Concrete foundation treated like a base plate and eccentricity question

[AlexH15]

Hello,

I am currently designing a concrete foundation that fits into an area of 6m wide x 7m deep x 1.2m thick. It will be holding a large belt winder that will create lots of shear and torque on the foundation. The moment and shear are so large that i need to anchor the foundation into the rock below it. Now that I am trying to find the bearing on the foundation I figured I could treat it like a base plate. Is this an ok assumption? Also my moment is so large that M/P = e is larger than the size of the foundation (i.e. e>N). I cant find anywhere that says this isnt ok but my instinct tell me it shouldnt be OK.

a basic sketch is attached that might help out

Thanks,

ah

 

[ishvaaag]

One problem that may develop is the foundation moving as much that it shears or breaks the anchors. Hence some length of the anchors needs to be ungrouted, and the entry to the anchored part preferably be flared to ease stress concentration. The anchor cables or bars need be designed for fatigue. The encasement in the rock may ease the expected displacement, but its strength checked for the dynamic solicitation. As long as both the rock and anchors work for enough cycles the scheme may be viable, but ensure no other unexpected worse situations may develop (for example not anchoring a side that may need eventually to be restricted from lift could be dangerous with a foundation unable to counterweigh the lifting force).

Being underground, count a way or other with any potential corrossion that may affect the anchoring system.

The contraption being a foundation for dynamics loads requires either a conservative and simple approach (that might require even more massive foundations) or a FEM structural model and analysis that cares for the relevant factors of its dynamics.