Downburst-induced transient response of a long-span bridge: A CFD-CSD-based hybrid approach

The long-span bridges, frequently located in the coastline and mountainous areas, are prone to suffering from the transient downburst winds associated with the thunderstorms. Therefore, it is important to examine the behaviors of long-span bridges under such wind events. In this study, the time history of non-turbulent downburst wind field is modeled using the impinging jet-based computational fluid dynamics (CFD) approach. It has demonstrated high-fidelity simulations of the downburst wind field, especially for the near-surface radial winds that are particularly significant for present investigation of bridge aerodynamics and aeroelasticity, with a reasonable computational cost. The simulated time-varying mean wind velocity field of a typical downburst event is validated using available field measurements. The correlated nonstationary fluctuations of the downburst are stochastically simulated by the Hilbert-wavelet scheme based on full-scale data, and then superimposed onto the CFD-based transient mean wind field. The obtained turbulent downburst wind field is employed as the dynamic inputs to the line-element-based three-dimensional (3-D) finite element model of the long-span bridge, and its downburst-induced transient response is acquired using the computational structural dynamics (CSD) approach. The aerodynamic and aeroelastic couplings between the downburst winds and the long-span bridge are modeled using the two-dimensional (2-D) indicial response functions that could well represent the transient bridge aerodynamics under non-synoptic winds. The time-domain buffeting response analysis of a long-span suspension bridge under the traveling downburst has been carried out utilizing the CFD-CSD-based hybrid methodology. The results highlight the importance of the transient and nonstationary effects on the non-synoptic wind-induced structural dynamic response.