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Phase II: Re-Tightening the Large Anchor Rods of Support Structures for Signs and Luminaires

Status:  Complete
Report Date:  10/05/2021

Summary:

The Minnesota Department of Transportation (MnDOT) funded two projects in an effort to mitigate anchor bolt connection loosening and develop improved pre-tensioning steps for its sign, luminaire, and traffic signal (SLTS) structures. The Phase I study proposed new pre-tensioning procedures, completed laboratory testing, did an in-depth literature review, and set up instrumentation. The next part of the work started by implementing the proposed procedures in the field and suggesting revisions to be investigated further in Phase II. Through this work, the structural monitoring objective was to better understand field fatigue forces on the anchor rods and develop a testing procedure to replicate field stresses accurately in the laboratory. In the Phase II project, lessons learned from both the field results and additional literature review were tested in the laboratory to balance the efficiency and efficacy of the revised pre-tensioning procedures. Feedback from stakeholders and experience from in-field inspections were considered for the revised procedures. Testing methods and conclusions were validated with finite element models and structural health monitoring. This final report brings all aspects of the work together and recommends improved procedures and additional studies.

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