Analysis And Experimental Study On Shear Lag Effect Of Extra Wide Double Box Steel Girder

Throughout the development history of Bridges,the bridge deck width increases with the continuous improvement of bridge span capacity,which makes the constant load account for an increasing proportion of the bridge design load.Thin-walled box girder is a reasonable and effective structural form considering its strength,stiffness,economy and reducing dead weight.As the cross section types of thin-walled box girder are various,it has been deeply studied and developed.Two-sided box girder is a form of thin-wall box girder extension.The double box girder has the characteristics of good wind resistance,large torsional stiffness and the ability to reduce the dead weight of the beam.For the calculation of shear lag effect of bilateral box girder,there is no explicit provision in relevant domestic and foreign norms at present,and there are limited design theories and experimental studies that can be used as references.Therefore,the research on shear lag effect of bilateral box girder section girder has scientific value,which is of great significance to the compilation of domestic and foreign design norms.In this paper,based on a double-sided box girder self-anchored suspension bridge,a reasonable and accurate simulation of the bridge structure is carried out by ANSYS large finite element analysis software.The research contents of this paper include:(1)The differential equation for calculating the shear lag coefficient of double box girder section is obtained by describing and deducing the classical comparator method.Based on the finite element software ANSYS,the applicability of the comparative bar method to study the shear lag effect of two-sided box simply supported beams is analyzed.(2)Based on the engineering background of an ultra-wide double-sided box steel girder suspension bridge,the external conditions are changed by changing the longitudinal position of the section based on the finite element software ANSYS and the field full-scale in-situ test(3)Based on the simple supported and cantilever systems commonly used in engineering,the influence parameters of the shear lag effect of double box girder under these two boundary conditions are calculated and analyzed,and the influence rules of different design parameters on the shear lag effect of double box girder are studied.Then the effective distribution width coefficient is introduced,the variation rule of the effective distribution width coefficient when the span width ratio changes is obtained,and the functional expression with the span width ratio as the independent variable is synthesized with the span width ratio.The main research results and conclusions of this paper are as follows:(1)Deduces the bilateral box cross section beam slab under concentrated load and uniformly distributed load,the differential equations and the corresponding shear lag coefficient to solve the expression,writing form with the help of computer to quickly estimate the shear lag of box girder cross section slab coefficient,at the same time help the preliminary design stage to improve the work efficiency of the bridge.However,there are some limitations in the comparator bar method,that is,the shear lag coefficient of the section can only be obtained by using the comparator bar method,but the change law of the longitudinal normal stress distribution along the section cannot be obtained,so it is not suitable for more accurate analysis in the construction design stage.(2)Slings and beams have great influence on transverse shear lag effect of double box girder.Through calculation analysis and experimental results,the shear lag coefficient of the roof at the bilateral box is large.When there is a sling at the section,the shear lag coefficient of the roof at the double box decreases significantly.The shear lag coefficient of the roof decreases when there is a beam at the section position.(3)Introduction of effective distribution width coefficient,fitting out of bilateral cases of bilateral box beam and cantilever beam under uniformly distributed load,its cross section in the wide span ratio as the independent variable of the formula of effective distribution width coefficient,and according to the formula,effective distribution width coefficient and bilateral box girder of box girder is obtained according to the rules and effective distribution width coefficient were compared.According to the comparison results,the correction coefficient of the calculation formula is proposed.