Aerodynamic Characteristics of Bridge Stay Cables Modified by Illumination Attachments: Large-Eddy Simulation and Wind Tunnel Validation

Stay cables are slender and lightly damped structural members that are highly sensitive to wind action. Although the aerodynamic effects of rain rivulets, ice accretion, snow accretion, and surface roughness on bridge cables have been widely investigated, the influence of architectural illumination attachments installed along stay cables remains insufficiently understood. Such attachments modify the original circular cable cross-section and may alter aerodynamic force coefficients, vortex-shedding characteristics, wake structure, and galloping tendency. This study investigates the aerodynamic characteristics of bridge stay cables modified by illumination attachments with different shapes, dimensions, and installation gaps. Large-eddy simulation was performed using OpenFOAM 5.0 to resolve the unsteady flow around a reference circular cable and ten illumination-modified cable configurations at a representative subcritical Reynolds number of Re = 9.42 × 104. The numerical model was first verified using benchmark aerodynamic properties of a circular cylinder and then validated against force measurements obtained from closed-circuit wind-tunnel experiments. The results show that illumination attachments significantly affect the drag and lift characteristics of stay cables, particularly at oblique wind attack angles. Among the representative wind attack angles considered, the drag coefficient generally increases when the attachment is exposed laterally or obliquely to the incoming flow, whereas the lift coefficient is strongly affected by attachment shape and angular orientation. Rectangular and double-rectangular attachments produce stronger wake disturbance, greater pressure asymmetry, and more complex vortex structures than circular attachments. The preliminary Den Hartog analysis further indicates that sharp-edged and direct-contact attachments may increase galloping susceptibility, whereas smaller circular attachments and separated-gap configurations show more moderate aerodynamic behavior. These findings indicate that illumination systems should not be treated as purely architectural accessories, but should be considered in the aerodynamic assessment and wind-resistant design of cable-supported bridges.