huangyhg

shear wall anchor bolts
i am having a heated conversation with a contractor. shear wall anchor bolts at the hold downs are subjected to both shear and tension correct?
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yes, but not at the same time. i would liken this to a baseplate - you would typically only design the anchors on the tension side for the shear (if you're going to use them at all).
technically correct, but in design, the bolts for the holddowns take only tension, whereas the other anchor bolts take only the shear.
mike mccann
mmc engineering
sorry, i meant to say you would typically only design the anchors on the compression side for shear.
i agree with mike. the holddowns resist overturning only. the sill plate should be anchored to the foundation wall for shear.
daveatkins
even though we add anchor bolts for shear, the anchor bolt in the holdown will still see both loads to some degree. it does not "know" it is supposed to be resisting tension only.
ok guys, lets get the anchor bolts vs shear bolts defined first. the big bolts at the ends are anchor bolts and all the little ones between are sill bolts. the names help avoid confusion.
the anchor bolts are designed for tension only even though the bean counters are correct that some incidental shear will creep in. let's not have any phd papers that make it into the code on this one.
the sill bolts do take uplift and shear. again, no phd papers. the incidental uplift on sill bolts is why we are now putting square washers on the sill bolts and use 3x sill plates when the shear gets too high. the problem is nail slip along vertical plywood joints between adjacent pieces of plywood. one side slips upward and the other slips downward. the downward slip isn't a problem because the sill plate has continuous support. the uplift side doesn't have support and ends up pulling upward on the outer edge of the sill plate. cross grain bending guys. no real solution here so the code guys are accepting 3x sill plates and square washers on the bolts to resist the localized uplift.
then - - if you get much slip from sloppy jamb bolting at the hold down bracket, the localized up lift may be more than localized. ever see a laborer try to drill bracket bolts from the side of the post away from the bracket. those holes can get really big.
sure makes you wonder about using lrfd to design wood, doesn't it?
old ca se

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