Tuesday, May 7, 2019

1940 Centennial Bridge over Mississippi River at Rock Island, IL

(Bridge Hunter; Historic BridgesJohn A. Weeks III; HAER3D Satellite)

John Weeks III
I was surprised to see the date of 1940. This bridge looks much newer than that. "The bridge was the first tied-arch span and the first 4-lane bridge across the Mississippi River....A 1998 study of the quad cities bridges found that the I-74 bridges were vastly over capacity while the Centennial bridge was underused, mainly due to the tolls. An agreement was worked out in late 2001 where the bridge would be transferred from the bridge commission to being owned jointly by the two states....The bridge was officially transferred to state ownership on July 13, 2005. The study turned out to be accurate. Late 1990s traffic of 16,000 vehicles per day grew almost overnight to 31,000 vehicles per day before the end of 2005." [John Weeks III]

I wasn't even going to look in Historic Bridges until I saw the date. ''It has five spans. From north to south there are two 395 foot arch spans, two 538 foot arch spans, and one 395 foot arch span." [Historic Bridges]

Photo from HAER IOWA,82-DAVPO,8--4 from ia0449

3/4 VIEW FROM SOUTHWEST - Centennial Bridge, Spanning Mississippi River at U.S. Highway 61, Davenport, Scott County, IA

HAER-data describes the bridges built before this one in the Quad Cities area. Then it has quite a bit of detail concerning this bridge. A tied-arch span requires frequent piers. But a firm bedrock was shallow in this area, so the piers were relatively cheap. The HAER reference indicates the foundation was either hard shale or clay that was so solid a spread foundation could be built on it without the use of H-piles. Another reference described the foundation as blue shale or limestone. HAER states that sheet piles were used to build cofferdams so that the piers were built in a dry riverbed. The shallow bedrock also allowed economic falsework to be used for the construction of the arches.

Pete Zarria Flickr, License: Creative Commons Attribution-NonCommercial-NoDerivs (CC BY-NC-ND)

Denise Kellums Greer posted
Out for a walk and s saw this beautiful flooded Mississippi sunset. Thought I'd share it with ya!
[Taken from Schwiebert Riverfront Park]

Photo taken by David Sebben
December 15, 1939 view from Illinois looking to Iowa
[You can tell this is a pioneering tied-arch bridge because they are using falsework and building it over the water rather than the current technique of building a span on barges and then floating it under the bridge and raising it into position.]

It appears that the two DOTs do not limit their poor maintenance to truss bridges. Or they maintain the deck, which the public sees, but don't maintain what holds the bridge up.

Inspection report (as of July 2015)
Overall condition: Poor
Superstructure condition rating: Serious (3 out of 9)
Substructure condition rating: Fair (5 out of 9)
Deck condition rating: Good (7 out of 9)
Sufficiency rating: 10.8 (out of 100)
[Bridge Hunter]

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