Seventh Street Bridge
Facts
- Overview
- Deck truss bridge over Tuolumne River on Seventh Street
- Location
- Modesto, Stanislaus County, California
- Status
- Open to traffic
- Future prospects
- To be rehabilitated or demolished. Project date: 2016.
- History
- Built 1916
- Builders
- - E. H. Annear (County Engineer)
- G. E. Cotton (Contractor)
- John B. Leonard of Union City, Michigan (Engineer)
- Leonard & Day (Consulting Engineer)
- Design
- Described in the book, Historic Highway Bridges of California, as a "canticrete" bridge, invented by John B. Leonard. A mixed design using steel trusses within the arch ribs, the trusses are cantilevered from the foundation piers and pinned together at the crest of the arch.
- Dimensions
-
Length of largest span: 101.1 ft.
Total length: 1,170.0 ft.
Deck width: 24.3 ft.
- Recognition
- Eligible for the National Register of Historic Places
- Also called
- Lion Bridge
Parrots Ferry Bridge - Approximate latitude, longitude
- +37.62694, -120.99389 (decimal degrees)
37°37'37" N, 120°59'38" W (degrees°minutes'seconds") - Approximate UTM coordinates
- 10/677028/4166317 (zone/easting/northing)
- Quadrangle map:
- Riverbank
- Average daily traffic (as of 2009)
- 15,719
- Inventory numbers
- CA 38C-23 (California bridge number)
BH 46304 (Bridgehunter.com ID) - Inspection report (as of September 2017)
- Overall condition: Fair
Superstructure condition rating: Good (7 out of 9)
Substructure condition rating: Fair (5 out of 9)
Deck condition rating: Good (7 out of 9)
Sufficiency rating: 51 (out of 100)
View more at BridgeReports.com
Update Log
- March 10, 2014: Updated by Craig Philpott: added alternate historical location name
- May 10, 2013: Updated by Nathan Holth: This bridge is at risk for demolition.
- July 24, 2011: Updated by Craig Philpott: added contractor names
- October 19, 2010: Updated by Craig Philpott: refined design description
- September 21, 2010: Added by Craig Philpott
Sources
- Craig Philpott - craigphilpott63 [at] gmail [dot] com
- The concrete bridge; a book on why the concrete bridge is replacing other forms of bridge construction ([c1913]) - 1913 booklet by John B Leonard re concrete bridges in CA
- The concrete bridge; a book on why the concrete bridge is replacing other forms of bridge construction ([c1913]) - 1913 booklet by John B Leonard re concrete bridges in CA
- Nathan Holth
Comments
Based off the design description, I would guess that the pinned crown connection in the “canticrete” structure has failed in some form. This would cause the two ends of the arched cantilevers to act independently and thus create the visible offset seen in the photos. What actual forces are causing the problem is hard to determine without visiting the site and maybe seeing some bridge plans. It could be a settlement problem at the foundation or some other structural dilemma.
The spalled concrete with the exposed rebar while not desirable is quite a common occurrence on structures of this age. The settlement or offset problem will control whether this structure can be saved not necessarily the spalled concrete which can easily be repaired for the most part.
Just thought I would throw my two cents in on the matter.
MG
I am not an engineer. Clearly the temporary repairs have been in place for some time already and there appears to be no recent movement. I suspect that one pier shifted or "sunk" some years back. Of large concern to me are the two large areas of spalled and fallen concrete with visible and rusted structural steel visible.
Is the unusual design the reason for the failure mid-span?
If this bridge isn't rehabbed soon it will have to be replaced--that is a serious failure going on there!
This page's URL is http://bridgehunter.com/ca/stanislaus/seventh-street/
This "canticrete" bridge is unusual. I don't know anything about it, but it sounds like the pin in the center is important, sort of like a three hinged steel arch? In Michigan, we have what is simply called a cantilevered concrete arch and it has no pin at the center and in fact there is a gap showing that each half is independent structurally (since cantilevers get their support from the pier) http://www.historicbridges.org/other/Belle/little_dscf7744.j...
http://www.historicbridges.org/other/Belle/