Cable-stayed bridges can be designed economically by cable prestressing. It is a most important and difficult problem to determine the optimum cable areas and prestressing forces in the design of cable-stayed bridges.
In this study, a computer program is presented which can analyze a plane cable-stayed bridge structure considering two nonlinear effects. The first one is the axial force-deformation relationship for the inclined cable due to the sag caused by its own dead weight and the other effect is the nonlinear axial and bending force-deformation relationship for the bending members, which can occur due to the interaction of large displacements of structure under normal design loads.
Two optimization techniques are presented to determine the cable areas and prestressing forces of the cable-stayed bridges using the nonlinear analysis program developed in this study. The first optimization method presented in this paper is based on an evolutionary procedure, in which the area of high stressed cable is increased step-by-step until an optimal area of the cable is obtained. The other optimization method is based on the strain energy criterion, in which the BFGS(Broyden-Fletcher-Goldfarb-Shanno) algorithm is used to minimize the objective function.
These proposed methods are applied to some cable-stayed bridges. The results show that the proposed methods are very useful to determine the optimum cable areas and prestressing forces.
