Sunday, August 9, 2015

The New Tilting Buildings

In the 60's we had our tilting buildings for earthquakes when there was extreme liquefaction.  That's when the loose sand turned to soup.  Many years of study and finally people understood not put buildings on loose sand.  No tilting buildings for decades.  Just a lot of pancaking.  Then that was fixed by putting a bit more steel in the concrete.  Now we have the new tilting buildings.  One of my pictures from the Nepal earthquake shows a building on its side, composed of a lot of glass.  Not one pane broken.  And Chile had a tall building tilt over with nothing broken.  A triumph of engineering?  No.  You won't survive this under a desk if the grand piano slides over.

These buildings are tilting on average soil.  It's from relying too much on shake tables.  When you set up one of those things you bolt the model to a big steel slab and shake the heck out of it.  But in the real world, you are on a foundation.  These guys just pour a slab and stick the building on top.  If they want to make it worse, they put in soft stories, which are somehow ok on shake tables.  We are now entering a stage of false seismic engineering, as good as the time when we built on loose sand.  I can't wait for the next big earthquake.

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