With the intensification of energy consumption, how to make rational and efficient use of wind energy has been studied all over the world. The construction of facilities to obtain wind energy requires an accurate assessment of the wind characteristics of the local terrain. In order to study the wind characteristics on an island in Southeast China, a 1:1300 terrain model is established, and the characteristics of mean wind and fluctuating wind are studied by numerical simulation and wind tunnel test. The results show that wind speed is affected by the incoming wind direction and local terrain. Wind speed on windward slopes and flat areas with no obstructions is higher, and wind speed on leeward slopes and valleys is lower. Then, the wind attack angle of each measuring point is mainly in the range of −10°~10°, which is much higher than that in flat areas. The positive and negative wind attack angles are controlled by the incoming wind direction, and the size is closely related to the local terrain. As for pulsation characteristics, the disturbance of the inflow determines the turbulence intensity. The incoming wind direction mainly affects the turbulence intensity on the hillside, while the turbulence intensity in the valley and flat area is controlled by the local terrain. In addition, the fluctuating wind speed power spectra on the island is more consistent with the von Karman spectrum, which is quite different from the Kaimal spectrum. The bandwidth on hillsides and valleys will not change with the change in inflow, but for flat areas, the bandwidth is greatly affected by the inflow direction.

Wind tunnel tests are a commonly used method for studying wind characteristics of complex terrain; but truncation of the terrain model is usually unavoidable and affects the accuracy of the test results. For this reason, the effects of truncated and original terrain models on the simulation of wind characteristics for complex terrain were investigated by considering both nontruncated and truncated models, with the truncated model considering the applicability of two types of transition sections. The results show that the effect of topographic truncation on profiles of mean velocity and turbulence intensity is different for regions and that inclination angle profiles are extremely sensitive to the changing topographic features upwind. In those cases, the spectra of streamwise velocity were overestimated in the low-frequency range but underestimated in the high-frequency range due to topographic truncation. At the same time, the less negative value of the slope of the spectra was found at the inertial subrange. Furthermore, the normalized bandwidth was also influenced by topographic truncation, which was narrowed in windward and leeward regions and broadened in the valley region. We should note that the performance of the transition sections used in this study was quite limited and even resulted in inaccuracies in the simulation.

This study aims to develop empirical formulas to estimate the flutter critical wind speed (FCWS) of cable-suspended bridges considering the effect of wind angle of attack (AoA). On the basis of simplified closed-form solution derived by Xinzhong Chen, the effects of wind AoAs and structural parameters on FCWS are introduced by modifying the flutter indexes. The simplified closed-form solution was transformed into a flutter index form, which facilitated a visual comparison of the impact of flutter derivatives and structural parameters on flutter performance. Based on this reformulated solution, an analysis was conducted to investigate the effects of wind AoAs and structural parameters on flutter indexes. This analysis revealed that, as the wind AoA increases, the critical flutter index transitioned from being a constant to a parameter dependent on structural parameters. When specifically targeting cable-suspended bridges, the critical flutter index could be expressed as a function of wind AoAs and frequency ratios. Following these findings, the empirical formulas were obtained using the nonlinear least squares method. Finally, the accuracy and applicability range of the proposed formulas were confirmed through numerical validation. The empirical formulas of FCWS of cable-suspended bridges are accurate when the AoA is less than 7°.

This study investigates the effectiveness of various aerodynamic countermeasures in enhancing the flutter performance of cable-suspended bridges through wind tunnel experiments. Two groups of countermeasures were examined: aerodynamic attachments and bridge deck gratings. Based on closed-form bimodal flutter solutions, the flutter mechanisms of three effective countermeasures were analyzed in detail. In addition, the generalizability of these countermeasures was assessed in terms of the flutter index across different wind angles of attack (AoAs). The results demonstrate that double stabilizers installed on upper surface (case UDS), side grating (case SG), and bridge deck grating (case 30%) improved flutter performance across all wind AoAs, particularly at 3° wind AoA, where they shifted the flutter type from torsional flutter to coupled flutter, thereby significantly raising the critical flutter speed. Notably, the bridge deck grating demonstrated the potential to more than double the critical flutter speed across the tested wind AoAs. The study also finds that the flutter index can be considered constant for coupled flutter; however, for torsional flutter, it is highly dependent on reduced wind speed due to significant variation in the uncoupled term.

Nonlinear flutter is a low-frequency, large-amplitude wind-induced vibration with multiple degrees of freedom (DoFs) involved, potentially leading to structural failure and fatigue. The effects of aerodynamic coupling on nonlinear flutter behavior of a quasi-flat plate under various angles of attack (AoAs) are extensively investigated in this study. The aerodynamic coupling effects arising from vertical motion on critical wind speed, response amplitude, flutter type, and modal frequency were thoroughly examined by comparing single-degree-of-freedom (SDoF) and 2-degree-of-freedom (2DoF) wind tunnel tests. The dynamic mechanism by which aerodynamic coupling influences nonlinear flutter behavior was further elucidated in terms of the amplitude-dependent damping ratio. Moreover, based on amplitude-dependent flutter derivatives, a nonlinear flutter analysis model was built to examine the effects of structural parameters on aerodynamic coupling. Results reveal that when the AoA increases to 6°, aerodynamic coupling has little effect on the critical flutter speed and modal frequency. Aerodynamic coupling introduces additional negative damping to the system, influencing nonlinear flutter behavior by altering sable and unstable limited cycles (LCs). The coupled aerodynamic damping ratio continuously increases with rising wind speed, rendering the aerodynamic coupling effects significant even at high AoAs. The aerodynamic coupling effects intensify with decreases in nondimensional parameters w_a0/w_h0 and r/b, as well as an increase in u. This study provides a valuable reference for the wind-resistant design of flat plate-like structures.