Sizing a bearing plate for a concrete slab

[Natterre]

I need to put a piece of equipment on top of a concrete slab. The slab has a rating of 250 pounds/square foot. The piece of equipment is 13,000 pounds. I would like to place a piece of plate on top of the concrete to distribute the weight out so I am under the weight limit of the slab. The question is how thick should the pad be? Is this just as simple as it needs to be stiff enough to transfer the weight? There is a similar thread, 507-168721, but it was never answered. Thanks.

 

[Once20036]

Hire an engineer.

 

[TehMightyEngineer]

Short answer is above by Once20036.

Long answer is it depends on a lot of things but likely is controlled by the strength required to transfer the weight to an area wide enough that doesn't overload the concrete. There's many other considerations as well (anchoring, correctly locating above supports, ensuring the slab isn't overloaded for the 250 PSF load limit, etc.).

This isn't the most complicated topic but if you're unsure of even where to begin in designing an equipment bearing pad then I'd recommend some reading or seek an engineer experienced in such a design.

Professional Engineer (ME, NH, MA) Structural Engineer (IL)
American Concrete Industries

http://www.americanconcrete.com

 

[TLHS]

If you're going to use something reasonably flexible like a plate, it becomes a beam on elastic foundation problem, which is going to take a fair amount of experience to set the parameters for in a realistic way.

Honestly, you may not actually need to do anything if the rest of the floor is lightly loaded, or you may need to do things you didn't expect if there was a live load reduction used on that number, or if there's seismic overturning on the equipment.

Hire someone local to come and look and throw something together.