Study On Shear-Lag Effect Of Girder For Composite Cable-Stayed Bridges

Combined with the cable-stayed bridge structure,it can simultaneously exert the material advantages of steel and concrete,and has strong economic competitiveness in the construction of long-span bridges.Studying the mechanical properties of this structure and perfecting the corresponding structural design methods are of great significance to ensure the safety of the bridge and optimize the structural design.Based on the Jiaojiang Second Bridge Project,this paper studies the shear lag effect of concrete bridge decks of multi-tank single-chamber steel box combined with cable-stayed bridges by numerical analysis.The results show that the shear lag effect of the main beam section in the cantilever construction stage and the bridge construction stage is quite different.The shear lag coefficient of the cantilever construction stage is smaller than the bridge stage;the main beam shear lag effect of the bridge construction stage The lateral distribution is uneven,the shear lag of the bridge to the tower and the middle span is significant,and the middle section of the adjacent cable exhibits negative shear lag effect;the influence of axial pressure on the shear lag of the deck can be divided into 4 In the region,the effective distribution width becomes larger as the distance of the force-applying point increases;the influence of the thickness of the concrete slab on the shear lag of the composite beam is negligible;reducing the stiffness of the shear joint can alleviate the shear lag of the deck Effect,the effective distribution width of the deck is small as the stiffness of the shear connectors increases.Through the comparative analysis of the current bridge design specifications at home and abroad,it is found that the calculation method of the effective width of the flange plate of the combined beam adopted by various countries is not only in different forms,but also has a large difference in calculation results.It is effectively calculated by the current highway bridge code in China.The safety reserve of the width value is low.According to the comparison of the effective width coefficients of the cable-stayed bridges with two different sections,the combined beam section under the combination of axial force and bending moment is verified.The applicability of the formula for calculating the effective width coefficient of the flange plate;this formula is applicable to the calculation of the cross section of the I-shaped double main beam,and can also approximate the effective width coefficient of the multi-tank single-chamber steel box section,but the calculation accuracy is reduced.