[Cob] Difference between cob and rammed earth (reinforcing)

[Bonnie Morse]

I think reinforcing with bamboo is a great idea.  I keep reading that a cob
house will withstand a 7.x earthquake at least as well as a wood-frame
house.  But we in the Pacific Northwest are overdue for an 8.x, or maybe
even a 9, earthquake.  If we get one in my lifetime, and all the wood-frame
structures in my town collapse, I'd like for my cob house (so far still a
sparkle in my eye) to be still standing.  After all...it might have to serve
as the local hospital for awhile!

I do have a lingering curiousness about your earthquake tests.  Of
necessity, you used a small structure...was it 5 feet tall?  Any small
"thing" will be stronger than a larger "thing".  So a 5' structure will
withstand a 7.2 earthquake much better than a 10' structure.  I assume--and
please correct me if I'm wrong--you compensated by building the walls
narrower than you would a real cob house.  Did you have to do anything else
in order to make your results reflect how a real house would behave?

Thanks,
Bonnie in OR

-----Original Message-----
From: coblist-bounces at deatech.com [mailto:coblist-bounces at deatech.com]On
Behalf Of Ian Marcuse


Reinforcing cob in earthquake zones is probably a good idea. Bamboo
would work fine I think, embedded vertically would help to prevent
shear failure. In our recent earthquake tests at UBC this year, the
need for this type of reinforcment was quite clear. Mind you at a 7.2
richter quake the cob held up briliantly without reinforcement, apart
from straw. At a >9 richter, the building seriously failed, but
without roof collapse. A 9 quake is however extremely rare. If you
have bamboo, I doubt that it would hurt. Does anybody have other
thoughts on this?

We hope to post a video of the quake test on the web soon

Ian Marcuse