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Monday, 28 July 2014 10:44cat

I-35W Bridge Beginning to Age

Written by  TheStructuralEngineer.info
The new I-35W bridge opened in 2008 The new I-35W bridge opened in 2008 FIGGbridge.com

Seven years after the Minneapolis I-35W bridge collapse occurred, the replacement bridge is starting to age. Bridge inspectors recently found cracks in concrete girders, a clogged drainage hole, and rust above the bridge’s piers. The new I-35W bridge over the Mississippi River was built in 2008 after the after the old bridge fell into the river on August 1, 2007. The collapse killed 13 people and injured 145. Improperly designed gusset plates were ultimately determined to be the reason for the collapse. Federal regulators also discovered that the gusset plates were not given proper attention during inspections. 

A $234 million contract was awarded to Flatiron to build a new bridge over the Mississippi. Flatiron was awarded the contract despite their bid coming in at a higher price and longer completion time than other competitors. The Minnesota Department of Transportation felt Flatiron’s bid had superior aesthetics and was the best design.

Most of the problems the inspectors found are minor and could be fixed relatively easily; they did uncover one “rather major” problem though. The bridge uses an anti-icing system to avoid having to spread salt on the bridge during the winter. The system had been leaking but the contractor felt that they built the system to the specification and should not be responsible for fixing the system. The fluid is non-corrosive but it was leaking down the concrete box superstructure for some time, which caused some concern. After a long battle, MnDOT wound up paying to fix the anti-icing system and also paid for aspects of the system that were not under warranty. The problem was eventually fixed after two years of repairs. 

Sources: startribune.com

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