Seismic Overstrength Factor for Foundation Design?

[dengebre]

Should the seismic overstrength factor (Omega) be used when determining the foundation design loads? I am specifically referring to the loads as they pertain to the soil-foundation interface, and not the design of the foundation itself.

 

[JoshPlumSE]

You might want to check out the NIST / NEHRP Seismic Design Technical Brief No. 7 "Seismic Design of Reinforced Mat Foundations".... NIST GCR 12-917-22

I believe it covers this question.

 

[jvvse]

I haven't seen a code that says you must design the bearing pressure or passive pressure for Omega, yet in California, our hospital jurisdiction (OSHPD) has told us very plainly that we must use Omega for soil bearing pressure and passive pressure.


I do steel a lot and so I know that AISC 341 for steel design specifies that all steel connection elements must be designed for Omega or the maximum force the system can deliver. So for example in footings, you must design base plates and anchor bolts for Omega, but any concrete design or soil design does not have to use Omega.