Please note that due to rigid corner walls, soil arching develops. The
amount of lateral forces(ko) s onto the short span of the wall will be
reduced. But even then, using the code, I find that shear in walls are
always a problem in buried structures.
>Subject: STR. DESIGN OF BURIED STRUCTURE
>Date: Mon, 19 Apr 99 08:35:37 EST
> I am seeking some comments with regard to the design of a
> deep wet well which will contain a submersible pump to
> discharge storm water. The structure will be a square box
> (4' x 4' interior dimensions) that extends from the ground
> surface to a depth of 32 ft. below grade. The structure
> will be reinforced concrete and is subject to an equivalent
> lateral pressure of 100 lbs/ft^3 (i.e. lateral pressure =
> 100 * depth). Utilizing PCA's "Rectangular Concrete Tanks
> Book", and with ACI 350 in mind, I'm getting a wall
> thickness at the bottom of the structure in the
> of 22" thick (shear design controlling). The client thinks
> this is ridiculous and we're over-designing. They also say
> they have never seen anything over 18" thick and usually
> it's 12" thick.
> What typical wall thickness have others arrived at for
> types of buried structures ?
> We are not utilizing shear reinforcing in the corner of the
> tank to handle shear (only the concrete's ability to take
> the shear). We are thinking it will be easier to construct
> with minimal rebar and more concrete. Any different
> philosophies out there ?
> Thanks in advance for any help.
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