Wood Shearwall Overstrength 3

[cal91]

I'm trying to find code provisions addressing overstrength but am coming up short.

It's intuitive to design both the sill plate anchors in shear for overstrength and the holdown anchors in tension for overstrength. At least for failure modes involving concrete.

However it seems many people don't design for overstrength. Is this actually common?

Thanks

 

[Deker]

For sill plate anchors transferring in-plane shear it is generally assumed that ductile failure occurs in the sill plate prior to concrete breakout, and therefore the overstrength factor would not apply. This is based on testing performed by the SEAOC Seismology Committee (Link #1, Link #2) and was codified in both CBC and IBC (Section 1905.1.8).

The holdown anchors do need to be designed for overstrength unless it can be shown that they will fail in a ductile manner. See this link for some discussion (Link #3).

 

[cal91]

Great. Thanks Deker.