Research On Static Behavior Of U-box Composite Continuous Girder In Rail Transit

The U-box composite girder is a new form of structure, which evolved from groove-girder in urban railway transit. It has the advantages of environmental friendliness, good adaptability to architectural landscape and low cost operation.The structure of the u-box composite girder is different from traditional box girder, T girder and groove-girder, the study of u-box composite girder fills the blanks of the research field in China.This thesis based on the (30 + 48 + 30) m u-box continuous composite girder and mainly conducted a study of the following areas:(1) The finite element analysis model was established by using ABAQUS(a large-scale general-pupose finite element program) to calculate and analyze the structural response under the single load and load combination. The result shows that the stiffness of structure is large,when acting on double line load, the cross section of roadbed slab downwarping, accompanied by partial concave deformation,The roadbed slab’s biggest rotating Angle and the vertical deformation is far less than standard permissible value. This thesis also analyzed the structural sensitivity, include influence of the plate thickness, length to width ratio and length to high ratio on mechanical performance,Study found that length to width ratio has little influence on the stress of u-box composite girder,Decreasing length to high ratio will enhance the safety of the structure, changing the length to high ratio will make a significant impact on stress and vertical deformation of gireder., especially on the u-girder section.(2) This thesis analyzed the force mechanism of the local structure of the bridge. In the case of the u-box composite continuous girder, the structure is very complicated. Due to the width of the bridge, the shear lag is obvious. This thesis focus on the force of the U girder web and the influence factors of shear lag,The result shows that in U-box girder combination part,the thicker the roadbed slab, the shear lag more obvious, in the U-box girder combination to the u-girder transition section part, due to the change of cross section makes the shear lag of the road bed slab more obvious; In U-box combination part, with the increase of road bed slab width, the influence of shear lag is more pronounced.In the u-shaped cross part, the change of road bed board width makes no difference.