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Re: Prescriptive BWPs

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"Ed Workman" <eworkman(--nospam--at)fix.net> on 07/20/99 02:15:11 PM

Please respond to seaint(--nospam--at)seaint.org
                                                              
                                                              
                                                              
 To:      seaint(--nospam--at)seaint.org                                   
                                                              
 cc:      (bcc: Paul Reilly/D03/Caltrans/CAGov)               
                                                              
                                                              
                                                              
 Subject: Re: Prescriptive BWPs                               
                                                              







-----Original Message-----
From: Paul_Reilly(--nospam--at)dot.ca.gov <Paul_Reilly(--nospam--at)dot.ca.gov>
To: seaint(--nospam--at)seaint.org <seaint(--nospam--at)seaint.org>
Date: Tuesday, July 20, 1999 7:30 AM
Subject: Prescriptive BWPs


>
>
>Zone 3, Wind Exposure B:  A current project for a tract builder has
provided an
>opportunity to assess the specification of BWPs
>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 .

Prescriptive means follow (ALL) the rules and don't look back.  I assume
that implicit in the prescription is the recognition that simple wood
structures have historically behaved adequately. And that this recognition
is from observation rather than investigation/analysis.
Thus, in "conventional" construction there are many elements which
participate to resist loads in addition to the BWP's.  If all are tied
together, and the structure is simple and regular it will end well.  to look
at it another way, iff the walls more or less line up (so that all share
similar deformations) all the gyp participates, etc.
To reiterate a thought from previous threads, this isn't a place to mix and
match resisting elements ( or design and prescription) but to organize and
lay out elements in a simple regular way so that concentration of forces is
avoided such that nominal connections, etc are adequate.

It's not for nothing that steel stud homes must be engineered, as they
frequently  include many other non-traditional elements such as finish
materials which provide far fewer elements capable of resisting lateral
loads.

Also , in looking back to the recent discussions of rigid/flexible it seems
to me that it would help to have a better picture of the load/displacement
behavior of a wood shearwall.  If strength is determined by nailing and if
"nail failure" is by bending,  isn't there "enough yielding" in a wall to
permit sufficient deformation as to allow the design strength of other walls
to be mobilized? Isn't this the basis for the prescription?