Study On Structural Behavior And Fatigue Model Test Program Of Orthotropic Deck Of Long-Span Flat Steel Box Girder

Orthotropic deck structure of flat steel box girder are complex, which have much welds, fatigue cracking problems have always been respected, and fatigue cracking cases are reported worldwide.The thesis based on the project of Chongqing Zhongdu Yangtze River Bridge. The thesis preliminary study the structural behavior and fatigue performance on the orthotropic deck of flat steel box girder. Firstly, the original bridge section of ANSYS finite element model is established, load step is used to simulate vehicle moving load, the analysis considers the effect of deck pavement, which analysis the stiffener rib, transverse diaphragm and top plate of the principal stress state, and to analysis the most unfavorable load mobile location. Then, the influence of the orthotropic deck design parameters (thickness of top plate, thickness of U rib and thickness of diaphragm plate) on the fatigue stress of fatigue sensitive parts was analyzed. Then, to design the fatigue test model. Finally, to research loading scheme and the arrangement of measuring points in the model test. The main research contents and conclusions are as follows:1. Through the establishment fine segment finite element model of Chongqing Zhongdu Yangtze River Bridge’s steel box girder to preliminary study the structural behavior on the original flat steel box girder bridge. And it obtained the most unfavorable position of bearing force and the most unfavorable load mobile location through the detailed analysis. Through the analysis, it is found that the different types of diaphragm plate has different influence on the structure of the joint, and the corresponding of the most unfavorable load position and the structural position of each kind of diaphragm plate are not the same, the influence of the H2 diaphragm plate on the structure is the most, the force of the original bridge is the most disadvantage when the first heavy axle of the vehicle load is at the top of the H2 diaphragm plate.2. To analysis the influence of the orthotropic bridge deck design parameters (thickness of top plate, thickness of U rib and thickness of diaphragm plate) on the fatigue stress of fatigue sensitive parts. Through these analyses, we get the influence of the thickness of top plate, thickness of U rib and thickness of diaphragm plate on the stress of the fatigue sensitive parts of the orthotropic bridge deck structure.3. Through the preliminary design of the structure of fatigue test model, using control variable method to explore the diaphragm plate stiffness, web plate stiffness influence on the equivalent model, then the main parameters of diaphragm plate height, web plate height and plate thickness were determined. Then verify the equivalence of the test model, and finally determine the basic parameters of the model.4. The orthotropic deck model test focuses on the fatigue performance of the fatigue sensitive point where stiffening rib and diaphragm plate joints, and stiffening rib and top plate joints the diaphragm plate edge of the opening part of the stress concentration position. Based on this, the test model points are set up with detailed and targeted. Finally, combined with the test site and equipment and other factors, the loading scheme is determined.