Cable for fastening structures and method of detecting damage to corrosion-preventive layer thereof

A cable for fastening structures, which comprises:

• a strand made up of a large number of element wires;
• a corrosion-preventive layer surrounding the peripheral surface of the strand;
• a cylindrical conductive resistance detector extending inside and over the entire length of the cable in a manner to surround said strand;
• an electrically insulating layer between said resistance detector and said strand;
• means for measuring resistance having:
• a means for forming a first resistance circuit through said resistance detector from one end thereof, a rupture through said insulating layer to said strand, and said strand and which has a first resistance which includes the resistance between the one end of said detector and the location of the rupture and the resistance at the ruptured point to the strand connected in series, and for forming a second resistance circuit through said resistance detector from the other end thereof, the rupture and said strand and which has a second resistance which includes the resistance between the other end of said detector and the location of the rupture and the resistance at the ruptured point to the strand connected in series, and a current flow measuring means for measuring current flow in said two resistance circuits;
• and
• an arithmetic unit connected to said resistance measuring means for determining the position and magnitude of the rupture from a comparison of the first and second resistances and the resistance of the entire length of said resistance detector.