Abstract:According to the different effect of cable force on internal forces of two kinds of main girds of cablestayed bridges with hybrid girders, the stepbystep arithmetic for the establishment of reasonable finished dead state was proposed. According to the loading requirement of steel gird and main tower, the cable force was decided, and the prestressed reinforcement was placed with the consideration of concrete girder under fixed cable force. Based on the arithmetic, taking the minimum bending and the tensioncompression strain energy of steel gird and main tower as objective function, the optimization problem was solved by the improved genetic algorithm. A finite element model of second Jiujiang Bridge was established based on Ansys to realize the mathematical optimization course of cable force. The result shows that the proposed algorithm is reliable for the cable force optimization of cablestayed bridges with mixed stiffening girders. Compared with traditional algorithm, the additional cable force adjustment can be avoided in the proposed algorithm. The improved genetic algorithm is superior for resolving the complex nonlinear model with multiparameter and multioptimizing variables.