Surrogate Function of Post-Tensioning Cable Forces for Cable-Stayed Bridges

Inclined stay cables in cable-stayed bridges are post-tensioned in order to counteract the effect of the deck dead load. The evaluation of the post-tensioning forces is tackled in previous literature using either of the iterative unit load method, the force equilibrium method, or by using optimization search methods. All of the above mentioned methods are computationally intensive which hamper their further use in an optimal design algorithm of the bridge. This paper presents a simple surrogate function that can be used to evaluate post-tensioning cable forces in semi-cable stayed bridge under the action of the dead load. The post-tensioning forces for several configurations of the semi-fan cable-stayed bridges are evaluated using genetic algorithms, and are approximated using a simple polynomial function. The developed surrogate functions are used to study the effect of the main span length of the bridge as well as of the pylon height on the distribution and magnitude of the post-tensioning cable forces.