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Layman's terms please! Tower collapse issue

MRC_Hans said:
I suggest you have somebody drop 33,000 tons of rubble (density of your choice) on the roof of your house. Then come back and repeat that statement. (Hint: Don't be in the house during the experiment)
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Better yet, dump 7.9 million gallons of water (29.9 million liters or approximately 12 olympic sized swiming pools) on your house. Water is as non-rigid as you can get.
 
Better yet, dump 7.9 million gallons of water (29.9 million liters or approximately 12 olympic sized swiming pools) on your house. Water is as non-rigid as you can get.
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Should just pour over the sides, no?
 
Well each Twin Tower had about 2 million liters of water fall on it every year for about 30 years, giving a total of 60 million liters of water!

Not much happened......
 
Apollo20 said:
Well each Twin Tower had about 2 million liters of water fall on it every year for about 30 years, giving a total of 60 million liters of water!

Not much happened......
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Your bad!!!!!!!

I did get soaked once by a fire plane water drop and thought I was going to die. It doesn't look like much in the videos but when it hits you for real it sucks.
 
I think what Heiwa is overlooking (and Apollo20 too, if he's serious), is that impact is a function of velocity and time together.

Heiwa seems to assume that if the upper block is not "solid", it must be macroscopically fluid, and thus would behave the same as water in stream, and break around the object.
At lower flow rates, you have a small mass of water impacting over a relatively long time, which allows the water to flow around the object.

At higher velocities (like, say, the deluge from a water bomber), the mass of water is huge, and it impacts over a very short time. It packs a helluva punch.

The same thing would happen with a large mass of rubble (rubble for Heiwa's fluid upper block). A lot of rubble (whatever consistency you want) impacting over a short time (and in a small area, since most of the mass is vertical, not spread out horizontally), will impact with a force not appreciably less than if it were rigid.

F = m(dv/dt)

F = impact force
m = mass
dv = change in velocity
dt = change in time

so, if m = 33,00 tons ~ 30x106 kg
dv = vinitial - vfinal, which I shall arbitrarily (since I don't know the speed at which the upper block fell) set to a conservative to dv = 5 m/s
dt = time of impact, which I shall arbitrarily set to a generous 1 second

F = 30x106(5/1) = 150,000,000 N

Put another way, that's the same as getting hit with a 1 kg cannon ball (over an impact period of 1 second) traveling at 150,000,000 m/s (half the speed of light!)

It is not an insignificant amount of force, and you can't just wave your hands and say "it never hits the towers", because even assuming the "fluid" upper block is deflected by the lower block, you have to account for the force applied to the lower section as it deflects all that mass over the duration of the impact.
 
Newtons Bit said:
Again, complete ********. The spandrels cannot brace the columns in the out-of-plane direction. This is simple engineering mechanics. Please explain to me how a 5/8" over the course of 208ft is going to brace a column against buckling.
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I predict that Heiwa will ignore this request as he has ignored all of my similer requests.

To address this issue would require him to admit that his theory that the exterior walls could not have buckled is wrong.
 
At lower flow rates, you have a small mass of water impacting over a relatively long time, which allows the water to flow around the object.
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Amazing the Grand Canyon even exists, huh?!
 
Heiwa

Fcr.gif


Can you demonstrate that you understand the consequences of having a mathematical function that includes an inverse square term in it?

(i.e. x over L squared)
 
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Apollo20 said:
Well each Twin Tower had about 2 million liters of water fall on it every year for about 30 years, giving a total of 60 million liters of water!

Not much happened......
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At 47 inches per year, my estimate is 4.8 million liters. :)
 
Ok, I made a rough estimate of NYC's annual precipitation. It's still a lot of water.....
My point was that there was no indication of how fast the water was being poured, which has since been pointed out by [X].
 
I note the scurvy JREF mob, companions and rascals are scowling again. It does abhor me. No real technical arguments?
 
Heiwa said:
I note the scurvy JREF mob, companions and rascals are scowling again. It does abhor me. No real technical arguments?
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Shouldn't you say technical arguments that you can understand? Maybe you should go to an elementary school and discus engineering with them (even playing field).

Why do you hand wave all engineering criticisms?

Face it man, You are out of your league as far a structural engineering is concerned.(every lurker can see this)
 
Heiwa said:
I note the scurvy JREF mob, companions and rascals are scowling again. It does abhor me. No real technical arguments?
Click to expand...

Please explain to me how a 5/8" plate (in the weak axis) over the course of 208ft is going to brace a column against buckling.
 
I have to hand it to Heiwa; his arguments comprehensively busted, his rebuttals non-existent, his calculations.....hidden (cough). And yet he thinks that he's got us on the back foot?

Nowt as queer as fowk, as they say.
 
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