Friday, July 7, 2017

Coplay-Northampton Bridge of Lehigh River

(Bridge Hunter, Historic Bridges, 3D Satellite)

Lehigh Valley History posted
The Coplay-Northampton Bridge was built in 1930 by Whitaker and Diehl Contractors. It spanned the Lehigh River with steel superstructure supplied by Bethlehem Steel. It was closed in May 2017 to be replaced by 2020.
According to the comments, the three year interval is not just construction. It is because they have done no preparation work such as EPA studies or identifying funding even though they knew the bridge was close to condemnation.

Inspection (as of 06/2009)
Deck condition rating: Poor (4 out of 9)
Superstructure condition rating: Poor (4 out of 9)
Substructure condition rating: Serious (3 out of 9)
Appraisal: Structurally deficient
Sufficiency rating: 16.6 (out of 100)


I dug into this bridge because the comments talked about a steel superstructure but the picture looked like concrete arches. Historic Bridges explains that the three approach spans on the west side are concrete encased steel girders. The Parker truss over the railroad also, obviously, required steel. The bridge was rehabilitated in 1958 and 1998. It seems that the 1998 work must have been more of a patch than a rehabilitation if it was condemned just 21 years later. I wonder what the source of failure is: the concrete arches themselves or the concrete encased steel girders. Historic Bridges indicates that encasing steel girders in concrete was a short-lived trend in the 1920s and 30s. If the girders are the problem, then reuse the graceful arches and replace the approach spans. If the arches are the problem, then we have learned that reinforced concrete is not maintenance free.

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