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RE:ACI Code and single layer steel in 12" wall

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I've always understood "basement wall" and "top-restrained retaining wall" to be  interchangeable, as opposed to a "cantilevered retaining wall".  Some may argue that a basement wall is less than or equal to 8' in height (I'm open to suggestions).  In a basement for a building on a sloping lot, a cantilevered retaining wall  may look the same as a basement wall, but the horizontal diaphragm cannot resist the lateral top-of-wall forces. 

Also, I've interpreted section 14.4 to mean that the only wall that doesn't come under the 14.3 provisions is the aforementioned basement wall - which almost never needs to be >10" unless you get pretty darned tall - is a site retaining wall that isn't part of a building.  I suppose a 12" thick concrete partition wall would be exempt, too, but if you're considering something like that, there's probably a reason you want more reinf. in your wall.


At 04:56 AM 11/5/2004 -0800, you wrote:
What exactly does ACI mean by "except basement walls"?  Are basement walls defined as walls supporting earth on one side and exposed to accessible space on the other.  Or do they include any underground wall, e.g. a stem wall on a spread footing?
 
Is there another minimum provision for basement walls?
 
TIA,
Jim Wilson, PE
Stroudsburg, PA

Scott Maxwell <smaxwell(--nospam--at)engin.umich.edu> wrote:
Chic:

You are thinking of section 14.3.4 (in the 2002 ACI at least). It states:

"Walls more than 10 in. thick, except basement walls, shall have
reinforcement for each direction placed in two layers parallel with the
faces of the wall in accordance with the following..."

Section 14.1.2 might provide your "out", however. It states:

"Cantilever retaining walls are designed according to flexural design
provisions of Chapter 10 with minimum horizontal reinforcement according
to 14.3.3."

In addition, the commentary for 14.1 states "Chapter 14 applies generally
to walls as vertical load carrying members. Cantilever retaining walls
are design according to the flexural design provisions of Chapter 10."

Personally, I am not sure that I would put a single layer of steel at the
centerline of a retaining wall as it is more "e! fficient" to place it
closer to one side (i.e. closer to the side against the retained earth),
but it certainly seems to be permissible from the code point of view.

HTH,

Scott
Adrian, MI



On Thu, 4 Nov 2004, Chic Gilligan wrote:

>
> Any advice on designing a 12" thick retaining wall, 6' high and how it
> may conform with ACI Code (pretty sure they require two layers for 10" and
> thicker.) Structurally it works, but don't know how to address code issue
> of two layers. I want only one layer of steel at centerline of wall.
>
> Chic Gilligan, PE
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