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RE: 2x2 Plate Washers for WSP Shear Walls (UBC)

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Bill,  I could not find a reference to the plate washer equivalent area
question but we would accept a round washer of equivalent area and
thickness.
  See the IBC 2305.3.10 and table 2306.4.1 footnote i and see also the IRC
R403.1.6.1.  Both require the plate washer in seismic design category D, E
and F in addition to the 3x sill if the design load is greater than 490 plf
(LRFD).  The exception for the 2x sill is for design loads less then 840
plf(LRFD) then they can be used as long as you have the plate washers and
the sill is anchored by 2x's the number of bolts required by design.

-----Original Message-----
From: Bill Allen [mailto:T.W.Allen(--nospam--at)cox.net] 
Sent: Tuesday, August 26, 2003 7:58 AM
To: seaint(--nospam--at)seaint.org
Subject: 2x2 Plate Washers for WSP Shear Walls (UBC)

Ref: UBC Table 23-II-I-1 (p. 2-288), footnote 3

My situation:
Visualize a concrete stem wall, 3x sill plate and raised floor framing.
The floor joists are framed flush, hung off the 3x sill plate with
hangers. Sheathing over sill plate. Stud wall framed above. Based on
this condition, the anchor bolts have to be dapped into the 3x (or 4x)
sill plate.

Using a 4x sill plate, if the dap is such that I still have 2-1/2" of
"meat" left (I know this is difficult for the nut on a 5/8" anchor bolt
plus a few threads, but bear with me), then I (believe I) still have a
"qualified" 3x sill plate.

The problem comes in getting in those *damn* square washers. The
diagonal on a 2x2 washer is almost 3", not leaving much edge or
tolerance in a 4" (nom.) stud wall.

Question 1: Is there a code provision for an alternate, equivalent round
washer? If a 2-3/8" diameter washer is equivalent, then a 2-1/2"
diameter hole saw would work. 

Since the Beginning of Time (i.e., publication of the 1997 UBC), I have
been under the impression that these washers are required for all
anchorbolts in shear walls (in Seismic Zones 3 and 4 which are the only
ones I care about). In reading Footnote 3, it almost appears that the
washers are only required if one is trying to use a 2x sill plate for
shear walls with less than 600 PLF.

Question 2: Is this just (more) cumbersome code wording or is it true
that these plate washers are _only_ required when one is trying to use a
2x sill plate on shear walls designed for less than 600 PLF in Seismic
Zones 3 and 4?

That's all for now. I have to go back and continue reading the Statement
of Qualifications for the gubernatorial candidates. Sheesh!

Regards,

T. William (Bill) Allen, S.E. (CA #2607)
V/F (949) 248-8588
San Juan Capistrano, CA

"Lord, I can't go yet. I've still got one more detail to do!"




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