| Limited by the line direction and higher technical standards,high-speed railway bridges often cross existing high-grade highways and railways at a small angle.Sometimes the beam height is restricted to very small due to the clearance under the bridge and the elevation of the bridge deck.At the same time,the landscape effect of the bridge is required to be high.The arch-shaped pylon cable-stayed bridge has outstanding landscape advantages and can meet the needs of the line crossing the existing traffic line with small angle.And its beam is supported by some stay cables,and the beam height is relatively small.The arch-shaped pylon cable-stayed bridge can just meet the needs of that high-speed railway cross-over bridge.At present,the arch-shaped pylon cable-stayed bridges are mostly highway bridges,and there are not many relevant studies.There is no relevant application and research on the high-speed railway arch-shaped pylon cable-stayed bridges.Based on the main bridge of Guangzhou-Shantou Railway across Shenzhen-Shantou West Expressway,the thesis mainly studies the determination method of reasonable arch axis and the influence of some structural parameters on the internal force and deformation of the high-speed railway arch-shaped pylon cable-stayed bridge.The main research works and achievements are as follows:(1)Combined with the structure and load characteristics of arch-shaped pylon,according to the condition that arch-shaped pylon bending moment is zero under the reasonable arch axis,the differential equation satisfied by the reasonable arch axis of arch-shaped pylon under the combined action of self-weight and cable force is derived;Considering the influence of the cable tension on the reasonable arch axis shape of arch-shaped pylon,a solution method for the reasonable arch axis of arch-shaped pylon with cable force optimization is proposed.And the solution steps and procedures are described in detail.(2)Based on Midas Civil software and preliminary design parameters,the finite element spatial simulation analysis model of the full bridge are establish;The arch-shaped pylon’s reasonable arch axes under three load conditions: dead load,dead load + single-line live load and dead load + double-line live load were obtained by using solution method for the reasonable arch axis of arch-shaped pylon with cable force optimization,denoted as axis A,axis B,and axis C,respectively.When the arch-shaped pylon adopts axis A,axis B and axis C respectively,compared with the arch-shaped pylon adopting the preliminary design arch axis(axis O),the maximum positive and negative bending moments in the plane of the arch-shaped pylon under the corresponding load conditions are greatly reduced,and the reduction is greater than 95%;At the same time,it was verified that initial arch axis has little effect on the solution results of the arch-shaped pylon’s reasonable arch axis under the same load condition.(3)When the arch-shaped pylon adopts axis O,axis A,axis B and axis C respectively,the influence of the arch axis on the internal force,stress and deformation of the arch-shaped pylon cable-stayed bridge is compared and analyzed.And the axis B is closer to the load pressure line of the operation load.Considering the principles of beautiful arch-shaped pylon and relatively simple designing arch axis,the axis B is fitted by the curve fitting method based on the linear least square model,then is used as the design arch axis of the main bridge of Guangzhou-Shantou Railway across Shenzhen-Shantou West Expressway.(4)With the help of the finite element model of the full bridge,based on the principle of control variables,the influences of structural parameters such as the main beam’s vertical bending stiffness,the bending stiffness outside the arch-shaped pylon surface and the stay cable axial stiffness on the internal force and deformation of arch-shaped pylon cable-stayed bridge are qualitatively analyzed. |
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