Determination of the damping ratio of the Yusufeli Arch Dam under low-magnitude earthquakes during operational conditions

Concrete arch dams rely on energy dissipation through material damping and boundary interactions to attenuate seismic vibrations, yet quantitative field measurements of damping under real operating conditions are scarce. In this study, we present a comprehensive damping assessment of the 275 m-high Yusufeli Arch Dam during its reservoir impoundment phase (2022–2025). Six low-magnitude earthquakes (Mw 4.0–5.0) provided crest‐level acceleration records via a centrally located tri‐axial sensor. A multi-band logarithmic-decrement technique was employed, with filter frequencies adjusted according to real-time water-level–dependent natural frequencies. The resulting damping ratios ranged from 0.8% to 4.7% (mean 1.95%, COV 23%), revealing a strong amplitude dependence: higher crest peak accelerations corresponded to increased damping, while no clear trend emerged with reservoir fill level. These results demonstrate that under service-level seismic inputs, a constant damping ratio of 1–2% can be reliably assumed across impoundment stages, with higher values only necessary for stronger shaking. The methodology’s reliance on a single, easily maintained sensor and direct response data offers a practical approach for structural health monitoring and model calibration. By decoupling damping from continuous hydraulic loading variations and focusing on measured excitation amplitude, this framework enhances the accuracy of seismic response simulations and supports more effective maintenance and risk‐mitigation strategies for large arch dams.