Study On Optimization Method Of Cable Force For Extradosed Cable-Stayed Bridge

In recent years, the extradosed cable-stayed bridge is developed into a new type of bridge structure form on the basis of the cable-stayed bridge. On the structural characteristics, the extradosed cable-stayed bridge is a new style between the continuous bridge and the cable-stayed bridge. The overall characteristics of extradosed cable-stayed bridge are: dwarf tower, stiff beam, centralized cable; primarily by the main beams to bear the majority of vertical load, vertical force of the cable bearing the remainder of the vertical load, while the level force of the cable stiffening the beam in order to improve the performance of the main beam. The cable force is very essential to the structure and properties of extradosed cable-stayed bridge. Therefore, it is necessary to optimize the power of cable force.The optimization of cable force of extradosed cable-stayed bridge is not only to meet the reasonable force, but also to ensure the safety of the construction process and operational phase, so in the beginning of the construction phase it is also very important to calculate the pull force, tensible force and cable force.In this paper, based on extensive collection of existing research materials at home and overseas, I have discussed the calculation characteristics of cable-stayed bridges, summarized and compared the calculating method of the cable force which is currently used and reasonable; to have the optimization theory applied to the calculation of the cable force of the extradosed cable-stayed bridges, at the same time, assuming that the direct constructed bridge, based on the impact matrix thought, taking the setting cable force as design variables, selecting reasonable finished internal force as object function to calculate the optimized setting cable force and the final cable force of the constructed bridge. Taking this cable force as a target, and during the construction phase through the backward-forward iterative calculation of setting cable force, ultimately, the reasonable setting cable force will be worked out.In this paper, the Xicao Changjiang River Bridge in Luzhou is taken as engineering background. Taking least bending and flexible strain energy in the beams as object function, using the MATLAB optimization Toolbox to calculate the setting cable force and through the MIDAS to analyse the state of construction phase and finished phase, and the reasonable finished cable force and setting cable force during construction phase can also be calculated finally.The calculation results show that the structure force during the construction phase and finished phase is reasonable, and the tensile stress on the upper edge and lower edge of the beams meets the requirements in the code of bridge design, at the same time ,the security and stability during the construction phase can also be guaranteed. So that, it is feasible that the optimization theory is applied to extradosed cable-stayed bridge cable force calculation.