Cable Force Optimization And Local Analysis Of Special-Shaped Single Pylon Cable-Stayed Bridges

Special-shaped single pylon cable-stayed bridge, because the unique shape, often become one of the city’s landmarks, which is not just for transportation use but also representing the economic development level and civilized degree of society of the city. In recent years, an increasing number of unique-shaped single pylon cable-stayed bridges were built. Such kind of bridge has impressive appearance, but the force problems are a great chanllenge for the designer.Therefore, how to balance the pylon shape and reasonable force is the key to the bridge design.Based on the preliminary design information of 2nd Da-xing Bridge in Ya’an, Sichuan, China, static characteristics, reasonable finished bridge state and local analysis of a special-shaped single pylon cable-stayed concrete bridge were studied. The bridge finite element model was established by Midas/Civil software to analyze the construction stages and the finished stage. For the finished stage, certain load effect such as live load, temperature and shrinkage and creep were studied.Based on fractional step method, the reasonable finished state of the special-shaped single pylon cable-stayed bridge was studied by using ANSYS first order optimization techniques. Firstly, the bridge structure was divided into five parts. Considering the bending strain energy, each part was distributed different weight coefficient with certain purpose to form the object function.And the object function was optimized to get a preliminary bridge state by using ANSYS first-order optimization method. Then prestressing tendons were set to get a new bridge state. Lastly, based on such new state, making the deviation of bending strain energy as the new object function, the final bridge state was acquired after the second optimization. CoMPared with the original design, a more reasonable finished bridge state that have less tendons and more reasonabe cable force was acquired.Based on the final bridge state, solid model was established to analysis the local force on special-shaped pylon. Considering the complex force of such structure, the local parameters which have influence to the local force, such as number of cross beam and its thickness of the top-and-bottom plate were studied, through which to optimize the pylon structure.