Determination of recovery length in spiral strands
- Loughborough Univ. of Technology (United Kingdom). Dept. of Civil Engineering
- South Bank Univ., London (United Kingdom). School of Architecture and Civil Engineering
On the offshore scene, the ever growing demands placed on moorings for conventional semi-submersible platforms, coupled with the requirements for guys to new structural forms such as compliant towers has led to the use of larger and longer ropes and spiral strands. Much emphasis has recently been placed on suitable forms of discard criteria based on the remaining fatigue life (or strength) of the spiral strands and wire ropes. It is now well established that, depending on the type of cable (strand or rope) application, the influence of broken wires on the strength of the cable is not directly equivalent to a loss of area of steel: the number and distribution of wire breaks around a cable cross-section and also along its length are both important. With sufficient friction, a broken wire will be capable of supporting its total share of the load in a relatively short length called the recovery length. The determination of recovery length for any type of steel cable, therefore, is of importance as a first step towards developing realistic guidelines for cable discard criteria. The present paper presents a theoretical model for predicting the recovery length in any layer of an axially preloaded spiral strand. Based on a series of theoretical parametric studies, a straightforward method is proposed for obtaining reasonable estimates of variations in the recovery length in any layer of a strand with changes in the lay angle. In view of the simple nature of the final results, these should prove of interest to practicing engineers. Moreover, the final recommendations should prove of some value in the context of length effects associated with axial fatigue loading of cables under laboratory conditions which has recently attracted much attention: the question here is how to determine a minimum length for test specimens whose axial fatigue life under laboratory conditions may safely be used to represent those of the much longer cables in the field.
- OSTI ID:
- 27913
- Report Number(s):
- CONF-940230--; ISBN 0-7918-1266-9
- Country of Publication:
- United States
- Language:
- English
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