Investigation Of Structural Suitability And System Of The Middle Tower In A Three-tower Suspension Bridge

With the development of economy, many countries are planning to build bridges across the sea. The width of the channel is huge, if use the original two-tower suspension bridge system, the span of the bridge will be very large; it may cause some problems such as the too large deformation of the stiffening girder. With the increase of the span, the project of each part in the suspension bridge will be greatly increased, construction cost is high, and it can’t take full advantage of the suspension bridge. Therefore engineers have proposed to build multi-tower suspension bridge, but the span of the multi-tower suspension bridge has been built is very small, and did not take full advantage of the large crossing capacity of the suspension bridge, until China built two three-tower suspension bridge: Taizhou bridge and MA ‘Anshan bridge, which main span are 1080 m, for the world’s first. But there are still many problems of this new bridge form need to be studied, this article takes the MA ‘Anshan bridge as the background, mainly for the following work:(1). First the development history and the construction achievements of suspension bridge in American, Europe, Japan, China are introduced. With the development of science and technology, a new system of suspension bridge with multi-tower and multi-span was proposed by bridge experts. Then the proposed programs of multi-tower suspension bridges in the design process and the research of large-span multi-tower suspension bridge by the scholars are introduced.(2). Theory and method of static and dynamic analysis of suspension bridge are introduced simply. First the theory of the static calculation for suspension bridge is introduced,originally is the theory of elasticity, then the deflection theory and finite displacement theory is currently used, each kind of theory is briefly introduced, the advantages and disadvantages of each theory and the difference between them are analyzed. Secondly the method of dynamic analysis of suspension bridges, the modal analysis theory and the method of modal analysis are introduced. The solution methods mainly are subspace iteration method and the Lenclos method.(3). The general situation of MA ‘Anshan Bridge is introduced, the numerical model of the bridge is established by software Midas civil, in order to better grasp the mechanics characteristics of three-tower suspension bridge, the model of a same main span two-tower suspension bridge is established. The calculation of Midas civil software and load test value were compared, the results show that the calculation of Midas civil software has a high reliability; the real force condition of the bridge is well. Finally, the self-vibration characteristics of the bridge is analyzed, the results show that the index of structural stiffness is well.(4). The structure system and the middle tower of the three-tower suspension bridge are studied. The suspension bridge model of different form, stiffness, height in middle tower is established by finite element analysis software Midas civil. The difference of differentstructures under live load in the displacement and internal force of main girder, the axial force of slings and main cable, displacement and internal forces of the middle tower and side tower,the main cable anti-slide, structural vibration characteristics and other aspects are analyzed,The relevant conclusions can provide a reference for the design of similar bridges in the future.