Characteristics of Locked Coil Strands Under Free Bending Available to Purchase

In published literature, the strand constructions dealt with have almost invariably involved only wires which are circular in crosssection. There are, however, instances when shaped wires are used in, for example, half lock and full lock coil constructions. The three main shaped wires used m such constructions are the wedge, half lock, and full lock "Z" or "S" shaped types. In a recent series of publications by the author and his associates, a theory backed by a number of large-scale and carefully conducted experimental checks has been developed for predicting the restrained bending fatigue life of axially preloaded spiral strands at terminations. Traditional approaches invariably assume that the maximum bending strains in the individual wires at the so called extreme fibre positions, govern the strand's free bending fatigue life. The newly developed (alternative) "contact stress-slip" approach assumes (in line with laboratory and field observations), however, the interwire fretting between often counterlaid wires in various layers of steel cables to be the factor responsible for individual wire" fractures. It must be noted that there is currently a paucity of theoretical and/or experimental results for locked coil steel cables. Only recently, some large scale restrained bending fatigue test data related to locked coil ropes has been published. It is by using this data that it has been possible to propose a "contact stress-slip" versus "fatigue life" curve for these cables which should be useful as a predictive tool in design applications. The paper outlines the salient features of the newly developed approach as previously applied to spiral strands. This is then followed by a detailed discussion of a broadly similar approach for analyzing restrained bending fatigue behavior of locked coil ropes, plus simple means of predicting their axial and plane-section bending stiffness.