Using ground-penetrating radar (GPR) to assess an eight-span post-tensioned viaduct: a case study

Abstract: An eight-span post-tensioned viaduct built in the 1960s showed some significant cracks as soon as it was open. Over the past few decades, periodical inspections have shown that these cracks were progressive. In 2002, an expert investigation was recommended, focusing on the state of the cables, and followed by a new structural design. The assessment of the structure was achieved by a combination of ground-penetrating radar (GPR) and gammagraphic techniques, followed by some windowing for the location and evaluation of post-tensioned cables. The results have informed the design of strengthening works, using complementary external post-tension. In a second step, GPR mapping was performed for the layout of coring corresponding to the position of the deviators. The methodology of non-destructive testing (NDT) techniques is discussed, showing the complementarity of NDT and how it could be optimized in this application.