Grid turbulence on the flutter stability of streamlined box girders in long-span bridges

Long-span bridges are increasingly vulnerable to flutter instability due to their reduced stiffness and natural frequencies, which amplify their sensitivity to wind-induced vibrations. While traditional analyses focus on uniform flow conditions, real-world atmospheric wind is predominantly turbulent, making it critical to evaluate the impact of turbulence on bridge aerodynamic stability. This study investigates the flutter characteristics of streamlined box girders under the influence of grid-generated turbulence. Using wind tunnel tests, flutter derivatives were identified through forced vibration experiments conducted in both uniform and turbulent flow fields, and free vibration tests were performed to determine flutter critical wind speeds under varying turbulence conditions. The results reveal that turbulence significantly alters the flutter behavior of streamlined box girders. In uniform flow, flutter is characterized by abrupt vibration divergence at a critical wind speed, while in turbulent flow, the response transitions to gradual amplitude growth without a clear divergence point. Turbulence parameters, including intensity and integral scale, influence aerodynamic damping and modify flutter derivatives, leading to changes in flutter critical wind speeds. A comparison of theoretical and experimental flutter critical wind speeds demonstrates the reliability of flutter derivatives identified using the forced vibration method. This research highlights the complex role of turbulence in bridge aerodynamics, providing theoretical and experimental insights into the effects of turbulent flow on flutter stability. The findings contribute to improved predictive capabilities for aerodynamic performance and offer guidance for the design and safety assessment of long-span bridges in turbulent wind environments.