It is too soon to know what caused the I-35 bridge in Minneapolis to collapse suddenly last night (4.9mb video). But at least one report indicated that a 2006 inspection of the forty-year-old bridge found “fatigue cracks and bending of girders that lift the approaching span.”
Another report says that federal inspectors rated the bridge “structurally deficient” in 2005, although it added that 80,000 bridges in the U.S. have earned that mediocre rating. However, as long ago as 2001, the state found that the bridge “exhibited several fatigue problems, primarily due to unanticipated out-of-plane distortion of the girders. Concern about fatigue cracking in the deck truss is heightened by a lack of redundancy in the main truss system.”
