Uplift Capacity of Sill Plate Anchor Bolts
Uplift Capacity of Sill Plate Anchor Bolts
(OP)
How does one determine the uplift capacity of an anchor bolt which holds down a wood sill plate? I have been limiting the capacity of a 1/2" diameter bolt to 315#, based on the bearing capacity of the 1" diameter washer (minus 9/16" diameter hole) against S-P-F wood. However, I think this is too conservative.






RE: Uplift Capacity of Sill Plate Anchor Bolts
That said...where do you get such a condition? Most of our wall designs are based on the shear on a shearwall where the anchor bolts are used to take lateral shear ONLY and the uplift at the end of the shearwall is contained by steel holddowns. Do you have a net uplift on a non-shearwall wall?
RE: Uplift Capacity of Sill Plate Anchor Bolts
RE: Uplift Capacity of Sill Plate Anchor Bolts
RE: Uplift Capacity of Sill Plate Anchor Bolts
Timber has a very high short-term strength and therefore under wind load you can generally use a significant "overload" factor. In the Australian code, a factor of 2 is allowed for this. Otherwise, your approach sounds correct.
Sven.
RE: Uplift Capacity of Sill Plate Anchor Bolts
RE: Uplift Capacity of Sill Plate Anchor Bolts
The value you gave is very conservative. If you consider the shear of the wood (that is ultimately the failure mode in uplift failure, even though initial "failure" is in compression parallel to the grain)under the shear plane of the washer, you will find a relatively high value. As an example, for your 1" diameter washer, you will have a shear area of 3.14xthickness. For nominal 2x lumber, the shear area will be 3.14x1.5=4.71 sq. in. At nominal 125 psi allowable shear stress, the load becomes 589 lbs. Obviously, the larger the washer, the greater the allowable load (up to a point!)
Compare this to about 950 lbf. allowable pullout of the anchor in normal concrete. (This varies significantly with anchor manufacturer and type, so check their tables)
RE: Uplift Capacity of Sill Plate Anchor Bolts
And here in Fl. Engineers use anchor bolts for overturning at SWS ends...a no no.
jeff