Bearing area for base plate with grout

[smvk3]

I have a 17" square baseplate sitting on a 7' square spread footing with 2" grout. When checking the bearing of the concrete, is the bearing area "A2" the area of the baseplate or is it (17" + 2*2")*(17" + 2*2") assuming the grout spreads out at a 45 degree angle on all sides? Or is it the smaller of the footing area, which is limited by 1.7*f'c*A1 where "A1" is the area of the base plate.

 

[KootK]

By the book, you've got two checks to do:

1) Bearing stress on the footing based on an area equal to the area of the grout that is in contact with the footing. for this check you can increase the bearing stress for confinement.

2) Bearing stress on the top of the grout base. This is the one that always makes me wonder. If I'm confident that the grout base will spread out at 45 degrees, can you increase bearing based on confinement? I usually don't because a) I don't trust the construction quality and b) generally the grout is of a high enough strength that it doesn't matter anyhow.

The greatest trick that bond stress ever pulled was convincing the world it didn't exist.

 

[smvk3]

On our general notes, we simply call out that a non-shrink grout must be used. Typically, what is the compressive strength of grout?

 

[KootK]

Something like Sika 212 comes in around 50 MPa.

The greatest trick that bond stress ever pulled was convincing the world it didn't exist.

 

[hokie66]

I use the area of the base plate. The chamfer is not guaranteed to be done, and if it is, it is not guaranteed to stay there.

 

[jayrod12]

Put my hat in the baseplate area group. It's more conservative and easier because I don't have to think about how much grout I'm providing, and if the contractor asks to change the grout thickness (either up or down) I'm not concerned.

 

[dcarr82775]

For the grout, it is the area of the baseplate. The grout is typically, but not always, a good bit stronger than the concrete below.