Ground Penetrating Radar (GPR) is an accepted electromagnetic evaluation technique used for the transportation infrastructure and a variety of other applications including concrete inspection, utility detection, geology and archeology. A well-established and accepted application of GPR is the accurate condition assessment of bridge decks as well as other reinforced concrete structures. Traditional bridge deck inspection methods include hammer soundings, chain dragging and visual inspection. The interpretation of these familiar techniques is subjective, and is operator dependant and may produce highly variable results. Significant advantages of using GPR for bridge deck assessment include the nondestructive nature of the technique as well as the ability of GPR to be used without requiring the removal of an existing asphalt overlay and to provide a quantitative record independent of operator interpretation. The most accurate bridge deck condition assessments using GPR have been performed using high frequency (1.5 GHz) ground-coupled antennas. The high frequency ground-coupled antenna provides excellent resolution of the reinforcing steel. It necessitates a slower data acquisition speed, however, since the antenna must remain sufficiently ground-coupled. Some GPR bridge assessments have been performed using 1 GHz air-launched horn antennas. The air-launched antenna permits faster data collection, at the expense of resolution. Three years ago Geophysical Survey Systems began manufacturing a 2 GHz air-launched horn antenna. In a collaborative effort between Geophysical Survey Systems and the Maine Department of Transportation, both the 1.5 GHz ground-coupled antenna and the 2 GHz air-launched horn antenna were used on April 13th, 2005 to evaluate the condition of an asphalt overlaid bridge deck located in Lewiston, Maine known as the Ramp D from Main Street over Maine Central Railroad. Ramp D is a portion of the Veterans Memorial Bridge which crosses the Maine Central Railroad and the Androscoggin River. The GPR data was collected along the bridge deck in lines parallel to the direction of traffic. The profile lines were perpendicular to the transverse direction of the uppermost rebar. GPR data lines were acquired at two foot spacing by simply walking the ground-coupled antenna system and by driving a vehicle with the air-launched horn antenna system. The GPR data was processed with GSSI's RADAN software program using the Bridge Assessment Module. The results were used to produce color-coded deterioration maps of the bridge deck. Results from the groundcoupled antenna and the air-launched horn antenna comparison demonstrated excellent correlation. In addition, the deterioration maps from both antennas were compared with visual data obtained from topside and bottom-side visual inspections and exhibited excellent correlation. The Maine DOT further confirmed the correlation by hammer sounding and opening the bridge deck to expose the actual areas of deterioration requiring repair. Consequently, it was concluded that the 2 GHz air-launched horn antenna is an effective tool and provides an accurate assessment of the condition of bridge decks.


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    Title :

    Comparison of 2 GHz horn antenna and 1.5 GHz ground-coupled antenna for bridge deck condition assessment using GPR


    Additional title:

    Vergleich von 2 GHz Hornantennen mit 1,5 GHz Boden angekoppelten Antennen zur Bewertung von Brückenbelägen mittels Bodenradar


    Contributors:
    Parrillo, R. (author) / Roberts, R. (author) / Delea, D. (author)


    Publication date :

    2006


    Size :

    13 Seiten, 15 Bilder, 4 Quellen



    Type of media :

    Conference paper


    Type of material :

    Storage medium


    Language :

    English




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