Friday, May 23, 2008

Learning from the China Quake

We are starting to get a better picture of how the buildings performed during the China quake. The question is whether the modern world will learn anything from it. As far as the actual earthquake mechanism goes, I think we will learn a lot, once all the computers have finished munching the seismic data. As I've said before, without monitoring on the ground at Ground Zero, we will never know the actual PGV.

We can't learn much from total rubble. When the 'seismic experience' guys finally tour the place, they will probably note every seismic design mistake in the book, such as no steel, no detailing, no connections, etc. It will be interesting if they can find buildings that have survived. I remember in the big India quake, there was this picture of total housing destruction, and in the middle of it was a house totally untouched! Must have belonged to a decent engineer!

The next interesting quake will be one to test all the flaky ideas that have popped up in the last 20 years. One of these is base isolation.

The idea is to put these suckers underneath a building. They are very popular for renovating old brick buildings, or trendy loft warehouses. When an earthquake hits, they deform and absorb energy. Some buildings have similar 'energy absorbing elements' distributed throughout the building.

These things are designed on shake tables, and you know what I think of those things! Nevertheless, we shall assume they are good, until a real earthquake tests them. I give a 50-50 chance that they'll be proven to be worse than useless, since they can only absorb so much energy before they hit their limit and make things much worse.

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