2017 extradosed bridge: (John A. Weeks-new; Satellite, at the time I looked, the image had just a couple of construction barges anchored in the middle of the river)
While researching the CN/SOO/Wisconsin railroad bridge, I discovered they are building a new 4-lane bridge for Stillwater, MN. The new bridge includes a trail with overviews. [Background] They plan to preserve the old lift bridge and make it part of a trail system. [Liftbridge]
The truss bridge was built in 1931 and rehabilitated in 1973. The replacement one-mile-long, bluff-to-bluff bridge started in 2013 was scheduled to be done in Fall 2016, but it was almost a year late (Aug 2, 2017). The new bridge does uses post-tensioning with almost 2,000 miles of segment strands. [video] (All of the videos are below in the order that they should be watched.)
Approaching the new Saint Croix Crossing bridge on the ramp leading up to the pedestrian / bicycle deck.
|Photo from Gallery from MNDOT|
The bridge itself will be only the second extradosed bridge to be built in the United States. An extradosed bridge is similar to a cable stayed bridge, but with a major difference. In a cable stayed bridge, the cables hold up the deck segments. That requires tall towers and a steep angle for the cables. An extradosed bridge uses the shorter towers to support the deck segments near the tower. The relatively shallow angle of the cables means that they mostly pull the deck segments together rather than holding them up. The result is that the segments are held tightly together, so they essentially perform as single beams. The extradosed style is more expensive than a beam bridge, yet cheaper than a cable stayed bridge. It requires fewer pylons than a beam bridge, but more than a cable stayed bridge. [John A. Weeks-new]John also explains that environmentalists fought a new bridge for decades because the river is designated as a National Scenic Riverway. It took an act of Congress in 2012 to allow the new bridge to be built without having to destroy the historical lift bridge.
|Jeremy Rawlings posted|
888 Ringer with 250ft of main boom setting precast segments for the St Croix River Crossing between Stillwater, MN and Houlton, WI. Summer of 2016.
Mike Weaver Looks like a 14000 in the background.Jeremy Rawlings Yep. While I was on this job we had two 888 ringers, a 2250, a 888 crawler, that 14000 and an MLC 165 and a Link Belt crawler. All of them were on barges except one of the ringers which was on the Wisconsin shoreline. There were a couple American friction rigs, a couple Link Belt 110s and a 16000 along with a few pickers on land.
|Jeremy comments on his posting|
Here’s the 14000 boomed down to get it under the bridge.
It did list the barge with it boomed down that far but list of the barge is exaggerated a bit because they were moving it. You can see the tugboat on the right side of the barge and there was another one behind the crane to push.
|Jeremy comments on his posting|
Here’s a picture where you can really see the list of the barge while being pushed by the tugboat and you can see both tugboats.
"Construction operations needed to be contained within a 400-ft zone in the river, and the National Park Service imposed strict timelines on barges transporting the precast segments from the casting yard through the locks, allowing only 72 hours per run, limiting the exposure of these vessels to the invasive zebra mussel. If any barge exceeded that time limit, it would have to go through a complete inspection and wash-down to prevent the mussels from passing between the Mississippi and St. Croix Rivers."
|Bill Pohlmann posted|
One of the little Japanese models [Kobelco] working on the historic Stillwater, MN lift bridge. Its replacement opened a few years ago and it's being converted to a bike and pedestrian bridge.
Robert Thiry love that ‘no parking’ sign.
Bill Pohlmann Yeah, the rivers are kind of high around here!
If this part of the river had a rapids, then multiple, short towers would be relatively cheap because the bedrock would be close to the surface. But this video indicates the towers are rather expensive because the pier caissons go down as far as 140 feet.
A different time lapse:
(new window) from MNDOT