Smart Installation and Monitoring System for Large Anchor Bolts of Support Structure for Highway Signs, Luminaires, and Traffic Signals

This project was aimed at providing an improvement on the current inspection methods for detecting loose anchor bolts used in highway support structures. A capacitance-based smart washer system was developed and the final prototype was studied in two stages. Stage 1 of the project performed tests in the laboratory to develop a sensor system prototype with a calibration curve that was able to correlate the capacitance reading and pretension inside the anchor bolts. However, when the system was applied a sign structure specimen, it was found to have severe insulation issues that could lead to failure of capacitance reading. Subsequently, a second prototype was developed using 3D printed PLA attachments to improve insulation. This prototype provided sufficient insulation from steel sign structures and output stable capacitance readings on sign structure specimen. A calibration curve was developed and the relationship between anchor bolt pretension and capacitance readings was finalized. Stage 2 of the project was to monitor the performance of the smart washer system in a long-term manner and in-field situation. It was found that the sensor system was sensitive to environmental factors especially rain that could short circuit system. After applying a simple double-layered plastic waterproof cover on the sensor system, the interruption from humidity was eliminated and stable capacitance readings were recorded again for consecutive 12 months. It is recommended that necessary waterproof protection should be introduced to the sensor system in the field environment to protect the system from environmental issues such as humidity. In conclusion, the concept and prototype of the smart washer system were proven efficient to detect pretension changes inside the anchor bolts. With proper waterproof protections for outdoor use, the smart washer system holds a great potential for improving inspections on loose anchor bolts of highway support structures.


  • English


  • Status: Completed
  • Funding: $140000
  • Contract Numbers:

    Project 20-30, IDEA 196

  • Sponsor Organizations:

    National Cooperative Highway Research Program

    Transportation Research Board
    500 Fifth Street, NW
    Washington, DC  United States  20001

    American Association of State Highway and Transportation Officials (AASHTO)

    444 North Capitol Street, NW
    Washington, DC  United States  20001

    Federal Highway Administration

    1200 New Jersey Avenue, SE
    Washington, DC  United States  20590
  • Project Managers:

    Jawed, Inam

  • Performing Organizations:

    Iowa State University, Ames

    Institute for Transportation
    2711 South Loop Drive, Suite 4700
    Ames, Iowa  United States  50010-8664
  • Principal Investigators:

    Chen, An

  • Start Date: 20180101
  • Expected Completion Date: 20181231
  • Actual Completion Date: 20181231
  • Source Data: RiP Project 41393

Subject/Index Terms

Filing Info

  • Accession Number: 01622414
  • Record Type: Research project
  • Source Agency: Transportation Research Board
  • Contract Numbers: Project 20-30, IDEA 196
  • Files: TRB, RIP
  • Created Date: Jan 14 2017 10:49AM