Wood shear wall question 1

[said the noob]

Hi,

Anybody familiar with CSA 086 regarding shear wall framing requirements for double bottom sill plate at base of shear wall and foundation connection? What would be the reason for this?

Thanks

 

[KootK]

If you point me to the code clause, I'll go check it out.

HELP! I'd like your help with a thread that I was forced to move to the business issues section where it will surely be seen by next to nobody that matters to me:

http://www.eng-tips.com/viewthread.cfm?qid=456235

 

[said the noob]

Hi kootk,

No clause specifically that I know of its just something an EOR stated in his drawings,

I am wondering if it is code related and the reason behind it,

 

[KootK]

Sounds like the EOR may be the guy to ask. I can't think of a hard reason for this but, perhaps, some soft ones:

1) Maybe forces are so high that you need anchor bolts acting over 3" of wood. Seems unlikely.

2) Maybe they want to be able to bolt the first plate and then nail another plate on top with recesses so the bolts don't show.

3) Maybe something to suit wall prefabrication if the walls are being prefabricated.

5) Perhaps trying to raise the wall above an envelope condition.

6) Maybe framing condition is such that the bottom plates need to be drag members and therefore spliced....?

Honestly, I'm just grasping at straws.




HELP! I'd like your help with a thread that I was forced to move to the business issues section where it will surely be seen by next to nobody that matters to me:

http://www.eng-tips.com/viewthread.cfm?qid=456235

 

[said the noob]

Thanks kootk

I am reading through csa 086 and nowhere does it mention this too, the base shear loads are not high, (it’s a straight forward 4storey wood frame with excessively long shear walls)

I will ask the eor, I suspect it is just something of a copy and paste, this note was in their general wood framing notes section

 

[jimstructures]

said the noob,

Would you post exactly what the eor put in their notes?

Jim

 

[JoshPlumSE]

Is this a high seismic application?

There is a deformation compatibility issue with sill plates connected to concrete foundations. There was a post northridge requirement for 3x sill plates hear in the US because of this. Though I believe that requirement was only invoked for higher shear forces. Regardless, the point was that as the wall wants to lift up off the foundation, the sill plate will bend too much which became problematic. Numerous sill plate issues were observed post Northridge.

Now, the US requirement softened that stance since then. Perhaps in favor of having more rigid square washers on the anchors....

But, it seems to me that an engineer with this old provision in the back of his mind might still want some extra rigidity at the sill.

 

[ZHE]

I have done some multi family buildings and have specified double sill plates due to architectural requirements of 1 1/2'' concrete flooring at upper level floors. The idea is to avoid the conflict between concrete and the sill plate shear wall edge nailing. But not sure if your EOR thinks the same.

As JoshPlum said, the IBC used to have the 3x sill plate requirements and was mainly for the sill plate cross grain bending under shear wall uplift. NDS simultaneously had a requirement of plate washer at each anchor bolt to eliminate cross grain bending. I believe IBC took out the requirement in 2012 or so and simply refered the cross bending issue to NDS which is the plate washer solution. So now the 3x sill plate requirement is no more enforced by IBC.