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Re: Retaining Wall Seismic Loads

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That sounds like apples v. oranges. At least 2 of the geotechs I work with are satisfied that the loads are not additive (YMMV). They cite some lab work done at UC that supports this view. /The speaker, Professor Nick Sitar from UCB, said the results of their study were published in the proceedings from the recent seismic conference in Sacramento. I don't have the proceedings, but will see if I can get a copy of the paper./
/ /
Chuck Utzman, P.E.
p.s. I have the paper in .pdf but its too big to post here (& pretty technical)

Rhkratzse(--nospam--at) wrote:
Not overturning or sliding damage, but I can recall seeing, many years ago, a photo of a concrete culvert -- concrete walls, floor, and top, maybe 8' tall and 10' wide or so -- with both of its side walls punched inward due to earthquake forces. Possible in the Anchorage era, around 1964 or so.

Since earthquake movement travels through the ground in waves it seems obvious that there will be some instantaneous and short-lived increase in soil pressure on a retaining wall. Whether it is justified to increase the strength of a wall to resist those forces is another matter entirely, which I will leave to others wiser than I.


In a message dated 7/21/09 7:09:18 AM, sgordin(--nospam--at) writes:
Maybe, this is due to the fact that the seismic soil pressures are so - to say the least - over-conservative? Does anybody on this List have a first-hand experience with the earthquake-induced sliding or overturning damage to a "regular" retaining wall (up to 12 feet tall, and not on a path of a larger landslide)? Thanks, V. Steve Gordin, SE
Irvine CA
----- Original Message -----
* From:* Garner, Robert <mailto:rgarner(--nospam--at)>
* To:* seaint(--nospam--at) <mailto:seaint(--nospam--at)>
* Sent:* Tuesday, July 21, 2009 06:52
* Subject:* RE: Retaining Wall Seismic Loads

We too follow our Geotech who frequently makes recommendations for revised safety factors as noted in this post. How can Geotechs "deviate" from The Code like this?

* From:* erik_g(--nospam--at) <mailto:erik_g(--nospam--at)> [mailto:erik_g(--nospam--at)]
*Sent:* Monday, July 20, 2009 8:54 PM
*To:* seaint(--nospam--at) <mailto:seaint(--nospam--at)>
*Subject:* RE: Retaining Wall Seismic Loads

* In the past when I added the seismic load to a basement retaining wall, the resulting footing was very large. I talked to the geo-eng and he said that I can use a F.S. of 1.1 for sliding & overturning, since the load is very short duration. If you do this the footing sizes are not so big. Just a thought. *

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