In this study, a 5:1 rectangular section was taken as the research object. An aerodynamic reduced-order model was used to verify whether the rectangular section had a similar oscillation mechanism to a circular section based on the results of two-dimensional unsteady Reynolds-averaged Navier–Stokes calculations. Computational fluid dynamics was used to study the vertical oscillation characteristics of the 5:1 rectangular section under the influence of different parameters. The results showed that the vertical oscillation of the rectangular section could be divided into two patterns according to the oscillation characteristics: “resonance-induced vibration” and “competition-induced vibration.” The resonance-induced vibration shows a quick development in amplitude, while competition-induced vibration has two stages before stabilization. The vibration amplitude, oscillation frequency, and lock-in region were affected by variations in the mass ratio. The damping ratio had less effect on the oscillation frequency and vibration amplitude than the mass ratio. However, a reduction in the damping ratio enlarged the lock-in region at a high reduced velocity. Additionally, the difference in the initial displacement had a considerable influence on the vibration amplitude of competition-induced vibration, while it had little effect on resonance-induced vibration.

Twin-box girders are a good option for long-span cable-bearing bridges due to their excellent stability. Nonetheless, the girder’s slots may generate vortex-induced vibrations (VIVs). Fortunately, appropriate aerodynamic measures can effectively suppress the VIVs in twin-box girders while reducing costs. To examine the effects of vortex isolation plates with varying aperture diameters and opening ratios on the VIVs, a segment model wind tunnel test was conducted. The results demonstrated that a reduction in the opening ratio improved the performance under heaving VIVs, but there was no discernible trend under torsional vibrations. It was also discovered that the opening size significantly influences the length of the lock-in region of torsional vibrations. Furthermore, heaving VIVs have a substantial correlation with both of the girder’s boxes, while torsional vibrations are mostly connected with the downstream section.

To investigate the non-stationary characteristics of the wind field at the U-shaped canyon bridge site and its impact on fluctuating wind characteristics, a wind observation tower was installed near a cable-stayed bridge. The Augmented Dickey–Fuller (ADF) test was employed to assess the stationarity of wind speed series, while the discrete wavelet transform (DWT) was applied to reconstruct the time-varying mean wind and analyze its effect on fluctuating wind characteristics. Results indicate that wind speeds in this region exhibit bimodal distribution characteristics, with the Weibull-Gamma mixed distribution model providing the best fit. The proportion of non-stationary samples increases with height. Autocorrelation function (ACF), partial autocorrelation function (PACF) tests, and power spectral density (PSD) analysis determined the optimal wavelet decomposition level for wind speed in this region. Analysis of non-stationary samples using db10 wavelet reconstruction reveals that the stationary wind speed model overestimates turbulence intensity but underestimates the turbulence integral scale. The downwind spectrum deviates from the Kaimal spectrum in both low- and high-frequency bands, whereas the vertical spectrum aligns well with the Panofsky spectrum. The findings demonstrate that the wavelet reconstruction method more accurately captures fluctuating wind characteristics under the complex terrain conditions of this canyon area.