Implementation and Analysis of Cable-Tensioning Strategies for Cable-Stayed Bridges

Cable-stayed bridges have become more prevalent in the last decades, due to the aesthetical structure, the use in large spans and the economic benefits compared with other constructions. These light structures are designed to deal with the external conditions and are constructed considering the site where they would be built. The behavior of the cable-stayed bridge can be controlled influencing one of its main structural components, the cables. The tension in the cables enables the possibility to control the displacements of the nodes selected. Combined with an optimization procedure, an ideal bending moment distribution through the entire girder can be obtained. The current work focuses on the methods which can be applied to find this optimal state through cable-tensioning. First, a review of the available methods is done, considering more classical / civil engineering-related approaches, using the Unit load method, but also a study of the application of more general optimization methods, which include a Gradient-free and the Gradient-based approach. The methods are implemented and tested on a simple structure using Matlab and the results are evaluated. A discussion is carried out on the applicability of certain approaches and some differences in results which these lead to. In conclusion, the limitations of the methods need to be considered in order to perform a proper analysis and to reach optimal tension state in the stay cables. For a general problem, the numerical approach is useful for the evaluation of the tension and can be adapted to variety of structures obtaining accurate results, while the symbolic approach is usually more adequate for examples with few variables, typical in educational examples and prototypes in research.