Create the different shaped steps as 3d objects.
Either an extruded rectangle or quadrant.
As for the railings, just extrude a circle to the correct height.
Then join them all together in the order you want.
I take it that's your model and you want to put a balustrade on top of
I would make a 3dpolyline, snap to the tops of the banisters, PEDIT then
Spline the poly, once you spline you will have a spiral shape but it
will no longer be snapped to the railings, so then I would put the
drawing in plan view, select the grips of the 3d poly and move them so
the curve passes over the center of the railings, should be fairly quick
and easy to do. then sweep or extrude along path.
or, as suggested, get architectural desktop :P
Polytechforum.com is a website by engineers for engineers. It is not affiliated with any of manufacturers or vendors discussed here.
All logos and trade names are the property of their respective owners.