The Research On Local Stability Of Orthotropic Steel Box Girder

Based on the segmental model experiment of steel box girder for SanChaJi Bridge in ChangSha City, the buckling problem of stiffened plate is studied. Main work in this thesis is described as follows:Firstly, the State-of-the-art of orthotropic steel box girder applied in bridge is introduced. The development of self-anchored suspension bridge and modern cable stayed bridge make the local stability more seriously.Secondly, this thesis introduces the theory solution of local critical buckling of plate simply supported along its four edges, and some country's code for local stability of plate are also introduced. The theory solution of critical buckling of stiffened plate and calculational method of some country's code for stiffened plate are introduced. The applicable scope of these codes is analyzed. The Japanese code is introduced in detail. The calculation for stiffened plate of SanChaJi Bridge is carried out by using Japanese code. The stiffeners' intertia moment for web plate is deficient by calculation results. The elastic analysis of stiffened plates of steel box girder for SanChaJi bridge is carried out by universal software ANSYS. The critical buckling stress of U-rib stiffened plate is high but web's stiffened plate with open stiffeners is low.Taking geometrical and material nonlinear and initial geometrical imperfections and residual stress into consideration, this dissertation put forward a method calculating ultimate strength of the stiffened plate: For common use size of plates, thickness of U- rib and space between the transverse diaphragms, the ratio of the average stress of ultimate strength to yield stress can all reach 0.8; but the ultimate strength of open stiffened plates is sensitively influenced by the amplitude and direction of initial geometrical imperfections and residual stress.Finally, 1:5 segmental model experiment of steel box girder of SanChaJi Bridge in ChangSha City is introduced. The experiment includes two models with different structural arrangements. One is open stiffened plates for web which destroys because of local bucking, the other is U-rib stiffened plates which destroys because of material yielding. At last, the paper put forward some problem worthy of studying more in the future...