Post Frame Post Embedment lenght

[Tom Olson]

I'm currently designing a post-framed building, and I'm trying to determine how deep to embed the posts. I'm designing as an unconstrained post with no collar. I'm using the equation: D^2=(6Va+8Ma/d/S'b). Can anyone tell me how to calculate the S' in the equation. I'm using 200 psf for the lateral soil.

 

[jayrod12]

the version of EP486 I have shows it as just S not S', I've used 200 for this value for all of the posts I've designed. Maybe I'm doing it wrong, but nothing bad has happened yet.

 

[Polecat]

Tom,
Without any soil data, you could use the formulas from the FL Building Code along with their Presumptive Soil Pressures. You can access the code free of charge here:

https://codes.iccsafe.org/public/document/FBC2017

You cannot print or search the document, but you can browse thru it.
Foundations are in Chapter 18, and you'll want to specifically reference the following:
Section 1807.3.2.1, using the soil pressures found in Table 1806.2
The value of S1 is the lateral pressure given in that table, which show 200 psf/ft as the presumed lateral pressure for Sandy-Gravel. You can replicate the formulas in Excel and use Solver to determine the depth.