1981: (
Archived Bridge Hunter;
Bridge Hunter;
John Weeks III;
Satellite)
Until 1979, these bridges
also carried US-20. It now carries BUS-20 as well as US-77.
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John Weeks
This 1,502' (458m) long bridge has a main span of 425' (130m).
The navigation channel is 400' (122m) by 80' (24.4m).
"An inspection in early May, 1982, found a fracture across the full width of the downstream horizontal tie girder. The fracture was heavily corroded, suggesting that the fracture happened just after the bridge was opened. Further investigation revealed that the strength of the steel varied considerably, with some of the steel not meeting minimum strength specifications. The bridge was closed on May 6, 1982. It remained totally closed for 7 months, with 2 lanes reopening on December 9, 1982. The repairs were completed and the bridge was fully reopened on May 9, 1983."
[When I had seen the rehabilitation date of 1983, I wonder what went wrong in less than two years. Now I wonder which country provided the steel.]
"Highway US-77 once ran north and south from border to border. The northern section of the road became redundant when Interstate I-29 was completed. As a result, US-77 was truncated at the interchange located at the north end of the Siouxland bridge." |
This shows that the tie-arch bridge was built with falsework in the river rather than with tie-backs. I wonder how far north the 9' navigation channel went in 1980 on the Missouri River.
"The Siouxland Veterans Memorial Bridge, from Sioux City, Nebraska, to Sioux City, Iowa, was opened to traffic in January 1981. In May 1982 Iowa Department of Transportation personnel discovered a fracture across the full width of the top flange on the down stream tie girder. The investigation into the cause of the fracture included chemical and physical testing and fractographic and metallographic examinations. Results of the latter examinations showed that the fracture originated at a gas-flame-cut edge of the 2 3/4-in.-thick A588 flange plate. It arrested at least once at a depth of 0.37 in. and possibly earlier at a depth of about 0.05 in. before propagating in a brittle mode across the flange. The fracture surface was heavily corroded, indicating that the fracture had occurred long before its discovery. The physical tests indicated that the plate in which the fracture occurred did not meet the specified toughness requirements. Additional tests on samples of material extracted from other parts of the girders revealed highly variable toughness properties, some of which did not meet the requirements of the specifications either." [
pubsindex]
"Steel for the bridge was provided by two suppliers, one who furnished most of the flange plates, and the other who furnished the remainder of the flange plates and all of the web plates....A number of locations were found where the toughness did not meet the specified requirement. Locations where 21 /2-in.-thick plates did not meet the requirement were also found. At this point in the investigation, an offer was made to IDOT by the supplier of the fractured plate to replace all flange plates that had been furnished by the supplier. This offer was accepted. Work to replace these flange plates was completed in spring 1983." To replace the flanges, they had to remove the dead load off of the tie girders. To do this, they built falsework and then jacked up the superstructure. The bridge was opened to limited traffic while the flanges were being replaced. [
onlinepubs]
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| 2009 photo by Jack Schmidt via BridgeHunter |
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safe_image for The Bridges of Sioux City, Iowa, Photo by Jack Schmidt
The second bridgehunting tour takes us to Sioux City, Iowa. In 2022, a museum curator did a presentation on the city's bridges, dating back to the first crossing in 1865. That presentation is now available for viewing. Enjoy the tour: |
This is that presentation:
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