Building Collapses in Rio

reply to post by psikeyhackr


We know that many columns lagged or were outside the collapse front (so no momentum exchange there) and just fell to the ground. So modeling all columns as part of the collapse front is not realistic. Though I agree that assuming a constant floor mass is also not realistic.

Originally posted by psikeyhackr
My Python program makes it possible for anyone to create a table with whatever mass distribution they want to see how it affects collapse time.

Yes, I've downloaded it and ran it. Nice.

12 seconds is the minimum with what you would call constant density. Making it bottom heavy increases the time.

Correct.

Originally posted by -PLB-

Originally posted by psikeyhackr
My Python program makes it possible for anyone to create a table with whatever mass distribution they want to see how it affects collapse time. 12 seconds is the minimum with what you would call constant density. Making it bottom heavy increases the time.

Thats odd, as the calculations are independent of the mass. After all, when you increase the mass of the lower floors, the mass of the top floors increase with the same amount.

psikeyhackr was referring to mass distribution, not overall scaling. It is invariant with respect to total mass, but a different distribution of that mass will affect the outcome. psikeyhackr is correct in saying bottom-heavy makes for a slower collapse, however this reaches a point of diminishing effect as the scaling increases. In the aforemention slab simulations, I ran linear mass distributions ranging from very top-heavy to very bottom-heavy, with the many orders of magnitude between.

The result of total collapse time as a function of that scaling order of mass is here:



Mass ratio is the horizontal axis, depicted logarithmically. Notice the difference in collapse times for the extremes is less than 4 seconds. The maximum collapse time asymptotically approached for any linear mass distribution is about 14.25 seconds.

So it matters, just not very much.

reply to post by IrishWristwatch


I guess I will have to do the the math myself to really understand this. But I do think I get the basic idea now. As speed increases, total inertia in a given time frame also increases. I must say that it is indeed counter intuitive to me, but its not the first time my intuition has been wrong. Thanks for the extensive explanation.

Originally posted by -PLB-
reply to post by IrishWristwatch

 

I guess I will have to do the the math myself to really understand this. But I do think I get the basic idea now. As speed increases, total inertia in a given time frame also increases. I must say that it is indeed counter intuitive to me, but its not the first time my intuition has been wrong. Thanks for the extensive explanation.

edit on 1-2-2012 by -PLB- because: (no reason given)

You're welcome. It ran counter to my intuition, too. I was surprised. That's why I thought it may be useful to show, and apparently it was.

reply to post by IrishWristwatch


Yes, I get it. I just thought that "Making it bottom heavy" was an English expression saying "making it very heavy". But it was instead a typo and was supposed to say "Making its bottom heavy". I am not an native English speaker, so sometimes I just make up the meaning of the words I read. Though, not as often as the average truther .

Originally posted by -PLB-
I am not an native English speaker...

No? You had me fooled. English is my native language, and I think you may have it down better than I.

Originally posted by -PLB-
reply to post by psikeyhackr

 

We know that many columns lagged or were outside the collapse front (so no momentum exchange there) and just fell to the ground. So modeling all columns as part of the collapse front is not realistic. Though I agree that assuming a constant floor mass is also not realistic.

Mathematics is never 100% realistic. Reality is very random and messy except whe it is gravity working in a vacuum.

But how did 4 ton girders get all of the way to the Winter Garden 600 feet away? How did steel get stuck into the AmEx building? Gravity and collapse cannot explain everything that happened on 9/11. So if something destroyed the core and steel being hurled 600 feet away was just a side effect then gravitational collapse programs are not going to account for that.

That program is to show how ridiculous the collapse only explanation is. Because that Python program assumes no realistic supports which 1360 foot buildings must have.

psik

Originally posted by IrishWristwatch
Mass ratio is the horizontal axis, depicted logarithmically. Notice the difference in collapse times for the extremes is less than 4 seconds. The maximum collapse time asymptotically approached for any linear mass distribution is about 14.25 seconds.

So it matters, just not very much.

But that collapse is MAGICAL. The masses are held up by NOTHING.

I am not doing this for smart alek mathematical purposes. Dr. Sunder said the north tower came down in 11 seconds. 4 seconds is a significant percentage of 11.

The reason a skyscraper must be bottom heavy is that more steel is required toward the bottom to support all of that weight above. So then energy is required to destroy REAL PHYSICAL SUPPORTS. That is why my physical model is actually more important than the Python program.

The Python program is just to combat all of the people who say we shouldn't care about the distributions of steel and concrete at all. If mass alone has some effect then the destruction of supports must have an additional effect also.

So how did the building come down in less than 25 seconds because that is about the longest time even including the collapse or ductification of the "Spire". Airliner, fire and gravity can't explain it and the Physics Profession should have told us that in 2002.

psik

Originally posted by psikeyhackr
Mathematics is never 100% realistic. Reality is very random and messy except whe it is gravity working in a vacuum.

Vacuums don't make "reality" less random, but I guess you mean to say easier to model in some situations. And indeed, models are never 100% realistic. But the chosen model should suffice for the data want to know. If you want to make accurate predictions of the collapse time, your model should include the kind of effects I suggested.

But how did 4 ton girders get all of the way to the Winter Garden 600 feet away? How did steel get stuck into the AmEx building? Gravity and collapse cannot explain everything that happened on 9/11. So if something destroyed the core and steel being hurled 600 feet away was just a side effect then gravitational collapse programs are not going to account for that.

Correction, you cannot explain everything. But your incredulity isn't an valid argument, nor is mine.

That program is to show how ridiculous the collapse only explanation is. Because that Python program assumes no realistic supports which 1360 foot buildings must have.

So why don't you add those realistic supports to your model, and see what the collapse time becomes? Without that, do you really think you can make any meaningful conclusion? Your argument is purely based on incredulity and assumption.

Originally posted by psikeyhackr

Originally posted by IrishWristwatch
Mass ratio is the horizontal axis, depicted logarithmically. Notice the difference in collapse times for the extremes is less than 4 seconds. The maximum collapse time asymptotically approached for any linear mass distribution is about 14.25 seconds.

So it matters, just not very much.

But that collapse is MAGICAL. The masses are held up by NOTHING.

Yes, I'm quite familiar with the scenario.

I am not doing this for smart alek mathematical purposes.

Neither am I. I did these things to learn, and I tell about them so others can learn. It saves them significant time (like... months), if they happened to be interested. If they weren't interested, maybe it makes them a little more so; if not, oh well.

Dr. Sunder said the north tower came down in 11 seconds.

I believe he was wrong about that. By about 4 seconds, roughly. Wouldn't be his only error, but the guy is only human.

4 seconds is a significant percentage of 11.

Yes, it is.

The Python program is just to combat all of the people who say we shouldn't care about the distributions of steel and concrete at all.

You succeed in that objective.

If mass alone has some effect then the destruction of supports must have an additional effect also.

Yes, it does.

Originally posted by psikeyhackr

But how did 4 ton girders get all of the way to the Winter Garden 600 feet away?

One way that could of happened is the girder was located at the top of the building and as the collapse progressed it was pushed out horizontally by the collapse front and because of gravity it fell in a parabolic fashion landing 600 feet away.

Mathematics is never 100% realistic.

I'm not sure what your point is here but there is math that explains most things. However, some equations are so complex that the time required to solve them is not worth it. Approximations are used and these approximate answers are good enough as long as there are explicit bounds (margins of error). For example, a very simplistic situation is polls. In all cases polls have margins of error. If you were to poll 100% of the voting population on who they are going to vote for in the USA presidential elections it would take a very long time and by the time the results are compiled the answer is several days/weeks/months old and outdated and no longer correct.

If your physical model doesn't show the same results as reality then your model is wrong. Gravity, fire, damage due to plane impacts explains the collapse of the twin towers. The tube in tube design can not be modeled as washers supported by paper rings with a broom stick handle through the washer centers.

Originally posted by -PLB-
So why don't you add those realistic supports to your model, and see what the collapse time becomes? Without that, do you really think you can make any meaningful conclusion? Your argument is purely based on incredulity and assumption.

My physical model is more realistic than any modification to the computer model.

What would be the relationship between the strength of the supports and the energy needed to crush it? What would be REALISTIC?

psik

accidental dup havin problems with my router

reply to post by psikeyhackr

My physical model is more realistic than any modification to the computer model.

If you mean a washer sitting on a paper ring over and over then no. Because it doesn't come anywhere close to the actual construction used.

A better method would to staple a bunch of paper rings end to end. Then spot glue the washers inside.

Originally posted by samkent
reply to post by psikeyhackr

 

My physical model is more realistic than any modification to the computer model.

If you mean a washer sitting on a paper ring over and over then no. Because it doesn't come anywhere close to the actual construction used.

A better method would to staple a bunch of paper rings end to end. Then spot glue the washers inside.

You are implying the washers are similar to the floors. The washers are only mass. Your spot gluing would be like truss connections. Where is your data on the strength of the truss connections relative to the weights of the floor assemblies? How could you control that relative to the weight of the washers? The washers are not all the same weight. I sorted them with the heaviest on the bottom. three of the thinnest washers are the same as two of the thickest.

I was able to make the paper loops as weak as possible relative to the supported weight.

A better model would be heavier with each level of support individually designed to be as weak as possible.

I can't prove it but I bet the net result would be the same. So why can't our engineering schools do something that simple. But now they would have the problem of explaining why they didn't already do it.

People get too concerned about how the model looks and equate the washers to floors in an analogy. They are just supported mass with inertia. The loops must be strong enough to support the mass but require energy to crush. A tube-in-tube model would be very difficult and expensive.

psik

reply to post by huh2142

If your physical model doesn't show the same results as reality then your model is wrong. Gravity, fire, damage due to plane impacts explains the collapse of the twin towers. The tube in tube design can not be modeled as washers supported by paper rings with a broom stick handle through the washer centers.

You can't do science like this.

You can't look at the towers, divine a cause and then model such that that cause is shown. That is a textbook example of pseudoscience. Tweaking the model to match the input it was developed from is the first rule of how NOT to do modelling.

Unless you have NEW data external to the data used to derive the model you cannot claim that any tweaks are legitimate.

There is a name for that practice if it is applied anywhere outside of 9/11 OS: Scientific fraud.

reply to post by IrishWristwatch

Regarding this last exchange: It only takes one introductory physics class, not even close to an undergrad degree, to separate the skilled from the lay person on this matter.

That's funny, because in my profession and in many others an undergrad degree is not proof of anything more than a base a ability to manipulate some formulae. Undergrad degrees don't typically require any understanding. You claim that idealization are used to great success, which is of course true. But idealization are ONLY used if they successfully predict things in the real world.

You can cite equations till you are blue in the face, but they only describe the assumptions built into your model. Whatever outcome you reach is only true for your model, not all reality, unless you can also show that your model also actual systematically predicts real world phenomena it is not valid scientifically.

This is what bugs me so intensely about you Irish, you think that no one can see through your jargon and spot the model underneath, a model which makes ROOSD and Bazant look like the height of sophistication.

Psikey has his tube with paper loops and washers, you have a tube with sand poured down it. All the math aside, Psikey's is a far better model of reality especially considering that his is how real world collapses happen whereas yours exists only in your head.

Can we please cut through the pompous cr4p and concentrate on the fact that Psikey's paper loops are an approximation of reality and your sand tube is an approximation of whatever it is that you would like to prove?

We can do the math, idealization and simplification only when we have established the model has some real world predictive power, doing it before is just a waste of everybody's time.

You can derive your model mathematically too of course, but it has to be rigorous formalism, none of these touchy feelly interjections you come up with. But whether you start with the model or the formalism either is worthless if it fails to predict novel events in reality.

Originally posted by Darkwing01
You can cite equations till you are blue in the face, but they only describe the assumptions built into your model.

What model?

Whatever outcome you reach is only true for your model, not all reality, unless you can also show that your model also actual systematically predicts real world phenomena it is not valid scientifically.

What model?

This is what bugs me so intensely about you Irish, you think that no one can see through your jargon and spot the model underneath, a model which makes ROOSD and Bazant look like the height of sophistication.

What model?

...you have a tube with sand poured down it.

What are you talking about?

...your sand tube...

What sand tube?

Originally posted by Darkwing01
Undergrad degrees don't typically require any understanding.

Maybe the touchy-feely crap you've studied. I'd like to see you get through first year physics for engineers (i.e., dumb physics). You could take the rest of your life and never do it; quite apparent.

Ah, but now I'm engaging you and that's what you want. Bye!