The Analytical Theory And Model Test Research On Local Stability Of Orthotropic Steel Box Girder

In this dissertation, the local stability of orthotropic steel box girder is systematically studied on the basis of researcher achievements and design specifications home and abroad, and combined with the construction practice of long span bridges with orthotropic steel box girder. The main contents of this dissertation are described as follows:1. the history, the state of the art in bridge engineering and technical problems of orthotropic steel box girder are investigated. Thus the developments of self-anchored suspensions and modern cable stayed bridges make the local stability more obviously.2. The theorical solution of critical buckling stress of plate simply supported along its four edges is analyzed, and some specifications of different countries on local stability of plate, as well as the theorical solution of critical buckling stress of the stiffened plate and calculation method of some overseas specifications for stiffened plate. Besides, the theorical background and the applicable area of these codes is analyzed. The elastic buckling characteristic of open stiffening plate and close stiffening plate are carried out, and some main structural parameters, which influence the buckling stress, are studied. The reasonable arrangements of longitudinal stiffener are discussed; calculations formulas of the required rigidity for longitudinal stiffener and transverse stiffener are also deduced.3. A model for optimization design of stiffened plate, inhibited by the the second stress of orthotropic deck system, is provided. Calculations formula of the flexural rigidity of grillage, calculating the second stress of orthotropic deck, is deduced. The structural cost is taken as the object function, the rigidity and allowed stress of deck plate are taken as the constraints, and optimization methods is FDM. A program is provided. Some significative conclusions, different from current design custom, are reached and can be used for design of steel box girder.4. The dissertation puts forward a method calculating ultimate strength of the stiffened plate with consideration of material and geometrical nonlinear, initial geometrical imperfections, residual stress. The theory can be used for the design of stiffened plate.5. Based on beam-column theory, the calculation form for the relationship of the stiffening plate's M-φ-N is deduced. And a simplified calculation means whichtake initial geometrical imperfections and residual stress into consideration, using step-by-step numerical method, is developed for studying the ultimate strength of the stiffened plate under axial compression. And a computer program is developed. According to comparison, this computer program is line with the software ANSYS.Based on this method, a model test of a series of stiffened plates with different structural arrangements is conducted; the ultimate load is achieved, the test result is nearly equal to the theorical analysis.6. Finally, the one-to-five model test of steel box girder based on SanChaJi self-anchored suspension in ChangSha City is introduced. The test includes two models with different structural arrangements. One is open stiffened plate for web which is destroyed because of local bucking, the other is U-rib stiffened plates which is destroyed because of material yielding. The test results are proved by means of theorical analysis. The experiment results can be referenced by design of steel box girder.