Sculpture Foundation

[XR250]

I need to design a 6'-6" x 4' concrete slab to support a 400 pound, 7 foot tall sculpture. The design loads are minimal so my reinforcing is basically there to control shrinkage cracking.
The slab is going to be 8 1/2 inches thick to get below the frost line and provide some amount of concrete below the epoxy anchors.
I was going to show the rebar mat centered top to bottom in the slab. Should I use more than the minimum of .2% reinforcing? Do I even need any?
Any other suggestions?

Thanks

 

[EZBuilding]

Have you considered overturning due to wind?

 

[XR250]

Yes, it ain't much

 

[phamENG]

XR - if this is going to be exposed so it acts sort of like a large but short pedestal, I'd be careful about the concrete spec and finishing to make sure it looks good. Otherwise, design for worst case of slab temperature/shrinkage strain and bending and call it a day. You could probably design it as plain concrete and get away with it, but there's a good chance you'll get some sort of cracking in there. Maybe a plain concrete slab with fibers? Finishing, though....

 

[XR250]

Thanks Pham.
It is going to be flush with grade so only the top is visible. I was going to spec slick finish.
Fiber vs. rebar - that is the question....

 

[jayrod12]

Fiber will require you to burn and scrape if there's going to be a slick finish. Just added labour for no reason. The reinforcing for this will be minor. And honestly I'd be putting reinforcing closer to the top if I'm doing a single mat, but I'd likely throw in #3 @ 12" each way top and bottom for good measure and sleep good at night. In reality the slab area is small enough that shrinkage cracking may not be a concern as long as the base is relatively level to avoid significant restraint on the bottom of the slab.

 

[dhengr]

XR250:
I’d try to slope the top of the ftg. slightly, to drain, away from the footprint of the sculpture. And, keep the top of the slab several inches above grade. I might consider thickening the ftg. under the footprint, by hand shaping/digging the for the bottom of the ftg., since 4 or 5” is not much A.B. engagement. As a lateral loading, I would consider 3 or 4 drunken college football linemen pushing on the sculpture about 5’ above grade, just for the fun of it, maybe to impress the cheerleaders.

 

[JoelTXCive]

I have done similar stuff and apply my own special load case for overturning.

I call it the "dumb high school senior prankster" loading scenario.

I would apply a 200 lb load chest high to make sure it doesn't overturn or your anchor bolts break out.

 

[XR250]

Thanks for y'all's insight.