Study On Fatigue Behavior Of Orthotropic Composite Steel Bridge Deck With Large U-Rib-PBL Bond

Traditional orthotropic steel deck has many advantages and is widely used,but it is prone to fatigue failure.The large U-rib PBL key composite steel deck reduces the number of welds,improves the strength of shear keys and the thickness of concrete composite structure layer,and greatly reduces the risk of fatigue failure by increasing the size of U-rib of traditional orthotropic steel deck and using continuous PBL keys instead of scattered studs as shear connectors.For this new orthotropic steel deck structure,the fatigue characteristics are deeply studied by using the method of fatigue failure test and fatigue simulation analysis based on fracture mechanics.The main research contents and results are as follows:(1)A fatigue model test scheme for large U-rib PBL bond composite steel bridge surface is designed,and the static characteristics of the test model are simulated and analyzed.The results show that the fatigue details of the large U-rib PBL bond composite steel bridge surface are the arc opening of the diaphragm and the connection of the U-rib diaphragm;The weld will cause high stress concentration on one side of the U rib at the U rib diaphragm connection,and cause the stress to be distributed in a gradient along the plate thickness,with the minimum stress in the center of the plate thickness and the maximum stress on the plate surface.(2)The fatigue crack propagation simulation analysis of the test model based on fracture mechanics is carried out.The results show that the fatigue crack at the arc opening of the diaphragm extends vertically downward along the plate plane,and the fatigue crack on one side of the U rib at the U rib diaphragm connection extends simultaneously along the plate thickness direction and the horizontal direction from the middle of the span to both ends in the plate plane;The type of fatigue crack is type I;The fatigue crack initiation stage is long in the early stage,accounting for90% of the total fatigue life,and rapidly expands to structural failure in the later stage.(3)The fatigue test model of large U-rib PBL bond composite steel bridge surface is made and the fatigue failure test is carried out.The results show that the experimental observation results of fatigue crack generation and propagation are in good agreement with the simulation analysis results;The fatigue load action times of the final fatigue failure of the test model are greater than the requirements of the code,and the fatigue performance of the large U-rib PBL bond composite steel deck is excellent;The fatigue failure mode of the large U-rib PBL bond composite steel bridge surface is that the fatigue crack at the arc opening of the diaphragm extends vertically downward along the plane of the plate to penetrate the lower edge of the diaphragm;Fatigue crack propagation will lead to stress release near the crack,but has little effect on the stress far away from the crack,and the crack only changes the local stress distribution;The crack propagation of fatigue details does not change the linear elastic state of the whole structure.There are 99 figures,24 tables and 64 references...