Ascertainment Of Cable Force Under Ideal Finish State And Reasonable Construction State Of Cast-in-place Cable-stayed Bridges

The cable-stayed bridge consisting of cables, stiffing girder and towers is a highly statically indeterminate and multiple-supports system. The key factors that influence its mechanics performance are the cable forces under dead loads and the preliminary cable forces. The methods of determinating the cable tensions under ideal finish state and reasonable construction state are researched in this paper based on the Dezhou New-River Cable-Stayed Bridge. The main contents and achievements are as follows:(1) Static analysis method and optimization theory of cable force for cable-stayed bridges are reviewed, which provided theoretical foundation for the determination of cable tensions under ideal finish state and reasonable construction state.(2) The method of ascertaining ideal finish state by substep algorithm is put forward, which is multiple utilizations of the least bending energy method and the stress balance method. The model of Optimizating cable tensions under dead loads is found, then the method of least squares is used to obtain the cable tensions under ideal finish state. This method is used to determining the ideal finish state of Dezhou New-River Cable-Stayed Bridge and good effect is obtained.(3) The forward-iteration calculation method of ascertaining the preliminary cable force is established, and the method of least squares is used to reduce the open error to the minimum. This method is used to determining the cable force under construction state of Dezhou New-River Cable-Stayed Bridge and satisfactory result is gotten.(4) The checking calculation of one-time pretension is processed according to cast-in-place construction to insure the safety of construction process based on the preliminary cable tension. The second pretension and the checking calculation are adopted based on the difficulty of construction, economical efficiency and construction period when one-time pretension is not applicable. The result of second pretension indicated that it is feasible for the construction, and the finish state coincidents with the requirements of ideal finish state precisely.(5) The theory of using frequency method to measure the cable force of cable-stayed bridges is expounded. The reason of measure error is analyzed systematically, meantime some measurements to reduce error are adopted.