Analysis Of The Transverse Internal Force Of Steel Box Girder Considering The Influence Of Transverse Diaphragm

Steel box girder has been widely used in the construction of long span Bridges in China due to its strong wind resistance,light dead weight and superior crossing ability.When the steel box girder roof ACTS on partial eccentric load,torsion and distortion will occur to the steel box girder,which will lead to deformation of the steel box girder and produce a large transverse internal force on the section of the steel box girder.Therefore,more and more scholars begin to pay attention to the transverse internal force of the steel box girder.On the basis of summarizing and perfecting the transverse internal force calculation method,this paper mainly studies the transverse internal force of steel box girder considering the influence of diaphragm.Taking single box and single chamber steel box girder as the research object,the following aspects are studied in depth.(1)Aiming at the single box and single chamber steel box girder,based on the existing calculation theory of the transverse internal force of the box girder,the calculation formula of the transverse internal force of the steel box girder considering the influence of transverse diaphragms is derived.By acting eccentric load on steel box girder,combining the traditional frame method and the shear strain energy of diaphragm,the formula for calculating transverse internal force considering the influence of diaphragm is established.This method makes full use of the shear strain energy of diaphragm and the distortion theory of box girder to establish the relationship between the distortion displacement of steel box girder and the deformation of frame,and then deduces the calculation formula of the transverse internal force of steel box girder with the influence of diaphragm.The theoretical solution calculated by the method in this paper is compared with the numerical solution calculated by the finite element software ANSYS.The maximum relative error is 9.64%,which verifies the correctness of the calculation method in this paper.(2)As for the transverse internal force of the steel box girder with or without considering the influence of the diaphragm,a comparative analysis of the two situations shows that the bending moment value at the diaphragm has changed with or without considering the positive sign(the positive sign only represents the force direction,the positive sign represents the inner tension,and the negative sign represents the outer tension).When the diaphragm is taken into account,the transverse internal forces of each plate are significantly reduced,and when the diaphragm is over 4m,the influence on the transverse bending moment becomes very small.(3)Combined with numerical examples,the analysis shows that the transverse bending moment of the steel box girder under vertical eccentric load decreases rapidly with the increase of eccentricity distance.The transverse moment at the Angle of the roof decreases with the increase of the aspect ratio H/B,and tends to be stable when the aspect ratio h/b is greater than 0.9.The transverse moment value of the box girder roof near the Angle of loading increases with the increase of the pitch Angle of the web.When the pitch Angle exceeds 35°,the transverse moment value decreases slightly.The transverse moment values at the Angle point B and the load action point far away from the roof increased with the increase of the pitch Angle.When the pitch Angle exceeded 35°,the transverse moment values would not change basically.The pitch Angle of the steel box girder web should not be greater than 35°in the design.The length of cantilever plate,thickness of each plate and span of steel box girder have little influence on the transverse bending moment.(4)Based on the calculation method and finite element method,the influence of diaphragm parameters on the transverse internal force of steel box girder is analyzed.It is found that the thickness of diaphragm has no influence on the transverse moment of roof,the number of diaphragms increases,and the transverse moment of steel box girder decreases obviously.