Friday, September 28, 2007

Bridge of the Week

The Cream of the Minnesota Monitor staff, Andy Birkey, looks at this week's "Bridge Fix of the Week", the Lafayette Bridge:
The Highway 52 bridge, also called the Lafayette Bridge, crosses the Mississippi River just south of Interstate 94 and connects downtown St. Paul with the city's west side neighborhood. Built in 1968, the four-lane bridge is 3,369 feet long. Each day, it supports an average of 81,000 trips over its structure. The bridge has a deck rating of five (out of nine), a superstructure rating of four, and substructure rating of seven, with a combined sufficiency rating of 49.5 percent. It has been evaluated as "Meets minimum tolerable limits to be left as is." The bridge is also rated "fracture critical," which means that the bridge has the type of structure that if one support should give way, the whole bridge could collapse. The Interstate 35W bridge that collapsed into the Mississippi was rated 50 percent.
He than points us to this story in the STRIB:
The bridge's history includes a temporary shutdown in 1975 -- less than a decade after it opened in 1968 -- when a crack "large enough to put your arm into" was discovered in the bridge's main beam after someone noticed a 7-inch dip in the roadway, according to a newspaper report. That fracture in the southbound lane nearly resulted "in [the] collapse of the bridge," a 2006 inspection report noted. The damaged component was jacked back into place and reinforced with bolted plates, the report said.
Read Andy for the set up, and the STRIB for some reality. Then call your legislator!


No comments: