International state of practice in the inspection of grouted duct post-tensioned concrete bridge beams and decks

Post-Tensioned concrete bridges have been used for both rail and road bridges for some 40 years. Problems were first noticed with road bridges due to the use of de-icing salts. However there have been collapses of post-tensioned concrete railway bridges. Following this series of collapses, the Highways Agency enforced a ban on the construction of post-tensioned bridges with metallic tendon ducts. The moratorium was lifted with the introduction of plastic tendon ducts.

This paper will focus on the analysis of impact-echo NDT of concrete beams with plastic tendon ducts - using both a conventional frequency domain analysis and also using the Japanese SIBIE (Stack Imaging of Spectral Amplitudes Based on Impact-Echo) method. It will be shown that the SIBIE method of analysis exhibits great promise in testing these previously difficult to inspect plastic tendon ducts, using impact-echo.