Research Of Mechanical Properties And Calculation Methods For Double-Truss Four-Line Plate-Truss Composite Continuous Steel Trusses

Truss with orthotropic steel bridge deck is one of the relatively reasonable structural types in long-span bridges of high-speed railways, because of its great rigidity, good integrity, excellent dynamic behavior, making low noise and so on. However, upper flanges of lower chords, longitudinal girders, transverse girders, as parts of the steel bridge deck, whose mechanical behavior are complex. Steel bridges with double trusses, bearing four line loads, are designed rather difficult.In the dissertation, mechanical properties and calculation methods of double-truss four-line plate-truss composite continuous bridges with orthotropic steel bridge deck are studied deeply on the background of Dongxin Ganjiang River Bridge of Nanchang transportation hinge high-speed railways which is under construction. The main research contents are as following:1. This thesis reviewed the development of steel-truss continuous bridges systematically and summarized the structural style and the mechanical properties of trusses with orthotropic steel bridge deck. Also the research status of the calculation method was summarized.2. According to the characteristics of four-line double-truss plate-truss composite bridges, determined to build finite element models of different levels and scale by using spatial panel-girder element method, plane simplified calculation method and spatial plate-shell finite element method for deck-slab system analysis. Then, a study and evaluation on different methods above in view of calculation precision, computational cost and the applied range of analysis have been made.3. Individual mechanical characteristics analysis of Dongxin Ganjiang River Bridge has been made by using spatial panel-girder element method and plane simplified calculation method. Accuracy comparison of the two method are made. Also effects of sensitive parameters on mechanical behavior of structure have been studied. Calculation principle of code for strength and stability are analyzed, also a bar member verification program has been compiled which was applied to check calculations of main truss.4. This thesis introduced several suitable construction methods of steel-truss continuous bridges and compared the different features between cantilever erection and dragging method. Combining with the construction procedure of Dongxin Ganjiang River Bridge, construction simulation calculation of steel-truss bridge was carried out and the condition of unstressed closure at mid-span was discussed. Also some useful suggestions are proposed to guide the construction procedure.5. This thesis analyzed the influence of individual mechanical characteristics on the joint stiffness and the gusset plate rigid region deeply, and gave some beneficial suggestions about the gusset plate rigid region to engineers.6. Adopting spatial plate-shell finite element method, individual mechanical characteristics for the orthotropic steel bridge deck analysis was performed, and a parametric analysis has been conducted. Combining with the analysis results, reasonable arrangement form and applicable range for long-span composite continuous bridges with orthotropic steel bridge deck was discussed.