Calculation model and mechanism analysis for rain-wind-induced vibration of stay cable

Rain-wind-induced vibration of cable was studied based on previous research achievements. According to the quasi-steady assumption, the governing equation of vertical motion of the cable was derived and the criterion for unstable motion and occurrence mechanism was studied. A comparison was performed between the oscillation responses of the stay cable obtained from calculated model and previous results. The results indicate that the analysis model can reflect the main characteristics of wind-rain-induced vibrationt of the cable which is amplitude- and velocity-restricted, and it is probably related with the periodic vortex shedding of wake flow. It is essential for the occurrence of rain-wind-induced or wind-induced vibration of cable that the derivative of lift coefficient with respect to transient angle of attack is less than zero. When rain-wind-induced vibration occurs, the aerodynamic force has a dual function for the vibration, and the maximum amplitude of stayed-cable is determined by the relative value of aerodynamic exciting force and aerodynamic damping force.

Wind-Tunnel Investigation of the Aerodynamic Performance of Surface-Modification Cables

The wind-induced vibration of stay cables of cable-stayed bridges, which includes rain-wind-induced vibration （RWIV） and dry galloping （DG）, has been studied for a considerable amount of time. In general, mechanical dampers or surface modification are applied to suppress the vibration. In particular, several types of surface-modification cable, including indentation, longitudinally parallel protuberance, helical fillet, and U-shaped grooving, have been developed. Recently, a new type of aerodynamically stable cable with spiral protuberances was developed. It was confirmed that the cable has a low drag force coefficient, like an indented cable, and that it prevented the formation of water rivulets on the cable surface. In this study, the stability for RWIV of this cable was investigated with various flow angles and protuberance dimensions in a wind-tunnel test. It was found that the spiral protuberance cable is aerodynamically stable against both RWIV and DG for all test wind angles. The effects of the protuberance dimensions were also clarified.

Influence of Wind Speed, Stay Cable Inclination Angle and Wind Yaw Angle on Formation of Rivulets

Combining lubrication theory and CFD technology, a finite element model is established to simulate the rain-wind-induced vibration(RWIV). Based on Spalart-Allmaras(S-A)turbulence type, COMSOL software is adopted to calculate the wind pressure coefficient and wind friction coefficient that vary with the location and time. To verify the veracity and rationality of this method, the formation and evolution of rivulets at different wind speeds are studied and compared with the existing experimental results. Furthermore, the time, location, height and width of the initial formation of rivulets are analyzed at different wind speeds, cable inclination angles and wind yaw angles. The results show that the three influencing factors mentioned above have great effect on the formation of rivulet, and the influencing tendency, range and degree are different from each other.