Browsing by Subject "Nondestructive evaluation"

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    Development of Flexural Vibration Inspection Techniques to Rapidly Assess the Structural Health of Rural Bridge Systems
    (University of Minnesota Center for Transportation Studies, 2008-09) Brashaw, Brian K.; Vatalaro, Robert; Wang, Xiping; Sarvela, Kevin; Wacker, James P.
    Approximately 4,000 vehicle bridges in the State of Minnesota contain structural timber members. Recent research at the University of Minnesota Duluth Natural Resources Research Institute (UMD NRRI) has been conducted on vibration testing of timber bridges as a means of developing rapid in-place testing techniques for assessing the structural health of bridges. The technique involves measuring the frequency characteristics of the bridge superstructure under forced flexural vibration. The peak frequency of vibration was measured and compared to a set of load testing data for each of 9 bridges. Each bridge was also inspected using commercially available advanced inspection equipment to identify any major structural problems with individual bridge components such as timber pilings, pile caps, and girders. Two bridges were identified that needed immediate maintenance attention. The relationship between the load deflection data and the vibration characteristics showed a useful relationship and the results indicate that forced-vibration methods have potential for quickly assessing timber bridge superstructure stiffness. However, improvements must be made to the measurement system to correctly identify the 1st bending mode frequency of the field bridges. This global vibration technique has potential benefits for routine inspections and long-term health monitoring of timber bridge superstructures.
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    Modeling Issues Associated with Sensor Technologies for the Nondestructive Evaluation of Timber Bridges
    (Center for Transportation Studies, University of Minnesota, 2007-08) Stech, Harlan
    This report documents progress made regarding the development and validation of a class of models examining the reliability of nondestructive vibrational inspection tests of single-spanned bridges. Two important problems were identified for special consideration. The first concerned the development of a mathematical formulation of the nonlinear boundary conditions needed to accurately model the end support structures of single-span (stringerbased) timber spans. A computational algorithm for the numerical approximations of such systems was derived, implemented and tested with the commonly available Mathematica software package. The second focal problem involved the modeling and analysis of a newly-proposed vibrational testing method. The method seeks to predict bridge strength from vibrational data, and (most importantly) without the need to estimate overall bridge mass. Models developed in this project have provided the first steps towards developing a mathematical understanding of these issues, as well as the creation of a new bridge testing protocol involving the measurement of bridge vibrational responses to forced vibrations both with and without controlled loading. This work has contributed to the development and application of new motion detection sensor technologies addressing the problem of monitoring and estimating bridge integrity.