(
Bridge Hunter;
Historic Bridges,
John A. Weeks III;
Satellite)
It is also known as the
F. W. Cappelen Memorial Bridge. He designed many of the bridges in Minneapolis in the early 20th century, including this one. He passed away while this bridge was being constructed.
The 400' main span was the largest in the world when it was completed. [several references] "The bridge is also noteworthy for its use of Melan style reinforcing, a late example of this early concrete reinforcing method, but perhaps used because it would provide greater stability for the immense span length required. Melan reinforcing uses solid or as in the case of this bridge trussed steel arches embedded in the concrete, as opposed to reinforcing rods (rebar)." [HistoricBridges]
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| Mulad via BridgeHunter, License: Public domain: Released by author |
The arches were built around the 1889 metal truss bridge that it replaced. [HistoricBridges]
The construction photo below shows the original spacing of the columns. Everything except the piers and arches were rebuilt in 1971-73. The original bridge was overbuilt, so the replacement used half as many columns. Extensive rehabilitation was done again in 2015-17. After reading about the problems that had to be fixed in 2015 [
wje], I have to wonder why they don't put an aluminum lined gutter in the top of the pier caps under the expansion joints. Then add downspouts to the gutters to carry the salt water down to the river without touching any of the concrete.
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| 1919 Construction Photo via HistoricBridges, Source: Minneapolis Photo Collection of Hennepin County Library |
This history of alterations provides another view of the original column spacing and shows the original light fixture design that was ignored in the 1970 rehabilitation and restored in the 2015-17 restoration..
John's 2009 photo shows the pier remnants from the truss bridge that were removed by the 2016 rehabilitation.
"The county chose accelerated bridge construction (ABC) using prefabricated bridge elements and systems (PBES) consisting of precast concrete spandrel cap beams, deck panels, and ornamental rail panels. The construction method reduced bridge closure time from two years to four months....Construction of the new Minnesota Vikings stadium increased costs by contributing to a concrete shortage, so the county looked for ways to save money. The precast concrete segments were made near to the river so they could be floated downstream on a barge and hoisted by water-borne cranes into their final positions. Crews also salvaged remnant piers from 1889. According to the Minneapolis Star-Tribune, the final cost of the estimated $28 million project was $43 million." [
ConcreteConstruction] (I saw a later figure of $51m.) A photo of some of the "water-borne cranes."
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Bill Pohlmann posted
16000 x 3 and a 10000 on the Mississippi in Minneapolis in 2016. Franklin Ave. bridge renovation.
Bill Pohlmann Kraemer North America. A 2017 APWA Project of the Year winner in the historical restoration/preservation category. Cranes were from ALL. |
I saved this figure, not because of the repair techniques, but because of the depiction of the Melan truss that was used for steel reinforcement of the arch.
The 2016 rehabilitation changed from four lanes of traffic to two lanes because biking and walking across the bridge is so popular in this neighborhood.
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ABC
Hennepin County’s Franklin Avenue Bridge, a historic five-span concrete open-spandrel arch structure, crosses the Mississippi River in Minneapolis, Minnesota, and serves as a critical link for local businesses and neighboring universities. Opened in 1923, the bridge is listed on the National Register of Historic Places and is recognized as a Minneapolis Landmark. Degradation and changing usage warranted an extensive structural rehabilitation and required closure of the bridge. ABC methods were selected for the deck replacement, reducing the closure time from two years to four months. The contractor replaced the existing deck and cap beams using precast concrete elements, connecting the deck panels with ultra-high performance concrete and sealing the deck surface with a premixed polymer concrete overlay. The bridge was closed to traffic on May 8, 2016, and opened again on September 1, 2016, 116 days after closure. This presentation includes design and construction details as well as lessons learned. |
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Screenshot
Removing one of the 236 35-ton deck panels after the 16" concrete deck had been sawed into panels. The crane is a 450-ton Manitowoc 16000. In addition to three 16000s, the contractor also had two 300-ton 2250s. They had five cranes because they worked on all five spans concurrently. |
This bridge was the second largest application of Ultra High Performance Concrete in the USA. It was used to fill the gaps between the deck panels. They mixed over 350 cubic yards with three (1 was a spare) onsite mixers. The forms had to be almost water tight. [
Screenshot]
The reconstruction ended up costing $51m and there are lots of cracks and spalling already (2018). The contractor claims that the flaws are just unsightly, that there are no structural issues. But "just" unsightly after just a couple of years is still wrong. Too much clay in the concrete and pouring pilasters over expansion joints may be the problems. The contractor claims both are easy fixes. The bridge is still under warranty and the problems will be repaired. [
StarTribune]
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