The Mechanism Study Of Rain-Wind Induced Vibration Of Stay Cabes Based On The Fored Vibration Device

With the increase of the span of cable-stayed bridges, stay cables accordingly become longer and longer. Stay cables are prone to vibrate under wind loads due to its large flexibility, small mass and low damping. Rain-wind induced vibrations of stay cables, which take place with large amplitude and low frequency under the combined action of the wind and rain, has severely affected the safety of cable-stayed bridges. As the complexities of this phenomenon, its mechanism is not fully understood until now. In the existing study of the mechanism of rain-wind induced vibrations, the aerodynamic forces acting on the cable and the rivulet are usually determined by the quasi-steady theory. This paper attempts to study the applicability of the quasi-steady theory by means of wind tunnel tests and theoretical analysis. There are six chapters in this paper.Chapter 1 is the introduction.In Chaper 2, A series of wind tunnel tests on a smooth cable model and a cable model with an artificial rivulet are carried out by using a 3-DOFs fored vibration system which is developed by the Wind Engineering Research Center of hunan university. There are six test cases, including fixed smooth cable, vertical vibration smooth cable, fixed cable with artificial rivulet, vertical vibration cable with artificial rivulet, rotational vibration cable with aritificial rivulet, and torsional-vertical coupling vibration cable with artificial rivulet. In Chaper 3, the mean and fluctuating wind pressures, power spectral densities offluctuating wind pressures, and three-components of aerodynamic forces of the cabe model and the artifical rivulet are obtained on the basis of the data from the wind tunnel tests. The effects of Reynold number, cable movement and rivulet position on the cable surface are studied in detail. Comparing the results of aerodynamic forces obtained from wind tunnel tests and quasi-steady theory, it is concluded that the quasi-steady aerodynamic forces reflect the main characteristics of the aerodynamic forces in rain-wind induced vibrations.In Chapter 4, the aerodynamic derivatives of cale model and rivulet are obtained based on the data from the wind tunel test. The results show that the precision of fluctuating aerodynamic forces obtained from aerodynamic derivatives is higher than that of quasi-steady theory. In Chapter 5, a 2-D imensional theoretical model of rain-wind induced vibrations with two degrees-of-freedom is established to investigate the mechanism of rain-wind induced vibations, in which the three-components of aerodynamic forces of the cabe and the rivulet are determined by quasi-steady theory.Chapter 6 is the conclusions and advices on future works.