9/11 Physics from Non-Experts

[GregoryUrich]

Why not do an estimate for one floor outside the core?

NIST actually provide some decent info on the office contents, although they don't provide weight. However good weight estimates can be obtained from load calculators used by commercial moving companies.

For the purposes of this little experiment, I have used the 3D model of the layout of the 96th floor of WTC1 as appears on page 95 of NISTNCSTAR1.

I count a total of 204 office cubicles. According to NIST these cubicles were fairly standard across the building, typically 8ft x 8ft, bordered on all four sides by panels, with a small opening.

Photos provided by NIST show at least one side in some cases reached to about shoulder height. Desks were typically wood of a typical large corner-orientated office design. The photos I've seen indicate these cubicles were generally pretty cluttered.

In addition, on the 96th floor I count 27 "small" enclosed offices (1.5 - 2x cubicle size). These appear to be enclosed by more substantial floor to ceiling internal walls.

I count 10 "medium" enclosed offices (3 - 4x cubicle size). And I count 4 "large" enclosed offices (6-8x cubicle size).

Now, for the cubicles, assuming all divides are an equal waist height (photos suggest some divisions were higher) and assuming the 8ft square figure with a 3ft opening in each cubicle, based on the layout of the floor I get a total of 3,852ft of dividing screens.

Anyone care to make a stab at how heavy these are? Just for clarity these do appear to be semi permanent rather than the light weight movable ones you also get in offices.

If we assume of height of about 1.2m (~4ft) and thickness of 3inches.

Now, what would these be made of? We've got a total volume here of 107m³.

If it's particle board, for example, we're talking 17 - 48 tonnes. If it's high density fibre board we're talking 53 - 155 tonnes.

Assuming the "cubicle - 200lbs" weight we were given is meant to be the divides, we're meant to believe these divides only weigh about 20 tonnes, and that for 25% more cubicles.

(If anyone does know what such divides are normally made of, it would be a help).

Using several commercial moving weight calculators and basic furnishing for one cubicle, I get typically around 400kg just for furniture. This doesn't include contents, computers, or anything like that. And I want to reiterate this is BASIC furnishings. Now my meagre basic home office files weigh in at 25kg, and I would estimate the average office (at least the ones I've ever been in) has at least 3 times as much, with a more paper-heavy job (accountant, for example) having as much as 10x as much paper work stored in their personal workspace. I think anything from 75 - 250kg worth of files per cubicle would be reasonable. Half way is 160kg. My computer (just monitor and case) weighs 30kg.

As you can see it begins to add up quickly. And I haven't addressed our 41 larger offices, which have heavier floor to ceiling internal walls (doors?), much more furniture and so on.

I look at the figures presented previously, and I'm highly skeptical.

I mean, 1,000 conference chairs weighing 20 tons? That's about 20kg a chair. Yet you claim this is excessively heavy "made of concrete". Now I doubt there'd be 1,000 conference chairs on every floor, but I'd guarantee you they weigh a LOT more than 20kg. My lame little swivel chair at home (horrible thing, by the way) weighs 10kg. I cannot physically pick up a decent conference chair on my own. I'd imagine they weight a good 50kg at least.

To illustrate my point, no account is made for stationary storage. When I was working at the Auckland offices of GlaxoSmithKline (about 100 staff) I helped with moving one of our several paper storage areas. Based on 80gsm photocopy paper, they had over half a tonne just of plain white copy paper (50 boxes of 5 reams), just in this one storage area. That's not including all of the other paper they had there, or the boxes of paper stored by photocopiers, or the other bulk storage areas (at least one, possibly three).

Now a couple of tonnes of white copy paper might not seem like much, but this is just one example of weights that haven't been factored in. What about kitchen facilities? Bathrooms? We received 20kg of mail a day, for a company with 100 employees. Multiply that by the 25,000 people who worked in each tower and you've got 5 tonnes of just MAIL.

How many ballpoint pens? How many staplers? How many tins of coffee and cans of soft drink? There's literally thousands of things here that have been totally ignored, and added together that amount to tonnes and tonnes of live weight.

-Gumboot

My estimate was for one floor outside the core. Why not do a similar estimate using what you think are reasonable values and we can compare? Remember that all rest rooms and at least some kitchen areas are in the core and shouldn't be included outside the core. Think also what reasonable number of meeting rooms would be. Moreover, we don't need 4 meeting chairs per person as I was trying to over-estimate earlier to avoid debate.

 

[Furcifer]

I should also point out my initial calculation about the increase in mass due to your "linear" assumption was based in the exterior walls not being as well scaled as i have now found them to be. Another quick calculation on my part reduces figure down to about 30%.

 

[tsig]

I used A36 steel as referenced in NIST, I mistakenly wrote A35 in my paper due to fat fingers. This I will also correct.

The buildings were a balancing act between gravity and structural strength

When the balance was upset.

Gravity.

 

[GregoryUrich]

Mass and mass distribution crucial to collapse and collapse times

Gregory Urich

The mass of each tower is very interesting, but NOT crucial to the collapse.

Free fall in gravity is independent of the mass of each tower after all!

The fact that, as NIST clearly state, the Towers fell from aircraft impacts alone is more significant.

Did the perpetrators know this beforehand, or not?

The NIST Report makes sure that it adds that the fires were the problem...

But if NIST are only figuring this out now, is it possible that the US government could be so unaware of something the perpetrators had probably calculated twenty years ago; as we calculate it now, with hindsight.

Or did the perpetrators just get lucky?

It looks to me like the Towers COULD NOT survive aircraft impacts!

I would like to know why somebody would say otherwise...

The mass and especially mass distribution are crucial to collapse and collapse times due to effects on PE. The strength of the structure is fixed. The PE is the energy available to do the work to overcome that strength and wreck everything. With less PE the tower may not collapse, or may not collapse totally, or may not collapse as quickly.

The towers did not fall att freefall speeds. If they did, controlled demolition would be a fact.

I don't yet know who the perpetrators are and make no assumptions about what they new prior to the attacks.

The towers were built to withstand the collision of a large aircraft at full speed. They did survive, if only for a short time.

 

[R.Mackey]

Nope

The mass and especially mass distribution are crucial to collapse and collapse times due to effects on PE. The strength of the structure is fixed. The PE is the energy available to do the work to overcome that strength and wreck everything. With less PE the tower may not collapse, or may not collapse totally, or may not collapse as quickly.

Nuh-uh. I explained this in my first response to you. The PE and aggregate toughness both scale linearly with mass.

Guess what else? The collapse time is really dominated by the inertia of lower structure. That also will scale linearly with mass, given that we don't change the dimensions, which we are not.

The towers did not fall att freefall speeds. If they did, controlled demolition would be a fact.

I don't yet know who the perpetrators are and make no assumptions about what they new prior to the attacks.

Fair enough, although you might want to consider the unavoidable fact of two jetliners impacting as having something to do with the collapses...

The towers were built to withstand the collision of a large aircraft at full speed. They did survive, if only for a short time.

As NIST points out, there is no evidence of this at all. There is only a letter, backed by a calculation even sparser than your paper, suggesting they might survive a hit from a 707 at cruising speed. This was before they were even built, and a proper consideration of impact mechanics and especially fire dynamics was utterly impossible.

The Towers also were not "designed" to do this, because it was never a requirement. Only a scenario that the designers considered potentially viable, and they considered a low-speed impact far more plausible.

 

[GregoryUrich]

Logarithmic?

No, i am not accusing you of giving false data. (which is refreshing departure from usual "truther" tactic) But I am accusing you of manipulating the data to such a degree as it has become unreasonable, at least for me and my experience.
And preposterous? I don't know about that. Has anyone ever measured the last piece of core standing in the videos? It would appear to have been considerably stronger that the rest wouldn't you agree? I wouldn't hesitate to assert that it was probably about the height of the fist change in the core construction.

What would the next dimension and plate thickness reasonably be after the first change?

Where would the next change likely be?

Wouldn't the load actually vary logarithmically due to scaled structure?

 

[pomeroo]

The mass and especially mass distribution are crucial to collapse and collapse times due to effects on PE. The strength of the structure is fixed. The PE is the energy available to do the work to overcome that strength and wreck everything. With less PE the tower may not collapse, or may not collapse totally, or may not collapse as quickly.

The towers did not fall att freefall speeds. If they did, controlled demolition would be a fact.

I don't yet know who the perpetrators are and make no assumptions about what they new prior to the attacks.

The towers were built to withstand the collision of a large aircraft at full speed. They did survive, if only for a short time.

Why do you feel it is necessary to assert this opinion as though it is fact? Almost everyone on this forum is familiar with statements by people who designed or worked on the Twin Towers. Some consideration--there is no way of knowing how much--was given to the possibility of a plane lost in fog, either soon after takeoff or just before landing, accidentally hitting a building. The scenario implies reduced speed. Nobody, to my knowledge, ever speculated on the outcome of a full-speed crash.

 

[Furcifer]

The mass and especially mass distribution are crucial to collapse and collapse times due to effects on PE. The strength of the structure is fixed. The PE is the energy available to do the work to overcome that strength and wreck everything. With less PE the tower may not collapse, or may not collapse totally, or may not collapse as quickly.

Yes, to a certain extent, but only in WTC1. It's always about WTC1. Remember it takes less than 4 floors of mass to push the system out of equilibrium and into global collapse. Even with the substantial reduction in mass you propose we still have global collapse, and it still falls within the realm of acceptable collapse times.

 

[tsig]

Gravity stands refuted.

 

[Furcifer]

What would the next dimension and plate thickness reasonably be after the first change?

Where would the next change likely be?

Wouldn't the load actually vary logarithmically due to scaled structure?

Why scale down the core dimensions on floor 66, if you are doing it already with the steel? A couple of hundred square feet of floor space?
66 and 98 stick out in my mind. typical column plates were 3 stories. But we have a splice at floor 98, which was were they started to reinforce the core on both towers.

And i don't know about logarithmically.

 

[Newtons Bit]

Newtons Bit: Saying "Hey I used the heaviest steel i could find" is hardly a concession. I'm not sure if reading more of the NIST report will help change my mind on that? Or are you saying the density could have varied in a linear fashion because the columns were built using various grades of steel on the ground, while maintaining the dimensions? I think you mean on the exterior, not on the core right? We were discussing the core. It hasn't been my experience to to taper a core gradually, nor have i seen any reference to this in the NIST report. If you have such a reference please send it to me, i have been looking hi and low.

It's a huge waste of money not to pick lighter shapes as you go up. Today, Wide-flanges run about a $1.50/pound.

In any building that I've worked on, the columns are always "tapered". Due to transportation limits, one can only deliver pieces of steel 40-50ft long to a construction site, though this can be a bit longer depending on the city's limit on oversized trucks as well as easy access to a navigable water-way. At each splice, the lightest column that works is always used. There's some general rules to that though, such as keeping the same depth of a wide-flange through the entire length of the column line. The architects on the WTC undoubtably wanted to keep a regular appearance on the outside, hence the box columns would appear the same on the outside, though the inside thickness likely was reduced as the column line ascended. For the interior core columns, I see no reason why they would not pick the lightest acceptable shape for each splice.

 

[GregoryUrich]

Nope nope

Nuh-uh. I explained this in my first response to you. The PE and aggregate toughness both scale linearly with mass.

Guess what else? The collapse time is really dominated by the inertia of lower structure. That also will scale linearly with mass, given that we don't change the dimensions, which we are not.

Fair enough, although you might want to consider the unavoidable fact of two jetliners impacting as having something to do with the collapses...

As NIST points out, there is no evidence of this at all. There is only a letter, backed by a calculation even sparser than your paper, suggesting they might survive a hit from a 707 at cruising speed. This was before they were even built, and a proper consideration of impact mechanics and especially fire dynamics was utterly impossible.

The Towers also were not "designed" to do this, because it was never a requirement. Only a scenario that the designers considered potentially viable, and they considered a low-speed impact far more plausible.

The structure is the structure. Aggregate strength depends on the structure. Varying the loads effects everything. This was one of the first calculations I did and am most sure about--to the point I feel no need to discuss it further.

Regarding the impacts I quote Gregg Roberts:

"GR: NIST’s estimates of the impact speeds are 443 mph ± 30 mph for the North Tower and 542 mph ± 24 mph for the North Tower. (ref 9) These speeds are far below the cruise speed stated on Boeing’s website, although of course cruise speed is not normally reached below 10,000 feet. Regardless, the question here is not whether the planes were flying above their rated speed or maximum safe speed, but whether the planes’ mass and speed exceeded what the buildings were designed for. Skilling says, and the Port Authority and NIST agreed,(ref 10) that they were designed to survive a 600 mph impact by a 707. Such a plane if fully loaded (as Skilling claimed the design assumed) would have 336,000 / 395,000 = 85% (ref 11) of the mass of a fully loaded 767 (which the impact planes were not, since they were not carrying full loads of fuel). (ref 12) Thus, the North Tower impact would have had less than 87% of the momentum and 64% of the kinetic energy designed for, while the South Tower impact would have had less than 106% of the momentum and 96% of the kinetic energy designed for. Correcting for the estimated fuel load of 10,000 gallons, I get 300,000 pounds for the 767s (close to FEMA’s 274,000 figure) and accordingly far lower momentum and kinetic energies than designed for. Thus, the impacts were either close to, or well within, the Towers’ capacity to absorb them without collapse."

The important reference is ref 10 = NISTNCSTAR1 pg. 6. This reference alone is a clear refutation of your claims above. Regarding this point, I respectfully request that if you don't agree, you take it up with NIST, not with me.

 

[GregoryUrich]

Why scale down the core dimensions on floor 66, if you are doing it already with the steel? A couple of hundred square feet of floor space?
66 and 98 stick out in my mind. typical column plates were 3 stories. But we have a splice at floor 98, which was were they started to reinforce the core on both towers.

And i don't know about logarithmically.

The core dimensions are scaled down at 66 because the plate thickness is getting too thin.

 

[GregoryUrich]

Skilling, the Port Authority and NIST agree it's a fact

Why do you feel it is necessary to assert this opinion as though it is fact? Almost everyone on this forum is familiar with statements by people who designed or worked on the Twin Towers. Some consideration--there is no way of knowing how much--was given to the possibility of a plane lost in fog, either soon after takeoff or just before landing, accidentally hitting a building. The scenario implies reduced speed. Nobody, to my knowledge, ever speculated on the outcome of a full-speed crash.

Skilling, the Port Authority and NIST agree it's a fact. See NISTNCSTAR1 pg. 6. It couldn't be any clearer!

 

[SYLVESTER1592]

The true "twoofer" revealed

The mass and especially mass distribution are crucial to collapse and collapse times due to effects on PE. The strength of the structure is fixed. The PE is the energy available to do the work to overcome that strength and wreck everything. With less PE the tower may not collapse, or may not collapse totally, or may not collapse as quickly.

The towers did not fall att freefall speeds. If they did, controlled demolition would be a fact.

I don't yet know who the perpetrators are and make no assumptions about what they new prior to the attacks.

The towers were built to withstand the collision of a large aircraft at full speed. They did survive, if only for a short time.

"With less PE the tower may not collapse, or may not collapse totally, or may not collapse as quickly. The towers did not fall att freefall speeds. If they did, controlled demolition would be a fact."

There you go, finally...
Gotcha
And I was not careful, right?

You have proven my points time and time again, another truther with an agenda. Unbelievable... Stating the weight estimation is wrong, and underestimating it yourself, is still a long way from the conclusion of controlled demolitions, but I see that's where you are going with this.

I guess, my first assesment and following evaluations were not that far off anyway...

 

[pomeroo]

Skilling, the Port Authority and NIST agree it's a fact. See NISTNCSTAR1 pg. 6. It couldn't be any clearer!

I stand corrected. I remember reading an interview, possibly with Robertson, that made the point that an aircraft hitting the Towers would have been presumed to have just taken off. Somehow I missed that reference on page 6 of NIST-NCSTAR 1 to 600 mph speeds.

“The Boeing 707 was the largest in use when the towers were designed. [Leslie] Robertson conducted a study in late 1964, to calculate the effect of a 707 weighing 263,000 pounds and traveling at 180 mph crashing into one of the towers. [Robertson] concluded that the tower would remain standing. However, no official report of his study has ever surfaced publicly.”[9]


Do you agree, speaking generally, that questions concerning the science of 9/11 have definitive answers? In other words, if you and R. Mackey argue to exhaustion, one of you will be proved right?

 

[GregoryUrich]

Black or white?

"With less PE the tower may not collapse, or may not collapse totally, or may not collapse as quickly. The towers did not fall att freefall speeds. If they did, controlled demolition would be a fact."

There you go, finally...
Gotcha
And I was not careful, right?

You have proven my points time and time again, another truther with an agenda. Unbelievable... Stating the weight estimation is wrong, and underestimating it yourself, is still a long way from the conclusion of controlled demolitions, but I see that's where you are going with this.

I guess, my first assesment and following evaluations were not that far off anyway...

Your statement says more about your own bias than mine. You can continue being suspicious. I'll continue following the evidence.

 

[tsig]

Why scale down the core dimensions on floor 66, if you are doing it already with the steel? A couple of hundred square feet of floor space?
66 and 98 stick out in my mind. typical column plates were 3 stories. But we have a splice at floor 98, which was were they started to reinforce the core on both towers.

And i don't know about logarithmically.

If you throw in a math term here and there maybe nobody will notice the lack of content.


To the appropriate tune
I got numbers

lots and lots of numbers.

But don't ask me what they mean

 

[SYLVESTER1592]

Many shades of grey

Your statement says more about your own bias than mine. You can continue being suspicious. I'll continue following the evidence.

There are many kinds of thruthseekers, some with an agenda or an preconceived idea about the truth and some without...

Your results raise questions, as do your associations, hence the suspicion. But to jump to controlled demolitions from a lower weight estimate, that's very typically biased, not much to do with evidence...

Yes, I'll keep my suspicions...

 

[GregoryUrich]

Exhaustion

I stand corrected. I remember reading an interview, possibly with Robertson, that made the point that an aircraft hitting the Towers would have been presumed to have just taken off. Somehow I missed that reference on page 6 of NIST-NCSTAR 1 to 600 mph speeds.

Do you agree, speaking generally, that questions concerning the science of 9/11 have definitive answers? In other words, if you and R. Mackey argue to exhaustion, one of you will be proved right?

If Mr. Mackey and I argue to exhaustion we will be exhausted.

Instead, I hope we will both become aware of the errors in our thinking and limitations of certain arguments so that we both come away with a better understanding of the issue at hand. Who knows, twoofers have become OCSs and vice versa. I'm willing to change my conclusions based on solid evidence and cogent arguments.