Determination of hanger installation procedure for a self-anchored suspension bridge

For self-anchored suspension bridges, stiffening girders or trusses should be erected prior to the air-spinning of the main cables. Since hangers are installed between pre-constructed stiffening trusses and main cables, tensioning processes are necessary for hanger installation in the case of a self-anchored suspension bridge. Since hanger tension variations in construction are quite dependent on the constructional plan adopted, the jacking force and probable maximum tension should be predicted and compared in the constructional design state so as to determine the most feasible and effective plan among the possible options. This is generally done by the use of a so-called geometrically nonlinear construction step analysis. A finite element (FE) analysis procedure, which utilizes elastic catenary cable element formulation for controlling the length of the cable members, is proposed for the development of a hanger installation plan, in particular for the self-anchored Yongjong Bridge. As a pre-requisite to a rigorous backward/forward construction step analysis, an unbalanced load-free FE model was established following a nonlinear shape-finding analysis procedure. Based on a series of comparative studies, an installing plan, which utilizes the synchronized jacking of a maximum of 80 strand jacks with the combination of a divided tensioning technique, is proposed and its successful application to the construction of the Yongjong Bridge is described.