SB: Re: Re: lateral bracing

["John Swearingen" <john@skillful-means.com>]

----- Original Message -----
From: "John Salmen" <terrain3@home.com>
To: <strawbale@crest.org>; "ruth harding" <rharding@sfu.ca>
Sent: Tuesday, April 10, 2001 7:11 AM
Subject: SB: Re: lateral bracing


> SNIP
>The other alternative is to really make them work together in which
> case you need to make those walls stiff - so you need to wire and stitch
the
> two skins together and do it well.
SNIP
> You could argue that the stucco bond to the straw is sufficient to hold
> everything together and you would probably be right but it is not
something
> the eng. can rely on predictably over the entire surface of the building -
> if there are pockets that did not bond they can cause a whole wall to
fail -
> the stucco mesh provides a little more certainty even if it may be
> redundant.
>
> John Salmen

I think the straw/stucco bond is very strong because of the extreme
roughness of the bale surface.  However, and particularly in seismic
conditions, it is crucial that the edge conditions of the stucco skin be
carefully detailed.   That is, the corners of the walls, around windows and
doors, and the tops and bottoms of the wall must be detailed so that the
whole building knits together.  The idea here is that forces are thrown into
the wall (from the ground), and to travel through the wall pretty
well--until they get to an edge.  Then, if not restrained, they will burst
out of the wall, literally break the wall to get out (pop staples, rip wood,
break stucco), because the forces want to continue in the direction they're
going.  So at corners and edges, you want to have solid and smooth
connections so that the forces are transfered to the next wall, around the
corner, etc.  The idea is for the building to hold together long enough to
either dissipate the energy in small movements and minor breakage; or to
transfer the forces back into the ground.  Bear in mind that different parts
of a building will move in different directions:  this very commonly occurs
at the foundation and the wall/roof connections.  This is a very common
point of failure in earthquakes, and also with high wind loads, and should
be made strong and continuous.  Although the straw/stucco bond is good, and
the plaster skin might be very strong, all of this still needs to be tied to
the other parts of the building.  Most of the tests of plastered bale walls
have ended when these conditions failed (which, by the way, precluded
learning the ultimate strength of the bale wall, and how it might fail).

John Swearingen


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