Accuracy of NDE in bridge assessment

摘要

NDE has a key role in helping to evaluate input parameters to bridge management systems. As the world's bridge stock increases in age, there is considerable interest in maintaining and extending the life of existing bridges, and hence the interest in bridge man- agement systems. A range of NDE methods have been identified and the accuracy of the time domain techniques has been related to signal wave- length. Using the widely accepted criterion of a minimum resol- ution related to wavelength, the techniques of ultrasonics and impact echo have been analysed in detail. The latter has been investigated with respect to post-tensioned concrete bridge beams. It was concluded that the minimum resolution achievable in a dis- persive medium such as concrete was a half wavelength, λ/2. It was also shown that the concept of using a null hypothesis with impact echo stating that : 'if no defect is identified, none exists' - is fundamentally flawed.