Experimental study on the wind-induced vibration of a dry inclined cable—Part II: Proposed mechanisms

The possibility of dry inclined cable galloping is of concern in the design of bridge stay cables. Although the phenomenon has only been observed in a few experimental studies, the fact that the mechanism of excitation is not fully understood makes it difficult to develop solutions with confidence. To clarify its physical nature, a series of dynamic and static model wind tunnel tests have been carried out in the current study. The present paper will focus on exploring the applicability of Den Hartog criterion and on an explanation of its driving mechanism. The spatial structure of the flow field surrounding an inclined cable will be examined to assist in better understanding of the phenomenon. Results show that the critical onset condition of the divergent motion predicted by the Den Hartog criterion (as applied to an inclined circular cylinder) agrees well with the experimental observation. However, satisfaction of the criterion only occurs within a critical range of Reynolds number. Further, within the critical ranges of wind speed and cable orientation, flow around the cable is found to be better organized. The resultant fluid forces acting at different longitudinal locations of the cable tend to point toward the same direction which generates greater cross-flow excitation force, and the axis-wise lift correlation is enhanced.