Influence of wind directionality on the three-dimensional distortion of buffeting force on a streamlined bridge deck: Insight into the pylon interference effect

The present work aims to experimentally investigate the influence of wind directionality on the three-dimensionality of buffeting force on a streamlined bridge deck, considering the pylon interference effect (PIE). The pylon has an obvious impact on the downstream flow structure under the skew wind, influencing the aerodynamic loads acting on the bridge deck. The results show that the most dangerous wind direction exists at 30 degrees for the downstream bridge deck, indicating the invalidation of the traditional "cosine rule." It indicates that the lift force will be amplified due to the PIE, depending on the yaw angle of the oncoming flow. When turbulence passes through the pylon, the large-scale eddies in the wake region will be broken into small-scale eddies, attenuating the integral length scale in comparison with that of the free-stream turbulence. Consequently, the lift spectrum and corresponding three-dimensional aerodynamic admittance (AAF) increase in the high-frequency domain, resulting in the decrease in the spanwise correlation under the skew wind. Notably, the two-dimensional (2D) AAF indicates that the 2D distortion effect of turbulence on the lift increases in the wake region, causing the 2D AAF to decay rapidly in the high-frequency domain.