Investigation on vortex-induced vibrations of dual parallel suspenders with different diameters: An enhanced response phenomenon

A suspender design with differing diameters was investigated during the conceptual phase. To evaluate the feasibility of this configuration, wind tunnel tests were conducted on a section model of the suspenders. An enhanced vortex-induced vibration (VIV) response was observed in the downstream suspender, which had a larger diameter than the upstream suspender. The vibration response, motion trajectories, and frequency spectrum of the suspenders were first investigated. Furthermore, aerodynamic damping ratios, surface wind pressures, and vortex evolution were analyzed to explore the mechanisms behind the response enhancement phenomenon. Results show that aerodynamic interference from the upstream suspender amplified the downstream response, reaching a maximum magnitude 2.2 times that of a single suspender. The aerodynamic negative damping effect is evident during the VIVs of the suspenders. Enhanced VIV response in the downstream suspender is associated with the dominance of cross-wind pressure modes, which account for 69 % of the total energy. Simultaneously, the newly formed downstream vortices with negative pressure merge with the vortices reaching from upstream, synergistically increasing the resultant cross-wind force. Findings suggest that the VIV response of the suspender can be enhanced at a specific spacing, indicating that using suspenders of different diameters should be approached with caution or avoided.