Study On Mechanism Of Dry Galloping Of Inclined Cables

In recent years, many field observations and wind tunnel tests showed thatinclined cables also manifest large amplitude wind-induced instable vibrations onlyunder the action of wind. This kind of wind-induced vibration is named as drygalloping. As galloping is a kind of large amplitude and divergent-type vibration, andit affects seriously in the construction and application of cable-stayed bridges. So theinfluence of dry galloping of inclined cables should be carefully considered in thedesign of cable-stayed bridges. However, the mechanism of dry galloping of inclinedcable has not yet been fully recognized up to now. Based on the current designcondition and actual application situation of cable-stayed bridges, the mechanism ofdry galloping of three-dimensional inclined cable is studied by means of CFDnumerical simulations and PIV tunnel tests in this thesis. There are five chapters in asfollows.(1) Chapter1is the general introduction. In this chapter, the classifications andtheories of galloping are introduced systematically; the research progress and theresearch means of galloping are summarized.(2) Chapter2simply introduces the essential theories of the CFD numericalsimulation.(3) In Chapter3, the flow surrounding three-dimensional vertical cable issimulated with LES turbulence model of CFD software. The numerical simulationsfocus on the flow characteristics and the variations of drag coefficients, liftcoefficients, Strouhal numbers and so on with Reynolds numbers. The results of CFDsimulation agree well with the former experimental results, the agreement proves theaccuracy of the LES turbulence model in circular section.(4) In Chapter4, the flow surrounding three-dimensional inclined cable issimulated with LES turbulence model of CFD software. The numerical simulationsfocus on the flow characteristics and the variations of drag coefficients, liftcoefficients, horizontal correlation and longitudinal correlation and so on withReynolds numbers and wind attack angles. The wind attack angle range, within whichof the dry galloping of inclined cables will take place according to the Den Hartogcriterion, are investigated in detail. The results of numerical simulation show thatdrag coefficients, lift coefficients and resultant forces all make contributions to the occurrence of dry galloping.(5) In Chapter5, the flow structure of the inclined cable axis plane isinvestigated with the particle image velocimetry (PIV). The wind attack angle isrestricted to0°,25°,30°and35°. The average velocity contours are obtained,and the comparisons of the results of CFD and PIV are conducted at the same windattack angle.