Fairly recently, a theoretical model for predicting axial fatigue life of multi-layered spiral strands from first principles was reported by the second author. The theoretical predictions were based on an extension of a previously reported orthotropic sheet model, and the theory could predict the strand axial fatigue life to first outer (or inner) wire fracture both at the fixed end and away from the terminations (i.e. in the free field). Some experimental data from other sources provided very encouraging support for the theoretical predictions for strands with outer diameters ranging from 39 to 51mm. Some large-scale experimental results on Spiral strands with diameters up to 127mm were recently obtained by others. The purpose of the present paper is to report the correlations between these test data and theoretical predictions which has been found to be very encouraging, providing further support for the theoretical model. Moreover, it has previously been argued that with proper design. of end terminations, it is possible to design test specimens in which (under axial fatigue loading) wire fractures occur away from the ends thus enabling one to apply the test data on laboratory specimens directly to the much longer cables in the actual structures. The present reported results throw some light on the plausibility of such suggestions and identify possible practical limitations of such approaches.
Steel cables are used for mooring certain types of offshore platforms such as semi-submersibles, guyed towers, etc., and are proposed as elements of mooring systems of wave energy devices. Permanent immersion of most of the cable in sea water is another important consideration. In the past, the only reliable source of information on the steel cable (wire rope and/or spiral strand) fatigue characteristics has been laboratory tests on cable specimens which can be very costly and time consuming.
