Moment Frame Foundation

[333OnlyHalfEvil]

Hey everyone,

I was just curious how everyone is designing foundations for moment frames. Do you do it by hand or do you use software? How do you do the triangular bearing pressure calc when resisting overturning? Does anyone have an example calc they can post?

Thanks.

 

[DaveAtkins]

I assume you are talking about a moment frame with fixed bases (pinned bases are simple).

I design the footing by hand. First, I check the maximum bearing pressure due to service loads. If the load is inside the Kern, the maximum bearing pressure is P/A + M/S. If the load is outside the Kern, the maximum bearing pressure is 2P/3aB, where a = L/2-e, L is the length of the footing, and B is the width of the footing. If the load is off the footing, then you need a bigger footing.

Then, you need to recalculate the bearing pressure using ultimate loads. Design reinforcing for the moment, check punching shear, and make sure the bars you choose are developed.

DaveAtkins