I-5 Skagit River bridge collapse
Road bridge collapse in Mount Vernon, Washington / From Wikipedia, the free encyclopedia
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On May 23, 2013, at approximately 7:00 pm PDT, a span of the bridge carrying Interstate 5 over the Skagit River in the U.S. state of Washington collapsed. Three people in two different vehicles fell into the river below and were rescued by boat, escaping serious injury. The cause of the catastrophic failure was determined to be an oversize load striking several of the bridge's overhead support beams, leading to an immediate collapse of the northernmost span.[2]
I-5 Skagit River bridge | |
---|---|
Coordinates | 48°26′43.8″N 122°20′28.1″W |
Carried | I-5 (4 lanes) |
Crossed | Skagit River |
Locale | Mount Vernon, Washington |
Maintained by | Washington State Department of Transportation |
ID number | 0004794A0000000 |
Characteristics | |
Design | Through-truss bridge |
Material | Steel |
Total length | 1,112 feet (339 m) |
Width | 72 feet (22 m) |
No. of spans | 4 |
History | |
Opened | 1955 |
Collapsed | May 23, 2013 |
Statistics | |
Daily traffic | 70925 |
Location | |
References | |
[1] |
The through-truss bridge was built in 1955 and connects the Skagit County cities of Mount Vernon and Burlington, providing a vital link between Vancouver, British Columbia and Seattle. It consists of four consecutive spans that are structurally independent. Only the northernmost span collapsed into the river; the adjacent span also sustained impact damage from the same vehicle, but not severe enough to result in a collapse. The overhead support structure was known to have been struck by a truck as recently as October 2012.
Not long before the accident, the bridge had been evaluated as safe. Although not structurally deficient, it was considered "functionally obsolete", meaning it did not meet current design standards. The bridge's design was "fracture-critical," meaning that it did not have redundant structural members to protect its structural integrity in the event of a failure of one of the bridge's support members.
Within a month of the collapse, two temporary bridges were erected and placed on the failed span's support columns while the permanent bridge was built. In September 2013, the permanent bridges were installed and work began to prevent similar failures of the remaining three spans.