MC: Older designs (or new designs in parts of the world where labor is cheaper than material) use more complex stirrup arrangements or cranked longitudinal bars.
Kiangan: I'm not sure what your "minimum area" is referring to -- do you mean designing an efficient truss of rebar (that will never see concrete)?
Or do you mean using a truss analogy method to size the rebar for an eventual reinforced concrete structure?
If the former, you'll have to put a lot of consideration into the connections between rebar. I have analyzed rebar cages for temporary situations prior to pouring concrete, and there are definitely some basic assumptions that you'll want to revisit -- if that is the direction you're heading, let us know and we can elaborate.