Sill Plate Requirements for shear walls exceeding 350 PLF 1

[carsonwjohnson]

I'm trying to find the provision that allows a 2x sill plate for walls less than 600 plf if the anchor bolt capacity is reduced (the exception to the 3x sill plate rule). It was in the 2010 CBC (IBC), but with the new 2013 version, not only can I not find the provision, I can't even find the wood structural panel table for nailed walls (it only has the one utilizing staples). I have found the table utilizing nails in the AFPA, but that one has no provision for the 3x sill plate rule at all. If anyone could point me in the right direction I'd really appreciate it.

 

[jdgengineer]

Its my understanding that the requirement for 3x sill plates at higher wall shears has been removed.

Nearly all of the seismic design for wood shearwalls and diaphragms has been removed from the main body of the code and instead refers to NDS SDPWS.

 

[carsonwjohnson]

Yeah I was thinking the same thing. The only place I see the 3x sill plate requirement is in the CBC on the tables utilizing staples. The problem is, the project I'm working on is a plan check, and the plan checker called me on the 2x option. I'm now trying to decide if I want to argue that the 3x requirement has been removed, or if I should just give him what he wants.

You'd think they'd at least leave the tables and requirements in the same book when they update these things. By the time we get used to where everything is, they just change it all again lol.

 

[jdgengineer]

Well for what its worth Kelly Cobeen who is one of the authors of Breyer's wood book and considered to be the wood seismic expert.

But with a plan reviewer you always have to decide if its worth the fight.

The body of the code is trying to remove all actually information and instead use reference documents instead. In theory I think it is good but in practice it is a headache.

 

[msquared48]

I can understand the possible logic here for the removal of the 3X sill plate requirement on three issues:

1. Using 3X vertical studs at the panel joints gives 1.25" each side for nailing. A 2X plate gives 2.5", greater than the panel joints.

2. The use of washers of specific size and thickness at the sill plate anchor bolts allows a 2X to be used instead of ta 3X.

3. As I recall, the 3X requirement originally did not specifically mention sill plates, only "all boundary members", which would include the top and bottom plates.

So, two questions ensue:

1. Was the requirement poorly written, allowing for misinterpretation, and it was subsequently corrected, or

2. Was the data from the Northridge event over-reacted to (CYA), misinterpreted, or is this a change based solely on economics and contractor/developer complaints...again?

Comments?

Mike McCann, PE, SE (WA)

 

[wannabeSE]

An explanation on what happened to the 3x plate requirement can be found in section 2305 on page 10 of the White Paper at

http://www.strongtie.com/ftp/articles/2010-Building-Code-Update.pdf

While this paper is written for the 2010 California Building Code, this section should also apply to the 2009 IBC.