Experimental Study On The Vortex-induced Vibration Of The Wavy Stay Cable

Cable-stayed bridge is accustomed to everyone in our life. It is composed of cross beam structure?bridge bearing system and other spare parts. In the design of stay cable with putting in use, stay cable is becoming a key factor which shorten life span of bridge. When the wind blows from the surface of stay cable, there is periodic vortex-shedding in the zone of wake, which will induce the transverse and streamwise unsteady load, then cause the vibration response. The long time vibration will incur the structural fatigue and also make the disaster events, so it is important to study the characteristics of the vortex-induced vibration of stay cable.Our research group presented a wavy stay cable which its top and bottom spread by sinusoid along the span direction. It can reduce the drag and lift coefficient compaired with traditional straight stay cable. This article is mainly aimed at conducting experimental study on the vortex-induced vibration of the wavy stay cable in high Reynolds number. First of all, we make a numerical simulation study and find that the wavy stay cable with ?/ D ?2 and ?/ D ?6 can make a good performance on drag and lift reduction. Their drag coefficient of ?/ D ?2, a/ D ?0.3 and ?/ D ?6, a/ D ?0.15 is 0.78 and 0.89. The reason is that periodic variation along spanwise direction on wavy stay cable leads to the formation of more stable three-dimensional free shear layers which change the pressure distribution on wavy stay cable and suppress the formation of mature vortices at further downstream positions. so they have characteristics of drag reduction and lift suppression. In wind tunnel, the force sensor was conducted to acquisit drag and lift and cobra probe for velocity correlation. When the Reynolds number is 4 5Re ?1?10 1?10, the drag coefficient of wavy stay cable with ?/ D ?2, a/ D ?0.15 is always small than straight one. The max drag reduction is 15.8% when Reynolds number is 10000. It can also supress the fluctuating lift when Reynolds number is 40000. In the experiment study of vortex-induced vibration, by using hot-wire anemometer, Laser displacement sensor, pressure scanning valve, smoke wire and other experimental methods, we studied the vortex-induced vibration(VIV) and Lock-in phenomenon of the wavy stay cable at Re=6800 20480 and the straight stay cable was introduced for comparison. The experimental results indicated that at the same mass ratio and damping ratio, the wavy stay cable with ?/ D ?2, a/ D ?0.15 and ?/ D ?6, a/ D ?0.075 can also be induced to vibrate as same as straight stay cable, the vibration suppression of wavy stay cable still be existed, the wavy stay cable with ?/ D ?2, a/ D ?0.15 is better than wavy stay cable with ?/ D ?6, a/ D ?0.075. Compared with straight stay cable, the vibration suppression is up to 10% with shorter “Lock-in” region, The main reason may be the large inclination of surface compared with straight stay cable. The vortex behind wavy stay cable along spanwise direction leads to the formation of three-dimensional free shear layers. These three-dimensional free shear layers is developing and interacts with each other, and it also makes effects on the vortex to reduce the drag.This article studies the flow around a static cable and vortex-induced vibration of the wavy stay cable in high Reynolds number. It will establish the theoretical foundation on the practical application of the wavy stay cable.