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Evan,
 
The 3x framing is required only at framing receiving nailing from abutting panel edges, not the edges of all panels.  If your plywood shear is split horizontally for multi-stories, split it over the manufactured rim joists, which will not have the 3x requirement to receive the horizontal line of edge nailing.  The 3x p.t. sill can be reduced to a 2x for walls under 600 plf, where 50% anchor bolt strength is used. If you cannot split the shear vertically on the rim joists, consider adjusting it so that a row 3x blocking can be installed to receive the abutting panel edges.
 
Pat Clark, P.E.
 
-----Original Message-----
From: Evan Mizue <eam(--nospam--at)baseengr.com>
To: seaint(--nospam--at)seaint.org <seaint(--nospam--at)seaint.org>
Date: Wednesday, March 21, 2001 11:58 AM

 
 
Subject:  UBC1997 Wood Panel Shearwall Recommendations
 
This question is in regards to the Uniform Building Code 1997 recommendations for wood structural panel shearwalls, Table 23-II-I-1. 
 
Note 3 below the table clearly states that all wood panel shearwalls with allowable capacities greater than 350 lb/ft are required to be framed with 3" nominal members at all structural panel edges.  I have reviewed the shearwall capacities listed at your web site, and no such requirement is listed (except for panels receiving closer edge nailing than 2" o.c.)
 
Using 3" nominal members (as top & bottom plates or as wall studs at panel edges) is a significant change to standard framing practices.  This change makes shearwall framing and constructability much more difficult.  Continuity is also a concern, as splices are required where 3x top plates over shearwalls must be spliced to the standard double 2x top plates. 
 
Please review the UBC 1997 Code Requirements and offer a recommendation as to whether the requirement for 3" nominal members is valid.  If so, are there any alternatives to engineer shearwalls with 500 lb/ft to 700 lb/ft capacities without significantly modifying standard construction practices for wall framing?  Please call or email.  Thank you. 
 
Thanks,
Evan Mizue
For Baldridge and Associates Structural Engineering, Inc.