You can take various approaches, and of course the complexity of your problem may require necessary complications. Basically, you will model your pile as a line element or as an arrangement of plates. If the pile is of variable section it will be a bit more complicated, but the alternatives are the same.
Now, do you refer to underground piles or columns that support buildings? A underground pile having trapecial web would be a rarety; conical piles there are and there are lookup tables for the mechanical capacities of them.
A H shape of trapecial web is a tapered member. In the elastic realm plus P-delta RISA-3D provides line elements for them (tapered webwise and flangewise), possible to check-design as well.
I also have posted Mathcad sheets of free download that serve to check the design of steel tapered members, in more than what on same the LRFD sheets have.
If the web itself in section is trapecial, either the plates modelling it will give stresses for design, or the traditional formulas for normal and shear stresses at a Bernoulli or Timoshenko beam you will use to determine stresses in the section.
If you have something more complicate you will be doing some nonlinear analysis with one able package (3D bricks even?), but this is outside my ordinary scope.