Cob: Earthquake.

[John Fordice]

Dear Itlone,
I was not meaning to slam Adobe.  I did not mean to imply that adobe
buildings are necessarily doomed to fail in an earthquake per se.  I did
mean that as a class of earth walled buildings which have failed in
earthquakes, adobe structures are probably by far the most numerous &
hence the most readily available resource by which to understand the
conditions under which earth walled buildings will fail in an
earthquake.  It is sad but true that many people have lost their lives
in the collapse of adobe buildings in many parts of the world.

The Getty study found that most of the adobe buildings in California
which were studied had experienced damage due to being in an earthquake.
 The fact that a particular adobe structure did not fail in a particular
earthquake does not mean that it was therefore not damaged.  Many of the
studied buildings sustained cracking, but remained standing.  This is
addressed in my previous posting in the paragraph on wall ratios.  The
good news is that those buildings did not fail.  The bad news is that
they were in fact damaged & hence liable to increased damage & more
prone to failure when the next earthquake comes.

I'm not sure of what a comparison of the magnitude of earthquake forces
in Arizona & California & other parts of the world would yield.  A more
accurate comparison might shed light on why Arizona adobes have
apparently not been thus damaged.  Also, a better knowledge of exactly
how the Arizona buildings are / were constructed in both the brick and
slurry methods would be very worthwhile & might also further clarify the
situation you describe.
Can you illucidate more ?

john fordice

  

ltlone wrote:
> 
> In reference to Adobe dwellings not withstanding earthquakes I disagree. We
> have many, many adobe structures in Arizona that have been here for
> centuries and are still in good condition. Slurry adobe (very similar to
> cob) structures are still around also. Arizona was extremely active in both
> earthquakes and volcanic activity before and after these adobe dwellings
> were constructed. We still have several earthquake faults here and get an
> occasional quake. In western and central Arizona we get jolted quite often
> from bad quakes in California and Mexico. Also, if I'm correct Adobe is Cob
> except it is made into bricks as opposed to being free formed like Cob. Cob
> is the same mix, as I understand it.
> JR
> At 12:18 AM 10/20/00 -0700, you wrote:
> >The reality of the "Cob versus Earthquakes" situation is that we don't
> >really know.
> >
> >In seismacally active California, we do have earth walled buildings, in
> >the form of Adobes, to which we can look for clues as to how earth
> >walled structures have historically faired in earthquakes.  It is true
> >that these adobe buildings are not the same as Cob, and the supposition
> >is that Cob, due to it's monolithic nature is probably stronger than
> >Adobe.  Be that as it may, these buildings are all that we have to look
> >to here by way of example, and so can serve us well in increasing our
> >understanding of the seismic / earth wall dynamic.  Two further points
> >relative to the benefit of studying adobe buildings are: 1.) Adobes are
> >the buildings with a history of failure; 2.) If cob is indeed stronger
> >than adobe, then incorporating an understanding how to prevent such
> >failure in adobe buildings into building with cob will, in all
> >likelyhood, result in a superior form of cob.
> >
> >Cob on !!!
> >john fordice