Damage detection and assessment by ambient vibration monitoring

Ageing is a fact of life. This applies for structures as well. Re-evaluation of structures therefore has become standard procedure and offers the chance to look at situations in the light of the newest technologies. Recent outstanding development in the field of traffic infrastructure can be applied to the nuclear facilities in order to improve existing methodologies. This contribution elaborates the options bridge monitoring methods offer for the assessment and seismic re-evaluation of nuclear facilities. The BRIMOS approach is based on the fact that the condition of any structure is represented in its dynamic behaviour. The so called 'Vibrational Signature' contains all information necessary for a detailed assessment and evaluation. The tools already in use comprise : - Parametric excitation, where spectra from external sources, such as earthquakes, are compared to the structure response; - Frequency analysis, where the response of the structure is monitored over a period of time and trends can be extracted; - Damping evaluation, where information content of the Vibrational Signature is extracted to allocated weak points and damages in the structure; - Eigen-form analysis, which allows a prediction of the behaviour of the structure under extreme loading conditions; - Furthermore loading history, life expectancy, fatigue condition, influence of environmental loads and operation conditions are assessed. (author)