0.5 seconds to tc for WTC 1 and 0.3 seconds to tc for WTC 2.

That is pretty surprising (to this layman). Is it correct?

[dailykoff]

29. Sure it's correct

if the "bending/fracturing of the steel supports" is produced by a thermonuclear explosion, or several.

[Debunking911]

31. Are you suggesting

there was a nuclear device in the buildings?

[dailykoff]

47. Let's call it a pretty good hunch. (n/t)

[Debunking911]

48. Is it supported by evidence like radiation?

Did anyone suffer from radiation sickness who was rescuing people that day? People who were saved in the building? That would be one of the easiest things to test for. The radiation would still be there. You may want to rent a giger counter.

[dailykoff]

49. The NYC EPA was located in the World Trade Center

and the CDC in Atlanta, which apparently has the data collected from NYC radiation measuring devices on 9/11, hasn't released it, at least to my knowledge.

And yes, plenty of people are getting sick and dying, including children, but the CDC doesn't give any of them physical exams because they're confident it's from "psychological trauma."

[mirandapriestly]

51. There are illnesses consistent with radiation, according to Indira Singh

and I've heard that elsewhere.

[eomer]

39. This paper says less than it appears to if you ask me.

The critical issue here is whether the upper block of floors would be able to crush each floor below it successively and, if so, how much its descent would be delayed by the loss of energy used up in the crushing. The paper at first appears to address this issue but on closer examination it really does not develop an answer to that question in any direct way.

First, the paper admits that the author does not know how to directly calculate the energy needed (E₁) and apparently from the wording believes that no one else knows how to calculate it directly:

Unfortunately there appears to be no simple way to calculate E₁ from first
principles since the collapse of just one floor of a WTC tower is an extremely complex
process involving the bending and fracturing of numerous support structures.

Next, the paper cites someone else's estimate of E₁ but tells us that the methodology for that estimate is not disclosed:

In spite of these uncertainties, some estimates of the magnitude of E₁, (the energy
needed to bring about the collapse of one floor), have been made. For example, Z. Bažant
et al. at Northwestern University, Illinois, have estimated that the maximum plastic
energy dissipated by the collapse of one floor, i.e. our quantity E₁, is approximately equal
to 5.0 x 10⁸ J. Unfortunately Bažant et al. do not give a detailed exposition on how this
value for E₁ was derived, stating only that it is based on “approximate design
calculations” for one WTC tower /3/.

Next up is another citation to someone else's estimate, again with the methodology undisclosed. This estimate is not based on a direct calculation of the vertical impact of a block of floors but rather is based on a calculation of a sideways impact together with the assumption that you can equate the energy needed to crush the structure from the side with the energy needed to crush it from above:

Another calculation that may be used to estimate E₁ was published by G.C. Lee et
al. in a MCEER Special Report /4/. Lee et al. assume that 36 exterior columns on WTC 1
were destroyed by the Boeing aircraft impact and conclude (without giving
computational details) that the energy absorbing capacity of these damaged columns
“does not exceed 7230 kips-ft” or about 10⁷ J. Based on this estimate, and remembering
that one complete floor has 236 exterior columns, it follows that the exterior columns
comprising one floor of a WTC tower have an impact energy absorbing capacity of about
7 x ⁷ J. From the relative cross-sectional area of a core column (0.1236 m²) compared
to an exterior column (0.0184 m²), we estimate that the effective strength of the core
columns is about 6.7 times higher than the effective strength of the exterior columns. A
consideration of the collapse of the 47 core columns therefore adds about 9 x 10⁷ J of
energy absorbing capacity. Thus, based on Lee’s calculations, the total energy absorbing
capacity of the structural supports of one floor of the WTC is estimated to be about 1.6 x
10⁸ J, which we equate to our quantity E₁ while noting that this estimate is significantly
lower than Bažant’s value of 5.0 x 10⁸ J. However, it appears that Lee’s results are based
on very rough estimates of the energies involved so that the level of agreement with
Bažant’s estimates is as good as might be expected in view of the approximations
involved.

Finally, another citation to someone else's calculation that, like the previous one, depends on the assumption that a vertical impact needs the same energy as a sideways impact to crush the structure. It's not totally clear but let's give benefit of the doubt that the cited paper in this case does explain its methodology:

A much better estimate for E₁, and one that is based on a very detailed analysis of
the aircraft impact events, may be derived from a paper published by T. Wierzbicki et al.
at MIT /5/. These authors have calculated the energy dissipated by the wing of a Boeing
767 cutting through the exterior columns of a WTC tower and report a value equal
to 1.139 x 10⁶ J per column. On this basis, 2.69 x 10⁸ J would be require to cut through all
236 exterior columns supporting one WTC floor. If we now assume, as previously
discussed, that the yield strength of the core columns is about 6.7 times higher than the
yield strength of the exterior columns, we estimate that an additional 3.60 x 10⁸ J are
required to collapse the 47 core columns supporting each floor. Thus, based on T.
Wierzbicki et al. calculation, we estimate a total of 6.29 x 10⁸ J of impact energy was
required to collapse one WTC floor, a value that is remarkably close to Bažant’s estimate
of 5.0 x 10⁸ J for the plastic energy dissipated by the collapse of one floor.

So, keeping score, the author first admits that no one knows how to calculate the needed quantity directly, then cites one estimate of undisclosed methodology, followed by an estimate that is based on a sideways impact rather than a vertical one and does not disclose its methodology and then finally cites another estimate that is based on sideways impact but that apparently does disclose its methodology. The author finds some comfort in the fact that these three estimates, each one of dubious origin, are all in the same ballpark and then adopts the third one for the purposes of the rest of his paper (the estimate of 6.29 x 10⁸ J that I bolded in the last excerpt).

I'm going to withhold judgement until structural engineers can do the math directly on a vertical impact. This sideways impact stuff isn't convincing to me since I have no way of knowing whether the assumption that vertical impact and sideways impact will be equivalent is valid or total bunk. It seems far fetched to say that we don't know how to calculate a vertical impact because it is too complex but still we somehow do know that a sideways impact would be the same and can be used as a surrogate.


_{Edit: minor wording}

[Debunking911]

40. What do you mean "by dubious origin"

I think these structural engineers are beyond reproach. Unlike Jones and Hoffman they have many published papers on structural/civil engineering. (Not greening but the others) I think the logical fallacy you are suggesting is that just because we are not given every detail of the calculation on the internet that it is a dubious origin. That Bazant and the others pulled the number from the sky.

It should be easy for someone to prove them wrong by publishing a peer reviewed paper saying as much. None has been passed to date. If E1 is wrong and it means Bazant's paper is wrong then anyone should be able to calculate where it's wrong and pass a peer reviewed paper to that effect.

[eomer]

43. I mean that Greening says the methodology is undisclosed.

Since you point to Bažant in particular, here is what Greening says about the Bažant estimate:

Unfortunately Bažant et al. do not give a detailed exposition on how this
value for E₁ was derived, stating only that it is based on “approximate design
calculations” for one WTC tower /3/.

I looked up the Bažant paper and here is the part that Greening is apparently referencing:

For our purpose, we may assume that all the impact forces go into the columns and are
distributed among them equally. Unlikely though such a distribution may be, it is never-
theless the most optimistic hypothesis to make because the resistance of the building to the
impact is, for such a distribution, the highest. If the building is found to fail under a uniform
distribution of the impact forces, it would fail under any other distribution. According to
this hypothesis, one may estimate that C {approximately equals} 71 GN/m (due to unavailability of precise data,
an approximate design of column cross sections had to be carried out for this purpose).

As you can see Bažant doesn't go into the details of how the calculation was done but does say that they did not have the actual design of the building to go by and therefore had to make up an assumed design, a design which they don't detail in the paper.

Bažant may be right but even a layman like me can ferret out some holes in the approach such as
using a hypothetical design for the building structure rather than the actual one. We don't know what design they tested in their analysis and we don't know for sure the actual design of the building since it was "disappeared" by Giuliani. It does seem to me there is some doubt about this calculation.

[KJF]

44. Good point

And let's not forget that Greening more than doubles the weight of the towers. For example, on page 23, he says that each tower weighs 510,000,000 kg (which is 562,178,768 (US) tons) and each floor weighs 4,636,363 kg (which is 5,110 tons). To get the weight of each floor he divided the total weight of the towers by 110 (the number of above-ground floors), conveniently forgetting about all that concrete, steel and machinery in the basements and thus distributing it across the above-ground floors.

The actual weight of the towers was less than half that - 250,000 tons - according to NIST. (p. 32 of the main report). btw, I once saw at discussion on what it would have taken for the towers to weigh 500,000 tons on a physics forum. The guys there calculated each building occupant would have had to weigh 22 tons.

In addition, Greening gets the South Tower's core the wrong way round, doubles the most probable amount of aircraft impact damage and fails to mention the hat truss.

[Debunking911]

45. You may have also read this....

From the same physics board member... It appears there is live load and dead load the NIST is talking about which are very different...

The 510,000,000 kg number greening used was taken from a source that did not explain where that number came from... I have since done a detailed search and the values quoted for the mass of a WTC Tower vary by quite a bit. Please also note that the mass of a Tower is implicit in values quoted for the total potential energy of a Tower since P.E. = 0.5Mgh. (Factor of 0.5 to allow for average height.) Quoted values for the P.E. vary all over the map too...

I have also tried estimating the mass using dead load and live load data from the NIST final report and come up with a mass closer to 400,000,000 kg. So, folks who want to discredit Greening's calculation can jump on this.... but fear not! Let's re-run the calculation using a fixed value of E1 and varying the mass between 510,000,000 kg and 300,000,000 kg. I have personally tested the results for WTC 1 since this was the slowest to fall and is the most stringent test of Greening's calculation. The collapse times (also including estimates of the delay from building resistance) come out as follows:

M= 510,000,000 kg, t = 13.48 sec; M = 450,000,000 kg, t = 13.56 sec; M = 400,000,000 kg, t = 13.67 sec; M = 350,000,000 kg, t = 13.84 sec; M = 300,000,000 kg, t = 14.16 sec.

Hence t changes by less than a second for a mass change of 40 %!

In other words, the collapse time is quite insensitive to M over a wide range. Upon reflection this is not so surprising since this is precisely what Galileo showed in his famous experiment at Pisa. If there is no resistance to the collapse, the Towers fall in 9.2 seconds - regardless of their mass! Mass comes into play only when resistance has to be overcome, and this depends on E1 more than anything else.

__________

So the weight of the building is not the issue. This member also thinks the towers fell do to a normal collapse and not controlled demolition. Though to be fair he thinks building 7 is still up in the air. That is mainly due to the final report which still unavailable.

[KJF]

50. NIST's figure

Is for the whole thing.

The issue with the weight isn't the speed of fall, but whether the top would fall at all and, if it did so, whether it was heavy enough to get the building to pancake.

Nice try at diverting the argument, though.

[libertypirate]

41. Dupe

[AlienSpaceBat]

46. I posted some data tables and graphs for momentum conserving collapse

in a previous thread which may be relevant here ?

http://www.democraticunderground.com/discuss/duboard.php?az=view_all&address=125x64808