SOME INSIGHT INTO THE WIND-INDUCED VIBRATION OF STAY CABLES IN THE CONTEXT OF RIGID STATIC INCLINED CIRCULAR CYLINDER

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.

[1]  Steven E. Ramberg,et al.  The effects of yaw and finite length upon the vortex wakes of stationary and vibrating circular cylinders , 1983, Journal of Fluid Mechanics.

[2]  Shaohong Cheng,et al.  Experimental study on the wind-induced vibration of a dry inclined cable—Part II: Proposed mechanisms , 2008 .

[3]  Shaohong Cheng,et al.  Spatial flow structure around a smooth circular cylinder in the critical Reynolds number regime under cross-flow condition , 2008 .

[4]  Gl Larose,et al.  Experimental study on the wind-induced vibration of a dry inclined cable—Part I: Phenomena , 2008 .

[5]  Masataka Shirakashi,et al.  Effect of the secondary flow on Karman vortex shedding frequency from a yawed cylinder. , 1985 .

[6]  Nicholas P. Jones,et al.  Wind tunnel testing of yawed and inclined circular cylinders in the context of field observations of stay-cable vibrations , 2009 .

[7]  J. Humphreys.  On a circular cylinder in a steady wind at transition Reynolds numbers , 1960, Journal of Fluid Mechanics.

[8]  A. Roshko.  On the development of turbulent wakes from vortex streets , 1953 .

[9]  Masahiko Kawamura,et al.  Spanwise Correlation Measurement behind a Circular Cylinder in Subcritical Reynolds Number Region , 1972 .

[10]  G. Schewe.  On the force fluctuations acting on a circular cylinder in crossflow from subcritical up to transcritical Reynolds numbers , 1983, Journal of Fluid Mechanics.

[11]  Stephen R. Snarski.  Flow over yawed circular cylinders: Wall pressure spectra and flow regimes , 2004 .

[12]  Hiromichi Shirato,et al.  Aerodynamic behavior of inclined circular cylinders-cable aerodynamics , 1990 .

[13]  Gl Larose,et al.  Aerodynamic behaviour of an inclined circular cylinder , 2003 .

[14]  E. Caetano.  Cable Vibrations in Cable-Stayed Bridges , 2007 .

[15]  Hiromichi Shirato,et al.  Rain-wind induced vibration of cables of cable-stayed bridges , 1992 .

[16]  Nicholas P. Jones,et al.  Evaluation of Viscous Dampers for Stay-Cable Vibration Mitigation , 2001 .

[17]  Hitoshi Yamada,et al.  Aerodynamic response of PE stay cables with pattern-indented surface , 1994 .

[18]  C. Farell,et al.  On flow separation and reattachment around a circular cylinder at critical Reynolds numbers , 1989, Journal of Fluid Mechanics.

[19]  C. Williamson.  Advances in our understanding of vortex dynamics in bluff body wakes , 1997 .

[20]  Hiroshi Tanaka,et al.  Correlation of aerodynamic forces on an inclined circular cylinder , 2005 .

[21]  John H G Macdonald,et al.  A unified approach to aerodynamic damping and drag/lift instabilities, and its application to dry inclined cable galloping , 2006 .