Void form under grade beam on interior of building? 1

[matty54]

Hi there,
I have a pile foundation supporting a PRMB connected on the perimeter with grade beams and void form underneath. I would like to run grade beams through the interior of the building from one pedestal to another but I am wondering if it is necessary to have void form under the interior grade beams and if so would I need to have the void form only in the area where it connects to the exterior piles? Am I defeating the purpose of the void form if I connect the interior grade beams to the exterior foundation without void form under them? My main reason for wanting the grade beams is to help support lateral forces from the exterior columns

 

[jayrod12]

The void form is intended to prevent soil uplift on the underside of structural elements. If you don't expect any sort of soil heave/swelling, then it wouldn't be necessary.

 

[matty54]

Yes, I guess I am wondering for underneath a heated building if you are expecting heave around the perimeter grade beam, should you expect it just inside the building footprint as well?

 

[jayrod12]

Maybe not, consult the geotech is probably the best place for an answer on that. What's the subgrade material in that area?

 

[matty54]

sand and gravel down for about 4m on top of glacial till. ground water is around 2m down

 

[jayrod12]

I'd be inclined to say no, there doesn't really seem to be heave susceptible soil. But I'm just a stranger on the internet, I'd get the project geotech to confirm.

 

[dik]

See reply in the other thread in Earth Retention Engineering. Try not to double post.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[matty54]

Thanks dik, I accidentally started this thread in the wrong forum. The soil in question is not really expansive, but some areas of the foundation will be above the frost line, which is why we are using the void form around the perimeter.

 

[CarlB]

If it's a continuously heated building, then frost should not penetrate below grade within building's interior. And if perimeter insulation employed per standards of Frost-Protected shallow foundations (ASCE 32), there should not be frost concerns for perimeter foundations either. The geotechnical engineer should be able to address those issues.

 

[dik]

bang on CarlB...

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[matty54]

Thanks CarlB