What would satisfy me is if you were up front as to what you are trying to get out of this. Every calculation has a context, every calculation is required for a reason. It is no secret you have a preconceived agenda. You misrepresent your work in comparison with others. It would be so easy to talk to Robert Fowler or Les Robertson, but you have not. You fail to comprehend the fact that nothing you have mentioned changes the facts of the collapse at all. What next, stubby-penciling the weight of the 767s using actual number of passengers and estimates of their carry-on weight? I just see this as being little more than "OMG they lied about the weight of the towers OMG Conspiracy it's all lies!!!111!!" - more pap for the twoofers.
9/11 Physics from Non-Experts
- Thread starter Totovader
- Start date
What would satisfy me is if you were up front as to what you are trying to get out of this. Every calculation has a context, every calculation is required for a reason. It is no secret you have a preconceived agenda. You misrepresent your work in comparison with others. It would be so easy to talk to Robert Fowler or Les Robertson, but you have not. You fail to comprehend the fact that nothing you have mentioned changes the facts of the collapse at all. What next, stubby-penciling the weight of the 767s using actual number of passengers and estimates of their carry-on weight? I just see this as being little more than "OMG they lied about the weight of the towers OMG Conspiracy it's all lies!!!111!!" - more pap for the twoofers.
Not really. I would call it a 22-gauge steel deck with 1 1/2" profile. I would probably have to call out a profile # as well, to make sure that the contractor ordered and installed the right thing.
GregoryUrich
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I have previously stated my motive in doing this work. I will repeat it here unless someone has missed it. I've seen work by the twoofers that doesn't hold up, but Bazant doesn't hold up either. I have not made up my mind yet about controlled demolition but video taped eyewitness testimony of explosions (not Dan Rather) is pretty convincing. Believe me, I would rather be fighting against a rag tag bunch of fanatics on a shoe string budget than well funded, well organized elements embedded within the government and military. We know Bush, Rumsfeld and Rice lied about foreknowledge. The PDB and news articles all over the world attest to this. Of course we can't say how much they knew. But I digress.
This work is to support better collapse time analysis. I am not satisfied with the work published at the Journal of Woo and in fact today I demanded a retraction of Ken Kuttler's WCT7 article.
My agenda will be based on the outcome of better collapse time analyses. If I find that the collapse times pretty much fit in with the official explanation, I will gladly go back to spending my freetime on more enjoyable things. If my result does not fit in with the official explanation, I will have more work to do. If my results are convincing, we all will have important work to do.
You say I misrepresent my work in comparison with others. How so?
You attempt to create a veneer of rationality, but your motives are unmistakable.
Since everyone has acknowledged that there is a lot of guesswork in all of these estimates, and since I've been disambiguated by everyone's thoughtful answers to my questions a few pages back, I feel I can put my two cents in.
In the midst of all the uncertainty, one point strikes me as potentially telling:
The reason it seems that way, to me, is that the types of businesses in the World Trade Center clustered around certain norms. I think it's a safe bet that the tenants who needed modifications for heavier loads weren't cannon foundries or brickmaking kilns or indoor aquaculture farms. If they neeeded higher load capacity it was most likely for server farms or paper, especially the latter. (Server farms are more constrained than paper files in load density, due to their cooling requirements.)
We can talk about the weight of desks and chairs, but the weight per desk and the approximate desks-to-employees ratios aren't going to deviate much from one business to another. No business is going to have 1/10 as many chairs, or 10 times as many chairs, as employees. (Movie theaters excepted.) But an estimate of the load of paper files for a given business could easily range over many orders of magnitude. So, it would be hard to disprove that the typical business in the towers had more than one rack of servers and one small file cabinet per employee without knowing private details of how those businesses were conducted. But the fact that some of them needed greater capacity strongly suggests that most of them trended similarly toward the heavy side.
Unless, of course, it can be shown that the tenants that required increased loads had special kinds of business needs compared with the other tenants, rather than just being the upper extremes of the same bell curve. If Mr. Urich can point to cases where tenants required extra capacity for reasons that would be unlikely to apply to other tenants, his case for a low mean live load would be stronger. Contrariwise, if anyone else can show that the tenants requiring higher loads needed them primarily for files, servers, or other needs that other tenants would be under similar business pressures to accumulate toward the point of exploiting the full design load, the case for a higher live load would be strengthened.
This whole question of total tower mass might not be relevant for understanding the collapse, but important aspects of it could be very relevant to fire models. The fuel load derives mostly from the live load outside the core. The difference between a live load 25% of design load, and a live load 75% of design load, could be very significant in addressing such questions as whether or not the fuel was actually exhausted in the zones where visible flames were observed to abate, how the fire might have developed over time had the towers not collapsed, and what parameters to use in modeling the post-collapse rubble pile fires. Dr. Greening's work would certainly benefit from more accurate figures here.
Respectfully,
Myriad
In the midst of all the uncertainty, one point strikes me as potentially telling:
The reason it seems that way, to me, is that the types of businesses in the World Trade Center clustered around certain norms. I think it's a safe bet that the tenants who needed modifications for heavier loads weren't cannon foundries or brickmaking kilns or indoor aquaculture farms. If they neeeded higher load capacity it was most likely for server farms or paper, especially the latter. (Server farms are more constrained than paper files in load density, due to their cooling requirements.)
We can talk about the weight of desks and chairs, but the weight per desk and the approximate desks-to-employees ratios aren't going to deviate much from one business to another. No business is going to have 1/10 as many chairs, or 10 times as many chairs, as employees. (Movie theaters excepted.) But an estimate of the load of paper files for a given business could easily range over many orders of magnitude. So, it would be hard to disprove that the typical business in the towers had more than one rack of servers and one small file cabinet per employee without knowing private details of how those businesses were conducted. But the fact that some of them needed greater capacity strongly suggests that most of them trended similarly toward the heavy side.
Unless, of course, it can be shown that the tenants that required increased loads had special kinds of business needs compared with the other tenants, rather than just being the upper extremes of the same bell curve. If Mr. Urich can point to cases where tenants required extra capacity for reasons that would be unlikely to apply to other tenants, his case for a low mean live load would be stronger. Contrariwise, if anyone else can show that the tenants requiring higher loads needed them primarily for files, servers, or other needs that other tenants would be under similar business pressures to accumulate toward the point of exploiting the full design load, the case for a higher live load would be strengthened.
This whole question of total tower mass might not be relevant for understanding the collapse, but important aspects of it could be very relevant to fire models. The fuel load derives mostly from the live load outside the core. The difference between a live load 25% of design load, and a live load 75% of design load, could be very significant in addressing such questions as whether or not the fuel was actually exhausted in the zones where visible flames were observed to abate, how the fire might have developed over time had the towers not collapsed, and what parameters to use in modeling the post-collapse rubble pile fires. Dr. Greening's work would certainly benefit from more accurate figures here.
Respectfully,
Myriad
DavidJames
Penultimate Amazing
For those unsure of where he stands, these quotes seem to make it pretty clear:
Regarding a video from PFT
As I have stated previously, you have claimed that various other works have "overestimated" the weight of WTC 1 and 2. However, as I have pointed out, the 500,000 ton figure most likely originated from a statement by one of the original design engineers, Robert Fowler, as the magnitude of the gravity loads at the base of the towers. You are claiming this is an overestimation of what you are calculating, which is an instantaneous weight of the WTC on the morning of September 11, which involves sustained and transient live loads. You are comparing apples and oranges attempting to discredit others, and it is disingenuous, intellectually dishonest, or (possibly) you simply do not understand the difference. I do not think you have read or understood Bazant in the slightest. You freely admit in your letter that your PE values came out in line with FEMA's, but now you claim the difference in mass should reduce the PE values.
But....let's get into the MEAT...how EXACTLY does Bazant "not hold up"? Please list your criticisms, concisely and coherently, and feel free to be as intellectually rigorous as you are able....
Newtons Bit
Penultimate Amazing
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- Apr 12, 2007
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- 10,049
First rule of thumb is only camber for 3/4 of the dead load deflection. Trying to balance it precisely will leave your floor looking like rolling hills...can't get the damn beams to go down!
Or it will leave your headed anchor studs sticking up out of the concrete. That's a fun one to try and explain to the owner.
Vulcraft has it's steel deck catalog online for those who want to see what they really look like. http://www.vulcraft.com/downlds/catalogs/deckcat.pdf
Skyscraper comparisons based on building mass divided by building volume:
The Empire State Building: 348 kg/m^3
Sears Tower Chicago: 218 kg/m^3
John Hancock Center: 166 kg/m^3
Taipei 101: 347 kg/m^3
Woolworth Building: 460 kg/m^3
WTC: M (kg)/1,680,000 m^3.
The Empire State Building: 348 kg/m^3
Sears Tower Chicago: 218 kg/m^3
John Hancock Center: 166 kg/m^3
Taipei 101: 347 kg/m^3
Woolworth Building: 460 kg/m^3
WTC: M (kg)/1,680,000 m^3.
Several responses in one!
Indeed I can, although I'm afraid it's from NIST NCSTAR1-1A -- I mistyped. Sorry if you looked and couldn't find it. The reference to 55psf SDL outside core, and 75psf SDL inside core for the mechanical floors is found in the original design documents, Figure 2-4, page 12 of NIST NCSTAR1-1A.
Also, if you prefer, there is a more detailed accounting in Table 6-6 of NIST NCSTAR1-2A on page 141.
There are some slight contradictions in the NIST report (and, indeed, in the design documents), but whichever SDL figures you prefer, I trust you'll agree that your current core SDL estimate of zero requires some attention.
I do try to stay above the insults, particularly when other participants do the same. I am a professional scientist, after all.
While I'm pulling up NIST quotes, let's turn to NIST NCSTAR1, the master report. On page 6 is this passage:
Just because the load was "considered" doesn't mean that it definitely fell within the structure's design envelope.
Furthermore, Gregg Roberts conspicuously avoids NIST's more detailed comments on the "600 MPH issue," found in Section 5.3.2, pg. 55:
I believe you'll find that the NIST's statements, when presented accurately and in context, are wholly consistent with my comments expressed here.
Oh, and regarding concrete, there is an additional contribution -- the beam-framed floors contained additional concrete around the beams themselves. However, this will probably not be significant against the total, and thus I expect to find well over half the total concrete in the foundatoin.
Indeed I can, although I'm afraid it's from NIST NCSTAR1-1A -- I mistyped. Sorry if you looked and couldn't find it. The reference to 55psf SDL outside core, and 75psf SDL inside core for the mechanical floors is found in the original design documents, Figure 2-4, page 12 of NIST NCSTAR1-1A.
Also, if you prefer, there is a more detailed accounting in Table 6-6 of NIST NCSTAR1-2A on page 141.
I believe it's the 96th floor, chosen as their "typical" truss floor for purposes of WTC 1 analysis. In any case, even at maximum the open space in the core will be about double what we see here, so there is considerable floor space in the core, and thus considerable SDL.
There are some slight contradictions in the NIST report (and, indeed, in the design documents), but whichever SDL figures you prefer, I trust you'll agree that your current core SDL estimate of zero requires some attention.
I don't agree because I'm not convinced all of those live loads are people. Things like catering carts, janitorial supplies, garbage cans, supply storage, etc. would all count against the live load, and would be there more or less around the clock. Regardless, time-averaging is also going to be too crude.
I do try to stay above the insults, particularly when other participants do the same. I am a professional scientist, after all.
While I'm pulling up NIST quotes, let's turn to NIST NCSTAR1, the master report. On page 6 is this passage:
NIST said:
Just because the load was "considered" doesn't mean that it definitely fell within the structure's design envelope.
Furthermore, Gregg Roberts conspicuously avoids NIST's more detailed comments on the "600 MPH issue," found in Section 5.3.2, pg. 55:
NIST said:
I believe you'll find that the NIST's statements, when presented accurately and in context, are wholly consistent with my comments expressed here.
Oh, and regarding concrete, there is an additional contribution -- the beam-framed floors contained additional concrete around the beams themselves. However, this will probably not be significant against the total, and thus I expect to find well over half the total concrete in the foundatoin.
rwguinn
Penultimate Amazing
you want ot edit that, Dr. G?
I hope that's a typo? kg/1.68e6 m^3? that sucker would float off, wouldn't it?
AHA! maybe that's what really happened!
Down is up, black is white! NWO strikes again
AZCat
Graduate Poster
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you want ot edit that, Dr. G?
I hope that's a typo? kg/1.68e6 m^3? that sucker would float off, wouldn't it?
AHA! maybe that's what really happened!
Down is up, black is white! NWO strikes again
You missed the "M" at the beginning. Dr. Greening is using a variable for the mass - one that he has referenced earlier.
What do you mean; it said not a single fact or piece of evidence, and proves the 600 mph wrong by a quick energy analysis. Are you really an engineer? Did you know that is the most ridiculous claim there is? You know why? People who make the 600 mph claim have no idea what they are talking about. It just makes truther look dumb. NIST does not say the building would take an impact from a high speed jet. In fact, the NIST study, and the study anyone can do using energy of impact can prove this 600 mph impact as false. And an engineer should be able to prove this 600 mph statement false on a napkin. I have proof from the real designer on the WTC that a slow speed impact, with low fuel, lost in the fog impact was studied. And it is that study that fits the NIST statement someone remembered all those years ago.
The original structural engineering Leslie E. Robertson design for an aircraft impact, but it was a slow speed landing configuration, less energy at impact than the 9/11 impacts!
Yes the slow speed impact that was in the design would have resulted in just local damage, not extensive damage to the core and a complete destruction of the exterior columns. The impacts on 9/11 were 7 to 11 times greater than the design impact.
This is not NIST, this is the real designer. A fact you could find if you wanted instead of repeating statments that you can prove wrong yourself.
Explain to me how a 707 can do 600 mph at sea level? Please give us the top speed of a 707 at 1000 feet MSL? Under what conditions would a 707 be doing 600 mph? Please include altitude and airspeed for KIAS, KCAS, or KEAS. Take your pick. JAQ but then I will JAQ too.
Just Answering Questions too; The 707 top speed at 1000 feet MSL is 355 KCAS. The top speed for all aicraft below 10,000 feet is 250 KIAS by regulation. The most likely speed for an aircraft lost in the fog trying to land would be 180 mph. The design parameters for an aircraft impact. There are more reasons why a landing aircraft is the most likely impact with a building, base on an airliner doing the deed. But pilot stuff is boring.
Review!: Leslie E. Robertson says low speed impact. Not 600 mph. Questions?
Article by Robertson:
http://www.nae.edu/nae/bridgecom.nsf/weblinks/NAEW-63AS9S/$FILE/Bridge-v32n1.pdf?OpenElement
Notable Quotes:
The two towers were the first structures outside of the
military and nuclear industries designed to resist the
impact of a jet airliner, the Boeing 707. It was assumed
that the jetliner would be lost in the fog, seeking to land
at JFK or at Newark. To the best of our knowledge, little
was known about the effects of a fire from such an aircraft,
and no designs were prepared for that circumstance.
Indeed, at that time, no fireproofing systems were
available to control the effects of such fires.
These charts demonstrate conclusively that we should
not and cannot design buildings and structures to resist the
impact of these aircraft. Instead, we must concentrate
our efforts on keeping aircraft away from our tall buildings,
sports stadiums, symbolic buildings, atomic plants,
and other potential targets.
ETA: Well, text here:
http://www.nae.edu/nae/bridgecom.ns...D8D5CBB9FC33B60C85257111006F3DCA?OpenDocument
http://www.nae.edu/nae/bridgecom.nsf/weblinks/NAEW-63AS9S/$FILE/Bridge-v32n1.pdf?OpenElement
Notable Quotes:
The two towers were the first structures outside of the
military and nuclear industries designed to resist the
impact of a jet airliner, the Boeing 707. It was assumed
that the jetliner would be lost in the fog, seeking to land
at JFK or at Newark. To the best of our knowledge, little
was known about the effects of a fire from such an aircraft,
and no designs were prepared for that circumstance.
Indeed, at that time, no fireproofing systems were
available to control the effects of such fires.
These charts demonstrate conclusively that we should
not and cannot design buildings and structures to resist the
impact of these aircraft. Instead, we must concentrate
our efforts on keeping aircraft away from our tall buildings,
sports stadiums, symbolic buildings, atomic plants,
and other potential targets.
ETA: Well, text here:
http://www.nae.edu/nae/bridgecom.ns...D8D5CBB9FC33B60C85257111006F3DCA?OpenDocument
Last edited:
GregoryUrich
Graduate Poster
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How do you reconcile FEMA's PE with a mass of 500,000 tons? The only way you can do it is by putting 260,000 tons in the basement. If you spread the SDL and live load portion over all the floors in the basement you get more than 1200 psf on floors designed for 500 psf.
Either FEMA is wrong or the 500,000 ton value is wrong. I think that is motivation enough for my work and it is one of the first things that got me interested in this issue.
Can we deal with this and come back to Bazant?
GregoryUrich
Graduate Poster
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- May 16, 2007
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Sanity check
Skyscraper comparison based on building mass divided by floor area:
Here it appears that my value fits in better with other building for the same era.
Skyscraper comparison based on building mass divided by floor area:
Here it appears that my value fits in better with other building for the same era.
Last edited:
gumboot
lorcutus.tolere
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I believe one of the things NIST actually did was calculate the fuel load per square foot in the towers. They didn't include things like paper inside cabinets, as they determined these would not catch on fire. However, given the temperature of the air on engulfed floors, I think it's possible the paper would have reached spontaneous combustion levels.
-Gumboot
You are acting as if the mass of a tower is a constant quantity; it is not. Mass may be represented as DL + f*LL, where f may be any percentage between 0 and 100% (theoretically). FEMA is basing its PE calculations on DL + 0.25*LL (Congratulations! You have independently validated FEMA's results!), which is typical because PE calculations are typically done in collapse cases, and D + 0.25 LL is the load case used in conjunction with extreme events (hurricane, earthquake, blast) which considers the low probability of an extreme event and can use a low percentage of live load accordingly (assuming that f follows some bell curve distribution centered around some percentage, the 25% may be assumed to fall on the left of the bell curve). (Generally, engineers have taken office loads as 25% sustained, 75% transient (for creep calculations, among others), this is no magic number however. We can argue all day long as to whether it should be 22%, 30%, 35%, etc...) The 500,000 ton figure, which as I have said several times now originated from a statement by Robert Fowler, one of the original engineers doing the "grunt work" tower calculations, is NOT a D + 0.25 LL, it is D + Lr*LL, where Lr is some live load reduction factor (see previous posts). Lr does not apply to all live loads, Lr is NOT less than 0.4. This is what I am talking about comparing apples and oranges; you are comparing two different load cases and arguing one is wrong because it is not something it was never intended to be. This is where you are in over your head as far as comprehension.
This is what I do not get about twoofers. Instead of running their numbers by people who could give them quick, easy answers (Ron Hamburger, Robert Fowler, Leslie Robertson), they talk to each other in an echo chamber of BS, or go onto an internet message board and argue with other people.
(PS I have zero confidence in your basement numbers, which do not affect the PE of the tower at all. Your floor loads, as I have said, for the D+0.25LL case, match up closely with NIST's and your PE matches up with FEMA. Your strawman, however, that 500,000 tons represents a D + 0.25*LL case, is wrong, and I would not be surprised to find that you are substantially underestimating the DL of the basement, as well as the LL.)
OKAY, now what EXACTLY is your criticism of Dr. Bazant's work?
rwguinn
Penultimate Amazing
You are correct. My apologies. I just figured Apollo20 was as thumb-fingered as the rest of us...
Anyone here never made a mistake typing? Raise your hands...
rwguinn:
I left M, the mass of a WTC Tower, as a variable since this has become the topic of this thread. You can substitute the high or low value of M and see what makes the most sense, 298 kg/m^3 or 151 kg/m^3.
Interestingly the WTC was claimed to involve lightweight construction and yet the John Hancock Center appears to be the most lightweight of the exampes I qoted, unless you support Gregory Urich's mass....
And by the way, on the point Mackey raised about whether or not the mass of the basement should be included in calculations of the mass of a tower, my guess would be "yes" since the lower six sub-floors that made up the basement appear to have largely collapsed and thus contributed to the potential energy release.
I left M, the mass of a WTC Tower, as a variable since this has become the topic of this thread. You can substitute the high or low value of M and see what makes the most sense, 298 kg/m^3 or 151 kg/m^3.
Interestingly the WTC was claimed to involve lightweight construction and yet the John Hancock Center appears to be the most lightweight of the exampes I qoted, unless you support Gregory Urich's mass....
And by the way, on the point Mackey raised about whether or not the mass of the basement should be included in calculations of the mass of a tower, my guess would be "yes" since the lower six sub-floors that made up the basement appear to have largely collapsed and thus contributed to the potential energy release.