Shear of Wood to concrete

[msquared48]

Outside of the Mu factor for the interstitial shear, does anyone have any test results for the lateral (longitudinal) shear value of wet-set wood sill plates on a concrete foundation wall (no anchor bolts or holddowns).

The reason I ask, is that I have a project in one of the areas damaged by a December storm on the Washington coast - an older house with no anchor bolts in the foundation. It appears that the house has been slightly shifted to the side off the concrete wall. The structure saw sustained 100 to 120 mph winds for three days straight, with higher gusts.

The insurance company is maintaining that the damage is due to settlement, which, to me, is ridiculous in relation to the lateral slip - transverse to the foundation wall. They are basing this movement on cracks in the foundation (uncovered) and refuse to pay the claim to date.

I would like to be able to put some tangible numbers together based on the current IBC code wind design parameters to include in my report.

Thanks in advance to all.

Mike McCann
McCann Engineering

 

[RARWOOD]

I will have to think about this one. On the surface it seems the only thing preventing sliding, would be friction between the wood and concrete.

One of the first things I would do is determine the number of anchor bolts that would be required to meet the current code. That might give you a starting point to get a feel for the resistence without anchor bolts.

Then I would look at how overstressed those bolts would have been under sustained loads of 100-120 mph winds. The numbers may be such that you can make a pretty good case, that even if the house meet current code it still would have substain wind damage.

You also might want to contect Simpson Strong Tie. They have done a lot of testing on hold downs, and may have done some without anchor bolts.

 

[Taro]

When calculating the slip resistance, you may also want to consider wind uplift. That would reduce the normal force on the wood/concrete interface and lessen the friction.