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RE: 3X Plates and Washers on Intermediate Anchors

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I still think you are right about the bolt holes becoming larger.  I've
never actually observed this condition, but I've seen plenty of nails
that are loose due to wood shrinkage.  I think that the wood will shrink
away from any exposed edge, so as the wood shrinks away from the bolt
hole, the hole will get bigger.

Kipp A. Martin, P.E., S.E.
Carollo Engineers
503-227-1747 (fax)

>>> gmadden(--nospam--at) 3/2/2006 9:41 AM >>>
Never watched a donut shrink. so I'll take your word on it. Ok, strike
that one out for a reason. :-)
-----Original Message-----
From: Garner, Robert [mailto:rgarner(--nospam--at)] 
Sent: Thursday, March 02, 2006 9:29 AM
To: seaint(--nospam--at) 
Subject: RE: 3X Plates and Washers on Intermediate Anchors
Shrinkage will decrease the hole diameter.  When a donut shrinks, does
the hole get bigger?

From: Gerard Madden, SE [mailto:gmadden(--nospam--at)] 
Sent: Thursday, March 02, 2006 9:17 AM
To: seaint(--nospam--at) 
Subject: RE: 3X Plates and Washers on Intermediate Anchors
I know that the allowable values in the code are based on testing. I
would think that the clamping force from the nuts with plate washers
greatly contribute to the capacity. If there weren't any nuts, the
would slide and bang ever so slightly back and force because the holes
in mudsill will not be snug and with shrinkage, the holes size will
increase over time.
-----Original Message-----
From: Bill Allen [mailto:T.W.Allen(--nospam--at)] 
Sent: Thursday, March 02, 2006 9:02 AM
To: seaint(--nospam--at) 
Subject: 3X Plates and Washers on Intermediate Anchors
So, as I understand it, the requirements for 3X sill plates for shear
walls with Fv > 350 PLF (CBC Table 23-II-I-1, footnote 3) and square
plate washers (CBC Section 1806.6.1) on intermediate anchors are a
result of observations that, when wood shear walls lift (due to lack
restraint at the hold downs), the sill plate will tend to split. The
square washer distributes the load better and the thicker 3X sill
will provide a better section to resist flexure. O.K., I understand
Maybe these are two separate issues.
What about another solution? What if the nuts (and washers) were left
off entirely? It certainly seems to me that would eliminate the
requirement for the square plate washers (if none were required in the
first place). I'm not sure if this would be a remedy for the 3X sill
plates. I understand the requirement for 3X members at abutting panel
edges to reduce splitting, but I'm guessing the 3X sill plate
requirement is to reduce flexural failure. I'm sure I will be
if I'm mistaken.
All code references are to the 2001 CBC (sorry).
Just a thought. Comments are welcome.
T. William (Bill) Allen, S.E.
Consulting Structural Engineers
 V (949) 248-8588 . F(949) 209-2509
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