Narrow Results

The escalating severity and frequency of extreme weather conditions, such as typhoons and thunderstorms, exacerbate the failure risk of transmission lines. In this study, a series of wind tunnel tests were conducted to investigate the rain-wind-induced vibrations (RWIVs) on an overhead transmission conductor. First, a conductor sectional model was fabricated to accurately represent the physical appearance and material of the prototype conductor. Then, experimental wind-rain conditions were simulated to investigate the impact of rainfall on the cross-wind buffeting vibration of the conductor, with attempts made to reproduce the phenomenon of RWIVs. Meanwhile, section model vibration tests were conducted on the conductor model with an artificial rivulet to investigate the effects of rivulet position, dynamic characteristics, mass, and wind yaw angle. Finally, high-frequency force balance (HFFB) tests were performed on the same conductor model, and the mechanism of the RWIVs was discussed from the viewpoint of galloping. The results indicated that the presence of rainfall slightly decreased the in-plane vibrations of the conductor when no RWIVs occurred. Due to the interference from the spiral aluminum wires on the conductor surface, this type of conductor is less susceptible to RWIV compared to smooth cables. The conductor model with an artificial rivulet exhibited significant vibrations at position angles $𝜃=48^{\circ }$–60${}^{\circ }$, essentially corresponding to negative Den Hartog coefficients.

Using wind tunnel tests, the aerodynamic characteristics of a suspended monorail transport (SMT) are systematically investigated under crosswinds for the first time. Two practical vehicle–bridge combination forms (single-line and double-line) are considered. As a contrast, single vehicle and bridge models are also studied to further reveal their aerodynamic characteristics. The mean and root mean square (RMS) wind pressure coefficients, aerodynamic coefficients and power spectrum density (PSD) distributions are used to numerically investigate the effects. The paper confirms that: (1) the mean wind pressure coefficients of the single vehicle and bridge models are close to unity at the center point of the windward side and gradually decrease from the center point to both sides. The maximum value of the RMS wind pressure coefficients mainly occurs at the top or bottom surface of the testing models due to the effect of vortex shedding; (2) the aerodynamic coefficients and the mean and RMS wind pressure coefficients are significantly increased for both the vehicle and bridge models when considering the aerodynamic coupling effects; (3) the aerodynamic characteristics of the bridge can be significantly affected by the location of the running vehicle, but the fluid flow can maintain relative stability during the meeting of the two vehicles.

To evaluate the crosswind stability (overturning and sideslip) of vehicles driving on the bridge, obtaining critical wind speed is essential. The traditional method is based on the aerodynamic forces of moving vehicles on the bridge and the analysis of force equilibrations. However, various shapes of the bridge make the flow field around the vehicle on the bridge very complicated to obtain. In this paper, a simplified method is introduced to calculate the critical wind speeds of moving vehicles on bridges based on the influence of coefficients of the wind environment on the bridge and the aerodynamic forces of moving vehicles on open fields. The aerodynamic forces of moving vehicles are simulated with dynamic mesh techniques. Besides, the characteristics of the wind environment on the bridge deck are studied to evaluate the driving safety and determine the influence coefficient. To further demonstrate the reliability, critical wind speed in different road conditions of the proposed simplified method shows very good agreement with the traditional method.

Based on the theories of computational fluid dynamics, aerodynamics, bridge dynamics and vehicle dynamics, a sea-crossing cable-stayed bridge with a main span of 532 m is taken as the research object in this study to explore the characteristics of dynamic response when two CRH3 high-speed trains pass each other under the context of wind–wave combination. Firstly, the CFD method is used to construct an aerodynamic calculation model of the vehicle–bridge system under the context of wind–wave combination. Also, the first wind tunnel and wave flume tests are conducted to verify the numerical results of aerodynamic coefficients. Then, the bridge dynamics model and vehicle dynamics model are established by using both the finite element method and the multi-body dynamics method. Finally, a three-dimension vehicle–bridge coupled model is constructed by using the multi-body dynamic software SIMPACK to explore the effects of average wind and regular waves. It is demonstrated that the dynamic characteristics of the vehicle–bridge coupling system under the condition of wind–wave combination are different than under the context of average wind alone. According to the research result, wave effect can affect or make a difference to the aerodynamic characteristics of the vehicle–bridge coupling system. In general, there is only a slight increase in the dynamic responses of bridge structure including mid-span displacement when compared with the condition of average wind alone, including mid-span displacement. Meanwhile, the wind and waves combined condition also has a negative effect on the dynamic responses and running safety of high-speed trains. Especially for the leeward vehicle, the dynamic responses of the leeward train change more abruptly than under the single static wind condition with the increase of running speed.