Kinematic production of molten steel and its cooling rate

Jazzy

Closed Account
the base of a column, through repeated kinetic impacts on that column, transfering energy from the floors onto said columns. So you agree this did not happen enough to heat the columns foot and/or foundation very much?
It was the first scenario I considered. Summing the smashing of a hundred floors from the column. I thought it added up to quite a lot, but not as dramatic as the arrival of the floors.

It's an interesting recycling of kinetic energy in a way, that retards the gravitational acceleration of the floors to give it back as heat at the column foundation.

Lots and lots of concrete crushing eats much of that energy, even while collapse is under way. The rubble block may be severely compacted, but it is MUCH less elastic than a steel column!
Edge on, I'd agree with you, but pancaked flat with a hundred others (and all their loads), with horizontal rebars? You've seen the wreckage museum...

Plus, you hit the ground over the full area of the towers and more.
I'm not sure that's a point either. I've already indicated inefficiency. The greatest heat would be found under the greatest mass. What did you think about the IR evidence?

Try to build a Newton's cradle witj layers of reinforced light-weight concrete. Compare with a regular steel cradle. Report what you find.
Straw man. At 115 mph, steel parts rubble, but rubble still may give some KE to steel, the compressive strength of concrete being similar. It's worth bearing in mind that steel is 3x denser.
That USA program Mythbusters made a massive cradle, with hollow steel balls filled with cement. The cement cracked of course, and the balls didn't transact KE much at all. Nevertheless they weren't doing 115 mph either.

It appears to me that hot steel bends more easily than cool steel (is less elastic).
I'm glad about that.

Mick said:
Surely the KE would be reflected before the next collision arrives?
I'm sure it would if you asked it nicely.

If it is actually like Newton's cradle, then it moved across the steel at the speed of sound in steel, about 5900 m/s
The steel behaves like steel.

Perhaps you could describe what you think is happening to this bottom piece at the actual real world molecular level, rather than in abstractions?
Phonons are moving through it. It's complicated, but you could start here:-

http://en.wikipedia.org/wiki/Phonon
 
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Oystein

Senior Member
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That USA program Mythbusters made a massive cradle, with hollow steel balls filled with cement. The cement cracked of course, and the balls didn't transact KE much at all. Nevertheless they weren't doing 115 mph either.
...
They did more?
Because if they did less - wouldn't the cement crack even more if you bang faster?
I think that is exactly the kind experiment that confirms my point: Concrete does not propagate elastic strain as well as steel, because some of the strain energy is lost to cracking along the way and never arrives at the other end (the bottom in this case).
 

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