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The aero-structural design of bridges is mainly controlled by the deck cross-section design. Design modifications on bridge decks impact the deck aerodynamics and the deck mechanical contribution, which also affect the bridge aeroelastic responses. The nonlinear inherent nature of bluff body aerodynamics combined with the nonlinearities of multimodal aeroelastic analyses result in complex relationships between the full bridge aeroelastic responses and deck shape design variables. This fact impacts the design process as it may lead to the development of complex feasible design regions in the chosen design domain, including disjoint feasible regions that may cause local minima. Given the limitations of metaheuristic optimization methods to deal with optimization problems with large sets of design variables, as required in holistic bridge design problems, gradient-based optimization algorithms can be recast to address global optimization problems. In this study, we propose the use of tunneling optimization methods to address this challenge. 

This study reports the nonlinear aerostatic stability studies carried out for a suspension footbridge with a curved deck spanning 275 meters over the Miño River between Spain and Portugal. The footbridge's aerostatic performance is controlled by its highly aesthetic but complex three-dimensional configuration, the high slenderness of the deck, the construction process, and the aerodynamic characteristics of the triangular 4.5-meter-wide bluff deck cross- section, which demands a detailed aerodynamic study. The analysis is conducted using a nonlinear modal-based method recently developed by the authors. The deck's rotation is driven not only by the aerodynamic moment-induced rotation but also by the drag-induced rotation due to the configuration of the cable supporting system and, very significantly, by the lift- induced rotation due to the deck's curvature.