79. Backpack + Base isolation

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Little black backpack

I was thinking today that my small black backpack may be one of the best purchases I've ever made. It's rare when I'm out of the house and don't have it with me, most usually when I'm going to the gym or to work. I bought it in 1993 when I bought my first PowerBook Mac laptop,

I spotted the backpack at a MacWorld booth that year. It is custom designed for that particular laptop, with a well padded area at the back for the computer, and special pockets for essentials like 3.5" floppy disks. When I stopped using the PowerBook a few years later, I also stopped using the backpack. 

But when I bought my first netbook I dug it out of storage and resumed using it. That old PowerBook is also in storage, but the hard drive is dead so it's not getting revived. After the netbook, came my current Chromebook. Both of these little machines fit in the outer flap, not in the main part of the bag and never in the padded area intended for my PowerBook. 

Besides the usual daily use, this backpack has held all my essentials on my train trips -- the padded area holds underclothes, the main pocket toiletries along with books and documents. I even wear it for Hardly Strictly Bluegrass so I have room for more bags and water. There are undoubtedly fiendishly clever backpacks on the market now that would make me green with envy, but I'm not aware of having any unmet needs, and I'm amortizing the hell out of this purchase.

Structural engineering

Speaking of fiendishly clever, a new building in Berkeley was written up recently in the Chron that uses a new method of base isolation to protect the upper floors from earthquake damage. Even after reading the article (this is probably behind a pay wall) -- actually two of them -- it still took me a long time to figure out how this system works. The ground floor looks normal, it has to be because it abuts a neighbor on one side, and the retail tenant on that floor actually occupies both the new space and the one next door. But everything above the ground floor rests on four large columns -- not on the edges but more toward the center of the structure. The columns include a dish like surface that the upper part of the column can slide around on in the event of a quake. If it were totally frictionless -- which it isn't, of course -- the top part of the building would not move at all in a quake until the end when it would slide into the low, center point of the relocated dish. 

This is a sample of the dish that moves under the top of the building. I'm unclear what the puck in the center is, possibly an abbreviated version of how the building actually sits in the dish?

This is one of the four actual comumns. The yellow beam is marked to show how much it can move but the gray band of sealant above the beam is the actual dividing line between ground floor and floating upper building. During a quake the lower yellow band on the column would move right and left relative to the upper yellow band, which should stay relatively still.

Besides the seriously expensive columns, the tricky part is running in utilities given that the building parts can slide a foot in any direction. Also, there needs to be a gap around the part of the building that doesn't move, so that surrounding buildings that are moving don't run into it. There's a massive band of sealant between the two parts of the building that will probably have to be replaced after a quake. I would have done that part differently, using something more like a door sweep. But I know there would be problems with that too.

In this particular building the seismic measures are a curiosity (the structural engineer's office is in the floating part of the building), but a system like this would make real sense when you had to take into account large weights like brewery tanks or wine vats. (Of if you wanted to prevent a potentially dangerous chemistry lab from being shaken.) You wouldn't need to spend effort securing each tank or vat since the entire floor would be isolated from the quake. 

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