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Re: Seismic on restrained retaining walls

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Title: Re: Seismic on restrained retaining walls

The 12' retaining wall exception appears in chapter 18A, DSA requirements, but disappears
in chapter 18. Further more section 15.6.1 appears to imply that all retaining walls shall
be designed with additional seismic loads. Does that mean that six or eight foot
retaining walls in backyards get additional seismic loads?

Tarek Mokhtar, SE
Laguna Beach, Ca

And the rule of thumb shall be to keep all of our retaining walls 11'-11" or less in height.

On Thu, Mar 20, 2008 at 9:12 AM, Hugh Brooks <hbap(--nospam--at)> wrote:
The Mononobe-Okabe equations do not apply to restrained walls where activation movement is restricted.
For seismic lateral on restrained walls Retain Pro uses  P = (soil density) x (k<sub h>) x (retained height)^2.  Application is approx. 0.60 x (retained height).  This is a slightly trapezoidal loading but with only slight error a uniform loading could be assumed.   K<sub h> is the acceleration factor appropriate to the site.
See Kramer, Geotechnical Earthquake Engineering, Section 11.6.2.
Hugh Brooks, SE
Retain Pro Software



Tarek Mokhtar, SE
TMM Structural Engineers, Inc
31645 S. Coast Hwy
Laguna Beach, CA., 92651
949-499-2777 Fax