Study On Theoretical Model And Large Wind-induced Vibration Characteristics Of Suspension Cable In Wake Region Of Bridge Tower

Suspension bridge has become the preferred structural form of long-span bridges because of its superior spanning performance,but the flexible system also determines that it is inevitably affected by wind loads.Especially in the wake region of bridge tower,the suspension cable is not only affected by natural fluctuating wind,but also disturbed by the wake flow of bridge tower,which will induce large wind-induced vibration at a specific wind speed.In this paper,the suspension cable in the wake region of Xihoumen Bridge tower is taken as the research object.The aerodynamic characteristics of the suspension cable in the cross-wind direction are studied by numerical analysis method.A mathematical model is proposed to simulate the windinduced vibration response of the suspension cable.The main contents of this paper are as follows:(1)Based on the equivalent linearization approximation theory,the amplitudedependent damping ratio and frequency are identified by the time-domain method,and the non-linear characteristics of the modal parameters of the suspension vibration system are analyzed.The amplitude-dependent damping ratio and frequency of the suspension vibration system are interpolated by cubic spline interpolation,which is applied to the numerical analysis of the wind-induced vibration of the suspension cable in the wake region of the bridge tower.(2)A new mathematical model describing the large-scale cross-wind vibration characteristics of suspension cable in the wake region of bridge tower is established.The proposed aerodynamic model includes three unsteady aerodynamic components,i.e.the resonance between regular shedding vortices behind bridge tower and suspension cable,the fluctuating wind buffeting effect under high reduced wind velocity and the non-linearity of the modal parameters of the vibration system.The semi-theoretical model considers sufficient aerodynamic interference effects of the bridge tower wake on the suspension cable,and the key parameters in the model have clear physical significance.(3)The reasonable values of key parameters in the mathematical model is discussed.The fourth-order Runge-Kutta method is used to solve the coupled wake oscillator model,and the response characteristics of suspension cable under different parameters are studied.The results of numerical analysis show that the model established in this paper predict the vibration characteristics of suspension cable in the wake region of bridge tower well when the parameters are reasonably selected.