SB: Re: Roof line question. (OT)

["Bill Hunt" <billhunt@redrock.net>]

> Can anyone give me an easy to follow discription on bond beams and clear
> stories on an adobe home.  My husband and I are having trouble
understanding
> how to do them.
>
> Thanks,
>
> Becky

Hi Becky- A search of the web for "adobe+bond+beam" yielded loads of info.
I can't do too much research right now, but  Fred Webster's article at
http://www.deatech.com/natural/cobinfo/adobe.html
discusses earthen building and siesmic forces in detail. He points out that
earthquake activity has occurred with historic regularity in most locations,
including New Mexico.  Here's an excerpt:

Some basic information about bond beams that should be somehow reflected in
the "adobe codes". include:

Bond beams should be continuous.
They should be stiff and strong in the direction perpendicular to the plane
of the wall (i.e., full, or near full width of the wall thickness with rebar
in both faces if designed as a beam to carry lateral forces).
They should restrain the out-of-plane deflection of the wall as much as
possible, although, if they hinge at the comers of the building, rather than
the resisting bending moment, this is all right.
In the up and down direction, bond beams should be flexible but strong
(i.e., no more than 5 or 6 inches in depth, with rebar at mid depth). Note
that this important concept is new and is the direct consequence of
observations made of shake table tests on adobe structures.
Bond beams should be positively anchored to the tops of the walls to prevent
the walls from slipping out from underneath them during lateral shaking and
to provide anchorage against uplift from wind.
Anchor rods should be closely spaced (i.e., 12 to 24 inches) to eliminate
stress concentrations from lateral forces or uplift.

Hope this helps-
Bill


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