Comparative Analysis of Wavelet and Hilbert Transforms for Vehicle-Based Identification of Bridge Damping Ratios

Much of the research has focused on identifying bridge frequencies for health monitoring, while the bridge damping ratio also serves as an important factor in damage detection. This study presents an enhanced method for identifying bridge damping ratios using a two-axle, three-mass test vehicle, relying on wheel responses captured by only two mounted sensors. Damping ratio estimation formulas are derived using both the Hilbert Transform (HT) and Wavelet Transform (WT), with a consistent formulation that confirms accurate estimation is achievable with minimal instrumentation, particularly when addressing the support effect. A comparative analysis of the two signal processing techniques reveals the superior performance of WT in identifying bridge damping ratios. The effectiveness of the proposed procedure and formulas is validated through a detailed parametric study, demonstrating robustness across bridges with varying modal damping ratios and different spans using minimal sensors. Moreover, the present study shows that responses from only the first two spans of a multi-span bridge are sufficient for reliable damping estimation, underscoring the practicality and scalability of the procedure for structural health monitoring applications.