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

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.