Create a square spiral along a bridge curve

Hi I held on for years to this piece of paper that would be folded around a square or rectangular volume along a modern type of Madison covered bridge . Either from one side only like an elefant tusk or two similar meeting with thinner part in the middle (I imagine) I think the thicker part in the middle would be to heavy.

How would I go about it?
In my mind I would draw a path flat then offset it on a face then pull or extrude along
Or do I first extrude the spiral along a thickening volume and then pull or extrude along a likely bridge curvature over a body of water (like my glass) maybe in glass or perforated lightweight mesh pattern?
I am NOT a civil engineer so its only a concept naturally.
Thank you very much for any of your amazing advice as usual.