4" thick cip walls in SDS D

[Prestressed Guy]

Is it permissible to design a bearing wall structure with 4” thick x 8 foot tall cast-in-place concrete walls in SDS D? The building has lots of wall so the shear stress never exceeds 1 square root, therefore can be reinforced to 14.3 levels per 21.9.2.1. Analysis indicates that I can get a 4” wall to carry all gravity and lateral loads. Is there any code reason that prevents me from using a 4” wall.

The only thing that I can find that mentions wall thickness is ACI 318 section 14.5 – Empirical design the thickness shall not be less than 1/25 the height or length but not less than 4.

 

[vandede427]

well, chances are you not designing this with the empirical method, but H/25 would limit you to 8'-4"

will this wall be formed on both side? b/c if so, you could have very bad voids, honeycombing, and consolidation issues.

also, in order to meet 1-1/2" cover each side, your bars could not be larger than #4, and that's in the perfect world where rebar is placed straight and plumb.

here's my two cents. it seems like you're limited to a 4" thickness b/c nobody would do this unless they absolutely had to. I'm betting that a 4" CMU wall would be a better finished product than a 4" CIP wall.

If it's one-sided, have you considered shotcrete?

 

[Prestressed Guy]

Thanks for the response.

You are correct that I am not using the Empirical method but if I can use 4” there it should be easy with rational design.

The forms will be ICF so bar placement is a function of the form ties and very accuracy placed. The horizontal reinforcement is snapped into ties on either side of center and the vertical bars are dropped in between. The exterior face has weather tight siding so the concrete is not exposed to weather and cover is only ¾”

The mix I use has a high percentage fly ash, 3/8” pea gravel, super-p and a viscosity modifier. It flows very well with a slump of about 7”. Think of this mix as a thick SCC. Internal vibration with a ¾” pencil vibrator in this mix yields pretty dense concrete.