ibc section 1805.7.2.1 logical error

huangyhg

ibc section 1805.7.2.1 logical error?
ibc equation 18-2 for calculating the depth "d" of a non constrained pole foundation seems to have a circular logic. the item "a" in the formula is calculated using "s1" which in turn depends on the depth d.  the equations can be solved by assuming a depth d and varying it until the assumption and final answer converge, but somehow i am not sure this was the intent of the code writers. am i missing something?
does anyone have a reference to literature on which this approach is based?  thanks
it's always been that way.  as far as literature, i've got a reference to "pole building design" by donald peterson 6th edition (1969) by the american wood preservers institute.  however, i don't have that reference.
does it mean that you get an allowable soil pressure based on a rough "d" (i.e. at d/3 depth) and then find the true d and simply make sure your actual d/3 is in the same general type of soil that was originally found?
in other words, don't you generally know what the approximate depth is anyway, with that rough range of "d" you then get the allowable soil pressure for that zone of soil type found near that depth, and then solve for d?
that's what i always do.
jed, this is the first time i've used those provisions, so they are not familiar. jae, yes that was what i was trying to confirm.  thanks for your replies.