Paper presented at the 26th Annual Southern African Transport Conference 9 - 12 July 2007 "The challenges of implementing policy?", CSIR International Convention Centre, Pretoria, South Africa. ABSTRACT: As inclined cables are primary load-bearing members of cable-stayed bridges, the accuracy of the method of analysing cable state is a key issue in keeping existing bridges safe. Typical cable characteristics are that they are susceptible to corrosion and tend to sag during their long service life, so it is essential to take these characteristics into account in the structural analysis to determine the actual behaviour of a cable in service. However, most of the recent methods of cable structure analysis are done on the material in a perfect state. The deterioration characteristics, such as cable corrosion and initial sag caused by the cable weight, are disregarded, which makes it difficult to apply the current methods when dealing with cable structures that are in service. By solving the boundary problem of inclined cable using the governing differential equation for the UL (Updated Lagrangian) formulation, this paper introduces a convergence iterative solution method for the analysis of cable structures of existing cable-stayed bridges. When using the iterative solution, it is convenient to determine the relationship between the co-ordinate difference of cable-end position, cable tension and cable weight. With the approach described in this paper, the effect of cable sag can be included without any approximations. Moreover, cable corrosion described by the method leads to good accuracy of results. The method meets the engineering requirements for the analysis of existing long-span cable structures. The results obtained from the method show that it is efficient and reliable. It can be conveniently applied in the analysis of large-displacement cable structures that are in service, which provides a new approach to structural health monitoring of long-span cable-stayed bridges.
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