Have you tried using livestock fence panels? They are usually 48 inches tall by 16 feet long and made of 1/4 inch galvanized steel. I've been using mine for over ten years!!! They do not fall apart and can withstand strong vines twisting through the panels. And they are inexpensive - $16 to $19 each.
I have several 8 foot tall 'triangular obelisks' that I made from cutting the length of a panel in half then folded over into a triangle shape and tack welded to close the triangle. Also have gobs of arches made by simply cutting off the bottom 'rung' from each end and sticking one end into the ground then bending the 16 foot panel over to form an arch and pushing that end into the ground.
Here is an old link to a post where I showed photos. Hope it helps. ~ Cat
The new rage here in gardening are tomato cages (massive ones too) that look like they have been painted or powder coated all different colors. BEAUTIFUL and a great idea curling the edges like that.
I love it! have you done any? i'd love to see pictures. One year, I was caught off guard by a Rose of Montana that got out of control. I quickly put two tomato cages side by side, a pole in the middle where they intersected, and then hurriedly draped the vine over it. I think it looked really good.