CRITICAL-EXAMINATION OF VARIOUS APPROACHES USED FOR ANALYZING HELICALCABLES

Using theoretical parametric studies covering a wide range of cable (a nd wire) diameters and lay angles, the range of validity of various ap proaches used for analysing helical cables are critically examined. Nu merical results strongly suggest that for multi-layered steel strands with small wire/cable diameter ratios, the bending and torsional stiff nesses of the individual wires may safely be ignored when calculating the 2 x 2 matrix for strand axial/torsional stiffnesses. However, such bending and torsional wire stiffnesses are shown to be first order pa rameters in analysing the overall axial and torsional stiffnesses of, say, seven wire strands, especially under free-fixed end conditions wi th respect to torsional movements. Interwire contact deformations are shown to be of great importance in evaluating the axial and torsional stiffnesses of large diameter multi-layered steel strands. Their impor tance diminishes as the number of wires associated with smaller diamet er cables decreases. Using a modified version of a previously reported theoretical model for analysing multilayered instrumentation cables, the importance of allowing for the influence of contact deformations i n compliant layers on cable overall characteristics such as axial or t orsional stiffnesses is demonstrated by theoretical numerical results. In particular, non-Hertzian contact formulations are used to obtain t he interlayer compliances in instrumentation cables in preference to a previously reported model employing Hertzian theory with its associat ed limitations.