Axial and Free‐Bending Analysis of Spiral Strands Made Simple

Abstract

Parametric studies based on previously reported orthotropic sheet theory have been carried out on a number of realistic and multilayered helical‐strand constructions with widely different strand (and wire) diameters and lay angles. Based on the results, a series of easy to use routines have been recommended which provide a simple means of obtaining estimates of various strand axial and free‐bending characteristics such as stiffness and hysteresis of axially preloaded strands experiencing axial or free‐bending load perturbations. Due to the presence of interwire friction, axial or free‐bending stiffnesses are found to be functions of the external load perturbations: Using the present routines, it is possible to obtain the upper (no‐slip) and lower (full‐slip) bounds to the stiffnesses and maximum possible specific loss under continued uniform cyclic loading. Simple formulations are also presented for estimating various wire kinematical parameters such as wire axial strains, interwire movements and strand overall effective Poisson's ratio. Practical limitations of the formulations have been discussed elsewhere, in the light of recent experimental findings. The proposed formulations are amenable to hand calculations and should prove useful for design office purposes.