Effects of surface roughness and cross-sectional distortions on the wind-induced response of bridge cables in dry conditions

Theoretical and experimental investigations to date assumed that bridge stay cables can be modelled as ideal circular cylinders and that their aerodynamic coefficients are invariant with wind angle-of-attack. These changes are neglected when the potential for bridge cable instability is evaluated, i.e. in terms of negative aerodynamic damping. On the other hand it has been demonstrated that bridge cables are characterised by local alterations of their inherent surface roughness and shape. Small deviations from ideal circularity determine significant changes with Reynolds number in the static drag and lift coefficients. The present study focuses on the dynamic response of a full-scale yawed bridge cable section model, for varying Reynolds numbers and wind angles-of-attack. Tests results show that the in-plane aerodynamic damping of the bridge cable section, and the overall dynamic response, is strongly affected by changes in the wind angle-ofattack.