Analysis Of Wind-induced Vibration And Passive Control Of Long-span Bridges

With the rapid development of bridge technology, the span ability of the bridge is continuously enhanced, and the stiffness of the bridge is decreasing, reflecting the flexible structure. The wind effect on the bridge goes into the vision of engineers and technicians since the collapse of Tacoma Bridge in 1940. After that, the wind-induced vibration of bridge is studied densely, and various basic wind-induced vibration mechanisms have been put forward. At present, the influence of vibration to the long span bridge induced by the wind cannot be neglected whether in construction phase or in operation stage. Meanwhile, the vibration of bridge induced by wind is also an important factor restraining the lengthening of the bridge span.From the research status quo of the wind-induced vibration and its control, the paper studies the wind-induced vibration and passive control of a long span bridge, on the basis of the predecessors' achievements at home and abroad. The paper puts forward the frequency domain and the time domain of the wind-induced vibration of long span bridges, and uses a variety of TMD devices to study the theories, effects and parameters of the passive control, and all these are programming realization. The main research contents include:(1) Analyzing the completion state of the bridge structure under the effect of a nonlinear static load. The paper introduces the analytical method and finite element method of the completion state of the suspension bridge, the completion state and cable force optimization of cable-stayed bridge, and the problem on the aerostatics stability of long-span bridges. It also has calculated the critical wind speeds in static instability of the two bridges, using the internal and external incremental double method .These are the foundation of modal analysis.(2) Analyzing the flutter of bridge structure in frequency domain. The multi-mode flutter automatic analysis method, one of the multi-mode analysis methods which are based on the finitude modes, is introduced detailed and used to analyze the rules and patterns of the flutter of the simple supported thin airfoil beam (SSTAB) and a suspension bridge across the Yangtze River being built.(3) Analyzing the buffeting of bridge structure in frequency domain. The paper uses the pseudo-excitation method (PEM), a method with a fast calculating speed, to deduce the buffeting of the long-span bridge. During the deduction, the paper uses more accurate bridge structure node equivalent aerodynamic force formula, and compares the method with the CQC method. At last, taking SSTAB and the erecting suspension bridge across the Yangtze River as the numerical example, the paper also does a validating analysis.(4) Analyzing the wind-induced vibration in time domain. Combining with the structure nonlinearity static result, the paper analyzes the flutter and buffeting calculation method in time domain. The paper also introduces the simulation method of self-excited force and turbulence wind velocity in the time domain, adds the aerodynamic stiffness, damper and mass on the original finite element model, uses the time history term of the self-excited force and buffeting force as applied force on the FEM model and realizes the combined flutter and buffeting analysis in time domain by using ANSYS.(5) Studying the passive control problem of the long-span bridge by the TMD. Combining with the calculated results in frequency domain of the wind-induced vibration, the paper analyzes the passive control method about the flutter and the buffeting in frequency domain, and studies the preferences of passive control parameter. Taking the TMD as an example, it introduces the basic theory of passive control, and deduces the control theory of STMD and DTMD and dynamic differential equation of TMD-structure. It also studies the TMD control issues of flutter and buffeting considering the self-excited force, calculates the flutter control efficiencies and buffeting control efficiencies of the SSTAB and the suspension bridge being built across the Yangtze River on the base of the STMD and DTMD individually, and studies the value selection of TMD's parameter.