Insulated Slabs on Grade
Insulated Slabs on Grade
(OP)
I am designing an insulated slab on grade at cooler/freezer rooms on an industrial project. We have rack loads of 20 kips max. I am looking for good design examples taking in consideration the properties of the insulation i.e. subgrade modulus, compressive modulus, flexural modulus. I have attached a decent breakdown in a document that I found published by owens corning and wanted others opinions. If there are any industry design guides that I could download for free, please let me know.
Thanks!
Thanks!






RE: Insulated Slabs on Grade
There are several threads on eng-tips... do a search
Dik
RE: Insulated Slabs on Grade
That's not my call. I'm simply designing the concrete slab.
I found the following, which answered my concerns about using the insulation's subgrade modulus or the soils subgrade modulus:
ACI 360R-44 section 13.2.1 - Insulation Modulus - "For slab-on-ground design, the strength of the soil support system directly below the slab is considered. In the case of a floor in a refrigerated building, consider the strength of the insulation in a similar manner. Some design methods use the modulus of subgrade reaction to account for soil properties. Insulation has a similar modulus."
RE: Insulated Slabs on Grade
RE: Insulated Slabs on Grade
Do you mean the insulation's subgrade modulus? This is given by the manufacturer. Owens Corning gives design examples. Freezermate gives design calculations as well, but doesn't do as good of a job in examples. Both list the subgrade modulus values on their websites. The values are much higher than the typical soil subgrade modulus values. For my design, the subgrade modulus for each layer was 610 pci. The subgrade modulus for the two layers that we're using is 305 pci. you typically divide the values they give by the number of layers because each layer will deflect. I was worried that the soil subgrade would need to be considered, but I think this is typically ignored. I'm assuming that as long as the stresses on the insulation are lower than the allowable stresses, the modulus of subgrade for the insulation is valid.
RE: Insulated Slabs on Grade
I am surprised how high the values are. For 4" of a low grade insulation (Foamular 150) you still get 300 pci - about double that of a decent subsoil.
PCA suggests using 75 pci conservatively in lieu of manufacturers data.
RE: Insulated Slabs on Grade