Influence Length of Wire Fracture and Wire-to-Wire Interaction in Helically Wired Strands under Axial Loads

Abstract

In this study, the influence length of wire damage and wire-to-wire interaction in helically wired strands were investigated both experimentally and numerically. Greased seven-wire steel strands (2 long and 11 short specimens) were tested, each with one outer wire damaged locally. Prior to fracture, the difference in strains between the damaged and intact wires was negligible at 1.2 m (2 ft) away from the damage location. Sudden fracture in the outer wire with 9% area reduction caused only slight or negligible dynamic effect. The influence length (IL, in feet) of the wire fracture can be empirically determined from the applied load (T > .5 kips) by IL=1.62T−.7. Calibrated with test results, the interaction among greased wires can be simulated by isotropic Coulomb friction with a coefficient of friction of .5. In an intact strand, axial stress in the core wire was found to be approximately 1.5 times that in any outer wire. As a result of the nonaxisymmetric section at the location of fracture, axial stress increased significantly in the two outer wires in direct contact with the fractured wire and changed slightly in the remaining wires.