Structural galloping suppression with high-frequency flutter

Abstract

Galloping presents a significant challenge in engineering, often causing large-amplitude vibrations in structures such as suspended electrical cables, bridges and towers, posing substantial risks and property damage. While injecting high-frequency excitations can mitigate structural galloping, current active suppression methods, which apply excitations after galloping has developed, are suboptimal, limiting their widespread adoption. In this study, a low-cost and easy-to-implement passive galloping suppression approach utilizing flutter-induced vibrations is proposed, exhibiting robust anti-galloping effects under natural wind conditions. By strategically placing flags, high-frequency fluttering forces generated by wind flow are exploited to impose surface loads on the structure rapidly. This preemptively suppresses low-frequency galloping, mitigating its onset effectively without necessitating substantial force. A distributed aerodynamic model is developed to simulate the suppression phenomenon, accompanied by a comprehensive analysis considering factors such as flutter characteristics, wind speed, and flag position and geometric parameters. The analysis also explores distinct suppression mechanisms that arise when the fluttering frequency approaches the second and third modal frequencies of the structure. The proposed galloping suppression approach has been successfully simulated and validated through theoretical calculations and experimental tests, and test results showcase a significant reduction in vibration amplitudes, with suppression ratios ranging from 85% to 95% across wind speeds of 3 m/s to 10 m/s. Additionally, this approach demonstrates effective suppression capabilities under variable wind speed conditions, indicating its reliability and practicality for mitigating detrimental galloping in real-world scenarios.