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White Pass & Yukon - Switchback Arch Bridge

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White Pass & Yukon Railroad

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View this photo at wpyr.com

Map 

Facts 

Overview
Abandoned arch bridge over White Pass on Abandoned White Pass and Yukon Railroad
Location
Skagway, Alaska
Status
Abandoned
History
Built 1900; Abandoned 1969
Builders
- Atlantic, Gulf & Pacific Co. of New York City, New York & Sacramento, California (Designer)
- E.C. Hawkins (Chief Engineer)
- George W. Catt (Chief Engineer)
- H.S. Wood (Designing Engineer)
- Michael James Heney of Cordova, Alaska
- Puget Sound Bridge & Dredging Co. of Seattle, Washington (Contractor)
Railroad
- White Pass & Yukon Railroad (WP&YR)
Design
Cantilevered 3-hinge Triangular steel arch
Approximate latitude, longitude
+59.60353, -135.14214   (decimal degrees)
59°36'13" N, 135°08'32" W   (degrees°minutes'seconds")
Approximate UTM coordinates
8/491977/6607267 (zone/easting/northing)
Quadrangle map:
Skagway C-1 SE
Inventory number
BH 50039 (Bridgehunter.com ID)

Update Log 

  • August 13, 2017: New photos from Jann Mayer
  • August 11, 2017: New photos from Luke
  • July 4, 2017: New photo from Luke
  • December 17, 2016: Updated by Christopher Finigan: Added categories "Pin-connected", "Riveted"
  • November 15, 2014: Updated by Luke: Edited builders
  • November 18, 2012: Updated by Luke Harden: Updated history section
  • January 5, 2012: Updated by J.P.: Added category "HAER documented"
  • November 4, 2011: Added by Nathan Holth

Sources 

Comments 

White Pass & Yukon - Switchback Arch Bridge
Posted August 13, 2017, by Jann Mayer (jannmayer [at] gmail [dot] com)

Also take a look at the footings - the are angled towards the center to take the compression loads from the bottom members.

White Pass & Yukon - Switchback Arch Bridge
Posted August 12, 2017, by Ed Hollowell (erhollowell [at] aol [dot] com)

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.

White Pass & Yukon - Switchback Arch Bridge
Posted August 11, 2017, by Jann Mayer (jannmayer [at] gmail [dot] com)

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.

White Pass & Yukon - Switchback Arch Bridge
Posted August 11, 2017, by Luke

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 - Switchback Arch Bridge
Posted August 11, 2017, by Ed Hollowell (erhollowell [at] aol [dot] com)

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.

White Pass & Yukon - Switchback Arch Bridge
Posted July 4, 2017, by Luke

The bridge still shows up in Google Earth...

White Pass & Yukon - Switchback Arch Bridge
Posted July 4, 2017, by John Smith (bridgehunter [dot] com [at] aol [dot] de)

bridge destroyed. Source: On Google Earth and the pictures placed there by tourists

Switchback Arch Bridge
Posted November 5, 2011, by Craig Philpott (cphilpott [at] puc [dot] edu)

What an interesting design. It must have been a fun search to find these pictures.