Linear Time-Domain Buffeting Analysis For Long-Span Cable-Stayed Bridge

Nowdays,with the cable-stayed bridge developing into an extra long-span and flexible phase,the problem of wind-induced vibration has become increasingly prominent.The problem of buffeting is inevitable at the building and using stage,which is not only related to safety at the buiding stage,but also affects the fatigue and driving comfort at the using stage.The buffeting can be analyzed both in frequency domain and time domain.With the development of computer technology,method of analysis in time domain has been widely applied because it can reflect the couse of time and include gemetric nonlinear behavior of bridge and nonlinear characteristic of aeroelastic dynamic.In this thesis,taking the Anqing Changjiang River raiway bridge as a project example,linear time-domain buffeting analysis for long-span cable-stayed bridge at using and building stage is studied.The research is mainly focused on the following aspects:1.Acoording to the properties of both the structural style and the vibration mode of long-span cable-stayed bridge and considering the correlation characteristic of natural wind,a practical method is introduced to simplify stochastic wind velocity field of long-span cable-stayed bridge for taking pylon wind field effect into account.2.The mean wind load,buffeting force and self-excited force are converted to the time-domain form.The buffeting force is obtained throuth the quasi-steady theory proposed by Scanlan,taking accouting of aerodynamic admittances.By applying two-variable Taylor expansion to the quasi-steady aerodynamic force model,the 12-order element aerodyamic damping matrix and aerodynamic stiffness matrix equivalent to self-excited force order are derived.The self-excited forces are input in ANSYS in form of the element aerodynamic damping matrix and aerodynamic stiffness matrix through Matrix27.A simplified method is then established for long-span bridge's buffeting analysis that can be easily implemented in a finite elememt program like ANSYS.3.The calculated model of time-domain buffeting analysis for the Anqing Changjiang River railway bridge is established by using the finite element program ANSYS.Then the analysis is completed based on the Newmark methed.4. The work is summarized and some conclusions about the study are drawn, besides, the further research problems are indicated.