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Old 23rd December 2009, 08:49 AM   #121
Newtons Bit
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Originally Posted by Michal View Post
I had a lectures with one of the tensor calculus fathers. Believe me, with use of this method you can create a lot ... a lot more than just a rock or soil. I remember him enumerating bridges, buildings and other difficult structures that were designed with use of this method, some spectacular ones were designed by him.
No. Tensor Calculus is used in conjunction with Hooke's Law to solve a solid mechanics problem. It cannot be used by itself to analyze an entire structure.

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Sure, Finite Element Analysis is a very good method, but not the only one and there were other methods in the past allowing to produce fine structure ... but I think we are going off topic now ...
And you would be incorrect. FEA is the only method to analyze an entire structure in its' entirety. Everything else is predicated upon analyzing each element individually.

So I will re-iterate: the technology to analyze a building for a plane impact did not exist in the 1960's.

Oh, and before you make up more , Tensor Calculus was created in 1890. Most of the research on it was finished during the very early 20th century.
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Last edited by Newtons Bit; 23rd December 2009 at 08:51 AM.
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Old 23rd December 2009, 09:17 AM   #122
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Originally Posted by Michal View Post
Originally Posted by BigAl View Post
(...)

It wasn't designed for a jet airliner flying at 500MPH.

(...)

The towers were also not designed to survive structural damage and unfought major fire. No modern steel building is.
those above are not true ... at least if it comes to WTC ... all other agreed
Are you suggesting the WTC was designed to survive a major fire over 4 or more floors without any fire fighting???
You really need some proof of that.

Any firefighter will tell you any structure on fire not being fought is in danger of collapse. Including WTC 1 and 2.
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Old 23rd December 2009, 10:07 AM   #123
W.D.Clinger
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Originally Posted by Michal View Post
I had a lectures with one of the tensor calculus fathers.
Lucky you. Which one? Riemann? Christoffel? Levi-Civita? Ricci?
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Old 23rd December 2009, 10:40 AM   #124
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Originally Posted by W.D.Clinger View Post
Lucky you. Which one? Riemann? Christoffel? Levi-Civita? Ricci?


You misunderstand. He referred to "one of the tensor calculus fathers", not "one of the fathers of tensor calculus". Clearly he was merely referring to his classes at some Catholic College.
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Old 23rd December 2009, 10:43 AM   #125
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Originally Posted by twinstead View Post
Can you provide any evidence that the towers were designed for a 500 MPH airliner? If I recall, they were designed for a much smaller airliner travelling at a much slower speed.

You need to do more than just say something isn't true. you need to back it up.

Actually they were "designed" for neither.

I hate when people say that "the towers were desinged to withstand a jet impact." That implies that the ability to withstand an impact from a certain sized jet was a design criteria prior to the design process. it was not. the ability of the building to withstand an airplane impact is the result of factors that have nothing to do with anyone saying "Gosh, i want to design a building that can withstand a jet airplane impact."

this is a minor quible on my part, i know. but it irks me just the same.
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Old 23rd December 2009, 10:48 AM   #126
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Originally Posted by Alferd_Packer View Post
Actually they were "designed" for neither.

I hate when people say that "the towers were desinged to withstand a jet impact." That implies that the ability to withstand an impact from a certain sized jet was a design criteria prior to the design process. it was not. the ability of the building to withstand an airplane impact is the result of factors that have nothing to do with anyone saying "Gosh, i want to design a building that can withstand a jet airplane impact."

this is a minor quible on my part, i know. but it irks me just the same.
The only reason I brought it up was because I assumed it was what he was talking about, and we both know that a "707 on landing descent lost in the fog" is usually translated as "a screaming slightly sub-sonic 757 fully-laden with fuel" by truthy-truthers. I'm aware that the whole airliner thing wasn't implicitly designed for.
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Last edited by twinstead; 23rd December 2009 at 10:49 AM.
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Old 23rd December 2009, 11:18 AM   #127
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Originally Posted by Newtons Bit View Post
This is non-sequitur. Finite Element Analysis requires setting up a matrix to describe the entire structure. The matrix row and height lengths are equal to the number of elements * the number of degree of freedom. A basic element for a 3D structure is 9 DOF. One would need a single element for each column, each beam and each truss for a simple but roughly accurate analysis. However this is for every single floor. That's 100's of elements per floor, perhaps 10,000 for the entire building. You're looking at a 100,000x100,000.

This is what is necessary just for the static structural analysis. A much larger number of elements will be necessary to model the dynamic and non-linear behavior of the structure. Which is iterative, so you have to solve in many many many times.

It's not possible without computers.

.
It is within the realm of possibilty that someone or a group might be able to do all the calc's by hand with zero errors ( the infinite # of monkeys arguement,,,,). However they would still be at it now if they were not only doing it once through but also adjusting for variable parameters such as the velocity and angle of the aircraft which would require doing it several times.

I assume that the present generation has had little experience doing calculations of any sort purely by mental manipulation, unaided in any way other than a calculator that can multiply, divide, add, and substract, and consulting log and trig tables.
That boys and girls is how it was done in the early 1970's. The very best computers in the world had storage and rate of calculation parameters that are miniscule compared to your basic modern cell phone.
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Old 23rd December 2009, 11:51 PM   #128
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Originally Posted by jaydeehess View Post
It is within the realm of possibilty that someone or a group might be able to do all the calc's by hand with zero errors ( the infinite # of monkeys arguement,,,,). However they would still be at it now if they were not only doing it once through but also adjusting for variable parameters such as the velocity and angle of the aircraft which would require doing it several times.

I assume that the present generation has had little experience doing calculations of any sort purely by mental manipulation, unaided in any way other than a calculator that can multiply, divide, add, and substract, and consulting log and trig tables.
That boys and girls is how it was done in the early 1970's. The very best computers in the world had storage and rate of calculation parameters that are miniscule compared to your basic modern cell phone.

REAL engineers do it with slide rules!!

I was SPOILED rotten (and didn't appreciate it). As a freshman, my parents went batguano nuts and bought me an HP45 calculator. $400. Ridiculous extravagance in 1970.

I ALSO had to buy a slide rule, because the school wouldn't allow me to use it to take tests. Too much of an advantage over kids who didn't have one.

I had a constant line-up of other guys wanting to use it. Constant. I could have, thought about, couldn't bring myself to, rent it by the hour. Could easily have paid for my nightly runs to the roach-coach for that meatball hoagie...

Ahhh the days.

But in 1963, they could (and I believe did) use some computing when they did some wind tunnel tests (at U Colorado or School of Mines, IIRC). Probably had about the power of a 286 on qualudes.

__

Funny story that I know of from friends...

In the late 70s, a major research lab in La Jolla, CA got some federal funding for a computer to do fusion research. A powerful one for the day (but I think too early for a Cray). As soon as the computer arrived, the business people literally stole it. To do book-keeping, payroll, accounting, etc. It took a threat to drop a dime back to the feds for the scientists to get their computer back.

Such were the struggles in the old days.

Anyone remember "batch processing"? Punch cards & 2 am, 3 am, 4 am "hourly runs" in the CompSci labs?

I do NOT miss those nights. Caffine & a syringe...

Last edited by tfk; 23rd December 2009 at 11:53 PM.
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Old 24th December 2009, 01:06 AM   #129
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Originally Posted by tfk View Post
REAL engineers do it with slide rules!!...
Spot on...teaches you to limit to significant digits AND keep track of the decimal points later.
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...I was SPOILED rotten (and didn't appreciate it). As a freshman, my parents went batguano nuts and bought me an HP45 calculator. $400. Ridiculous extravagance in 1970....
...before that era we never knew what RPN meant/

Quote:
....I ALSO had to buy a slide rule, because the school wouldn't allow me to use it to take tests. Too much of an advantage over kids who didn't have one....
...I remember the deep trauma when my son (then about 5 years old) sat idly watching television and hitting the extended slide of my Slide rule against the aluminium corner of a bench. Ruined the slide rule - unrecoverable.

Quote:
...In the late 70s, a major research lab in La Jolla, CA got some federal funding for a computer to do fusion research. A powerful one for the day (but I think too early for a Cray). As soon as the computer arrived, the business people literally stole it. To do book-keeping, payroll, accounting, etc. It took a threat to drop a dime back to the feds for the scientists to get their computer back....
.... my similar war story is about a small commercial machine (IBM 1401) could calculate a water supply network pressure/flow regime in about 45 minutes. Put the same source card deck on an early IBM 360 and it took three minutes. Then we tried it on a big CDC machine. Same card deck. Took several minutes top read the cards on the "off line spooler" then 1.7 seconds for the calculation stuff. And that was 40 years back.

Quote:
.....Such were the struggles in the old days.

Anyone remember "batch processing"? Punch cards & 2 am, 3 am, 4 am "hourly runs" in the CompSci labs?

I do NOT miss those nights. Caffine & a syringe...
....including the night I conned my way into the sanctum to single cycle the machine through what I thought was a bug in system code. Found my error. Had to apologise to the machine on bended knee. The operators of that day still remember on the rare occasions our paths cross.

The first model XT could walk faster than that old machine.

Edit
PS The computing power to do Finite Element stuff came10-15 years after I left the "front line" so I know what it is but I never did it.

Last edited by ozeco41; 24th December 2009 at 01:09 AM.
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Old 24th December 2009, 02:12 PM   #130
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Originally Posted by tfk View Post
REAL engineers do it with slide rules!!

I was SPOILED rotten (and didn't appreciate it). As a freshman, my parents went batguano nuts and bought me an HP45 calculator. $400. Ridiculous extravagance in 1970.
I did not think the HP45 came out until 1974 or so..... so long ago and one's years all blend......

Quote:
I ALSO had to buy a slide rule,
My physics teacher in high school sold them to us then taught us how to use them. I had a circular slide rule with an insert that contained many physics and chemistry constants and formulae.


Quote:
But in 1963, they could (and I believe did) use some computing when they did some wind tunnel tests (at U Colorado or School of Mines, IIRC). Probably had about the power of a 286 on qualudes.
,,, and perhaps 25 times the space required to house it.


Quote:
Anyone remember "batch processing"? Punch cards & 2 am, 3 am, 4 am "hourly runs" in the CompSci labs?
Barely. I was in physics and we got a short course in BASIC but no COBOL or futzing around with punch cards. That was for the lah-de'dah engineering school. I do remember one friend of mine, a first year engineering student who had just completed his punch cards that would, if done right, produce a calender for the year 1976. He accidentally dropped them and they scattered. That was his first howl.
Then, as he was re-collateing them by hand he let out another wail. He had of course numbered the cards but now found that he had numbered the first few;
1,2,3,4,5,5,6,7......
As it turned out he had only doubled the one numeral in the entire stack so in the end he figured out which one was 5 and which one was (now) 5a.

I heard stories though of guys who dropped their stacks of cards into mud puddles or spilled coffee on them.

A few years later I was given a course in PASCAL by my employer. It was supposed to be the language a new ATC communications console was to be programmed in but the gov't kept changing the requirements until the whole project was shelved as costs mounted.
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