Research Of Influence Of Prestressed Function In Vextical Orientation On Shear Lag Effect For Box Girde

With high mechanical property and structural strength, box girders have been widely used in continuous girder bridges and continuous rigid frame bridges. Since the box girder bridge is featured by wide lateral flange plate, thin box wall and large web spacing, etc.,non-uniform shearing deformation will occur when the flange plate is subject to the load,resulting in that the normal stress of the section is no longer distributed along the cross section in a straight line, but in a curve line, which is the shear lag effect. Ignoring the influence of shear lag effect will lead to unsafe structural design which, in severe cases, will cause damage to the bridge structure.The action of prestressed function in vertical orientation on the girder is axial load in essence or closely related to axial load. Currently, there are few researches on the shear lag effect under the axial load. Based on the principle of shear lag effect, this paper points out that the shear lag effect will occur in the box girder under the axial force and prestressed function in vertical orientation, and carries out the numerical analysis for the influence of the shear lag effect on the thin-walled box girder through the finite element software ANSYS, obtains and summarizes the rule of vertical distribution along the span for the shear lag effect. It aims to research the shear lag effect of the box girder under the axial force and prestressed function and the change rule of the shear lag effect, so as to provide some reference for engineering practice.Main research work: discuss the distribution rule of vertical stress caused by the axial force through the numerical analysis, with thin-walled box girders under two basic boundary conditions, simple support and cantilever, as the objects of calculation, make a distinction between the two different types of loads, i.e. symmetric load and eccentric compressive load,as well as top plates with and without the cantilever for box girders, and then carry out the calculation and comparative analysis, thus to reflect the change in lateral distribution of normal stresses of top and bottom plates in each controlled section under different loads as well as the variation of the shear lag effect along the vertical direction, so as to provide a reference for structural design and theoretical research. In addition, a 16+2 ? 20+16m real continuous box girder bridge is used as the engineering background in this paper to research the shear lag effect on the girder section from the prestressed function in vertical orientation applied during the construction. The normal stresses on the section of the prestressed concrete continuous box girder bridge in different vertical positions are calculated and analyzed through theoretical calculation and finite element program. The influence of pre-applied force on the shear lag effect of each controlled section for the continuous box girder bridge is discussed in case of the reinforcement distribution of post-tensioned members, along with the variation of the shear lag effect along the bridge in the vertical direction. The prestress loss in the construction stage is calculated according to the specifications and realized in the finiteelement program. Besides, the shear lag effects produced by the prestressed function in vertical orientation with and without the consideration of the prestress loss are compared and analyzed to serve as a reference for actual engineering design and construction.