Study On Automobile Ride Comfort For A Long-span Suspension Bridge With Wind-induced Vibration

Buffeting is a kind of usual and stochastic vibration with limited amplitude under natural wind. Although buffeting may not cause the bridge destroyed in whole, it can induce the fatigue for structure elements if it is not carefully dealt with. The excessive amplitude of vibration may also jeopard driving and pedestrian so as to make them not comfortable and safe. It is very indispensable to carry out the study of automobile ride comfort with wind-induced. Upon this, the research is focused mainly on the following aspects: 1. Firstly, the FEA software ANSYS is adopted to set up the model of a long-span suspension bridge in this thesis. Its natural vibration characteristics are analyzed, and the model used for calculating is checked at the same time. Then the static analysis under wind load is performed. And partial results are shown. According to the characteristics of wind field on bridge, WAWS method is utilized to simulate the fluctuating wind velocity time history. Based on the quasi-steady aerodynamic forces theory, the expressions of the aerodynamic forces acted on per length of the whole bridge deck are introduced. Buffeting responses calculation programs are worked out to analyze linear and nonlinear buffeting behavior in time domain. The programs can be used to calculate the linear and nonlinear,static and dynamic responses of the bridge. Finally, buffeting responses of the suspension bridge under forty-two kinds of load conditions are calculated. And partial results are shown. 2. Model of "pavement surface-vehicle-human"vibration system is established,and the representative one-quarter automobile model with three degree of freedom is introduced to carry out dynamic analyses of the vertical vibration system. MATLAB programs are programmed to resolve the dynamic derivative equations, in order to obtain the acceleration time history of human, which makes preparation for putting into the ISO stardard to evaluate the vertical automobile ride comfort. 3. A comparatively systemic summary is maken according to main evaluation standards and evaluation methods of the structure vibration comfort between inland and outland. The evaluation methods which can be applied to this study by the newest ISO standard is concluded. Other five assistant methods of evaluating horizontal automobile ride comfort which adopts spectral frequency domain analysis are listed for contrast. After the turbulent wind forces acted on the bridge is calculated, horizontal and vertical automobile ride comfort is evaluation.