Tag Results for Minneapolis (6)

  1. De-icer considered in bridge collapse

    Just hours after the Minneapolis I-35W bridge collapse on August 1, 2007, we pointed out that a de-icing system was installed on the ill-fated bridge in 1999. Now the NTSB is looking at that de-icing system, according to today's St. Paul Pioneer Press. The article quotes several recent research papers that conclude the active agent in the liquid de-icer, potassium acetate, can be as caustic as lye when in contact with certain kinds of concrete aggregate (the rocks and sand that are mixed with cement to form concrete) and cause severe corrosion, as seen at the Colorado …

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  2. Did MnDOT Make a Fatal Choice?

    PHOTO: Harry Goldstein, IEEE Spectrum A report in todayâ''s Minneapolis Star-Tribune states that the Minnesota Department of Transportation â''last winter considered bolting steel platesâ'' to the trusses on the 35W bridge â''to prevent cracking in fatigued metal,â'' and even went so far as to ask contractors for advice on the best way to accomplish the task. The move was prompted by the URS Corporation June 2006 report, which recommended â''three equally viableâ'' retrofit approaches: (1) Steel plating of all 52 fracture critical truss members. This approach will provide member redundancy to each of the identified fracture …

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  3. Reports on Bridge Condition Raise Questions

    Here are some early gleanings from the hundreds of pages of inspection documentation MnDOT have released. A draft report prepared by the engineering firm URS Corporation in June 2006 emphasizes that Bridge No. 9340 was designed in accordance with the 1961 American Association of State Highway and Transportation Officials (AASHTO) Standard Specifications for Highway Bridges , "which was based on a completely different fatigue design method that was revamped in the 1974 interim edition. The poor fatigue details on the truss spans, particularly those inside the main truss tension chords are difficult to inspect, have raised concerns on the …

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  4. The Day After: MnDOT's Got Some 'Splainin' to Do

    from press conference in Minneapolis at 2 pm CDT, August 2, 2007: Gov. Pawlenty stated that MnDOT has hired Wiss, Janney and Elstner, forensic engineers who will conduct a parallel investigation to the one being conducted by the NTSB; this same firm investigated Boston's Big Dig. MnDOT will conduct emergency inspections on three other bridges in Minnesota with a similar steel truss arch design. MnDOT will also investigate all "structurally deficient" bridges: As of 2007, Minnesota has 13,026 bridges, and 1000 bridges in total that fall into the category of structurally deficient; 77,000 bridges are so designated across the United …

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  5. Video reveals moment of bridge collapse

    A video taken from a bridge surveillance camera located on near the north side of the bridge shows the moment the structure gave way, falling from south to north. The video clearly shows the bridge's design. This is a box truss bridge--the steel girders supporting the road deck are not anchored into supporting concrete caissons in the water, but rather arc over the river and connect to concrete piers standing on the shore on either side of the river. Also: White House Press Secretary Tony Snow said this morning at a news conference that the 2005 inspection report …

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  6. More on Minneapolis Bridge Collapse

    The reports issued in 2005 and 2006 by the Minnesota Department of Transportation are not currently available. However, some tidbits about the bridge's condition can be gleaned from the MnDOT's press releases about repairs to 35W bridge, which collapsed about six hours ago. From a September 2, 2004 release: The left three lanes in both directions will be closed throughout the night until 5 a.m. Friday morning. The closures are needed so workers can repair a bridge panel in the northbound lanes and conduct the annual fall inspection of the I-35W bridge anti-icing system. The anti-icing system was installed in 1999--32 …

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