Study On Theory Of Stress-free Shapes Method On Steel Box Girder For Long-span Cable-stayed Bridge

As the bridge span increases, the effect of the geometrical nonlinearity of such structures becomes even more influence factors in bridge design and construction. With reference to JingYue Yangtze River Highway Bridge, using unstrained geometry method based on theory of geometric nonlinear and forward-iteration method,this thesis carried on a more thorough study on influence factors on prefabricating and assemble steel box girder。The main contents of the research as follows:(1) The basic thought of geometric nonlinear theory based on finite element method is elaborated, and treatment methods on geometric nonlinear of cable-stayed bridge is introduced: Two-node catenaries cable element (with arbitrary rigid arms); Co-rotating coordinate system and geometric stiffness matrix of beam element; and solution procedure of geometric method is introduced.(2) Methods of determining reasonable finished state of cable-stayed bridges; Forward-iteration method on calculating cable-stayed bridge stress-free shapes is studied, and the method is appled on JingYue Yangtze River Highway Bridge to computer tension cable of finished bridge.(3) Assembled geometry and unstrained geometry is introduced and their differences and relation are studied; And solution for each of them is elaborated; the basis thought of stress-free shapes control method is emphasized, with reference to JingYue Yangtze River Highway Bridge, forward-iteration calculation is carried on in accord with construction progress, and assembled geometry and unstrained geometry is computed.(4) Error evaluation and analysis is studied in the progress of steel box girder prefabrication and cantilever assemble, and error solution progress based on self-adaptive stress-free shapes control method is researched, and this method is applied on JingYue Yangtze River Highway Bridges while there are error in the progress of construction.(5) With reference to JingYue Bridge, source of prefabricating error is investigated, and main design influence parameters are distinguished using sensitive analysis of parameters; And steel box girder cantilever assembled error is studied, put forward source of cantilever assembled error.