Study On Shear Lag Effect And Calculation Method Of Main Girder With Box Cross Section For Single Cable Plane Cable-Stayed Bridge With Slanted Pylon Of Maxin Bridge

Single cable plane cable-stayed bridge, its central dense cable area of the main grider adopting a closed thin-walled box girder cross-section, the widthness of box girder's roof but the thickness and of web plate, more serious shearing deformation of flange, which resulted in Lateral Non-Uniform Distribution of box girder Bending Normal Stress, that is shear lag effect. The pylon, girder and pylon pier are rigidly connected in order to slow down insufficiency of torsion stiffener caused by single cable plane and increase the stability of the construction, there will produce the strong shear lag effect in the box girders under a load.The moment and the stress distribution in the main grider is really complicated by the impact of the layout and stiffness for cable-stayed, the form for the main girder cross-section, the layout for loads, under the combined effect of pressure and bending load, the normal stresses distribution in the wide and thin flange is more complex.Therefore, study on this topic not only have great Theoretical value, but also has a strong practical engineering value.Aimed at the structure of Xiamen Xinma Bridge, This paper established a FEM model of 2D beams for full-bridge based on DoctorBridge software and then calculated global structural feature of the bridge,studied the key section of the plane stress distribution; With the advantage of accurate spatial stresses of ANSYS software, this paper also established a FEM model of 3D for full-bridge, analyzed variation law of the stress distribution for structure key section under the dead load ,and combined results of the plane stress by DoctorBridge, then analyzed the shear lag effect in segment of steel box girder, analysis focused on shear lag effect of single box and multi-cell in bridge.Analyzed shear lag effect from two aspects.On one hand, the first method is conventional, this method doesn't distinguish the axial force and bending moment in cross-section,and analyzed shear lag effect with multiple stresses; On the other hand, tne second method is according into the shear lag effect of classic definition strictly, this method filtered out section axial force and analyzed shear lag effect under pure bending, then compared with the analyzed results.Aimed at characteristics of beam-column in cable-stayed bridge's the main girder, Studied the effects of axial force in further, analyzed ratio of the bending moment and axial force impact section shear lag,then derived function relationship between ratio of the bending moment and axial force and integrated shear lag coefficient. For the complexity of stiffened plate in steel box girder section, this paper used equivalent method,the method is that space board module simulate stiffened plate approximately,equaled stiffened plate to a certain thickness plate element and derived the formula, then proved by ANSYS finite element partial model.put forward a finite element method which considerd shear lag effect-the "equivalent shell" theory.