Analysis Of Wind-induced Vibration Of Ice-covered Cable Of Cable-stayed Bridge

A layer of ice can form on the surface of the stay cable in cold winter conditions.The ice coating will change the aerodynamic shape of the stay cable,which will more easily stimulate the wind-induced vibration of the stay cable,especially the gallop vibration.Wind-induced vibration can cause great damage to the cable-stayed bridge,seriously affecting the service life of the bridge,and even cause fatal damage to the cable.Therefore,it is very necessary to study the wind-induced vibration of ice-covered cable.In this paper,with a cable-stayed bridge as the engineering background,the vortex-induced vibration and galloping of ice-covered cables are studied by CFD numerical simulation method.The specific research results are as follows:(1)Through numerical simulation,the Rigid Body module in the fluid analysis software CFX was used to simulate the fluid-structure coupling between wind and ice-covered cable.The correctness of the proposed method was verified by comparing with previous experimental data.(2)Selecting the longest stay cables of a cable-stayed bridge Bridge to analyze the vortex-induced vibration and tripping vibration of ice-covered stay cables with single cables and tandem cables.The vortex-induced vibration responses of the crescent and D-shaped iced cables at different reduced wind speeds were analyzed.It was found that the vertical amplitudes of the crescent and D-shaped iced cables reach the maximum at a certain reduced wind speed,the phase difference between Lift coefficient and vertical vibration displacement changes from 0 top,and the frequency ratio approaches to 1.As the reduced wind speed continues to increase,a "step" decline in amplitude will occur.Crescent,D shape and no ice lasso vortex-induced vibration amplitude and the reduced wind speed curve can be found: The maximum amplitude of D-shaped ice-covered cable is the largest,followed by that of no-ice cable,and the maximum amplitude of crescent ice-covered cable is the smallest.,and the maximum amplitude of the corresponding reduced wind speed is reduced in turn.By analyzing the vortex-induced vibration of crescentic and D-shaped series ice-covered cables,it is found that the variation curves of vibration amplitude and lift and drag coefficient of upstream cables are very small compared with those of single cables,while the vibration amplitude and lift coefficient of downstream cables are much larger than those of upstream cables and single cables.(3)In order to study the galloping stability of ice-covered cable,the lift and drag coefficients of crescent,D-shaped and sector ice-covered cable under different wind attack angles were calculated by FLUENT,and the discrete points of the lift and drag coefficients were fitted to obtain the change curve of the lift and drag coefficients of three kinds of ice-covered cable with the increase of the wind attack Angle.The lift and drag coefficients and their derivatives of wind attack angles were substituted into Den Har Tog formula to obtain the galloping force coefficients of the three kinds of ice-covering cables under different wind attack angles.The results show that the galloping force coefficients of the three ice-covered cable models are all less than 0,and there is the possibility of galloping instability.Taking the crescent shaped ice-covered cable as an example,the galloping response of the ice-covered cable was analyzed.It was found that the galloping vibration trajectory presents an ellipse.When the wind speed is low,the galloping vibration of the ice-covered cable is convergent.When the wind speed reaches the galloping wind speed,the ice-covered cable exhibits divergent vibration.The galloping stability of three types of cable with different ice thickness was analyzed.It was found that the galloping stability of the crescent and D-shaped cable models are more likely to occur with the increase of ice thickness.With the increase of ice thickness on the windward side,the sector ice ice cable is less prone to galloping,while with the increase of ice thickness on the leeward side,the sector ice ice cable is more prone to galloping.Considering the three types of icing,the stability analysis of the downstream cable of two series icing cables with different spacing was carried out.It was found that the trailing force coefficient of crescent icing is always less than 0 when the wind attack Angle is 45°,and the wake may occur when the wind attack Angle is 2～4 times and 8～10 times the cable diameters.The possibility of near instability exists in the sector ice layer stay cables at2 to 6 times the cable diameters,and the gallop force coefficients are all greater than 0at 8 to 10 times the cable diameters.The short-range instability of D-shaped ice cover occurs in the zone of 0°～15° wind attack at 2 times the cable distance,and the gallop force coefficient is less than 0 when the wind attack Angle is 0° at 10 times the cable distance.