Research On Reasonable Finished State Of PC Cable-Stayed Bridges

The long-span cable-stayed bridge,a kind of indeterminate flexible structure with many redundant degrees,consists of three basic members:girder,tower and cables.Its'internal forces are not unique under finished state.Weather the inter forces are reasonable decides the level of this design.If the structure and loading are fixed,we always can make out a set of cable forces to make some aims that response the force state of finished structure optimum under fixed structure and loadings.This is the reasonable finished state under this aim.Engineers have concluded many methods to determine the reasonable finished state of prestressed concrete cable-stayed bridge.Each method has its character and condition.In this paper,we take the design of Zhongxian Yangtze River Bridge for example,proposed a comprehensive method that uses both the Minimum Bending Energy Method and the Stress-Balance Method to determining the reasonable finished state of this bridge.In use of the comprehensive method,the Least Squares Method is used to adjust the cable forces,under the controlling conditions according to the moment of main beam. Taking the cable forces of the finished bridge as variables,we can form an optimization model which is subjected to the restriction considering the requirements of uniform of the cable forces,the resistance of the side and assistant piers,the bending forces of the towers and the dead moment feasible field of the main beam.Make out the optimization model and then attain a reasonable finished state.This method is the combination of the Minimum Bending Energy Method and the Stress-Balance Method.In the end,taking the Zhongxian Yangtze River Bridge as example,introduced the step of the determination of the reasonable finished state of the long-span prestressed concrete cable-stayed bridges by the comprehensive method in detail.The result has laid the foundation on the next step of the determination of the construction state,and has the reference value to the constructions of cable-stayed bridges.And the influence of shrinkage and creep to the main beam bending moment which under the different finished state is analyzed,too.Finally,the method of the determination of the construction state,the contents of construction controlling and the method of construction of the Zhongxian Yangtze River Bridge have been introduced in this paper.According to the influential factors of the reasonable finished state of the cable-stayed bridges,this paper has gave the main technical requirement of construction.