Improved multi-sensor for force measurement on pre-stressed steel cables by means of eddy current technique

The increase of demands on reinforced concrete elements, such as for bridge constructions, requires more and more a long-term monitoring using multi-sensor techniques. Dynamic load inspection and maximum load detection are sought-after. Magneto-elastic force measurement of pre-stressed reinforcing concrete cables is also an investigative method to detect steel failures. Examinations of coil impedance and reactance measurements on eddy current sensors placed on mechanically stressed steel specimens demonstrate a high dependency on the magneto-elastic effect. This stress measurement on steel bars such as pre-stressing or reinforced concrete cables can be achieved by calibration of the material properties such as magnetostriction and an additional measurement of the magnetisation state.