Theoretical Estimation of the Response of Helically Armored Cables to Tension, Torsion, and Bending

This paper concerns the mechanical behavior of ACSR (aluminum conductor steel-reinforced) conductors under static-loading conditions, which may comprise any combination of tension, torsion, and bending. The model described is quite general and can be applied to other types of helically armored cables. A stiffness matrix is developed and relations are given for axial, torsional, and flexural rigidities and for coupling parameters. For small curvatures, the flexural rigidity is comparable to the upper limit accepted in current practice by ACSR users. As the curvature increases, however, frictional forces develop between the outer layers and sliding of wires may occur, with the result that the flexural rigidity decreases. The tension level also influences the flexural rigidity of the conductor. Actually the model does not consider the flexural rigidity of the system as a fixed entity but as directly influenced by local compressive forces and internal radial and tensile forces. The analysis can also apply to situations where a given number of initial constituent wires have failed and the load is transferred to neighboring wires, leaving the conductor unbalanced; it will be seen how internal arrangements manage to accommodate the local perturbation.