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Re: Design of Wood Top Plates

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Richard Lewis wrote:
> I have seen many suggestions on this list, however, only one person alluded to
> what I believe to be the correct solution, IMHO  :o)
> I had this concern several years ago when just for kicks I tried to calc out
> the double top plate of a stud wall.  To my amazement it didn't work, yet
> just about 100% of all construction I have seen uses a double top plate.  I
> called an engineer at NDS and he told me the following:
> The top plate is in flat use.  The shear values given in NDS are for vertical
> use taking into account splits.  The values in NDS are basically for vertical
> use with 1-1/2 wide members.  The shear values in the code are given
> expecting some amount of probable split, which I don't remember.  Anyway, the
> important part is, when you lay it flat the likely hood of getting a
> horizontal split almost disintegrates so the Ch factor in the code of 2.0
> should be used to increase the allowable shear value.  


It would be nice if the NDS actually said this.  It has a paragraph that 
states (semi quoted):

" If fv < Fv' for sawn lumber bending members, and if the actual 
shear stress parallel to grain does not exceed the following maximum 
allowable shaer design values for unsplit members(Ch = 2.0):

	fv </= 2.0*90*Cd*Cm*Ct for Southern Pine

the alternate provisions in 4.4.4 shall be permitted to be used for 
calculating the shear force.