A Study on the Influence Line Analysis of Suspension Bridges

The purpose of this study encompasses the development of practical suspension bridge analyses methods and its related programs which can be used on the actual day to day applications. The suspension bridges are composed of cables, hangers, towers and girders, and among these, the cables and hangers are special elements which are not capable of providing resistance against bending and compression while only capable of resisting against tension. When the suspension bridges are loaded, the whole structure display very complex nonlinear behavior due to excessive cable deflection. In order to perform structural analyses of suspension bridges which behave nonlinearly, the initial shape analyses are needed to establish the initial shapes which will correspond to the design shapes. Once the initial shapes are established, dead loads are applied to the initially shaped models to establish design shapes, and the geometric nonlinear analyses are performed for each load at this stage. Because the structural analyses involving initial shape analyses, dead loads and others require iterations based on the nonlinear theory, much time and efforts are needed to find solutions and it is difficult to avoid numerical errors due to the iterations. Much difficulties are associated in finding the design values required at various structural elements due to the fact that influence line analyses methods, the performance of which are required for designs, can not be applied in nonlinear theory. This study has developed linearized analyses methods for suspension bridge for the purpose of providing practical suspension bridge analyses which dosen't require the initial shape analyses and reiterated computations, but on which the influence line methods can be applied. The method of this study has found to be effective when structural analyses result of the study had been compared to already established design and analyses results.