Minnesota Department of Transportation

511 Travel Info

Blatnik Bridge repair project

Duluth

Orange barrels on a highway

Background

Construction began on the Blatnik Bridge in 1958. The 7,980-foot steel truss bridge opened to traffic in 1961. It is the second longest bridge in Minnesota.

The Blatnik Bridge was built with a fracture critical design, a popular approach to bridge building in the 1960s and 1970s when the U.S. interstate system was being built. Unlike bridges built in more recent years, the fracture critical design does not contain redundant supporting elements. This means if the bridge’s main components fail, the bridge would be in danger of collapse. This does not mean the bridge is inherently unsafe. Rather, it means these components require more frequent in-depth inspections, which are done every other year. In the off years, bridge inspectors conduct routine inspections, which include monitoring any previously reported discrepancies. 

MnDOT has 123 fracture critical bridges in its inventory. As MnDOT replaces these bridges, it does so with redundant designs.

Improvement History

  • 1993-1994 – Approach span widening, new deck and roadway lighting
  • 1995-1998 – Complete repaint
  • 1996 – Outline Lighting System
  • 2008 – Steel repair and spot paint
  • 2010 – Center span suspender cable evaluation
  • 2012 – Partial superstructure paint, steel repairs and new expansion joints