Research On Shear Lag Effect Of Wide Main Girder Concrete Cable-stayed Bridge In Construction Stage

The box section has good mechanical properties such as strong ability to bear positive and negative bending moments,large torsional stiffness and good stability.It also has the characteristics of thin box wall,large web spacing,wide transverse flange and high section efficiency index.Because of these advantages of box girder,box section is the most common form of long-span bridges at present.In thin-walled box girder structures,the phenomenon of shear lag effect is widespread and can not be ignored.If neglected,it will lead to some parts of the stress is too large,resulting in its structure can not meet the requirements of structural safety.It is of great engineering value and research significance to fully consider the shear lag effect of thin-walled box girder in design calculation and construction.Based on the research background of the wide girder concrete cable-stayed bridge under construction,the shear lag effect of the main girder of the bridge is studied by combining theoretical calculation and analysis,finite element software simulation and actual engineering stress test.The specific research contents of this paper are as follows:(1)Based on the energy variational method,the shear lag effect of wide girder concrete cable-stayed bridge is studied in this paper.The calculation formulas,differential equations and solution formulas for the cross section of the bottom plate with inclined angles are derived.Considering that the shear lag effect of edge and floor is composed of the web effect of the corresponding height of edge and floor and the flat floor effect of the corresponding width,this paper adds the influence factor of the height of edge and floor to the original warping displacement function,and ignores the influence of itself on the moment of inertia of the section,just like the top and floor.(2)According to the numerical results of large-scale finite element software ANSYS,the applicability of theoretical calculation in simple-supported beam andcantilever beam is verified,and the shear lag effect of key sections(quarter section,half section and quarter section)of simple-supported beam and cantilever beam with single box and three-compartment section with different inclination angles under different loads(concentrated and uniform loads)is analyzed respectively.?(3)Based on the research background of the construction project of the wide girder concrete cable-stayed bridge,the applicability of the theoretical calculation in the cable-stayed bridge is verified by three methods: theoretical calculation,numerical simulation and actual bridge test.The shear lag effect of the change of the construction stage on the root section and quarter span section of the main tower and the opposite side bottom plate of the average stress of the roof and bottom plate are also analyzed.The influence of shear lag effect.(4)The influence of the thickness of diaphragm,top and bottom slabs and side and bottom slabs on the shear lag effect of cable-stayed bridges during construction is studied by numerical simulation,and the corresponding conclusions are drawn.