Hyperbolic Signature Extraction of Deeper Rebar Layer in Concrete Bridge Decks Using GPR

Abstract

Bridge collapses were reported worldwide. More than a quarter of the bridges in the United States are obsolete and deficient. The evaluation and maintenance of concrete bridge decks has drawn significant attentions from the government and its people over the past decades. A non-destructive evaluation (NDE) technique, ground penetrating radar, is preferred for its high speed, which causes minimal traffic interruption. The evaluation is generally based on rebar reflections. The reflections from the first rebar layer are usually strong enough to evaluate either the concrete material above this layer or the rebar corrosion condition. However, in most cases, only one third of the deck can be evaluated this way. Deeper rebar reflections are usually too weak to be detected because of the high attenuation through long distance and the masking effect of the first layer. Further processing is needed to extract the information from the second rebar layer. In this paper, a migration, image enhancement, and demigration process is proposed. The main idea of the proposed approach is to enhance the rebar reflection intensity by increasing the signal to noise ratio without significantly distorting the radargram. Its effectiveness is validated by the simulation study discussed in this paper.