Solid Bodies versus Rubble: Results

In the now-closed thread "WTC7 and the girder walk-off between column 79 and 44," Tony Szamboti said:

Quote:

Here is something anyone can do. Take a 5 lb. bag of sugar or 2 lb. box of rice and put some sides around a scale with ounce graduations with at least a 10 lb capacity, and pour the sugar or rice from the same height as what Dave Thomas dropped his bag of rice from. I'll bet you don't see much more than 5 lbs. for the sugar or 2 lbs. for the rice if any at all.

My reply, from p. 86 of the thread:

Quote:

Y'know, you should be careful what you wish for!

Tony's reply from p.87:

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I am all for you doing a test with a bag of sugar or rice dropped on a scale and then pouring the same mass of loose sugar or rice onto the scale from the same height the bag was dropped and showing the results.

Tony's reply

from page 87:

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There would be some effect due to proximity and it is on the order of milliseconds that each load would have to be applied with respect to each other to have a cumulative effect. However,the WTC rubble would not have been compacted until a significant number of stories were demolished and that would not have been right away, which is the point of the issue with the missing deceleration and the load required to continue the collapse early on. Let's see what happens with Dave Thomas' new test, which he seems eager to do, with a bag of rice or sugar and poured rice or sugar. I think the proximity needs to be quite close and that is why I said little to no amplification will occur with the poured material.

My reply

from page 88:

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Well, quality work takes time! All is shaping up nicely, with a VP of research giving the required nod to get me some high-speed camera time, complicated by the absence of the usual camera operator this week, and the travel status of said VP. So it could take a few days, yet. Meanwhile, I have been loaned a mahvelous 60-pound scale, and can start in on the stiffness calcs tomorrow!

and more from

page 88:

Quote:

Got a definite date, but it's still a couple of weeks away - Tuesday, Aug. 14th. (A TV science channel will be in town, and I get to piggyback on the time-consuming HS camera setup.) Being a derail of the girder walkoff anyway, I'll just start a new thread when results are in. Hasta luego, Dave

Well, here I am, a new semester about to start, and I thought I'd clear off a couple items from my desk.



The experiment is in! Here's the YouTube:

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I AGREE

Now, the responses weren't quite as large as I'd been expecting, which I think is due to the instrument response of the clunky old scale. I tried a few quick experiments with various accelerometers, and didn't get all my questions resolved.



What I did find throughout, and what is important, after all, is the simple fact that the rubble piles pack as much or more force than the solid counterparts!



Take a look at the rice in the video above. While the bagged rice hits all at once, the loose rice does a "rope-a-dope" action that actually intensifies the impact!



Bottom line:

Quote:

Take a 5 lb. bag of sugar or 2 lb. box of rice and put some sides around a scale with ounce graduations with at least a 10 lb capacity, and pour the sugar or rice from the same height as what Dave Thomas dropped his bag of rice from. I'll bet you don't see much more than 5 lbs. for the sugar or 2 lbs. for the rice if any at all.

Also, if anyone has ideas on how to configure a good comparison with good accelerometers, let us know here. I'm telling you, it's a little trickier than you might think!



Discuss.

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