Research On The Key Technologies Of Linear Control And Parameter Sensitivity Of Steel Box Girder Cable-stayed Bridge With Three Pylons

The unique structural features, beautiful appearance and the economic cost of multi-pylon cable-stayed bridge make it more and more popular in the long span cable-stayed bridge construction. At present, scholars’ study of multi-pylon cable-stayed bridge stays in the design theory,and the relatively study of construction control issues related to them is few. With the background of Jianghai Direct-vessel Channel Bridge in this paper, several aspects are studying as the following:(1)The determination of reasonable construction state of three-pylon steel box girder cable-stayed bridge.Firstly, five calculation methods of reasonable construction state, the construction steps and the characteristics and difficulties of them are introduced. Then the improved difference method is used for the forward iteration calculation of initial cable force, aiming at the determination of reasonable construction state of Jianghai Direct-vessel Channel Bridge. It solves the problem that individual cable is sensitive and it is not convergent by using normal difference method, which caused by the asymmetry of the structure and loads, the small rigidity and other factors. At last, the determination of the main girder’s location elevation is discussed.(2)The calculation of the stress-free fabrication geometry of steel box girders.Based on the overall construction control mind, do a research on the calculation of stress-free fabrication geometry. Based on the existing fabrication geometry calculation methods, derive and calculate respectively the fabrication geometry of the steel box girders installed by large segment hoisting construction and cantilever-splicing construction. And it compares fabrication geometry with installation geometry and design geometry of the steel box girders that are constructed by these two methods.(3)Structure analysis of parameter sensitivity.There are many parameters that can influence the stress and deformation of the structure. This paper chooses some parameters including load, rigidity and temperature to analyze the structure’s sensitivity, know the influence of these parameters on the girder alignment, the cable force, the stress of steel box girders, steel pylons and cables, and the displacement of the top of the pylons and know the sensitive parameters of the structure to provide a basis for later construction control error analysis and decision.(4)Analysis of the closure problems Jianghai Direct-vessel Channel Bridge’s.Analyze the influence of temperature rising, lowering and gradient on the girder alignment, the cable force, the length of closure segments, and the axial deviation of the main girder in the closure state. Analyze the influence of change of closure on the girder alignment, the stress of steel box girders, steel pylons and cables, and the displacement of the top of the pylons. And then put forward several adjustment measures for these influences.