A two-degree-of-freedom aeroelastic model for the vibration of dry cylindrical body along unsteady air flow and its application to aerodynamic response of dry inclined cables

A two-degree-of-freedom aeroelastic model is proposed to study wind-induced response of bridge stay cables in the context of a rigid circular cylinder model oscillating in an arbitrary orientation with respect to the oncoming unsteady flow. Compared to the existing analytical models and wind tunnel studies, the proposed model can take into account the unsteady characteristics of natural wind and predict the evolving history of cable response. The validity of the proposed model is verified by the results from an earlier wind tunnel study. The rationality of defining a cable aerodynamic stability criterion using solely the Ur-Sc relation is discussed. Two different unsteady wind models are used to investigate the impact of flow unsteadiness on the wind-induced response of stay cables. A case study is presented to evaluate the aerodynamic behavior of a real bridge stay cable in unsteady/turbulent natural wind. Results show that while the emergence of critical Reynolds number regime is crucial for the onset of dry inclined cable galloping, the spanwise correlation of aerodynamic forces acting on a cable and the sustained duration of critical flow condition are the determining factors for the continuous growth of unstable cable response and the eventual occurrence of this type of aerodynamic instability.