Friday, June 10, 2016

Generally Useless Seismic Upgrading


Fastening the walls to the foundation is a great idea, but only for single-story totally wood houses.  These are the cases where the foundation slip was the main cause of damage.  So, if you have a shack, then do it by all means.

It does diddly-squat for a brick house, which you can plainly see in the picture.  Once again, basic physics is being ignored, which is the sad general case.  :(   If you want to protect your house against 'Da Big One', then expect only 10 cm/s on firm ground.  If you are on a swamp, then prepare for 100 cm/s.  The only way to upgrade for that is by using deep screw piles.  This worked in Christchurch and will work for you.  For these old houses it has the added advantage of levelling the house.  A walk in High Park, in Toronto, shows them all tilting with no mortar in the chimneys.  This is the worst level of preparation.

ps.  a proper lift should reduce background seismic noise by a factor of 10.  To make you feel good about spending your life savings to save your life, do a seismic noise test before and after, with my handy-dandy accelerometer kit (not invented yet).  :)

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