A computational fluid dynamics–based numerical parametric study for the characteristics of the solitary wave–induced forces on typical coastal twin bridge decks is conducted in this study. At first, the second-order solitary-wave model is developed followed by a verification process with the analytical one and a related experimental study. The laminar flow model and shear stress transport (SST) k-ω model are adopted and the comparisons of their results demonstrate that they can make close predictions for the bridge deck forces. Then, the general characteristics of the wave forces for a fixed deck gap and variable deck gaps with different still water levels (SWLs) and various submersion coefficients are observed. In addition, the characteristics of the wave forces on the landward bridge deck are presented by normalized factors based on the wave forces on the seaward deck. Finally, the hydrodynamic interference effects between the twin bridge decks are investigated and the effects of the deck vibrat...

In order to reveal the influence of initial excitation on the bifurcation phenomenon of bridge decks, a new perspective of flow characteristics is developed based on the computational fluid dynamics numerical simulation method. Then, the bifurcation mechanism of vortex-induced vibration (VIV) response and nonlinear flutter response of the H-shaped section is investigated. The results show that when the wind speed is 2 m/s, under a small torsional excitation of 0.5°, the flow field of the H-shaped section will develop into the vortex shedding mode of the vertical vibration, resulting in vertical VIV. However, while under a large excitation of 6°, the flow field will directly transform into the vortex shedding mode of the torsional vibration, resulting in torsional VIV. Therefore, the bifurcation phenomenon of the VIV response is observed. When the wind speed is 4 m/s, the H-shaped section exhibits a nonlinear flutter limit cycle oscillation under a large excitation of 8°, but its response can be ignored under a small excitation of 0.5°. This phenomenon is attributed to the significant change in the transition of the vortex shedding mode from a small amplitude to a stable large amplitude, and the flow field lacks enough energy to complete the transition of the vortex shedding mode, resulting in the bifurcation phenomenon of the nonlinear flutter response. When the wind speed is 3.0 m/s, the large excitation will change the vortex shedding frequency of the new H-shaped section, resulting in the torsional VIV.

Long hangers around the bridge tower are subjected to severe vibrations caused by the tower wakes. This study adopted an active suction/blowing control measure at the tower corners to control hanger vibrations and included four combination measures: upstream suction (US), upstream blowing (UB), downstream suction (DS), and downstream blowing (DB). The effects of control cases on the near-wake flow structures of the tower were first studied in two-dimensional RANS simulation, and the vibration behaviors of the hanger and control mechanism were further analyzed. The cases associated with UB and DS cannot effectively suppress hanger vibrations, and both lead to unfavorable upward trends in the aerodynamic coefficients of the tower. Especially for the cases associated with DS, at a specific control speed, the second-order frequency of the drag coefficient of the hanger is very close to its natural frequency, resulting in significant longitudinal vibration. The cases associated with US and DB are effective control schemes with longitudinal peak amplitudes of the hanger reduced by 94.1% and 94.5%, and lateral peak amplitudes reduced by 95.8% and 97.0%, respectively, compared with the case baseline. This is because the dominant frequency of the lift of the hanger is away from its natural frequency, and the fluctuating wind loads on the hanger are effectively suppressed. Finally, the control effect and vibration suppression mechanism for typical cases were further reproduced in three-dimensional large eddy simulations.

To investigate the characteristics of wind fields at the bridge site in mountain-gorge terrains more accurately and rationally, an updated curved boundary transition section (BTS) was proposed in this study. The flow transition efficiency considering the updated curved BTS was first investigated and compared with those in previous studies. Then a mountain-gorge terrain model in which a long-span bridge straddles was configured as a typical numerical example by establishing two different BTSs in the computational domain for comparison purpose. Furthermore, the effects of different BTSs on the characteristics of wind fields at the bridge site with two different ranges of terrain region were comparably investigated. The results show that the updated curved BTS is very user-friendly with a straightforward expression and has a better flow transition efficiency than those reported previously. The wind speeds at the bridge site with the updated curved BTS outperform those with the ramp BTS. An appropriate shape of BTS can probably be more important than the size factor of the terrain region in terms of predicating the characteristics of wind fields at the bridge site in such mountain-gorge terrains. It is hoped that this updated curved BTS can serve as basics for analyzing the wind fields at the bridge site in mountain-gorge terrains, which will be of benefit to investigate the structure performance under wind loads not only in the design stage but also in the service stage.

This paper presents an efficient approach for dynamic stress analysis of a long-span bridge under the combined action of stochastic traffic and wind loads based on the stress influence function, which converts the stress finite-element analysis problem into a problem of stress integral or summation. The Aizhai Bridge in China is used as an example to demonstrate the numerical procedure for the stress analysis. First, the finite-element model for the Aizhai Bridge is established, and the critical locations of the bridge are determined by refined analyses. By using influence line analysis, the stress influence functions to calculate the dynamic stress response of the bridge under random traffic and wind loads are obtained through segmented polynomial fitting. Second, the random traffic flow simulation program is compiled by adopting the Monte Carlo–simulation method. The moving equivalent dynamic vehicle loading, representing different types of running vehicles on the bridge, is calculated based on the full interaction analyses of a single-vehicle–bridge–wind system, and the database of the equivalent vehicle load is established. Finally, the stress induced by the combined action of the random traffic and wind loads is obtained by summing the product of the stress influence surface function and equivalent vehicle loads and by integrating the product of the stress influence line functions and wind loads where the dynamic effect is considered by introducing the dynamic influence coefficient. The proposed method is validated by comparing the results with those from analysis with commercial software, and it is found that that the proposed method is feasible and efficient.

This study investigates the effects of inhomogeneous wind fields on the aerostatic stability of a long-span cable-stayed bridge, which straddles a typical mountain-gorge terrain. Inhomogeneous wind fields, with featured wind speeds and wind attack angles, along the bridge’s main beam were firstly analyzed by using the computational fluid dynamics (CFD) approach. Then, a nonlinear methodology was implemented by adopting the ANSYS parametric design language (APDL) technology to analyze the aerostatic stability of long-span bridge under inhomogeneous wind speeds and inhomogeneous wind attack angles. The effects of inhomogeneous wind attack angles, inhomogeneous wind speeds, and both inhomogeneous wind speeds and inhomogeneous wind attack angles on the bridge’s aerostatic stability were comprehensively investigated. The aerostatic deformation of the bridge’s main beam and the variation of the cable’s axial force were also analyzed. The results show that the critical wind speed of the aerostatic instability under inhomogeneous wind attack angles is much smaller than that under homogeneous ones, and the performance of the aerostatic stability under inhomogeneous wind attack angles mainly depends on the peak wind attack angle rather than the average value of those inhomogeneous wind attack angles along the main beam. The wind-load effects acting on the main beam under inhomogeneous wind speeds are larger than those under homogeneous ones, and the critical wind speed of the aerostatic instability under inhomogeneous wind speeds is mainly determined by both the average and peak wind speeds along the main beam. The shapes of vertical displacements and torsion angles along the main beam are mainly dominated by the wind attack angles. However, the lateral displacements along the main beam are relatively independent, where the shapes are generally symmetrical to the midspan line and the values are mainly dominated by the oncoming wind speeds.