Analysis On The Optimal Ratio Of The Height Of Pylon And Span Of Loy-pylon Cable-stayed Bridge

Loy-pylon cable-stayed bridge is a new type of bridge structure form developed on the basis of cable-stayed bridge. On the structural characteristics, low-pylon cable-stayed bridge is a new style between continuous bridge and cable-stayed bridge. The beam bears the majority of vertical load and vertical force of the cable bears the left. At the same time, the level force of the cable reinforce the beam in order to improve the performance of the beam. In our country, the number of low-pylon cable-stayed bridge is not too many, and the research on its structure characteristics is not enough. In this paper, though summarizing and analyzing the existing research materials at home and aboard, I have used influence matrix method to optimize the cable force. Then change the height of the pylon to study the influence on beam and cable and so on. Last choose a appropriate objective function to optimize the height of the pylon.Firstly, the paper presents the development and study of this kind of bridge. Low-pylon cable-stayed bridge is a kind of novel structure, with the advantage of superior performance and economic indicator, it develops rapidly home and abroad. Because the construction experience and research work is insufficient, more studies need to be done.Secondly, the paper introduces the overall design, such as the section of beam and the arrangement of span, cable and pylon. And reviews the static analysis theory of low-pylon cable-stayed bridge, such as finite element method, live load calculation and geometric nonlinear and so on.Additionally, compare different kind of optimization theories of cable and use MADIS/Civil to establish the model. With the help of MATLAB, optimize the cable of actual bridge with influence matrix method. Put the optimized force into the relevant model, and then analysis the bending moment and displacement of the beam.Finally, make several groups of appropriate height of pylon, and use influence matrix method to optimize them respectively. Analysis the influence of beam and cable after the height of pylon is changed. Use MATLAB's curve fitting tool to fit beam bending energy, the beam bending moment at the top of the pier and the cable quantity. Establish a appropriate objective function with the consideration of beam bending energy, the beam bending moment at the top of the pier, the cable quantity and displacement, then compute the most optimal height of the pylon to make the beam and cable under a reasonable condition.