Structural Optimization Of Prestressed Concrete Extradosed Cable-Stayed Bridge

Extradosed cable-stayed bridges are hybrid system bridges whose mechanicalproperties lies between traditional cable-stayed bridges and continuous beambridges. In the past20years, extradosed cable-stayed bridges have rapidlydeveloped and widely used both at home and abroad, because it has manyadvantages such as excellent mechanical properties, low costs, convenientconstruction and beauty.Relying on the design proposal of Nanfei river bridge in Hefei city, the papertries to study the structural mechanical properties of prestressed concreteextradosed cable-stayed bridge and optimize the key design parameters. The chiefcontents are described as follows:1. Using the finite element analysis program Midas/Civil2010, finite elementmodels of Nanfei river bridge are established. According to the calculations of theconstruction and service stages, the mechanical characteristics of the bridge aregiven. Then the problems about characteristic parameters of extradosedcable-stayed bridge are analyzed and discussed.2. The effects of the main design parameters (the height of towers, the lengthof non-cable segments and the ratio between the side span and the main span) onthe mechanical properties of the structure are analyzed and the reasonable values ofthese main design parameters are obtained．3. According to sensitivity analysis of prestress and cable force to integralstiffness, the more economical allocation ratio of tendons and stayed cables isdetermined. Considering the constraint condition of cable force, moment anddisplacement, the mathematical model of cable tension optimization is establishedand the optimum cable tensions in the reasonable finished state under dead load aredetermined.4. The cable allowable stress of extradosed cable-stayed bridge are analyzed,including both static strength and fatigue strength, to discuss the reason that itsvalue is different from the traditional cable-stayed bridges.