Long-Term Damping Characteristics of a Cable-Stayed Bridge

Damping ratio is a crucial factor in assessing the vibrational serviceability of flexible large-scale structures such as cable-supported bridges. While the natural frequencies of structures have been estimated from operational modal analysis (OMA) with relatively minimal scattering, damping ratios have shown a high degree of scattering due to analytical uncertainty and in environmental and operational variations (EOV). To examine the damping ratio in context of EOVs, an automated damping estimation framework is applied with minimal user intervention to 2,5 years of long-term data acquired from a sparse continuous monitoring system. Daily and long-term fluctuations of damping ratios are examined. Environmental and operational factors such as temperature, wind environment and level of excitation are examined in context with damping ratios. The probability distribution of the damping ratio is also suggested based on statistical methods.