Mitigation of Vortex-induced Vibration of a Long-span Bridge using Flexible Membranes

In recent years, several in-service long-span bridges have experienced unexpected vortex-induced vibration (VIV). For example, in 2020, the Humen Bridge was closed for nearly 10 days due to large-amplitude VIV, causing significant economic losses and negative social impacts. Once a bridge experiences VIV, rapid vibration mitigation thereby minimizing economic losses and negative social impacts are crucial. Therefore, there is an urgent need to develop a rapid and economically feasible mitigation measure that allows for modular design and quick assembly. Flexible membranes (FM) have been proved to be effective in suppressing VIV of bluff bodies, however, the effect and design of FMs for VIV mitigation of bridges have not been fully studied. In this study, the unexpected VIV recently observed in a cable-stayed bridge is described, and a comprehensive experimental study of VIV mitigation using FMs is presented. A series of wind tunnel tests are carried out on a sectional model of the bridge girder, to study the effect of installation location, arrangement, geometric size, material of FMs on their VIV-mitigation performance. After a series of aerodynamic optimization, segmented FMs installed under the wind fairings of the girder at intervals can successfully mitigate the large-amplitude VIV of the Π-shaped girder. Above all, FMs can be used as a temporary vibration mitigation measure in emergency treatment of VIV of a long-span bridge, buying valuable transition time for the implementation of subsequent permanent vibration mitigation measures.