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

Long-span bridges are vulnerable to flutter instability, which can lead to catastrophic failure if not properly assessed. Traditional analyses have focused on smooth flow conditions, which do not fully reflect real-world aerodynamic conditions where boundary layer turbulence plays a significant role. This study delves into the flutter characteristics of streamlined box girder bridge decks, focusing on the effects of boundary layer turbulence. A novel analytical approach is introduced, incorporating spanwise correlation of self-excited aerodynamic forces into flutter analysis. Initially, wind tunnel tests involving forced vibration of segmental models were conducted in both smooth and turbulent flows to determine the flutter derivatives of the bridge deck. This was followed by an investigation of flutter critical wind speeds under varying conditions using taut strip model free vibration tests. The highlight of this research is the development of a comprehensive three-dimensional flutter analysis method that integrates the spanwise correlation effect. Findings indicate a significant influence of boundary layer turbulence on the flutter derivatives, with the observed flutter critical wind speeds in turbulent conditions surpassing those in smooth flow. The study also notes a decrease in flutter critical wind speeds with increasing turbulence intensity and integral scale. Importantly, the incorporation of spanwise correlation effects into the analysis yields theoretical flutter critical wind speeds that closely match those observed in wind tunnel experiments. This research contributes to a deeper understanding of aerodynamic behavior in bridge decks under turbulent conditions and enhances predictive capabilities in bridge aerodynamics.