Identification of Tendon Ducts in Prestressed Concrete Beam by SIBIE

Abstract

The impact-echo method is well-known as a non-destructive testing for concrete structures. It is based on the use of low-frequency elastic waves that propagate in concrete to determine thickness or to detect internal flaws in concrete. In this method, the presence and the locations of defects in concrete are estimated from identifying peak frequencies in the frequency spectra, which are responsible for the resonance due to time-of-flight from the defects. In practical applications, however, spectra obtained include so many peak frequencies that it is fairly difficult to identify the defects correctly. In order to improve the impact-echo method, Stack Imaging of spectral amplitudes Based on Impact Echo (SIBIE) procedure is developed as an imaging technique applied to the impact-echo data, where defects in concrete are identified visually at the cross-section. In this study, the SIBIE procedure is applied to identify grouted or ungrouted post-tensioning ducts in prestressed concrete beam. It is demonstrated that the ungrouted duct can be identified with reasonable accuracy.