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Mid-America Transportation Center

Evaluation of Air-Coupled Impact-Echo Test Method

Final Report
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Researchers

  • Principal Investigator: Jeramy Ashlock (jashlock@iastate.edu 515-294-6176)
  • Project Status
    Complete
    About this Project
    Brief Project Description & Background
    The goal of this study is to assess the accuracy and feasibility of implementing an air-coupled impact-echo testing approach into routine practice. A reinforced concrete test slab will be constructed with defects of known type and location, and the accuracy of the approach in identifying the location, depth, and type of defects will be determined. Field tests will be performed on a bridge deck, and the results will be compared to other NDE methods. If the approach shows promise, preliminary design recommendations will be made for a prototype vehicle-mounted or towed system.
    Research Objective
    The proposed project will assess the accuracy of the air-coupled impact-echo method in measuring slab thickness and delineating the location and depth of voids and delaminations.
    Potential Benefits
    The expected results include an improved understanding of the accuracy and reliability of the ACIE method for the condition assessment of bridge decks and pavements. Based on favorable results of prior research, it is anticipated that the Iowa DOT may adopt the method as a complement for rapid nondestructive evaluation. The primary product will be a final summary research report and technical brief. Any computer programs developed for analysis of the data will be made available to MATC and the Iowa DOT.
    Abstract
    One the most important and difficult decisions faced by transportation officials on a regular basis is how to best allocate limited resources toward the repair and maintenance of transportation infrastructure. To aid in the decision-making process, efficient and reliable condition assessment tools are needed so that structurally deficient bridges, pavements, and foundations can be identified and ranked in terms of their health. Such information enables decision-makers to distribute resources towards those assets in greatest need of repair or retrofit. The goal of the proposed research is to investigate a promising innovation in the Impact-Echo (IE) Nondestructive Evaluation (NDE) method, whereby traditional ground-coupled transducers are replaced with air-coupled transducers. The accuracy of this method in detecting the location and extent of various defects in reinforced concrete bridge decks, such as delaminations, voids, and cracking, will be determined in the laboratory using a test slab. To provide improvements in the quality of the data, signal processing techniques and an active noise-cancelling technique will be examined. The air-coupled impact-echo approach will then be performed on a bridge deck and compared to results of other NDE methods as part of an existing pooled-fund structural health monitoring (SHM) study. Pending successful performance of the air-coupled impact-echo method, preliminary design recommendations for a mobile scanning system will also be developed in the proposed study. The advantage of an air-coupled IE method is that testing time would be greatly reduced by eliminating the requirement of physically coupling transducers to the structure at each measurement point. The method could therefore be implemented in a mobile scanning system for accelerated 2D profiling of bridge decks and pavements, enabling the structural health of transportation infrastructure to be assessed and monitored with greater efficiency. A mobile scanning system may also eliminate the need for lane-closures and traffic direction crews.
    Project Amount
    $ $52,866