Varied Bridge Assessment Techniques Explored
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FEATURE
Varied Bridge Assessment Techniques Explored
Published online: 18 February 2009 Ó ASM International 2009
Two articles appearing together in the November 2008 issue of Materials Evaluation pair different techniques with ground penetrating radar (GPR) for bridge deck condition assessment. In ‘‘Condition Assessment of Bridge Decks by Complementary Impact/Echo and Ground Penetrating Radar,’’ researchers from Rutgers University, University of Vermont, and the Federal Highway Administration use a complementary application of impact/echo technique, which detects delaminations as reflectors within the deck, and GPR, which bases delamination detection on identification of deteriorated sections of the deck. The correlation of data from a limited section of deck assists in the definition of a suitable deterioration threshold in the GPR data for the whole bridge deck, separating structurally sound from deteriorated sections. Authors Nenad Gucunski, Carl Rascoe, Dryver Huston, and Frank Jalinoos provide descriptions of the two techniques and their implementation in the field. They discuss bridge deck interpretation results obtained from this complementary approach. Impact/echo detects and quantifies delaminations whereas GPR attenuation measurements provide information about material degradation. Since the tests provide these different measurements, they can only be correlated to assist in the definition of a suitable deterioration threshold in the GPR data separating structurally sound concrete from deteriorated sections with the deck. As the authors conclude, ‘‘The presented approach utilizes, in the best possible way, the strengths of GPR and impact/echo techniques. It exploits the ability of GPR to conduct surveys at highways speeds of large areas of
bridge decks, and the accuracy of the impact/echo technique in the detection and characterization of deck delamination to obtain, in a fast and economical way, the accurage condition assessment of a deck.’’ Kenneth Maser from Infrasense, Inc., demonstrates how GPR and infrared thermography can be economically combined using a multilevel survey approach that exploits the strengths and minimizes the limitations of each technique, so that more information can be provided through the combination than could otherwise be obtained using each technique separately. The techniques were used on 45 bridge decks in Wisconsin. The work included infrared thermography and ground penetrating radar data collection, visual surveys of the underside of the deck, and selective core sampling.
Field testing on grids with a portable seismic property analyzer. Image courtesy of Nenad Gucunski
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The author explained, ‘‘The strengths and limitations of each technique were considering in carrying out the data analysis. For example, ground penetrating radar reinforcement bar depth data were used for each deck to determine the depth limitations of infrared thermography detection. Where the reinforcement bar was too deep, infrared thermography was used to identify overlay disbonding, whil
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