The fact that the ends of the half arch do not meet the abutment is quite odd. Loads must be transferred up to the stringer and horizontally to the abutment wall.
You have posted photos of some of the most famously beautiful bridges in this country. Here in the Midwest we see films shot on these locations and wish we could see more of the bridges. Very nice work.
Interesting engineering and design. The approach arch on each end of the bridge is actually an unsupported or cantilevered half arch. I would be much interested in more information or discussion of this detail.