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[SEAOC] Re: [SEAOC] Seismic Design of Foundations

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For grade beams supporting moment frames, we do design for the special 
sesimic section of the code for concrete frames, disregarding the fact 
that it is below grade.  However, on foundations for shear walls we do 
not.  I just check the moment and shear at the critical section, and 
provide normal reinforcing to carry the forces.

James A. Lord wrote:
> When designing a foundation of a seismic lateral resisting system, is it necessary to
> design the foundation using all the concrete seismic design provisions?
> Two instances for discussion:
> 1. Moment resisting frame, & you are counting on some fixity at the base.  Do your grade
> beams have to have the same details as a flexural member of a concrete SMRF?
> 2. Shear wall system.  For overturning, you need to extend the foundation beyond the end
> of the shear wall a several feet.  For the extension, must you use the same details as a
> concrete SMRF?
> Let's hear what the current practice is.
> James Lord, S.E.
> jlord(--nospam--at)