Multidisciplinary Health Monitoring of a Steel Bridge Deck Structure

Fatigue cracks in orthotropic bridge decks are an important cause for the necessary renovation of existing bridges. Parallel utilization of various technologies based on different physical sensing principles can potentially maximize the efficiency of structural health monitoring (SHM) systems for these complex structures. A multidisciplinary SHM system composed of acoustic emission, strain measurements, and vibration measurement has been applied to a test steel bridge deck under a fatigue loading in a lab environment. Having the main focus on acoustic emission and strain measurement, the present paper provides an evaluation of the performance of the SHM system in terms of detection of the crack initiation, localization, and growth. During the destructive test, the strain measurement was employed as a local monitoring method, and acoustic emission was utilized as a local/global monitoring scheme. The monitoring performance was validated using visual inspection and time-of-flight diffraction (TOFD) measurements. Some of the main observations in this study are: (i) good agreement between the estimated crack size based on the strain measurement and TOFD measurement, (ii) the earlier detection of the crack activity by acoustic emission compared to the 10% deviation of the strain measured at a few millimeters away from the crack initiation location, and (iii) localization of multiple active cracks by acoustic emission.