Aerodynamic damping of an inclined circular cylinder in unsteady flow and its application to the prediction of dry inclined cable galloping

The mechanisms and onset conditions related to dry inclined bridge stay cable galloping have been studied both experimentally and analytically over the past two decades. The existing literatures are however limited to the smooth flow condition, of which the unsteady/turbulent nature of natural wind is ignored. This inconsistent flow condition from the site could potentially distort the actual aerodynamic interactions between a cable and the oncoming wind, and lead to an improper solution for designing vibration controlling means for stay cables. In view of this, the current paper aims at proposing a quasi-steady analytical approach to qualitatively study the effects of unsteady/turbulent wind on the aerodynamic behavior of an inclined cable. The impact of unsteady/turbulent flow on the aerodynamic stability of an inclined and/or yawed cable in unsteady flow conditions is extensively studied. Results suggest that the existence of flow unsteadiness in the natural wind may increase the risk of a stay cable to experience galloping type of motion. In addition, a case study is presented to evaluate the aerodynamic stability of a real bridge stay cable in unsteady wind. The critical onset conditions predicted by the proposed model are found to agree well with the site observations.

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