On the official Alias site there is a video tutorial on modeling a spiral staircase:
http://www.alias.com/eng/community/tutorials/index.jhtml;$sessionid$UNGAV1RHWYUQNQCLCWSCFEWAJMK0KIV0
That's a start.
http://www.alias.com/eng/community/tutorials/index.jhtml;$sessionid$UNGAV1RHWYUQNQCLCWSCFEWAJMK0KIV0
That's a start.