Study On Effect Of Shear Lag Considering Longitudinal Stiffeners Of Curve Steel Box Girder

With the development and progress of engineering technology,thin-walled steel box girder has been favored in bridge construction for its excellent bearing capacity.Compared with the concrete box girder structure,the shear hysteresis distribution of curved steel box girder is different because of the influence of initial curvature and the cross-sectional setting of transverse diaphragm and stiffening rib structure,therefore,It is necessary to carry out research on it.Aiming at the curved steel box girder with longitudinal stiffening rib structure,this paper studies the stress distribution law of curved steel box girder under the composite deformation effect when considering the influence of longitudinal stiffening rib,taking into account various deformation forms such as bending,shear hysteresis,torsion and distortion of curved steel box girder.(1)Based on the equivalent conversion section,considering the influence of longitudinal stiffening rib on the structural mechanics performance,the governing differential equations of shear hysteresis control of curved steel box girder are deduced,and the differential equation is solved by simple numerical solution,which named the Galerkin method.Because the various plates that make up the steel box girder structure have obvious thin-walled characteristics,the cross section of the steel box girder is prone to distortion deformation,therefore,the differential equation of distortion control of curved steel box girder is deduced.In this case,the homogeneous solution of the distorted differential equation and the analytic expression of the non-homogeneous solution are derived,and the integral constant in the expression is determined by using the initial parameter method,taking the distortion warping deformation of the simple supported curved steel box girder only bearing the uniform load.(2)Using ANSYS to establish a numerical model of simple supported curved steel box girder,the obtained numerical results are compared with the calculated values of the derived formula,and the results show that the analytic value is in good agreement with the finite element calculation value.When the curved steel box girder does not set the transverse separator,the distortion warping stress proportion is larger;According to the calculation results of cross-sectional section,the distortion warping stress is 30% of longitudinal bending stress.The vertical displacement of steel box girder and the longitudinal positive stress of the top bottom plate can be significantly reduced by the longitudinal stiffening rib structure of the section.The calculation results show that when the longitudinal stiffening rib is set,the influence on the stress calculation result of the top floor can reach 12% and 8% respectively.(3)Based on the finite element software,the influence of different factors on the stress distribution is analyzed according to the related factors that affect the stress distribution of the cross section of curved steel box girder.For the example of this paper,when the value of curvature radius is greater than 500 m,the stress distribution of the structure can be calculated according to the linear beam.The stress distribution law of roof and bottom plate can be improved significantly by setting longitudinal stiffening rib in roof and bottom plate position,and the stress value should be reduced.When the longitudinal stiffening rib structure is set in the abdominal plate position,the effect of improving the stress distribution of the section is not obvious.The research in this paper improves the analysis of the mechanical properties of curved steel box girder with longitudinal stiffener structure,which provides a reference for the design and manufacture of steel box girder.