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RE: 1997 NDS Equation Error?-->2x2x3/16 washers on 3x sills

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Dave:

"2308.12.8 requires that all sills have 2x2x3/16 washers. With no mention of
sill plate size, it applies to all sills. This is clearly not for sole
plates at upper levels."

Section 2308 is from the "conventional construction" prescriptive
requirements.  3x sill plates are not going to be used for non-engineered
conventional construction in most situations. I agree the code says plate
washers are required for conventional construction, which almost always uses
2x sill plates.


Here is a copy of a message from an ICBO engineer:

"-----Original Message-----
From: carr(--nospam--at)icbo.org [mailto:carr(--nospam--at)icbo.org]
Sent: Wednesday, November 14, 2001 4:20 PM
To: HaanSM(--nospam--at)ci.anchorage.ak.us
Subject: Re:IBC 2305.3.10 2x2x3/16 plate washers 


Scott,

I agree with your reading of the IBC and (while I do not have any more
specific knowledge of the intent) offer the following additional
information/comments:

IBC 2305.3.10 is based (somewhat loosely) on 97 NEHRP ( See Sec 12.3.4.4).
It is applicable at shear walls in engineered design of structures
classified as SDC D, E or F. Also, the exception to IBC Sec 2305.3.10 is
really derived from footnote 3 to UBC Tables 23-II-I-1 & 23-II-I-2 (as
modified in errata) which implies that the plate washers are a requirement
to allow installation of a 2x sill in lieu of the 3x.

Contrast that with conventional construction requirements in IBC Sec
2308.12.8 (as well as IRC Sec R403.1.6.1) which require the plate washers
for all sill bolts in any structure considered SDC D, or higher and built
using the conventional provisions. The latter IBC requirements for
conventional construction are reminiscent of the UBC criteria in 1806.6.1.
There occassionally have been opinions (see UBC Handbook Sec 1806.6) that
UBC Sec 1806.6 was meant to apply only to conventional construction (no
engineering involved). If that was the case, then the IBC has made that
application clearer.


Hope this proves useful.

Alan Carr, P.E.
International Conference of Building Officials
Northwest Resource Center
(425) 451-9541 ext. 114

Check out ICBO's website: http://www.icbo.org";



Scott M Haan P.E.
Plan Review Engineer
Building Safety Division 
Development Services Department
Municipality of Anchorage
http://www.muni.org/building
phone:907-343-8183  
fax:907-249-7399
mailto:haansm(--nospam--at)ci.anchorage.ak.us



-----Original Message-----
From: David B Merrick [mailto:mrkgp(--nospam--at)pacbell.net]
Sent: Thursday, November 15, 2001 8:08 AM
To: SEAINT
Subject: RE: 1997 NDS Equation Error?


I sent his message with quotes and with a too wide format So here it is
again..

For Seismic Cat. D or E: section 2308.12.8 requires that all sills have
2x2x3/16 washers. With no mention of sill plate size, it applies to all
sills. This is clearly not for sole plates at upper levels. A
clarification that sole plates are exempt would be helpful.

For IBC 2305.3.10, the 2x2x3/16 washers are only required for 2x sill
plates.

Are 2x2x3/16 washers required for sole plates? A sill plate is a  bottom
plate  on the foundation. A  sole , is also a  bottom plate  higher up
in the framing. The last sentence of IBC 2305.3.10 references nailing of
a sill to line 8 of table 2304.9.1. Tabulated line 8 uses the term  sole
. The IBC disregards the difference in meanings of the terms  sill  and
sole . The term  bottom plate  can be used when both  sill  and  sole
apply. Most likely, the table needs the term  sole  changed to  bottom
plate , or else the larger washers applies to all bottom plates of 2x
material.

Sole plate pressure treatments that appear to be of a light green color
are of Hem-Fir. Pressure treated Doug Fir is more of a light chocolate
color with deeper knife cuts. The deeper cuts are needed for the harder
material. This reduces the bolting values by about 9 to 11% and the
nailing by 7%.

The wood to concrete bolting, Mode IIm probably should exclude the side
member moment. See Tech Report 12 page 16. On page 13,  Case A  maybe
more likely than  Case B  for the side member. It may be that the qs
should apply to the full area of the sill plate. I would call it the
Mode IImc. That change would reduce the Mode IIm capacity, in that the
calculated moment applied to the concrete, being checked as the main
member, will increase. The Mode IIm failure of a wood to concrete
connection rotates the bolt a small angle to fail the concrete. That
rotation is less than the rotation required for the wood rotational
resistance Ms.

David Merrick, SE
mrkgp(--nospam--at)pacbell.net.



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