A Novel Procedure for Damping Ratio Identification from Free Vibration Tests with Application to Existing Bridge Decks

Damping is an inherent structural property that plays an important role in the overall behavior of dynamical systems, and it can also represent a potential indicator of their health. However, its estimation is often affected by significant uncertainties, which are attributable to measurement noise, test conditions (e.g., environment, level and type of applied loads), and identification technique. In this contribution, a novel procedure is developed for modal damping ratio identification from free vibration tests, which exploits a tuned version of the Variational Mode Decomposition (VMD) technique for signal decomposition. Once the time history response of each mode is extracted, relations among areas forming from the free-decay time-domain response are used to estimate the modal damping ratio of each mode. This approach mitigates the detrimental effect of noise contamination likely occurring in real signals. Two applications are presented to illustrate the efficiency of the proposed identification strategy. The first example deals with the analysis of a theoretical signal (with pre-defined frequencies and damping ratios) for validation purposes. A real signal related to the free vibration response of a prestressed concrete bridge deck is finally examined. Based on the obtained results, the proposed identification strategy proved to be efficient and suitable for automatic implementations, thereby resulting particularly attractive for practical applications.