Department of Civil and Environmental Engineering, University of Windsor
Department of Mechanical, Automotive and Materials Engineering, University of Windsor 401 Sunset Ave., Windsor, ON., Canada N9B 3P
Wind-induced cable vibration is a contemporary issue in cable-stayed bridges, which potentially threats the safety and durability of the structure. A thorough understanding of the fundamental physics underlying these phenomena is a priori for developing effective remedies to resolve the issue. In the present paper, possible mechanisms associated with two different types of wind-induced cable vibration phenomena have been studied based on a set of wind tunnel experimental data on a rigid circular cylinder. A number of analyses were applied to the unsteady surface pressure data sampled on the cylinder model to elucidate the possible mechanisms of these phenomena. Negative aerodynamic damping ratios were identified in the ranges of Reynolds number and cylinder orientation where divergent galloping type of response is expected to occur. A breakdown range of wind-cable relative angle was detected in which the regular Karman vortex shedding was suppressed within the subcritical Reynolds number range. In the critical Reynolds number range, however, the symmetry of surrounding flow field beyond this breakdown range could be altered drastically, leading to considerable changes in the lift force which is responsible for the negative aerodynamic damping ratio values. Significant increase of correlation length of sectional aerodynamic forces was also detected within this breakdown range in the critical regime. This, combined with the negative aerodynamic damping, is proposed to be a possible necessary onset condition for the galloping of dry inclined cables. The limited-amplitude instability, which occurred in the subcritical Re range, on the other hand, was found to be caused by the mitigation of regular Karman vortex shedding in the breakdown range while the spatial flow field was strongly correlated. In addition, the decay in correlation of aerodynamic forces in the critical Re range was believed to be key to the suppression of this unstable response.