An analytical model of time-averaged wake airflows for bridge deck and its application to drag load predictions for twin-deck sea-crossing bridges

In parallel twin-deck sea-crossing bridges, strong wind conditions in marine environments cause the wake generated by the windward deck to significantly alter the airflows around the leeward deck, thereby influencing the aerodynamic forces acting on it. Aerodynamic drag loads are critical in determining the lateral deformation and wind resistance stability of sea-crossing bridges. Accurate estimation of these loads is essential for structural safety. This study proposes a practical analytical model to predict the time-averaged wake field of bridge decks, enabling rapid evaluation of the wind environment and aerodynamic forces on the leeward side deck. The model is developed based on mass and momentum conservation principles and assumes a Gaussian distribution for the time-averaged streamwise velocity deficit, requiring only a single parameter to characterize the velocity profile. Simulations of four common bluff body sections are used to determine the wake expansion rate, providing a basis for model application. The model’s effectiveness is validated through wind tunnel experiments and CFD simulations. A case study of a sea-crossing bridge demonstrates the model’s capability to analyze aerodynamic interference and wake flow patterns. This analytical model offers a fast, reliable, and practical tool for optimizing aerodynamic loads in the design of twin-deck sea-crossing bridges.