Span Rigid Frame - Continuous Composite Girder Bridge Buffeting Time-domain Analysis

Along with the quick development of the transportation business, large span bridge with rigid frame-continuous girder has been widely generalized and applied in engineering field. At the same time, the wind-resistant problem becomes more and more essential. Wind-induced buffeting, which is inevitable during the construction stage and operation stage affects not only the construction safety but also the structure's anti-fatigue performance and driving comfortableness. Thus, the influence of buffeting on bridges should be analyzed and evaluated in detail.As a simply and effectively practical method, the traditional frequency-domain analysis method has been widely adopted in buffeting analysis. But the method can not take the geometric nonlinearity and aerodynamic nonlinearity into account while long-span bridges always exhibit a nonlinear behavior under the natural wind. The time-domain analysis method takes the both nonlinearities above into account and shows the whole time history of structure responses. Based on the method put forward by Miyata T, the paper obtains the 12-order element aerodynamic damping matrix and aerodynamic stiffness matrix which is equivalent to the self-excited force by applying two-variable Taylor expansion to the quasi-steady aerodynamic force model. On the other hand, by substitution of the turbulence wind obtained from G. Deodatis' simulation method into Scanlan's buffeting model, the buffeting force is calculated. The contributions of mean-wind load, buffeting and self-excited forces are considered in the analysis. Finally, the influence of nonlinearity is evaluated.Based on the above theory, time-domain buffeting analysis model of long-span bridges is built, the (80+3×145+80)m rigid frame-continuous girder of Baima river bridge on Wen-Fu railway is analyzed as a example. The results show that:1. The longest double cantilever erection stage is most sensitive to the wind-induced buffeting and becomes the most unfavorable stage while anti wind-induced buffeting. 2. Taking the turbulence wind load into account, the structure responses are significantly greater than that only under mean-wind load.3. The structure's responses decrease to a certain extent after considering the contribution of self-excited force.4. The peak value of the buffeting response of the Baima River Bridge increased dramatically after taking into account the geometric non-linearity factor. For example, the peak value of the displacement response in the lateral direction increased respectively by 18% and 13% for the longest double cantilever erection stage and the operation stage. So it's quite necessary to consider the influence of the geometric nonlinearity factor during the buffeting analysis.