The Study On Structural System And Mechanical Behaviors Of Through Steel Tied-arch Composite Bridge On High-speed Railway

Through tied-arch composite bridge shows several advantages such as great spanning capacity, large stiffness, low architecture height, low noise and well dynamic behavior. With rapid construction of high-speed railways in China, this type of bridge will get more and more applications. It's an attractive solution especially for the high-speed railway bridge across urban roads, rivers, expressways and railways, where expectations and demands for landscape are usually high.Based on the engineering background of 140m TingSihe Bridge on Wuhan-Guangzhou Passenger Dedicated Line, the research systematically studied the structural system and the mechanical behaviors of through tied-arch composite bridge and its application. The main creative research works include several aspects as follows:1. The analytical solutions of internal force and deformation of through tied arch bridge were deduced, considering the influence of the angle of the arch axis curve during the deduction process. A simplified mechanical model for the through tied-arch bridge was established by dividing the structure into beam-arch body and suspenders. On the basis of model test and theoretical analysis, the axial forces of the suspenders acting on the beam-arch body were replaced with a uniform load. According to the deformation coMPatibility conditions, the analytical calculation formulas of the internal forces, deformations and the force ratio of arch to collar beam were deduced. The analytical solutions for several project examples fit in well with the results of the finite element method. And the precision of the analytical solutions in this paper is also distinctly higher than the one without regard to the influence of the angle of the arch axis curve.2. The optimum cross section of box member under both axial forces and bending moments was deduced on the principle of minimum stress. And based on the principle of maximum stiffness of bridge, the reasonable value ranges of ratio of rise to span and stiffness ratio of arch to collar beam were proposed on condition that both the arch and the collar beam adopted optimum box cross-sections.3. The approximate analytical solutions of internal forces and deformations of the composite deck with longitudinal and transverse beams for the through tied-arch bridge were presented before or after the concrete reached its design strength. Using beam grillage method and boundary element method, the approximate analytical solutions of both the longitudinal forces of the composite deck under the first mechanical system and the internal forces and deformations of the composite deck under the second mechanical system were deduced. The equilibrium condition, deformation capability conditions of and boundary conditions were satisfied during the deduction process. A project example was used to verify the precision of the approximate analytical solutions in this paper.4. Using the spatial finite element method, the mechanic characteristics of seven composite decks with longitudinal and transverse beams were studied systematically for large span through tied-arch composite bridge on high-speed railway. Several engineering measures to relieve the stresses of the transverse beams caused by out-of-plane bending moments and the tensile stresses of the concrete slab were put forward. These measures are very useful and practicable for the composite deck design.5. The quantity and position of the braces for large span through steel box tied-arch composite bridge on high-speed railway were optimized by spatial finite element method. Some valuable conclusions about rational quantity and position of the braces were obtained to provide a reference for designers. 6. A 1:8 scale-down model test of 140m through tied-arch composite bridge on Wuhan-Guangzhou Passenger Dedicated Line had been completed. The mechanical states of the steel deck and the composite deck were studied by several loading cases. The approximate analytical solutions in this paper agree well with the results of the test, which verified the correctness of the computational methods and the analytical solutions in the paper.The researches above have been successfully applied to TingSihe Bridge on Wuhan-Guangzhou Passenger Dedicated Line and XinKaihe Bridge on Harbin-Dalian Passenger Dedicated Line. Remarkable economic and social benefits have been achieved in these bridges.