I built these arches in 2013.. They go up very fast, just a minute or two. They have withstood 50mph winds.
i used 15' of 1/2" grey emt, flex strips cable tied on outside of pipe facing down. one 1/2" steel emt in the center of arche. this kept pipe vertical. i used paracord tied on the bottom edge, pull paracord until arch if formed. basically the arch is held up with one bolt in the center.