Research On The Shear Lag Effect Of Main Girder With Single Box And Triple Cells Used In Cable-stayed Bridges

The box girder has been used widely in modern cable-stayed bridges due to its excellent structural performance. The stress distribution of section in wide and thin box girder subjected to simultaneous bending and axial forces doesn't conform to the assumption of the plane section, and the transverse stress distribution is uneven; with the increasing of bridges' span and the lowering of security repertory, to consider the uneven of stress distribution in calculation of design and construction control, and to analyses the shear lag effect in the process of bridges' construction and using are bound to have important engineering value and theorical significances.With the Jianning Bridge in Zhuzhou as the subject background, after systematically expatiating on the previous analytical theories and methods of calculation of shear lag effect, the thesis selects spatial finite element method and applied method to study the shear lag effect of main girder with single box and triple-celled used in cable-stayed bridges, and it also experiments on the construction control and load test investigation. This thesis presents "illustration method" which describes the shear lag effect of main girder with single box and triple-celled by the shear lag coefficient curve illustration and transverse distribution chart of longitudinal stress. The thesis points out that when whole designing this find of bridges only by the plane analytical program, the safety coefficient of the constructing state and the top slab should be set up higher than the finished state and the bottom slab respectively. At the same time the thesis points out that the influence of longitudinal pre-stress, diaphragms and crosslope can not be ignored when researching on the shear lag effect. Main contents are shown as follows:(1) After comparing all kinds of applied methods, three-bar stimulation analysis method which is simple is selected to calculate coefficients of shear lag on some cross section of box girder.(2) Based on the spatial finite element method, the thesis adopts the program-ANSYS to analyze the shear lag effect of main girder with triple-celled single box when under construction and also in the finished state. Considering the characteristic of the shear lag effect of main girder with single box and triple cells the thesis presents "illustration method" which is a method describes the shear lag effect...