Arch Tower Cable-stayed Design Parameters And Geometric Nonlinear Analysis

Based on the preliminary design of a single tower cable-stayed bridge with an arch-tower called Ben River Bridge in a city, the main static analysis results, dynamic analysis and stability calculation of the arch-tower cable-stayed bridge is presented. This thesis concentrates on the design parameters and the geometric nonlinearity of the arch-tower cable-stayed bridge. Systematical research is carried out by using the parameter analysis and the finite element method to investigate the influence of the main structural design parameters, such as the ratio between the height of tower and the length of main span, the length of unsupported deck adjacent to the end of main span, the length of unsupported deck adjacent to pylon and the stiffness ratio between girder and pylon, on structural displacement, internal force and tension of cables, when the bridge is under live load. Finally, the effects of geometric nonlinearity on structural static behavior of arch-tower cable-stayed bridge under the first stage of dead load, the second stage of dead load and live load respectively are examined. All results can be references to the design of the same type bridge.In this thesis the main conclusions are showed in the following: 1. Parameter analysis shows that with the increase of the ratio between the height of tower and the length of main span, the moments and displacements of the key sections of the main girder and pylon and the maximum tension of cables experience a gradual decreasing trend, however the absolute value of negative reaction of side-span support increase tremendously. Also, with the raise of the length of unsupported deck adjacent to the end of main span, the moments of the main girder and pylon decrease progressively, but the maximum deflection of the girder, horizontal displacement at the top of tower and negative reaction's absolute value of side-span support increase progressively. Especially, the tension of cables near to the end of the girder increases rapidly. 2. With the climb of the length of unsupported deck adjacent to pylon, the hogging moment of the girder near to pylon drops monotonously. By contrast, the longitudinal moment of the bottom of pylon has a slow descending trend. What's more, with the ascent of the stiffness ratio between girder and tower, the moments of the main girder, the maximum deflection of the girder, horizontal displacement at the top of tower and the absolute value of negative reaction of side-span support climb monotonously, but the moments of the pylon decrease monotonously. Interestingly, the change of the tension of cables is small.3. Under the first stage of dead load, the second stage of dead load and the live load, large displacements has the most obvious influence upon arch-tower cable-stayed bridge, followed by axial force and bending interactions and cable sag effects respectively. Compared with the first stage of dead load and the second stage of dead load, under live load, the effect of geometric nonlinearity is smaller.4. According to the geometric nonlinear behavior of arch-tower cable-stayed bridge under live load, It is concluded that as for little span arch-tower cable-stayed bridge, geometric nonlinearity has a small influence on the relationship between load and displacement. Geometric nonlinearity will have an obvious effect on this relationship only if the live load exceeds normal load tremendously.