Geometry and friction of helically wrapped wires in a cable subjected to tension and bending

Helically wrapped wire cables were first introduced to overcome the difficulties in transporting and installing straight wires. Presently, helically wrapped wire cables are used as the important load-carrying elements in many structures such as suspension bridges, cable-stayed bridges, tall guyed towers, power transmission lines, and flexible electrical conductors. In design and analysis, cables are traditionally assumed to carry axial load only; thus, studies on the bending behavior of the cables have been limited. Although the small curvature assumption of the cable may be valid for most part, the possible development of a large curvature at the bearings and anchorage cannot be ignored nor avoided. In this study, an analytical model was developed for the helically wrapped wires in a cable subjected to tension and small bending, with full consideration of the helically wrapped wire geometry. Using the developed model, an approximate upper limit of the cable curvature -for which the conventional Bernoulli-Euler-Navier kinematic beam assumption can be adapted to evaluate the stress in the wires-was obtained.