Abstract
Real-time estimates of natural frequencies, mode shapes and damping of a structural system can be interpreted to its structural health. In this regard, real-time estimation of damping ratios for full-scale structures can be useful by itself or in conjunction with real-time estimates of natural frequencies. Such estimates also allow for continuous health monitoring. This paper demonstrates an approach of assessing real-time damping in full scale bridges and demonstrates this on one of the iconic steel bridges in Ireland, the Daly’s “Shaky” bridge. This is the only suspension bridge in the city of Cork, Ireland and renowned in popular culture for its lively behaviour. From existing vibration data evaluated from an image processing technique, the damping estimates of the Daly’s bridge are evaluated based on an automated enhanced frequency domain decomposition (AE-FDD) technique. The method provides accurate estimates of natural frequencies and mode shapes and additionally yields the damping ratio corresponding to each vibration (and/or torsional) mode. This technique of real-time damping estimation can be easily adapted for other full-scale structures in an automated real-time framework.
Highlights
Bridges are aging globally, and limited resources are available for their repair and rehabilitation
This paper presents an enhanced frequency domain decomposition (EFDD), which is implemented in an automated framework, which provides windowed estimates of modal damping using pedestrian excitation on the Daly’s bridge
The method is based on decomposing the power spectral density (PSD) function matrix into its spectral components, where individual SDOF systems correspond to each mode
Summary
Limited resources are available for their repair and rehabilitation. Advances in statistical signal processing techniques, data acquisition methods and intelligent monitoring strategies have prompted a growth in output-based smart sensing – especially for systems embedded with a dense array of wireless sensors [6] These techniques, developed mostly to identify the changes in the infrastructure system’s inherent properties, rely on basic SHM approaches that involve identification of structural modal parameters [7, 8]. Despite uncertainties and limitations in monitoring a structure through natural frequencies and damping ratios, they remain the most popular and often the most robust technique for SHM In this regard, significant attention has been directed towards pedestrian-induced vibrations in footbridges [12, 13]. The study presents this improved real-time framework for damping estimation, which can be implemented in other full-scale bridges
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