Tensile testing of a wire rope strand

Abstract

Experimental tests are reported on wire rope strands subjected to static axial loads. The wire rope strands are held with a polyester resin and silica filler in conical end grips which are capable of full end fixity, partial restraint, or zero torsional resistance (free ends). Strain gauge load cells monitor the tensile load and the associated twisting moment developed in a strand which is restrained at both ends. A new instrument (‘extrometer’) was designed to record simultaneously the extension and rotation over a predetermined gauge length. Strain gauges are used to measure the surface strains on the wires in the outer layer of the strand. Preliminary tests on seven-wire strands demonstrate that the extrometer instrument provides reliable results. The extension and rotation characteristics recorded on a seven-wire strand under tensile load agree reasonably well with the corresponding theoretical predictions, but the wire surface strains reveal an unequal load sharing between nominally identical helical wires. The experimental data presented here is more complete than previously published work on the tensile behaviour of strands and should assist in the development of theoretical methods and numerical schemes suitable for design purposes.