Grade Beam Detail Question
Grade Beam Detail Question
(OP)
I have always seen grade beams poured separately from the slab at grade level with dowels going from the grade beam into the slab. What is the disadvantage of pouring the grade beams integrally with the slab on grade (example 2'-0" deep grade beams)? I am figuring this it must be an ease of construction condition to do the pours separately but I am not sure why.
I know that elevated floors are required to have the beams cast integrally with the slab which I am more familiar with than grade beam supported slabs.
I know that elevated floors are required to have the beams cast integrally with the slab which I am more familiar with than grade beam supported slabs.






RE: Grade Beam Detail Question
In the separated circumstance of the slab-on-grade, it is easier to deal with temperature and shrinkage issues in the slab.
Also, if this grade beam is a tension link, then it would be better to allow the slab to float on top of the grade beam with no connection between the two.
So the answer to your question is not so much economics, as how you model the interaction of the two in your structural solution to your foundation design.
Mike McCann
McCann Engineering
RE: Grade Beam Detail Question
I had forgotten I just designed a 'ribbed' slab last year for a slightly expansive soil area and I detailed the slab to be cast monolithically with the grade beams. It did not require deep foundations.
The existing project I am looking at now was done in south Louisiana so I am pretty sure it is expansive soils. It is a structural slab supported by hundreds of interior timber piles with grade beams only around the perimeter. And the slab is cast separately from the grade beams with dowels going from the beam into the slab.
There are tilt panels around the perimeter so I think the idea was to add some stiffness around the perimeter to carry the walls, and other than that the 8" structural slab was sufficient at the interior. I am not really sure why he didn't just cast the the grade beam monolithically with the slab around the perimeter though. By adding all the dowels, he did restrain the shrinkage of the slab at the perimeter to some extent, and there are no tension tie beams.
RE: Grade Beam Detail Question
Really, in most concrete, with adequate reinforcing throughout the sections, whether you have a joint or not really doesn't always affect the behavior of the concrete structure once completed.
I do agree with Mike above that maybe some shrinkage issue was thought about.
RE: Grade Beam Detail Question
Are the wall panels sitting on the perimeter beams or on the slab edge?
RE: Grade Beam Detail Question
Due to the piling, there will be little if any settlement of the slab. If the tilt-up walls are not on piling too, they could settle/heave differentially with respect to the slab. Perhaps this is why they are not tied?
Mike McCann
McCann Engineering
RE: Grade Beam Detail Question
RE: Grade Beam Detail Question
RE: Grade Beam Detail Question