Method for calculating pole foundation deptt, IBC equation 18-1
Method for calculating pole foundation deptt, IBC equation 18-1
(OP)
Hello,
I am using IBC equation 18-1 to calculate the depth of a pole foundation. I'm comfortable with this method, although it does lead to a larger than expected pier foundation (3' diameter, 6.5' depth). Still, it's a small amount of concrete and the bulk of the cost of the construction will be the mob and setup of the drill.... so I'm not too bothered with the size.
My problem is that my design reviewer is giving me lots of push back to reduce the size by incorporate the weight of the concrete footing as a resistance to overturning and as an added resistance to lateral load due to the friction at the base. However my understanding is that the methods described in IBC 1807.3 does not account for either of those things. We've discussed this, but without any success. Perhaps I am missing something, can anyone clarify if I should incorporate the weight of the concrete into my design calcs using this method?
Notes:
- The axial load is minimal (weight of a column) in my design; it is very much a lateral load, creating a moment at the foundation.
- I've allowed for the 1/2" movement by doubling the lateral bearing pressure.
I am using IBC equation 18-1 to calculate the depth of a pole foundation. I'm comfortable with this method, although it does lead to a larger than expected pier foundation (3' diameter, 6.5' depth). Still, it's a small amount of concrete and the bulk of the cost of the construction will be the mob and setup of the drill.... so I'm not too bothered with the size.
My problem is that my design reviewer is giving me lots of push back to reduce the size by incorporate the weight of the concrete footing as a resistance to overturning and as an added resistance to lateral load due to the friction at the base. However my understanding is that the methods described in IBC 1807.3 does not account for either of those things. We've discussed this, but without any success. Perhaps I am missing something, can anyone clarify if I should incorporate the weight of the concrete into my design calcs using this method?
Notes:
- The axial load is minimal (weight of a column) in my design; it is very much a lateral load, creating a moment at the foundation.
- I've allowed for the 1/2" movement by doubling the lateral bearing pressure.





RE: Method for calculating pole foundation deptt, IBC equation 18-1
Mike McCann, PE, SE (WA)
RE: Method for calculating pole foundation deptt, IBC equation 18-1
RE: Method for calculating pole foundation deptt, IBC equation 18-1
Bob
RE: Method for calculating pole foundation deptt, IBC equation 18-1
So unless you get approval from the building official I would only use EQ 18-1 for the design.
Garth Dreger PE - AZ Phoenix area
As EOR's we should take the responsibility to design our structures to support the components we allow in our design per that industry standards.