Experimental Evaluation of Low-Cost, Portable, and Rapid Nondestructive Evaluation Methods for Timber Distribution Poles
1 online resource (160 pages) : PDF
University of North Carolina at Charlotte
Power line workers have long been required to climb timber utility poles to perform maintenance. Although routine pole inspection and maintenance programs are in place to optimize asset management and reduce the risk posed to workers, such work continues to be dangerous. Conventionally, power line workers have conducted visual and manual inspections on timber utility poles prior to performing maintenance, but these inspection practices have been found to be unreliable. Nondestructive evaluation methods have been developed in attempt to improve the accuracy of these pre-maintenance inspections, but these methods often require costly specialized equipment as well as extensive analysis to determine the condition of the timber and can expose the pole to conditions leading to decay-causing fungi. This study is conducted to establish a basis for developing a low-cost, quick, portable nondestructive testing device that can be routinely utilized by power line workers to assess the safety of poles prior to accessing supported electrical infrastructure. A review of related literature is conducted and four nondestructive test methods (guided stress wave propagation, experimental modal analysis, acoustic resonance, infrared thermography) are selected for evaluation through full-scale controlled experimental tests conducted in a laboratory environment. The development of the experimental test bed, procedures used for data collection for each test method, and destructive characterization of decay below the ground line are documented. Analysis of test data is focused on vibration-based methods for condition assessment of the timber utility poles. An analytical model of the installed timber poles is created using the Rayleigh-Ritz method and parameter identification through optimization-based model updating is pursued using two approaches to develop a method for condition assessment of the tested poles. Verification of the analytical model is conducted by comparing the predicted natural frequencies and mode shapes to experimental estimates obtained from experimental modal analysis. Additionally, the destructive profiling of section properties below the ground line is used to validate the nondestructive test results. Both parameter identification approaches are determined to be promising for the detection of severely decayed poles; however, the introduction of a parameter to explicitly model the loss of stiffness and mass from decay below the ground line is found to result in lower prediction errors and accurate estimation of section loss. Remaining challenges and recommendations for future research to promote the development of a low-cost, rapid, and portable device for condition assessment of in-service timber distribution poles are discussed.
Young, DavidGergely, Janos
Thesis (M.S.)--University of North Carolina at Charlotte, 2016.
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