Session 4 -Structural Health Monitoring of Bridges The Use of Dynamic Data for the Structural Health Monitoring of Bridges

SUMMARY This paper gives a brief overview of the structural health monitoring process and then presents the results of work done on laboratory scale reinforced concrete bridge decks to illustrate some of the advantages and problems in using vibration data for structural health monitoring. Ten 5m by 2.5m reinforced concrete bridge decks were incrementally loaded to failure. At each load increment a full modal survey was performed. Variations in natural frequency with level of damage were identified, but several problems were noted regarding the efficient identification of modal properties, the effect of indeterminate boundary conditions and the tracking of modes between different damage states. Finite element model updating was used to relate the changes in modal properties to stiffness changes in the decks, but this process was again limited due to the complexity of the deck structure and the need for prior knowledge of the damage location. Finally, alternative signal processing techniques were applied to the frequency response function data, including principal component analysis and spectral distance measures. Although these approaches lack the physical meaning of modal parameters, they did prove to be a more efficient and robust method of comparing the vibration data. In particular, they are more suited to use in a real time active monitoring scheme than the modal methods