Also take a look at the footings - the are angled towards the center to take the compression loads from the bottom members.
Luke- Very interesting reading description of the bridge in your link. It seems it was built as a cantilever and converted to an arch at completion. The highest connection at the abutment was under tension supporting the cantilever until the opposite sides were ready to join. At that point the load was shifted from tension at the abutment(s) to compression at the center of the structurer making it an arch with a pin connection. Two 80 foot side spans went from being anchors for the cantilever to simple spans. 240ft. for the longest span and 400'6'' plus the two 80' side spans.
This bridge was still standing in late June of 2017, although part of the timber approach is collapsing. I'll post my photos of it in the near future.
Switchback Arch was the original name the railroad gave it, and the historic article explains how it functions as a 3-hinge arch: https://books.google.com/books?id=RDUxAQAAMAAJ&pg=PA218&dq=S...
White Pass & Yukon RR is still running during the Summer.
How is this an arch? It is a cantilever design.
The railroad refers to it as "Steel Bridge" and since they own it I expect that is the proper name.
I don't have a measurement but when built it was considered the tallest cantilever in the world according to the railroad.
Owners claim construction date of 1901.
bridge destroyed. Source: On Google Earth and the pictures placed there by tourists
What an interesting design. It must have been a fun search to find these pictures.