| Vortex-induced vibration(VIV)is a wind-induced vibration phenomenon that easily occurs in long-span bridge or their components of blunt body at low wind velocity.The arch ribs of long-span arch bridge are mostly blunt body sections,which are prone to vortex shedding when the incoming wind flow around the sections.Before the arch rib of cantilever is constructed to the closing state,the structure will show more gentle dynamic characteristics,so it is more likely to be affected by the wind and cause vortex-induced resonance than the bridge state.Different from the horizontal main girder and the vertical pylon,the axis of the arch is curved,and the cross-sectional dimension varies significantly along the axis of the arch.The two-dimensional(2D)numerical analysis based on the assumption of strips cannot fully reflect the vortex vibration response of the arch rib.In order to more accurately analyze the vortex-induced resonance performance when the arch rib reaches the maximum cantilever state during the construction stage,this paper takes an arch bridge as the engineering background.The finite element model was established and the modal characteristics of the arch rib were calculated.The flow characteristics around a typical section are simulated and the aerodynamic interference between the two arch ribs is discussed.The three-dimensional(3D)fluid-structure interaction analysis of the structure is realized and the vortex vibration performance of the arch ribs during construction is evaluated.The main research contents of this paper are as following:(1)Taking the arch rib model in the construction stage as an example,the modeling process is introduced.After that,the finite models of the arch rib in the maximum cantilever state and the closed state of the arch bridge during the construction stage were established for analysis,and the dynamic characteristics of the first eleven orders of the maximum cantilever state and the first ten orders of the closed state are obtained.the vibration modes and corresponding frequencies of arch bridge are analyzed and discussed respectively in the above two stages.(2)The computational fluid dynamics(CFD)and vortex-induced vibration theory are briefly introduced.After the aerodynamic coefficients of tandem rectangular,square and single rectangular sections are verified by numerical simulations,the drag coefficients,lift coefficients and its excellent frequency and the magnification factor of moment coefficients of the double arch rib section under different aspect ratio,spacing ratio and wind angle of attack are obtained respectively.The formula for the variation of the vortex shedding frequency with the aspect ratio of tandem rectangle under different wind velocity is fitted.Combined with the above 2D fixed analysis of the double-arch-rib-tandem-rectangular aerodynamic interference research and the low-order modes and frequencies of the arch rib,the possible wind velocity of the vertical bending and torsional vortex-induced resonance of the arch rib is evaluated and analyzed.(3)The fluid-structure interaction theory was briefly introduced,and then a 3D fixed square column and a 3D aerodynamic square column were established based on ANSYS WORKBENCH.By simulating the flow around the 3D fixed square column,the aerodynamic coefficient of the square column was identified and verified,and the reasonable mesh division method and calculation time step were determined.The vortex-induced resonance phenomenon of the aeroelastic square column was simulated by bidirectional fluid-structure interaction,and the rationality of the above meshing method and calculation time step was further confirmed,which guides the establishment and calculation of the 3D arch rib aeroelastic model.(4)The establishment method of the 3D aeroelastic arch rib model and the division principle of the flow field area are introduced.The vibration response of the aeroelastic arch rib under different incoming wind velocity was simulated by bidirectional fluid-structure interaction,and the vertical and torsional amplitudes were plotted as a function of wind velocity.The vortex vibration locking interval of the arch rib during construction was observed,and the time-history curves of displacement and lift coefficient were analyzed by frequency spectrum.Combined with the results of two-dimensional numerical simulation,the vortex vibration characteristics of the arch rib were discussed finally. |
