Analysis And Research On Shear Lag Effect Of Through Wide Box Tied Arch Bridge

The lower-bearing tie-bar arch bridge is one of the most common forms of the bridge in China.Because of its beautiful shape,new structure and strong environment-adapting ability,it can meet the requirements of the large bridge and occupy an important position in the bridge construction of our country.The tie-bar arch bridge is a kind of beam-arch combined structure system,which can give full play to the structural characteristics of the beam bending and arch compression,and the outer part belongs to the static fixed structure system,so that the structural system is not high in the requirement of the geological environment,and the applicability is improved,so the tie-bar arch bridge is widely applied to the highway and the railway of China,The construction of urban bridge.The differential equation of control and boundary condition of single box seven-chamber box girder are deduced by energy variational method,and the formula of stress calculation of each flange plate is obtained.Compared with the results of finite element model analysis,it is proved that the energy variational method and solid element model are feasible to analyze the arch bridge of bearing wide box tie bar,and the formula of comprehensive shear lag coefficient under compressive and bending load is also derived.After that,the solid model and the rod system model of the single box seven-chamber tie arch bridge are established by using the Midas/Civil.The shear lag effect of the characteristic section roof under the whole bridge loading and the most unfavorable loading is analyzed,and the results show that the box girder roof near the fulcrum is positive The negative shear lag effect appears simultaneously,the maximum shear lag coefficient appears at the junction of the web and the upper flange of the middle fulcrum,and the positive shear lag effect of the compression zone away from the fulcrum is obvious.The distribution law of longitudinal shear lag in arch bridge construction stage and after bridge formation is further analyzed.The results show that removing the support makes the stress value of the main beam roof in the range of 37.5?72.5 m from the end fulcrum,the back fulcrum,the side span 3L/4 ? the middle fulcrum and the middle fulcrum.A stress mutation also occurs near the point of action of the L/4? concentration.Finally,the calculation coefficient of flange effective width of single-box seven-chamber tie arch bridge is compared and analyzed.The results show that the coefficient calculated according to the code is too large to ensure the safe use of the structure.The coefficient of middle-branch section is 0.87,which is too different from the finite element result 0.48.To sum up,the variation law of shear lag coefficient of lower bearing tie arch bridge is closely related to construction stage,loading form,thrust range of arch foot and fulcrum position.In the design stage,different effective width correction coefficients should be considered in different beam sections;in the construction stage,the stress value mutation at the junction of web and upper flange in the range of thrust action of arch foot should be monitored emphatically;in the use stage of bridge formation,bias load has obvious influence on shear lag coefficient,but the value is small,which is not the main monitoring basis.