Lift-off-validated assessment of cable force prediction methods for cable-stayed bridge using vibration-based approaches

Cable force estimation is critical for ensuring the structural health of cable-stayed bridges. This study assesses the accuracy of three vibration-based models – classical string theory, a least-squares beam formulation, and a two-mode beam combination – using lift-off test results as ground-truth validation. Field measurements were analysed to extract natural frequencies, which served as inputs to predict axial forces. The correlation between estimated forces and lift-off measurements was evaluated using the Pearson coefficient and mean absolute error (MAE). Results show strong agreement between vibration-based estimates and lift-off forces, with correlation coefficients ranging from 0.8610 to 0.8619. Beam-theory approaches outperformed the string model, achieving 7–8% lower MAE confirming that incorporating bending stiffness and multi-mode effects improves accuracy. However, small numerical differences suggest axial tension remains the dominant factor, with flexural rigidity having minor influence on long and slender cables. The near-perfect correlation between the beam-based models (r > 0.9996) highlights their internal consistency. Overall, these findings demonstrate that vibration-based models are reliable tools providing essential insights for structural health monitoring and maintenance strategies.