Analysis of Multilayered Structural Strands

Abstract

The main characteristics of an analytical model for realistic multi‐layered structural strands and some new developments are presented. The results include easily used graphs for determining the pattern of interwire/interlayer contact forces and the associated relative displacements in a large spiral strand with its ends fixed against rotation. Because of interwire frictional phenomena, the effective axial stiffness of a strand is a function of the load perturbation applied. Simplified methods for obtaining upper and lower limits to the stiffness are presented. The lower bound is the “full‐slip” large‐disturbance modulus, which is independent of the friction coefficient and is obtained in a conventional load‐extension test. The small‐disturbance “no‐slip” modulus can be significantly larger. Very encouraging agreement is found between the predicted full‐slip moduli for several real constructions with widely varying strand and wire diameters and lay angles, and experimental data for long specimens. Numerical examples are presented to facilitate the use of the present paper to forecast various aspects of the behavior of other spiral strands.