I'm pretty sure this will work for you - Add a new frame property using Section Designer type, not the standard concrete or steel shapes. Choose concrete column design and click "section designer" button. Use concrete column draw option and click in the center of the screen to draw/add it.. the circular concrete section is part of the list of icons which has the square with a dot in the middle as the first shape. If your pile is 36" circular, for example, draw a circular solid concrete shape, then right click it to specify diameter and choose reinforcing "yes". Next, in SD draw a steel pipe shape at the centroid of your solid concrete circle then right click the steel pipe to change the diameter and wall thickness for your casing. After you've done that, right click your concrete section to specify rebar details. You should now see PMM interaction surface for design, and moment curvature as well. The pile section should behave as a composite steel/concrete section as you defined it. I'd be curious to know if this doesn't work.
