Analysis On Shear Lag Effect Of Curved Corrugated Web Steel Box-Concrete Roof Composite Box Girder With Double Box Single Room

At present,there are many researches on the shear lag effect of the straight-line corrugated steel web composite box girder in China,but there are few researches on the shear lag effect of the double box single chamber curved corrugated steel box concrete roof composite box girder,so it is of great significance to study it.When the composite girder bridge with double box single chamber curved web and steel box-concrete roof is subjected to vertical symmetrical force,it is affected by a series of factors such as initial curvature and so on.The longitudinal normal stress distribution on its section will be more complex.In order to understand its change rule,this paper uses theoretical method and finite element method to analyze the normal stress distribution and shear lag effect of such composite girder with zero curvature and small curvature respectively.The main contents and research results are as follows:(1)Based on the basic assumption and the quadratic parabola as its warping displacement function,the control differential equation of shear lag of the straight double box single chamber corrugated web steel box-concrete roof composite box girder bridge is derived by the variational method,and the analytical expressions of longitudinal normal stress,shear lag coefficient and deflection of the beam under different load conditions are obtained under the simple support boundary condition.The stress,shear lag effect and deflection of simply supported composite box girder under different working conditions are analyzed by using the derivation theory and ANSYS.It can be seen from the analysis that the error between the theoretical calculation results and the finite element calculation results is small,which verifies the correctness of the two;when the symmetrical vertical load is different,the peak point of the normal stress of the wing plate is located in the web position,and the shear lag effect of the concentrated load is more obvious than that of the uniform load;when the theoretical method is used to analyze the deflection of this kind of composite box girder,the shear deformation should be included This influence factor.(2)In order to analyze the shear lag effect of double box single chamber curved web steel box-concrete roof composite box girder conveniently,this paper first analyzes the torsional effect of this kind of straight composite box girder and establishes the differential equation,which is the basis for the theoretical derivation of this kind of curved composite box girder.After that,considering the factors of bending,shear lag and torsion,this paper uses the energy method to deduce the differential equation of bending and torsion control of the double box single chamber curved wave web steel box concrete roof composite box girder,and uses the Galerkin method to solve the differential equation combined with the boundary conditions,and finally uses the derived theoretical formula to calculate the shear lag effect of this kind of curved composite simply supported box girder It is necessary to analyze and establish a finite element model to verify the correctness of the theoretical method in this paper.By comparing the theoretical solution and the finite element solution,it can be found that the theoretical calculation results in this paper are in good agreement with the finite element results,which verifies the rationality of the theoretical derivation;under different working conditions,the normal stress distribution in the inner and outer side of the beam wing plate is asymmetric,and the overall performance is that the normal stress on the outer side of the wing plate is greater than that on the inner side of the symmetrical position,and the center line of each lower wing plate in the inner and outer box chambers The internal normal stress is greater than the external normal stress at the symmetrical position;under different loads,the maximum value of the shear lag coefficient of the upper wing plate is always at the position of the outermost web,and the maximum value of the concentrated force coefficient of the lower wing plate is always at the position of the inner web of the outer box chamber;the change of the shear lag coefficient of the beam wing plate is more obvious under the uniform load than that under the concentrated load.(3)The finite element model of the composite continuous box girder with double box single chamber curved web steel box-concrete roof is established.The distribution of stress and shear lag coefficient in the middle of beam span under different working conditions is analyzed,and the ANSYS value is compared with the theoretical value in this paper.The comparison results show that the ANSYS value is in good agreement with the theoretical calculation results of this paper,and its error is within the scope of engineering accuracy;and under different loads,the development law of the normal stress and shear lag coefficient of the inside and outside of the curved composite continuous box girder is roughly the same as that of the curved composite simply supported box girder.(4)Based on the finite element software,the influence of curvature radius and diaphragm spacing on shear lag effect of simply supported box girder with curved web and steel box concrete roof is studied.The results show that: under the same span,the smaller the radius of curvature is,the larger the stress gap between the inner and outer sides of the wing plate is.For example,when the radius of curvature is 400 m or more,the shear lag coefficient is almost equal to that of the straight beam,which can be calculated as the straight beam;the reasonable arrangement of the diaphragm can effectively redistribute the stress and reduce the shear lag effect.