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Prescriptive BWPs

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Zone 3, Wind Exposure B:  A current project for a tract builder has provided an
opportunity to assess the specification of BWPs in leiu of engineered walls
working with thrifty rectangular layouts, a textbook stack of building levels
(two story max) and a tidy prefab truss system.  The developer was excited to
incorporate the new BWPs as the perception was that the '97 prescriptive
requirements would be more economical with savings in both engineering and
construction.  This was my first exposure to the specification of BWPs, as I
typically analyze the entire structure using local models to assess demand.  I
was disappointed to find that I could not support the inclusion of BWPs as I
found the prescriptive holdowns to be undersized and prescriptive shear nailing
to be inadequate.

My premise for this unfavorable consideration is that multiple piers on a single
wall line will perform in concert only if the relative rigidities are the same
and specified to service the total demand .  Given two or three small
prescriptive BWPs on a 45' wall,  the forces will be drawn to, and act upon
these  elements (most rigid) prior to engaging less rigid elements (gyp panels).
If my BWPs are three 4' wide panels with prescriptive holdowns, they get
blown-away before the gyp panels can be engaged due to the difference in
rigidity of the piers.

I would like to hear if I have any company in this observation.  All comments,
flames, debate encouraged.

Paul Reilly