Wednesday, February 7, 2018

A Plague on All Our Houses - Tilted Buildings in Earthquakes

I like SpaceX.  If they muck up the physics then things go boom.  I suspect they misjudged the exponentials for a booster coming from a much higher altitude.  But they have instruments and believe the results.  This won't happen again.

Not so with Earthquake Engineering.  They caught the disease of 'social physics' many years ago.  Everything was 'debated' and they never believed what the instruments and observations were telling them.  Unlike spacex, things don't go boom while they are still around, only much later.  They make their money hanging on to 40 year old assumptions.  And they make even more money when they are flouncing around hanging up red tags.  This is a business of 'reputation' and "veritas in wine".

So, for the last several earthquakes, we've had buildings tilting.  The engineering world attacked resonance, with 'energy absorbing' and wonderful moment connectors.  The buildings do not pancake.

Is this a victory for engineering?  Are tilting buildings good for Society?  Don't forget that if a cheap condo just tilts a little bit, it is unservicable and has to be destroyed.  Do you want every building in your city doing that?  At only 40 cm/s, pgv?

So, the great failure of this industry is ignoring real physics, and going for the imaginary physics of the shake table.  Expect more tilting buildings, and if you live in one, forget the grand piano on wheels.  :)

Also, once again, we have demonstrated the uselessness of 'early warning'.

Note in passing

Peak accelerations flatten out on soft soil at 30%.  That's why everybody uses this number, and it works well on a shake table.  PGV continues to zoom up with larger earthquakes.  Nobody wants to tackle that.

Didn't pancake.

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