Floating Slab vs. Stem Wall Foundation for Grain Storage bins
Floating Slab vs. Stem Wall Foundation for Grain Storage bins
(OP)
I have been asked my opinion on what seems to be a rather large floating slab. The problem is that I am a steel connection/erection engineer and have little to no experience in the Grain bin foundation field.
The bin is 48'(diam)x74'(wall height) with corrugated steel walls (Sukup design). We're assuming 4000 psf soil capacity. The initial numbers (from consultant) are of a floating slab with a max diameter of about 56'(inside diam of donut is 40'). This doesn't fit the area the owner wants to put the bin, so we're wondering whether a ring wall or stem wall foundation would reduce the footprint of the foundation. Seems to make sense to me, but the EOR has said it typically doesn't.
If someone could give me a little insight into this process I would really appreciate it. Even a yes or no would set the record straight.
Thanks,
Lindsay
The bin is 48'(diam)x74'(wall height) with corrugated steel walls (Sukup design). We're assuming 4000 psf soil capacity. The initial numbers (from consultant) are of a floating slab with a max diameter of about 56'(inside diam of donut is 40'). This doesn't fit the area the owner wants to put the bin, so we're wondering whether a ring wall or stem wall foundation would reduce the footprint of the foundation. Seems to make sense to me, but the EOR has said it typically doesn't.
If someone could give me a little insight into this process I would really appreciate it. Even a yes or no would set the record straight.
Thanks,
Lindsay






RE: Floating Slab vs. Stem Wall Foundation for Grain Storage bins
Try a square slab rather than round to fit the property better.
Check with the geotech to see if there are other options- higher bearing at deeper depths, or use piers, or possibly higher bearing with increased allowable settlement.
If the design does not allow partial uplift with wind loading, consider removing that restriction.
RE: Floating Slab vs. Stem Wall Foundation for Grain Storage bins
This isn't too far off from the floating slab size proposed.
Since this doesn't fit your site, have you considered drilled piers and a cap slab?
RE: Floating Slab vs. Stem Wall Foundation for Grain Storage bins
Another question. I'm having a hard time finding good info on the pre-engineered bins themselves. Do the contents of the bins typically bear on the slab (reduced to 8" in the middle of the donut), or is the load carried out to the increased depth donut?
RE: Floating Slab vs. Stem Wall Foundation for Grain Storage bins
You need to get plans from the bin manufacturer to verify exactly how it is loading the slab.
RE: Floating Slab vs. Stem Wall Foundation for Grain Storage bins
Anything other than a symmetrical found. about the bin wall system starts to get more complicated, because the stab canti's. w.r.t. the bin wall get longer and shorter. Drilled piers are certainly a possibility, and they should be symmetrical with the bin wall too, and they may have a ring beam on top of them to deal with their concentrated found. loads vs. the relatively uniform bin loadings, and punching shear in the slab. They would allow you to reduce the outside dia. of the doughnut, but would probably not be less expensive.
RE: Floating Slab vs. Stem Wall Foundation for Grain Storage bins
I think it a good idea to have this information before going off on various support systems any of which might be appropriate depending on the answers above.
Perhaps, too, and I am sure that most are aware, there have been some very classic silo foundation failures in the past - the Strathscona failure being a prime example. One may also see reference to another failure in Tschebotarioff's Foundation Book (1951) where a silo was placed on a stiff clay overlying a softer clay. Bozozuk also talks about silo failures (see National Research Council of Canada).
RE: Floating Slab vs. Stem Wall Foundation for Grain Storage bins
RE: Floating Slab vs. Stem Wall Foundation for Grain Storage bins
Thank you all very much for your help.
Lindsay
RE: Floating Slab vs. Stem Wall Foundation for Grain Storage bins