This study deals with the modeling of the static behavior of synthetic wire ropes. The objective is the determination of the validity domain of two analytical models (Costello and Labrosse) used to predict the overall axial stiffness. First investigations have been performed for isotropic material. The results of the two analytical models are compared with a three-dimensional finite element cable model, using a non-dimensional analysis. Next, Labrosse's model is extended for synthetic fibers rope applications. Tests performed to obtain experimental stiffness measurements are then presented. Finally, predicted stiffness is compared to test results thus validating the analytical approach.
Synthetic spiral stranded cables, which are often composed of steel chain at the ends and a central synthetic fiber rope, are increasingly finding applications as offshore oil exploration goes to deeper sites. It is well known that a main advantage of such elements is their ability to support large axial load with comparatively small bending or torsion stiffness. It is therefore essential to be able to model the mechanical behavior of very long mooring lines. Large synthetic ropes are assemblies of millions of fibers. The rope is made up of strands, which are obtained from twisted yarns, where each yarn is made of parallel fibers, see Leech (2002). In this work, the case of a synthetic fiber (aramid) is considered. Several analytical models are available to predict the mechanical behavior of simple straight strand cables subjected to axial loads. The first approaches only incorporates effects associated with tension, the bending and torsion stiffnesses of the wires being neglected. Such developments have been performed by Hruska (1951,1953) and by Knapp (1975) for a rigid core. More recent and complex analytical models are based on beam theory assumptions: the behavior of wires is described using Love's curved beam equations.
