SIMPLE DERIVATION OF THE STIFFNESS MATRIX FOR AXIAL TORSIONAL COUPLING OF SPIRAL STRANDS

Coupled extensional-torsional behaviour of realistic multi-layered helical strands is addressed. Simplified routines are presented for obtaining the upper and lower bounds to various strand stiffnesses. Such straightforward formulations (aimed at practising engineers) have been derived by extensive theoretical parametric studies on a number of multi-layered spiral strand constructions covering a wide range of cable (and wire) diameters and lay angles. Numerical examples are presented to facilitate the use of the formulations, whose possible practical limitations have been critically addressed.