Research Reports

Development of Best Practices for Inspection of PT Bridges in Minnesota

Principal Investigator:

Kyle M Berg, Andrea J Schokker

April 2012

Report no. MnDOT 2012-09

Projects: Inspection of In-Place Bridges Constructed with Grouted Post-Tensioning Ducts

Topics: Bridges and Structures , Safety

This report focuses on post-tensioned bridges built in Minnesota prior to 2003. The scope is limited to providing a targeted check of bridges that are most likely to have grouting related corrosion problems based on a review of plans and inspection notes. The project consisted of three phases: 1) review of plans and inspection reports of 40 post-tensioned bridges constructed prior to 2003, 2) selection of 10 bridges for a limited onsite inspection of the exterior of the bridge, and 3) invasive inspection of three select bridges. The bridges were selected to represent different bridge construction types to provide a spot check of the post-tensioned bridge inventory in Minnesota. One of the three bridges has corrosion and voids due to poor grouting, one has major corrosion problem related to construction issues (but appears to have good grout), and one showed no tendon corrosion or grouting problems during the invasive spot checks. Recommendations are given at the end of the report specific to the bridges that were investigated as well as for a general inspection plan for post-tensioned bridges in Minnesota. A concise guide for bridge inspection staff is provided that is specific to post-tensioned bridges.

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