Study On Aerodynamic Force And Flow Field Characteristics Of Stay-cables

Cable-stayed bridges surfer a great of dynamic loads, for example wind load, seismic load, pedestrian load, traffic load and so on. As the importance of wind load to designing cable-stayed bridges, in particular stay-cables, it is of immediate significance to master it for the safety and economics of bridges in design phase. It is regrettable that few people attach great importance to the fact that there will be a large lift in critical Reynolds number regime for two-dimension circular cylinders. So far, for circular structures, like stay-cables or bridge towers, the difference of the characteristics of aerodynamic drag between critical Reynolds number regime, transcritical Reynolds number regime and subcritical Reynolds number regime have been paid attention merely, the lift in critical Reynolds number regime have been neglected too often. What’s more, whether the larger lift is a factor which could influence the oscillation of stay-cables needs further study. So the relation between the characteristic of aerodynamic force, flow field characteritics and Reynolds number are problems which need to be studied currently.Firstly, starting with the Reynolds number effect on stay-cable model in low speed test section, the character of aerodynamic force and flow field with different Reynolds number regimes were studied, particularly in critical Reynolds number regime. In subcritical Reynolds number regime, mean drag force decreased slowly and mean lift force waved around zero with the increased Reynolds number. Wind pressure distributed symmetrically, stationary point of the stay-cable model swinged periodly near equilibrium position with a fixed frequency which was the same as the vortex shedding. In the first phase of critical Reynolds number regime, Wind pressure distributed asymmetrically, the asymmetrical bubbles were generated on both sides. What’s more, mean drag force decreased dramatically with a great lift coming into being. In the second phase of critical Reynolds number regime, Wind pressure distributed symmetrically, mean drag force decreased dramatically again and mean lift force went back to around a small value in the end.Posteriorly, the correlation of fluctuating lift force of stay-cable model were studied with different Reynolds number and different axial spacing in high speed test section. In the regime of axial spacing 1≤ s <3 and Reynolds number 1.0×105≤ Re <1.6×105, the correlation of fluctuating lift force were significant correlation or high correlation. When s=1, significant correlation, s=2, high correlation, tiny correlation under other circumstance.Finally, synthesizing the research achievement, the reason why only one ring had the large lift, while others had little lift were the larger axial spacing and greater Reynolds number. Thus, the generation of great lift-the generation of asymmetrical bubbles-were independent and didn’t influence each other.