Think stiffness. The load distribution to a structure with various element configurations (concrete, steel, plumb, batter, etc.) is a function of the relative element stiffness.
For example, in a pier bent with 10 vertical piles and 2 batter piles, the batter piles will take probably 90 percent of the lateral load. That is because the axial stiffness of the batter piles is much higher than the bending stiffness of all of the vertical piles (assuming they are relatively long).
I can give you a better explanation with respect to your specific case if you can provide more details. In the meantime, an excellent reference (if you can find it) is the Handbook of Port and Harbor Engineering - Geotechnical and Structural Aspects by Gregory P. Tsinker. Section 7.8.2 has a whole discussion with theory, formulae, and application. This book may still be in print, but I don't think you will find it easily unless you work in a marine engineering office. It's not old either - 1996. If you are really in a bind, I can copy the 10 pages and fax/e-mail them.
Hope this helps. Reply with more details if you need more info.
Steve Famularo
OCC