Research On Mechanical Properties Of Steel-Concrete Joint Section Of Hybrid Girder Cable-Stayed Bridge On High-Speed Railway

With the rapid development of China’s high-speed railway construction and the improvement of the bridge construction level,the hybrid girder cable-stayed bridge has become an advantageous bridge type for railway-specific bridges with its excellent mechanical properties and outstanding economy.The steel-concrete joint section is a unique and extremely important part of the hybrid girder cable-stayed bridge,with a complex structure.The study of the mechanical properties of the steel-concrete joint section is of great engineering significance to ensure the rationality and safety of the whole bridge.The newly built Nanyu Railway Bridge across the Yu River,with a design speed of 350km/h,is the first ballastless rail cable-stayed bridge for high speed railway with a main span of 330 m.In this paper,the mechanical properties of the steel-concrete joint section of the Bridge across the Yu River are studied and analysed against the background of the project.The main research elements of this paper are as follows:(1)By numerically calculating the properties of each section in the longitudinal bridge direction of the steel-concrete joint section,the variation law of its Stiffness and its influence are analysed.The ABAQUS FEM software was used to establish an equal scale finite element model of the steel-concrete joint section of the Bridge across the Yu River.The stress distribution,vertical deformation condition and shear hysteresis effect of the joint section were analysed by calculation,and the safety and reasonableness of the structure were evaluated.(2)First,based on the quantitative analysis of the overall model of the steel-concrete joint section,the overall study has obtained the variation law and influence range of the force transmission ratio of each main member along the longitudinal bridge direction.Then,the FEM model of the local cell of the steel-concrete joint section was established,and the stress distribution law of the cell and the shear distribution law of the shear bond were obtained from the local calculation analysis,which complemented the overall analysis,and further discussed and summarised the force transfer mechanism of the steel-concrete joint section with the compartment before and after the bearing plate.(3)According to the force characteristics and transmission mechanism of the steel-concrete joint section,the simplified calculation method of the steel-concrete joint section and the simplified calculation model of the cell are proposed,and the accuracy and application range of the two methods are discussed.(4)A semi-open steel cell construction that improves the quality of concrete placement in the cell is proposed and the safety of this construction form is verified.Based on a simplified calculation model of the cell,the shear member stiffness,the length of the joint section and the axial stiffness of the cell were selected as the influencing parameters,and the effect of their changes on the force transfer behaviour of the steel-concrete joint section of the cell was discussed.Finally,based on the relevant results and literature,some suggestions are made for the structural design of a steel-concrete joint section with a cell front and rear bearing plate,and a design process for a steel-concrete joint section is proposed.