Optimization of tensioning strategy for asymmetric cable-stayed bridge and its effect on construction process

A cable-stayed bridge is a bridge that consists of one or more pylons, with cables supporting the deck. Cable-stayed bridges have come into wide use recently because of their economy, stability, and excellent appearance. It is possible to achieve a uniform moment distribution in the stiffening girders mainly by prestressing the cables, which leads to a more economical design in material and weight than other types of bridges. However, to achieve a more uniform moment distribution is a vague objective, so it cannot be easily defined as the optimization problem. In other words, the minimization of the cost or weight as the objective is not directly related to the optimization of the cable prestressing. Therefore, it has been considered as one of the most important, difficult, and also interesting topics among many researchers and bridge engineers to determine the optimal tensioning strategy and how to apply the prestressing forces of the cables of a cable-stayed bridge. A number of approaches to determine the optimal cable tensions have been proposed in the literature (Negrao and Simoes, Comput Struct, 64:741-758, 1997; Wang et al., Comput Struct, 46:1095-1106, 1993; Agrawal, J Bridge Eng, 2:61-67, 1997; Janjic et al., J Bridge Eng, 8:131-137, 2003). Among these approaches, the unit load method (Janjic et al., J Bridge Eng, 8:131-137, 2003) is considered in this paper because it can take into account the actual construction process while other approaches are based on the configuration of the final structure only. In this paper, "two-step approach" based on the unit load method is newly proposed to find the optimal tensioning strategy especially for the atypical asymmetric bridge under construction, which has continuous deck supported by one pylon and stay cables. Some numerical results will be given to show the validity of the new approach suggested in this paper.