Measurement of modal curvatures using optical fiber strain sensors and application to damage identification using vibration monitoring

Vibration monitoring is a well-known technique to determine wether a civil engineering structure is damaged or not. From the vibration tests, natural frequencies, modal displacements, damping ratios and modal curvatures can be determined using system identification methods. These modal parameters are subsequently used for damage identification. If a structure is damaged, the changes in modal curvatures tend to be more local than the changes in modal displacements, so modal curvatures are more useful for damage localization. The possibility of directly measuring modal curvatures using optical fibre strain sensors, instead of calculating them from modal displacements using a numerical integration procedure, is a big step forward in the exploitation of modal curvatures for damage identification. As a practical application, the damage identification at the Tilff bridge is discussed.