ACCURACY OF NDE IN BRIDGE

NDE has a key role in helping to evaluate input parameters to bridge m anagement systems. As the world's bridge stock increases in age, there is considerable interest in maintaining and extending the life of exi sting bridges, and hence the interest in bridge management systems. A range of NDE methods have been identified and the accuracy of the time domain techniques has been related to signal wavelength, Using the wi dely accepted criterion of a minimum resolution related to wavelength, the techniques of ultrasonics and impact echo have been analysed in d etail. The latter has been investigated with respect to post-tensioned concrete bridge beams. It was concluded that the minimum resolution a chievable in a dispersive medium such as concrete was a half wavelengt h, lambda/2. It was also shown that the concept of using a null hypoth esis with impact echo stating that: 'if no defect is identified, none exists' is fundamentally flawed. (C) 1998 Elsevier Science Ltd. All ri ghts reserved.