Conduit normally requires support on both sides as it is being bent otherwise it tends to go oval shape. If you bend it to sharply it will flatten out in one spot. Will work fine with rebar.

If i was making this i would use conduit instead of rebar. Use half or three quarter and the correct bender. If you want a long arc use the bender to make a series of short bends that blend into a long arc. Might take a couple of practice pieces before you like the way it looks. Or you can make a few sharper bends and make the sides and the roof lines flat, easier to bend. And there are all kinds of connectors for joining conduit together. Take a trip though your local electric supply, might give you a few ideas.

Don't know if this is what you want but it might be something to think about.

http://www.shedandshelter.com/syntheticcovering/syntheticcovering.htm

There are several plans made with short section of conduit and the tools required would be a hammer, drill, and a saw.