Abstract: A tension measuring method installs a reel having a cylindrical coil forming part on a cable to be measured, forms a coil by winding a conductor around the coil forming part, measures a magnetic hysteresis loop of the cable by supplying a current to the coil to generate a magnetic field, and computes a tension of the cable using a parameter determined from the hysteresis loop. A magnetic field sensor and a magnetic flux sensor are provided inside a through hole in the coil forming part, and the cable is positioned inside the through hole. The magnetic field is varied so that the hysteresis loop includes a near-saturation magnetization region, to measure the hysteresis loop using the sensors. The parameter is selected from a magnetic flux or a magnetic flux density, a remanent magnetization, a coercivity, a magnetic permeability, and a hysteresis loss in the near-saturation magnetization region.

Abstract: A tension measuring method installs a reel having a cylindrical coil forming part on a cable to be measured, forms a coil by winding a conductor around the coil forming part, measures a magnetic hysteresis loop of the cable by supplying a current to the coil to generate a magnetic field, and computes a tension of the cable using a parameter determined from the hysteresis loop. A magnetic field sensor and a magnetic flux sensor are provided inside a through hole in the coil forming part, and the cable is positioned inside the through hole. The magnetic field is varied so that the hysteresis loop includes a near-saturation magnetization region, to measure the hysteresis loop using the sensors. The parameter is selected from a magnetic flux or a magnetic flux density, a remanent magnetization, a coercivity, a magnetic permeability, and a hysteresis loss in the near-saturation magnetization region.

Abstract: A coated PC steel stranded cable includes: a stranded cable in which a plurality of elemental wires each composed of steel are twisted together; an anti-corrosive coating having an outer circumferential portion that coats an outer circumference of the stranded cable; an outer coating that coats an outer circumference of the anti-corrosive coating; and an optical fiber provided at a position inwardly of an outer circumferential surface of the outer coating and corresponding to a strand groove in the stranded cable so as to follow expansion and contraction of the stranded cable.

Abstract: A coated PC steel stranded cable includes: a stranded cable in which a plurality of elemental wires each composed of steel are twisted together; an anti-corrosive coating having an outer circumferential portion that coats an outer circumference of the stranded cable; an outer coating that coats an outer circumference of the anti-corrosive coating; and an optical fiber provided at a position inwardly of an outer circumferential surface of the outer coating and corresponding to a strand groove in the stranded cable so as to follow expansion and contraction of the stranded cable.