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Re: Retaining Wall Loading

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If your structure is in a seismic zone, then definitely you should include H
and E in your load combinations. The dynamic effect of the seismic force in
a retained mass of soil was studied by Mononobe and Okabe as a particular
case of the Coulomb theory, which assumes a wedge of soil exerting a
pressure against the wall.

Unlike your statement that the soil seismic load becomes less severe than
the original pressure, this dynamic effect actually increases the static
pressure H due to the dynamic force from the soil wedge. In addition, if the
wall has a heel, the inertia force from the portion of the backfill above
the heel should be considered too.

Javier Encinas
ASDIP Structural Software

-----Original Message-----
From: J. Karim Hosseinzadeh <jkh(--nospam--at)>
To: seaint(--nospam--at) <seaint(--nospam--at)>
Date: Monday, May 01, 2000 4:31 PM
Subject: Re: Retaining Wall Loading

>I know this answer is late, but I now have a similar design situation and I
>am pondering against my past experience, whether I should combine earth
>pressure with seismic. UBC 97 Code sections 1612.2.2 & 1612.3.3 don't say
>that H "should be" combined with seismic, what it says is, "where H is to
>considered" it should be added to the basic load combination. Now the
>question is "where" do we consider H. I have always been taught to ignore
>seismic forces acting on the portion of the building which lies underground
>such as a basement. The reasoning is that the inertia forces of the
>earthquake and the ground movement are in opposite direction. Therefore the
>retaining wall either moves away from the retained earth or pushes against
>it. At either case the load acting behind the wall becomes less severe than
>the original earth pressure.
>I would be interested to know if there are any hard rules about this
>J. Karim Hosseinzadeh
>JAMKAR ENGINEERING, INC.               Tel. 949 250 0522
>Newport Beach, California                            Fax 949 250 1527
>----- Original Message -----
>From: <RainCat1(--nospam--at)>
>To: <seaint(--nospam--at)>
>Sent: Wednesday, April 19, 2000 5:03 PM
>Subject: Retaining Wall Loading
>> Are seismic loads applied to a retaining wall in combination with the H
>> UBC97 section 1612.2.2 & 1612.3.3 indicate that the H load should be
>> with seismic. ASCE 7-95 does not give load combination that include E &
>> Could anybody shed light on this? Thanks a lot!
>> Rainier C. Catubig, S.E.
>> San Diego, California