RISA Foundation - apply multiple loads to single spread footing

[mcdermott2]

I have a vertical tank on a circular base plate four anchor bolts. I modeled the tank in RISA 3D with 4 pins (each representing one anchor bolt) and as such have four nodes where I have reactions.

When I bring this over to RISA-Foundation, I would like to size a single spread footing to handle these loads. If I apply a single spread footing to a node that is in the middle of the four nodes, the point loads are not applied at the top of the spread footing.

What is the best way to model a spread footing with multiple loads like this?

My current method is to model things differently - instead of modelling where I have 4 pins, I just included a single fixed boundary point in the middle of the bolt circle, and use those results for my spread footing design. This does work, but I wanted to reach out to see if there are other ways that people suggest going about this.

 

[BadgerPE]

This is a little late, but since it sounds like you may do something like this frequently, here is my response.

When analyzing multiple points from 3D in Foundation, I would not use the spread footing function. Instead, I would draw in a slab element in Foundation. If this is sitting on piers on top of the footing, you can then draw a pier at each support point to fully capture reactions as they are generated from 3D forces.