Changing Bridge Aerodynamics under Nonstationary Winds

The nonstationary winds during tropical cyclones and non-synoptic events have been extensively observed and analysed; however, the significance of nonstationarity in the consideration of wind load effects has not been widely investigated yet. In this study, the effects of nonstationarity on changing bridge aerodynamics have been discussed from both linear and nonlinear viewpoints. For linear aerodynamics change, the conventional 1-D indicial response function has been extended to a 2-D case since an additional time scale, resulting from the time-varying transient nonstationarity, is introduced in the wind–structure interactions. For nonlinear aerodynamics change, the conventional hybrid model has been generalized to consider the additional effective angle of attack due to the time-varying mean wind speed. The bridge buffeting response under the tropical-cyclone and downburst winds were comprehensively examined based on 1-D semi-empirical linear model, 2-D semi-empirical linear model, 1-D hybrid nonlinear model, 1-D generalized hybrid nonlinear model and 2-D generalized hybrid nonlinear model, where the ability of these models to capture the changing linear and/or nonlinear bridge aerodynamics under nonstationary winds is highlighted. The results demonstrated the important effects of the transient nature of nonstationary winds on the changing bridge aerodynamics and hence on the structural response.