The I-20 Mississippi River Bridge in Vicksburg, MS is a long span steel truss bridge completed in 1973 and carries four lanes of heavy interstate traffic.  The main piers in the river are deep foundation caissons.  Around the year 2000, multiple issues were found during an inspection involving expansion joints in the superstructure and in the bearings on the pier tops.  An investigation revealed that two of the main piers had begun to slowly move toward the center of the river, threatening the safety of this vital river crossing.

This presentation will cover the ensuing long-term structural health monitoring program and some of the structural modifications that have been made over the years to keep the bridge operational.  Topics include structural monitoring instrumentation, thermal expansion and contraction, and truss, bridge joint, and bridge bearing structural modifications.