Slab On Grade
Slab On Grade
(OP)
Hello !
I have to design a slab on grade foundation for a small shelter. I have attached a sketch for this. The load due the shelter will be only around 30 KPa. If I design the slab for cantilever action that can cause due to frost upheaval, do I still need worry for some other stuff? It's no a problem if the shelter as a whole move upward or downward uniformly. Your thoughts on this will be much appreciated.
Thanks.
I have to design a slab on grade foundation for a small shelter. I have attached a sketch for this. The load due the shelter will be only around 30 KPa. If I design the slab for cantilever action that can cause due to frost upheaval, do I still need worry for some other stuff? It's no a problem if the shelter as a whole move upward or downward uniformly. Your thoughts on this will be much appreciated.
Thanks.
RE: Slab On Grade
RE: Slab On Grade
RE: Slab On Grade
RE: Slab On Grade
Yes. The frost heave could be hugging or sagging. I just assumed center upheaval because it gave me higher bending moment. As I can design the slab for maximum consideration, if bearing pressure is OK, do you think that the foundation should be frost protected ?
RE: Slab On Grade
- Remote location difficult to access?
- No building services that would be sensitive to movement?
Your concept would work I think. And, while it seems extreme at first blush, it may be an economical solution depending on your answers to the questions above.
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: Slab On Grade
I've never designed for upheaval as you suggested....but also always show insulation. I suspect the insulation or even a frost wall would be cheaper than designing the slab as you have proposed. See link below.
http://www.ecohome.net/guide/slab-grade-technical-...
RE: Slab On Grade
Dik
RE: Slab On Grade
It is for Winnipeg. Frost dept aroun 2.5 m. Air freezing index 3251 degree F. About 5 feet of silt and clay fill. I am thinking to replace about 3 feet of the fill and replace with gravel compaction. My bearing load is low around 30 KPA. 8 inch slab is good enough for maximum load that can be there if frost upheaval occur.
RE: Slab On Grade
RE: Slab On Grade
The document below is an excellent resource for designing stiffened slab on grades.
http://nebula.wsimg.com/8724fe0dc68dace148fa5880b8...
The method is essentially designs grade beams that deal with heave or loss of support at the perimeter of the building. When a portion of the soil loses support the grade beams act as cantilevered beams. This is mainly good for residential or light weight framed buildings. You can modify it of course if you have heavy walls like CMU once you understand the methodology.
This reference is actually still referenced in the Florida Building Code which means it is also probably still referenced in the International Building Code. But I figure the frost heave and expansive soil issues will be very similar since both involve volume changes of the soil supporting the building. Check it out it is a pretty good resource.
John Southard, M.S., P.E.
https://www.pdhlibrary.com/
RE: Slab On Grade
Dik, also from Winnipeg...
RE: Slab On Grade