(Bridge Hunter broke Mar 22, 2023;
John A. Weeks III;
Satellite)
The 510' (158.5m) main span has a clearance of 149' (45.4m) and a deck height of 160' (50m). [JohnWeeks] John's text provides a lot of information, and it is well worth reading. In summary, the first wrought iron truss bridge collapsed on Aug 20, 1904, because of a severe thunderstorm. The design of the bridge was strong enough to handle the lateral forces of a wind storm, but the towers were not anchored to the foundations and one of the towers was blown off its foundation! The second bridge was closed in 1984 because it used pin-connected trusses. MN_DOT got worried about the pins being a non-redundant point of failure. When they inspected the pins after they blew up the bridge, they discovered the pins were in excellent condition. Just because the
Silver Bridge had a bad pin doesn't mean that all pins are bad. That is good because I go out of my way to walk on pin-connected bridges to take photos of them. And the new arch bridge had problems with cold weather.
This is a bluff-to-bluff bridge and thus requires some non-trivial approaches. The east approach is particularly impressive. (I've noticed that the right ascending bank is always called the east side. In this case, this long approach is actually on the northwest side of the river..)
I became aware of this bridge because of this video of the Apr 2023 flooding.
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Mary C Kennedy posted
Miss at downtown St Paul today [Apr 23, 2023] in major flood stage at 17.62 feet. Crest is mid week at 18.88 feet. Could see some empty barges down river waiting it out. |
The short approach on the west side (left) is higher than the long approach on the east side (right)
If I am remembering correctly, it was just about a half-year ago that shipping on the Mississippi was being impacted by low river levels. Now it is being impacted by high river levels.
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