The Analysis And Reseach Of Shear Lag Effect In Thin-walled Box Girder

With the accelerated pace of the reform and opening-up and modernization,thetransportation construction industry has undergone rapid changes, the bridge project ismoving in the direction of diversification development which closely related to us.Box-section beam is widely used in the deck of continuous beam bridge and continuousrigid frame bridge because of it’s good structural characteristics and mechanicalproperties.When the box girders flange under the load, it has a uneven sheardeformation and the sectional normal stress along the cross-section is not a straight linedistribution but a curve distribution, this is so-called shear lag phenomenon. The reasonfor this phenomenon is that the box girders have wide horizontal flange plate and bigweb spacing and the thin walls of the box features. But if we ignored the shear lag effect,it will lead to the transverse crack of the corresponding parts and unsafe structuraldesign, and in severe cases it may result in the destruction of the bridge structure.Inorder to study the shear lag effect of continuous rigid frame bridge box girder, thesectional normal stress of prestressed concrete continuous rigid frame bridgecross-section which takes the Tongzi River Bridge engineering as a background iscalculated and analyzed by theoretical calculations and finite element program. Themain research work of this thesis includes the following aspects:(1) The paper first introduces the development of prestressed concrete continuousrigid frame bridge and follows by a review of the Research and research methods athome and abroad about the shear lag effect.(2) Based on the existing shear lag effect research methods, the three analogymethod for solving the shear lag effect is introduced in detail. Its formula is derived andthis paper ultimately derives the theoretical formula which is use the three analogymethod to solve the box beam shear lag effect.(3) Taking the Tongzi River Bridge (the main span combination is108m+2x200m+108m) as the engineering background, it calculates the shear lag effect withthe three analogy method at0#block of Tongzi River Bridge intermediate piers andsolves the coefficient of shear lag finally.(4) This paper uses the space finite element software ANSYS to establish a0#block full-scale mock-up and make an assay of the shear lag effect when the TongziRiver Bridge is under constant loads.Taking out three different cross-sections at0# block, this paper analyzes the shear lag to find out the discipline of the shear lag in thecross section.(5) Finally, this paper compares the computed results of the three analogy methodand the finite element method.