九江长江公路大桥宽幅主梁结合段剪力滞效应分析

Analysis of Shear Lag Effect of Joint Section of Wide Main Girder of Jiujiang Changjiang River Highway Bridge

九江长江公路大桥主桥为双塔双索面混合梁斜拉桥。该桥主梁宽高比大,钢-混结合段构造和受力复杂,剪力滞效应显著。为研究钢-混结合段剪力滞效应分布对主梁受力及结构布置的影响,选取含结合段的主梁节段建立模型,采用有限元法分析结合段钢梁及混凝土梁关键截面顶、底板在设计控制工况内力作用下的应力和剪力滞系数分布。分析结果表明:结合段混凝土梁存在较强的剪力滞效应,底板靠斜底板处剪力滞系数最大,达到1.5,在未考虑纵向预应力作用的情况下,混凝土梁底板存在较强的顺桥向拉应力,建议根据剪力滞系数分布加强纵向预应力布置。

The main bridge of Jiujiang Changjiang River Highway Bridge is a hybrid girder cable-stayed bridge with double pylons and double cable planes.The width-to-depth ratio of the main girder of the bridge is great,the structure and force conditions of the steel and concrete girder joint section are complicated and the shear lag effect there is obvious.To study the influence of the shear lag effect distribution of the joint section on the force conditions and structural layout of the main girder,a section of the girder having the joint section is selected to set up a model and the finite element method is used to analyze the stress and shear lag coefficient distribution of the critical section top and bottom plates（slabs） of the steel and concrete girders under the internal force of designed control load cases.The results of the analysis show that considerable shear lag effect exists in the concrete girder of the joint section and the shear lag coefficient of the bottom slab close to the inclined bottom plate is the greatest,being up to 1.5.Under the condition that the longitudinal prestressing is not considered,the fairly strong tensile stress along the bridge exists in the bottom slab of the concrete girder and it is thus proposed that the longitudinal prestressing layout should be reinforced according to the shear lag coefficient distribution.