ABSTRACT
The design of cable-stayed bridges involves balancing multiple responses coming from different fields. Streamlined single-box and twin-box deck cross-sections have been effective alternatives for the wind-resistant design of long-span bridges in the last decades. The relative efficiency of these two types of deck is currently under discussion as each one presents advantages with regard to some aeroelastic phenomena and structural responses but diminishing the performance with respect to others. Furthermore, deck shape modifications can lead to different effects on the bridge aeroelastic responses depending on the deck typology adopted. The performances of each deck cross-section are contrasted in this study using aero-structural shape optimization techniques, parametric studies, and sensitivity analyses. The optimum design of long-span bridges must accomplish all the conditions established by the codes of practice or the specific project specifications with the minimum cost, lowest weight, or any other economic metric or sustainability indicator chosen as the objective function in the optimization problem. A cable-stayed bridge with a 1316-meter span considering these two deck geometries is used as an application example. The formulation of the optimization problem reported in this study will consist in the identification of the optimum deck shape and cable supporting system size that leads to the minimum amount of material for the whole bridge. The set of static loads includes self-weight and several live loads simulating classical traffic loads, while the aeroelastic responses are the flutter critical wind velocity, and the buffeting deck accelerations caused by turbulent wind. A comprehensive comparative analysis among the results obtained for the optimum solution with single and twin-box decks will be presented, discussing the modifications introduced in the deck shape to deal with each structural and aeroelastic requirement.
