Damage assessment of a gradually damaged pre-stressed concrete bridge using static load tests and non-linear vibration characteristic

The detection of damage in bridges is mainly done by visual examination. However, defects as for instance partial rupture of a prestressing cable cannot be visually observed. It is well known that damage changes dynamic structural parameters like eigenfrequencies, modeshapes and damping. Since the sensitivity of changes in modal properties is sometimes low, this paper presents an approach that makes use of non-linear dynamic behaviour. The basic idea is that non-linear dynamic effects, i.e. the amplitude dependency of the modal parameters and the occurrence of Higher Harmonics, vary with changes in structural condition, due to failure of tendons or cracks for instance. This paper presents the experimental results of tests with a gradually damaged reinforced concrete beam and the application of this method to a prestressed concrete bridge. The results concerning damage assessment are compared to the results of static load tests as a classical and often used method to assess the state of a structure.