[Cob] Hybrids - structural flexibility issues

[Amanda Peck]

So, windows and doors (which do lots more than a tiny non-opening window in 
the way of imitating a seismic event in a building) need to be carefully 
planned--because they by their nature are a different material/different 
structural period than anything we are likely to be building with????

Can we use "standard building practice" as outlined in the various books, or 
do you have other links, suggested readings?  I'm planning lots of windows 
(well, probably a couple of patio doors worth, but they're small buildings) 
in the south side of my buildings.  The amount of room one needs for a 
straw-bale column was why I was planning on going FROM straw bale infill to 
cob for the whole wall there.

.......................
Otherfish (who should know) wrote:

There is nothing wrong with, and alot to be gained in building hybrid
structures.  Stabilized or protected earth bag, cob, and strawbale  all have
a lot to offer and can make an excellent building if done in a manner that
takes into account the nature of how each acts structurally.

A very critical part of that consideration, and one which I've not seen in
this current discussion, is what can be called the structural period of a
material.  As has been already acknowledged, they each have a different
level of felexibility ( ie: period ).  Altho I don't know for sure, I
suspect that earth bag  & cob are probably fairly close in flexibility with
earth bag being a bit more flexible than cob.  However, there is a great
difference between the inherent flex of a strawbale wall versus that of cob.
The point of this is that when subjected to seismic or wind forces, each of
these materials is going to act differently.  So if you build a structure in
which you have any of these three wall materials (and whatever roof or floor
structures each material is supporting) relying on onother of these
materials for lateral (sideways) structural support, it's asking for
trouble.

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