Static, dynamic and fatigue characteristics of helical cables

Extensive parametric studies have been carried out, using the orthotropic sheet theoretical model of Hobbs and Raoof, on a wide range of spiral strand constructions, with outside diameters, d, and lay angles, a, in the practical ranges, 16.4 mm ≤ d ≤ 184 mm, and 11 ≤ α ≤24 , respectively. The effects of an external hydrostatic pressure on certain structural characteristics of sealed spiral strands, used in deep water applications, have also been studied in some detail, for water depths ranging from 0 m to 2000 m. The results, based on such theoretical parametric studies, have, for example, been used to refute claims by Jolicoeur that, by a simple modification, a significant improvement to the original orthotropic sheet model of Hobbs and Raoof , had been found. In addition, using such studies, axial fatigue life design S-N curves have been developed, which cater for the effects of an externally applied hydrostatic pressure on sheathed spiral strands. Simple (hand-based) formulations have also been developed for estimating the maximum frictional axial and torsional hysteresis along with ,the associated axial load range/mean axial load, and range of twist/2, respectively, at which they occur, relating to both, the in-air conditions and also when a sheathed spiral strand is subjected to an external hydrostatic pressure. The previously reported work of Raoof and his associates, in connection with the response of helical cables (spiral strands and/or wire ropes) to impact loading, has been extended to include the development of closed-form solutions for predicting the extensional-torsional wave speeds and displacements, in axially preloaded helical cables, experiencing a half-sine type of impact loading at one end, with the other end fixed. The influence of the lay angle on the response of a spiral strand to three different (i.e. unit-step, triangular and half-sine) forms of impact loading functions, has also been analysed, with much emphasis placed on the practical implications of the final results in connection with non-destructive methods of wire fracture detection under service conditions....