I-Beams in Soldier Piles

[bruinboy]

I'm trying to size the steel for a concrete soldier pile and was wondering how I model the beam when determining the point of zero shear. I modeled it as a cantilever beam, with the very end of the pile embedded in bedrock considered fixed. Then I found the point of zero shear by summing the passive and active forces. I then took moments around that point, but only above that point to size the steel. The building official who I talked to told me it was wrong to model it as a cantilever beam. Am I doing this right? I'd be happy to provide any more info, thanks. My reference by the way is the alternate design example in the CalTrans Soldier Pile Systems manual.