Article Article
Delamination Detection in Octagonal Prestressed Concrete Piles Using Impact Echo

The objective of this study was to develop an innovative signal interpretation algorithm for impact echo (IE) for effective delamination detection in octagonal prestressed concrete piles. A series of numerical simulations (3D FEM) was first conducted to investigate feasibility of the IE testing for octagonal pile testing. Based on the 3D FE analyses, an advanced signal interpretation algorithm was proposed to analyze the IE test results. That includes (i) a signal decomposition scheme for extracting resonance modes from the propagating surface waves, and (ii) an energy-based approach for separation of damaged regions from solid concrete. The proposed algorithm was implemented in the field to evaluate the presence, depth and severity of delamination as a result of chloride-induced corrosion. The surveys were conducted on six octagonal concrete piles. IE test results are presented as 2D delamination maps that show the locations of likely delaminated regions along with the depth information. For the comparison purposes, the delamination maps were related to the results obtained by two different NDT methods, i.e., ground penetrating radar (GPR), and electrical resistivity (ER). Delaminated regions predicted by the IE tests have a reasonably good agreement with the results from GPR and ER, which describe areas of likely deterioration and highly corrosive environment, respectively. The findings in this study demonstrated that the proposed signal interpretation algorithm for the IE is effective in detecting and characterizing delamination in octagonal prestressed piles.

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