Evaluation of the Conditions of the San Francisco-Oakland Bay Bridge and the Richmond-San Rafael Bridge using GPR

摘要

Ground Penetrating Radar (GPR) [1] has emerged as a viable non-destructive technique in assessing reinforced concrete bridge decks for locating concrete deteriorated areas caused by steel corrosion and presence of moisture and chloride within the concrete deck. California Department of Transportation (Caltrans) elected to evaluate conditions of the San Francisco-Oakland Bay Bridge and the Richmond-San Rafael Bridge using GPR. The purpose of the survey was to locate and map deterioration in the concrete deck through the overlay wearing surface on the bridge. The bridges are scheduled to have deck rehabilitation performed in the near future, and the results of the GPR survey will be used to locate areas that will require partial and full depth concrete repair. The San Francisco-Oakland Bay Bridge is located on the Interstate 80, between San Francisco and Alameda counties. It is made up of two bridge segments: a cantilever portion between Oakland and Yerba Buena Island, and a suspension span from the island to San Francisco. The eight mile long bridge carries five traffic lanes in each direction. The Richmond-San Rafael Bridge is located on Route 580 in Contra Costa County, California. It is composed of four distinct sections: the East Approach structure, the Main Structure, the West Approach Structure, and the Concrete Trestle Section. The four mile long bridge carries three traffic lanes in each direction. These surveys produced predictions of deterioration that compared favorably with ground truth data and conventional destructive survey techniques. The bridges were surveyed at traffic speed and without lane closures. AutoCAD contour maps were produced on all structures, showing varying degrees of predicted deterioration.